CHAPTER-I - Shodhgangashodhganga.inflibnet.ac.in/bitstream/10603/40656/6/06_chapter_01.… ·...

CHAPTER- I GENERAL INTRODUCTION AND LITERATURE SURVEY

1

CHAPTER-I

Sr

No

Title Page

no

11 General 2

111 Need of Supercapacitor 2

112 Nanomaterials for Supercapacitors 7

12 Literature Survey on Tin Oxide (SnO2) and Ruthenium

Oxide (RuO2) Thin Films

8

121 Literature Survey on SnO2 Thin Films 8

122 Literature Survey on RuO2 Thin Films 10

13 Literature Survey on SnO2 RuO2 and SnO2-RuO2 based

Supercapacitor Electrodes

12

131 Literature Survey on SnO2 based


12

132 Literature Survey on RuO2 based


13

133 Literature Survey on SnO2-RuO2 based


17

14 Orientation and Purpose of Dissertation 19

References 22


2

11 General

111 Need of Supercapacitor

The growing demand of energy sources in recent few years has

become the concern topic for researchers due to the lack of renewable

energy sources The use of fossil fuels for energy production is also a

burning issue regarding the worldrsquos ecology and economical concern

Global warming fuel dependency and pollution are few examples to divert

from fuel-based economy to electricity-based civilization Some

conventional sources of energy are solar energy wind energy etc but this

energy production is highly depending on natural phenomena and we do

not have control over these phenomenarsquos Therefore there is immense

need to develop energy storage devices to store the generated energy for

future use In this aspect the electrochemical power sources are emerged

as the new sources for store and production of electrical energy The

electrochemical power sources are more efficient than the fuel-based

system because they provide clean energy which is necessary demand

according to environmental issues

Electrical energy storage is required in many applications such as

telecommunication devices cell phones standby power systems and

electric hybrid vehicles [1] Many applications are demanding local storage

or local generation of electrical energy Therefore there is a strong need of

development of improved methods for storing energy when it is available

and retrieving when it is needed The electrochemical power sources

include batteries fuel cells and supercapacitors The electrical energy

storage in these sources is according to fundamentally in two different

ways [2]

a) Indirectly in batteries as potentially available chemical energy

required Faradic oxidation and reduction of the electroactive

reagents to release charges that can perform electrical work


3

when they flow between two electrodes having different

electrode potential and

b) Directly in an electrostatic way as a negative and positive

electric charges on plates of capacitor

The most common electrical energy storage device is battery

Batteries are closed systems with anode and cathode are charge transfer

mediums that take part in redox reactions This means the energy storage

and conversion occurs in same compartment in batteries Whereas in case

of fuel cells the anode and cathode are only the charge transfer media and

active masses undergoing redox reaction are supplied from outside the

system means they are open systems [3] Batteries can store large amount

of energy in relatively small volume and weight The power performance

of battery is limited by its electrochemical reaction kinetics active

materials their conductivity and mass transport Most Batteries exhibit

relatively constant operating voltage because of the thermodynamics of

the battery reactants as a result it is difficult to measure their state-of-

charge (SOC) correctly [4] The irreversible chemical reactions in batteries

leads to the transformations of the active mass which limits the cycle life of

the batteries up to only several hundred cycles In recent years the power

requirement for various applications increased markedly and this leads to

design special high power pulse batteries often with sacrifice of energy

density and cycle life

Capacitors are fundamental electrical circuit elements that store

electrical energy in the order of microfarads and assist in filtering

Capacitors store electrical charge Because the charge is stored physically

with no chemical or phase changes taking place the process is highly

reversible Conventional capacitors consist of two conducting electrodes

separated by an insulating dielectric material When a voltage is applied to

a capacitor opposite charges accumulate on the surfaces of each electrode


4

The charges are kept separate by the dielectric thus producing an electric

field that allows the capacitor to store energy

The capacitance C of a capacitor is given by the ratio of stored

charge (Q) to the applied voltage (V) as

V

QC = (11)

For a dielectric capacitor the capacitance is dependent on the

dielectric constant (K) thickness of the dielectric material (d) and

geometric area (A) [1]

d

KAC = (12)

The two important parameters for electrical energy storage devices

are energy density and power density The energy (E) stored in capacitor

is directly proportional to its capacitance

2

CV2

1E =

(13)

The power density (P) of capacitor is energy expended per unit time and is

given by [5]

ESR4

VP

2

times

= (14)

Where ESR is the equivalent series resistance which is the net

resistance offered by the internal components of capacitor ESR plays an

important role in lowering the capacitance of a capacitor

Conventional capacitors have high power density but they have low

energy density they are able to deliver the stored energy at very high

discharge rates but the stored energy is less compared with batteries and


5

fuel cells On the other hand batteries can store very large amount of

energy but deliver that energy at very slow rates Therefore the new

energy storage device named electrochemical capacitor or supercapacitor

is invented to minimize the disadvantages offered by both conventional

capacitors and batteries and coupled the advantages of both [6 7] The

reason why supercapacitors are able to raise considerable attention is

visualized in Fig 11 where typical energy storage and conversion devices

are presented in the so-called lsquoRagone plotrsquo in terms of their specific

energy (horizontal axis) and specific power (vertical axis)

Fig 11 Ragone chart showing logarithmic plot of specific power vs

specific energy for various energy-storage devices [8]

A simplified Ragone plot explains that the fuel cells can be

considered as high-energy systems whereas supercapacitors are

considered as high-power systems Supercapacitors fill in the gap between

batteries and conventional capacitors in terms of specific energy as well


6

as in terms of specific power this gap covers several orders of magnitude

Thus supercapacitors may improve battery performance in terms of

specific power or may improve capacitor performance in terms of specific

energy when combined with the respective device

The various advantages of supercapacitors are [9] a) High specific

capacitance value in Farads and several hundred Farads (greater than

ordinary capacitor) b) Virtually unlimited cycle life in thousands or

millions c) Rapid charging and discharging the energy stored d) High

power density and e) Do not contain hazardous or toxic materials so easy

to dispose

Supercapacitors can stand alone as energy storage device for high

power applications or for hybrid supercapacitor-battery system that can

address simultaneously power and energy requirements Supercapacitors

coupled with batteries fuel cells are considered promising mid and long-

term solutions for low and zero emission transport vehicles by providing

the power peaks for startndashstop acceleration and recovering the breaking

energy Supercapacitors will supply power to the system when there are

surges or energy bursts since supercapacitors can be charged and

discharged quickly Supercapacitors are making a difference or better

performance in many areas like automotive industrial traction and

consumer electronic

The capacitance of a supercapacitor can arise from the charging or

discharging of the electrical double layers (electrical double layer

capacitance) or from Faradaic redox reactions (pseudocapacitance) In

former case storage of energy is achieved in a way as a traditional

capacitor The high capacitance value than ordinary capacitor is due to the

charge separation takes place at the very small distance in the electrical

double layer that constitutes the interphase between an electrode and the

adjacent electrolyte [6] Increased amount of charge is stored on the highly


7

extended electrode surface-area created by a large number of pores In

later case of pseudocapacitance most of the charge is transferred at the

surface or in the bulk near the surface of the solid electrode material

Hence in this case the interaction between the solid material and the

electrolyte involves Faradaic reactions which in most instances can be

described as charge transfer reactions The charge transferred in these

reactions is voltage-dependent resulting in the pseudocapacitance [1]

112 Nanomaterials for Supercapacitors

Nowadays many researches on the supercapacitors aim to increase

both power and energy density as well as lower the fabrication costs using

environment friendly materials This can be achieved by making high

surface area electrodes having high reversible redox reactions In this

aspect nanostructured materials have attracted considerable interest due

to their unique properties arising from quantum size effect It is realized

that the properties of materials at nanoscale can be significantly different

from the bulk properties and have profound influence on the physico-

chemical characteristics of a material such as electrical optical magnetic

catalytic etc [10-17] that have vast technological applications The

electrode materials used for supercapacitors are carbon conducting

polymers and metal oxides Among them oxide nanomaterials exhibit

unique physical and chemical properties due to the high density of surface

defect sites that are observed for structures with nanoscale dimensions

However to afford the production needs of cheap clean reliable and

durable materials with controlled properties for realistic and practical

applications of nanotechnology the request of mass production of thin film

will probably represent one of the most important issues of producing

nanomaterials Chemical methods for design of nanomaterials [18] would

probably contribute to a great extent


8

12 Literature Survey on Tin Oxide (SnO2) and Ruthenium Oxide

(RuO2) Thin Films

121 Literature Survey on SnO2 Thin Films

SnO2 is n type wide band gap semiconductor material that

crystallizes in rutile structure The basic building blocks of the rutile

structure (Fig 12) are a tin (Sn) atom surrounded by six oxygen (O) atoms

placed approximately the corners of a regular octahedron The lattice

parameters are a=b=4737 Aring and c=3186 Aring [19 20]

Fig 12 Crystal structure of rutile SnO2 [21]

There are two main oxides of tin stannic oxide (SnO2) and stannous

oxide (SnO) The existence of these two oxides reflects the dual valency of

tin with oxidation states of +2 and +4 SnO2 possesses the rutile structure

and SnO has the less common litharge structure [22] The optical bandgap

of SnO is not exactly known but it lies somewhere in the range of 25ndash3 eV

which is less than the optical bandgap of SnO2 which is commonly quoted

to be 36 eV [23] Thus SnO exhibits a smaller band gap than SnO2 In its

stoichiometric form SnO2 acts as an insulator but in its oxygen-deficient

form SnO2 behaves as an n-type semiconductor


9

Due to wide bandgap SnO2 has been used extensively as a

transparent antireflection coating in optoelectronic devices such as flat

panel displays and thin film solar energy cells [24] More interestingly the

conductivity of the SnO2 semiconductor is modulated by the chemisorbed

species on its surface For example the absorbed oxygen receiving

electrons from the conduction band produces an electron depletion layer

under the absorbing surface and a potential barrier between particles and

thus decreases the conductivity of the SnO2 [25 27] This makes SnO2 a

good candidate for gas sensors whose conductivity will increase sharply

when exposed to a reducing gas SnO2 has been actively explored as the

functional component in detecting combustible gases such as CO H2 and

CH4 [28] Korotcenkov et al studied the gas response of nanosize SnO2

thin films deposited by SILD (successive ionic layer deposition) method

and observed good gas response for ozone and H2 [29] Due to the high

gravimetric lithium storage capacity of SnO2 and its low potential for

lithium ion intercalation it is regarded as one of the most promising

candidate for anode materials in Li-ion batteries [30] In addition SnO2 is

chemically inert very hard and can resist high temperatures during

heating

To continue to exploit the possible applications of SnO2 it is

essential to control its size and morphology to achieve tailored properties

Recently these useful properties have stimulated the search for new

synthetic methodologies for well-controlled SnO2 nanostructures Several

reports on high-temperature physical SnO2 synthesis have been published

[31 32] Chemical methods for the preparation of thin films studied

extensively because such processes facilitate the designing of materials on

molecular level Murakami et al used spray pyrolysis method for

deposition of SnO2 thin films using organotin compounds which led the (1

1 0) and (2 0 0) orientated films on glass substrate [33] Deshpande et al


10

used M-SILAR (modified successive ionic layer adsorption and reaction)

method for deposition of nanocrystalline SnO2 thin films at room

temperature the films have agglomerated structure [34] Her et al used a

hydrothermal process for large-scale production of SnO2 nanoblades on

glass substrate in a controlled aqueous solution at temperatures below

373 K [35]

Compared with high-temperature physical synthetic methods the

chemical methods appear to be of particular interest for deposition of SnO2

thin films because they offer the potential of facile scale-up and can occur

at moderate temperatures

122 Literature Survey on RuO2 Thin Films

Ruthenium (Ru) is a polyvalent hard white metal is a member of the

platinum group The oxidation states of Ru ranges from +1 to +8 and -2 are

known though oxidation states of +2 +3 and +4 are more common Fig

13 shows the crystal structure of rutile RuO2 where ruthenium (Ru) atom

is coordinated with six oxygen (O) atoms

Fig 13 Crystal structure of rutile RuO2 [36]


11

The ruthenium (IV) oxide (RuO2) with oxidation state +4 is the

stable oxide of Ru at room temperature and in a wide temperature range

RuO3 is unstable at room temperature and readily decomposes to give

RuO2 and O2 RuO2 has a low resistivity of 40 microΩcm and a good thermal

stability up 1073 K it is finding numerous applications as a buffer layer or

contact electrode material for ferroelectric memory devices and high k or

ferroelectric thin film capacitors [37] In electronics this metallic oxide

plays a significant role for example as field emission (FE) cathodes for

vacuum microelectronic devices and as promising candidates for

integrated circuit development [38] RuO2 have been reported as an

effective low temperature oxidative dehydrogenation (ODH) catalyst [39]

It is used as an electrode for chlorine evaluation for dimensionally stable

anodes [40] In energy storageconversion devices ruthenium hydroxide

is an essential element for removing the CO-like poisoning in the Pt Ru

anodes of the direct methanol fuel cells [41]

There are various ways including physical as well as chemical

methods used to prepare RuO2 RuO2 films can be prepared by using

physical methods like pulsed laser deposition (PLD) and sputtering The

chemical methods like dip coating sol-gel SILAR spray pyrolysis were

reported for the preparation of RuO2 thin film The RuO2 films are also

synthesized using electrochemical methods The commonly used

precursor for RuO2 deposition is ruthenium chloride (RuCl3xH2O) As the

present work is based on chemical methods the literature survey for

deposition of RuO2 is concentrated on chemical methods only Patake and

Lokhande used single step chemical method for deposition amorphous and

porous RuO2 thin films with optical band gap of 22 eV [42] A spray

pyrolysis method used by Gujar et al [43] for deposition of amorphous

RuO2 thin films with network like morphology at 573 K substrate

temperature the films showed an optical band gap of 24 eV RuO2 thin


12

films was prepared by pyrolysis process in a nitrate melt at 573 K and

used as anode catalyst for water electrolysis the impedance results in

oxygen evolution region showed the electrocatalytic activity of RuO2 [44]

RuO2 nanocrystalline films were obtained by dip coating from alcoholic

solutions of Ru(OEt)3 by Armelao et al [45] Zhitomirsky et al

electrosynthesized RuO2 films on different substrates via hydrolysis by an

electrogenerated base of RuCl3xH2O dissolved in water [46 47] Hu et al

used the anodic deposition method for deposition of hydrous RuO2 from

RuCl3xH2O in aqueous media withwithout adding acetate ions as the

complexing agent [48] Anodic cathodic and cyclic voltammetric (CV)

deposition of RuO2 from aqueous RuCl3 solutions was investigated using

stationary and rotating disk electrodes (RDE) by Jow et al [49]



131 Literature Survey on SnO2 based Supercapacitor Electrodes

In recent years SnO2 is considered as promising electrode material

for supercapacitors due its low cost high chemical stability and

environmental friendly nature Sb doped SnO2 powder was prepared by

Wu using sol gel process showed a maximum specific capacitance of 105

Fg-1 for electrode annealed above 900 K [50] Prasad and Miura

potendynamically deposited SnO2 thin films which showed a specific

capacitance of 265 Fg-1 [51] Mane et al obtained nanocrystalline and

hydrophilic SnO2 thin films at room temperature using an electrochemical

method a mixed phase of SnO2 was observed with maximum specific

capacitance of 4307 Fg-1 [52] Wu et al cathodically deposited amorphous

tin oxide (SnOx) on graphite substrate a maximum specific capacitance of

298 Fg-1 was observed [53]

SnO2 is also used as second component material in composite

electrodes Hwang and Hyun synthesized tin oxidecarbon aerogel


13

composite electrodes by sol-gel method which showed a specific

capacitance of 70 Fg-1 [54] Jayalakshmi et al prepared SnO2-Al2O3 mixed

oxide by using single step hydrothermal process with specific capacitance

of 119 Fg-1 [55] Hu studied the supercapacitive performance of

nanostructured SnO2Polyaniline composite which showed a specific

capacitance of 3035 Fg-1 [56] SnO2ndashV2O5ndashCNT electrode synthesized by

hydrothermal method showed a specific capacitance of 121 Fg-1 [57]

132 Literature Survey on RuO2 based Supercapacitor Electrodes

Hydrous RuO2 usually represented as RuOxHy or RuO2middotxH2O is a

good electrode material for supercapacitors In 1971 Trasatti et al studied

the electrochemical behavior of RuO2-based dimensionally stable anodes

(ie DSA) for chlorine evolution and proposed that the anhydrous RuO2

crystals show capacitive-like i-E responses [58] Furthermore Conway et

al investigated extremely high redox reversibility of RuO2 from the studies

of hydrous hyper-extended RuO2 thin film on Ru metal [59]

A sol-gel method was used by Zheng et al to prepare RuO2

electrode a specific capacitance of 720 Fg-1 was observed for electrode

heat-treated at 423 K [60] Lee et al used liquid-phase chemical bath

deposition route at room temperature to synthesize amorphous RuO2 thin

films of spherical nanoregime grains which showed a specific capacitance

of 416 Fg-1 [61] Kim and Kim used an electrostatic spray deposition

method with high dc voltage in a range of 0-40 kV for deposition RuO2 thin

film an average specific capacitance of 650 Fg-1 with good high rate

capability was observed [62] RuO2xH2O was prepared by electrophoretic

deposition and heat-treated at 523 K a network of nanoparticles (10 nm)

was developed with porous structure showed a specific capacitance of

734 Fg-1 [63] Porous and hydrous RuO2 thin film electrode was fabricated

by cathodic electrodeposition on titanium substrates showed a specific

capacitance of 786 Fg-1 [64] Anodic deposition of RuO2 electrodes was


14

done by Hu et al showed a specific capacitance of 552 Fg-1 [48] Patake

and Lokhande used M-CBD method for deposition amorphous and porous

RuO2 thin films with a specific capacitance of 50 Fg-1 [42] Gujar et al [43]

obtained a specific capacitance of 551 Fg-1 for RuO2 thin film prepared by

spray pyrolysis method Park et al studied the effect of film thickness on

supercapacitive performance of RuO2 thin films deposited by cathodic

electrodeposition a maximum specific capacitance of 788 Fg-1 was

observed [65] RuO2 films were grown on metal substrates at

temperatures from 373 to 573 K using ruthenium ethoxide solution as the

precursor showed a specific capacitance of 593 Fg-1 [66] Oxidation of

RuCl3H2O with H2O2 was used to synthesis hydrous RuO2 by Chang and

Hu showed a specific capacitance of about 500 Fg-1 [67] Lin et al adopted

a two-phase thermal route for synthesis of RuO2 nanoparticles which

showed a specific capacitance of 840 Fg-1 [68] Structural electrodes of

anhydrous RuO2 vertical nanorods encased in hydrous RuO2 was prepared

via chemical vapor deposition (CVD) followed by electrochemical

deposition the electrodes were thermally reduced which showed a

specific capacitance of ~ 520 Fg-1 [69] Anhydrous mesoporous RuO2 was

synthesized by a simple non-ionic surfactant templating method using

Pluronic 123 which showed a specific capacitance of 58 Fg-1 [70]

Hydrous RuO2 was prepared by Barbieri et al using sol-gel method the

effect of annealing temperature on the specific capacitance was studied

which showed the specific capacitance increased from 738 to 982 Fg-1

with increase in annealing temperature upto 423 K above which decrease

in specific capacitance was observed which is attributed to the

improvement in electronic pathways in high temperature treated samples

[71] Liang et al used a solid-state route for preparation of nanoscale

hydrous RuO2 that showed amorphous nature at lower temperature with

maximum specific capacitance of 655 Fg-1 [72] Zhao et al studied the


15

electrochemical performance of lithium ruthenate (LixRuO2+05xmiddotnH2O)

material which showed the specific capacitance of 391 Fg-1 with an energy

density of 657 WhKg-1 using Li2SO4 as an electrolyte [73] Sugimoto et al

[74] studied the charge storage mechanism of nanostructured anhydrous

and hydrous RuO2 based oxides evaluated by various electrochemical

techniques (cyclic voltammetry hydrodynamic voltammetry

chronoamperometry and electrochemical impedance spectroscopy) The

effects of various factors such as particle size hydrous state and

structure on the pseudocapacitive property were characterized Hu et al

studied the effect of sodium acetate (NaCH3COO) concentration plating

temperature and oxide loading on the pseudocapacitive characteristics of

RuO2middotxH2O films anodically plated from aqueous RuCl3middotxH2O solution a

maximum specific capacitance of 760 Fg-1 was observed [75] RuO2

nanoparticles were synthesized by instant method using Li2CO3 as

stabilizing agent under microwave irradiation at 333 K which showed a

specific capacitance of 737 Fg-1 [76]

RuO2 based materials have the advantage of offering higher energy

density but the cost and relative scarcity of Ru precursors are major

disadvantage Considerable efforts have been devoted to the development

and characterization of new electrode materials with lower cost and

improved performance The research is going on combining RuO2 with

second electrode material in order to increase the dispersion of the oxide

RuO2 was electrochemically prepared onto a carbon nanotube

(CNT) film substrate with a three-dimensional nanoporous structure

showed both a very high specific capacitance of 1170 Fg-1 and a high rate

capability [77] RuO2 was loaded into various types of activated carbon by

suspending the activated carbon in an aqueous RuCl3 solution followed by

neutralization a maximum specific capacitance of 308 Fg-1 for activated

carbon loaded with 71 wt Ru was observed [78] A hydrous


16

RuO2carbon black nanocomposite was prepared by the incipient wetness

method using a fumed silica nanoparticles the electrode exhibited a

specific capacitance of 647 Fgminus1 with high charge utilization of RuO2 Panic

et al prepared RuOxHycarbon black nanocomposite material by the

impregnation method starting from RuOxHy sol as a precursor The

highest specific capacitance of about 700 Fg-1 of composite was registered

[79] Liu et al has been reported a new method for preparation of

RuO2carbon nanotube based on spontaneous reduction of Ru(VI) and

Ru(VII) for the deposition of Ru oxide on multi-walled carbon nanotubes

(MWCNT) a maximum specific capacitance of 213 Fg-1 was observed [80]

RuO2carbon composites with microporous or mesoporous carbon as

support were and prepared by two procedures which consists i) repetitive

impregnations of the carbons with RuCl3middot05H2O solutions and ii)

impregnation of the carbons with Ru vapor It was observed that

mesoporous carbon is better support than microporous carbon prepared

using method (i) with maximum specific capacitance of 650 Fg-1 [81]

Yong-gang and Xiao-gang synthesized RuO2TiO2 nanotubes by loading

various amounts of RuO2 on TiO2 nanotubes The symmetric

supercapacitors based on these nanocomposites were fabricated by using

gel polymer PVAndashH3PO4ndashH2O as electrolyte showed a specific capacitance

of 1263 Fg-1 for RuO2 loaded on TiO2 nanotube [82] Hydrous crystalline

binary (RundashTi)O2middotnH2O synthesized by a mild hydrothermal process by

Chang and Hu the maximum utilization of RuO2middotnH2O (ca 793 Fg-1) occurs

at the composition of 60 M TiO2middotnH2O with annealing at 473 K [83] Liu

et al used a co-precipitation method for the synthesis of mesoporous

Co3O4RuO2middotxH2O composite with various Ru content by using

Pluronic123 as a soft template A capacitance of 642 Fg-1 was obtained for

the composite (Co Ru = 11) annealed at 423 K which is greater than for

the composite prepared without template [84] Pico et al prepared


17

RuO2middotxH2ONiO composites by a coprecipitation method it was observed

that the specific capacitance increased from 60 to 202 Fg-1 as the RuO2

content increased from 0 to 100 wt [85] An ultra thin layer of RuO2

produced by magnetron sputtering deposition method was grown on the

well-aligned cone-shaped nanostructure of polypyrrole (WACNP) The

modification of RuO2 on WACNP results in a capacitance (~302 Fg-1)

which is higher than that of WACNP by three times [86] Hydrous RuO2

particles were electrochemically loaded into poly (3 4-

ethylenedioxythiophene) doped poly(styrene sulfonic acid) PEDOT-PSS

matrix by employing various potential cycles in cyclic voltammetry and to

fabricate the PEDOT-PSS-RuO2middotxH2O electrode An increasing trend in

specific capacitance with loaded amount of hydrous RuO2 particles in

PEDOT-PSS was noticed A maximum specific capacitance of 653 Fg-1 was

achieved [87]

133 Literature Survey of SnO2-RuO2 Supercapacitor Electrodes

As RuO2 is the most promising electrode material for

supercapacitors more research is now focused on the developing methods

in order to achieve highest utilization of RuO2 It was observed that the

high specific capacitance of hydrous RuO2 could not be maintained under

the ultrahigh-power operation which is an unavoidable issue in

developing an electrode material for supercapacitors Due to the high cost

of Ru precursors and the possible synergistic effects occurring among

RuO2 SnO2 TiO2 and Ta2O5 [88-91] binary (RundashSn RundashTi RundashTa) and

ternary (RundashSnndashTi RundashSnndashTa) mixed oxides are worthy being developed

and studied

Among the various oxides studied as co material for RuO2 SnO2

with proper doping has advantage of high conductivity [92 93] SnO2 and

RuO2 crystallize in the same tetragonal (rutile-like) structure The lattice

parameters of SnO2 and RuO2 are quite close to each other (SnO2 a=b=


18

47382 Aring and c= 31871 Aring RuO2 a=b= 44994 Aring and c= 31071 Aring) [94]

RuO2-SnO2 binary oxide coated titanium electrodes are one of the most

important anodes in the chlor-alkali industry because they can be easily

formed a rutile-phase that is regarded as a favorite structure The SnO2

additive stabilizes RuO2 based electrodes and enhances their catalytic

activity for oxygen evolution [95-97] and chlorine evolution [98 99]

Yanqun and Dian synthesized nanometer sized RuO2-SnO2 by the citrate-

gel method using citric acid as complexing agent Pure fine and

amorphous powders were obtained at 433 K the crystalline and single-

phase powders of (Sn Ru)O2 were produced at 673 K the material

obtained has good thermal resistant properties It benefits for the

preparation for the active oxide coatings [100]

In the application as supercapacitor electrode Hu et al [101] used

modified sol-gel process for deposition of rutheniumndashtin oxide composites

It was observed that co annealed hydrous RuO2 and SnO2 at 473 K for 2 h

showed maximum specific capacitance of 690 Fg-1 for Ru1-δSnδO2 for Sn

content of 02 Kim et al used a DC reactive sputtering method for

preparation of composite RuO2-SnO2 electrode a maximum specific

capacitance of 888 Fg-1 was observed [102] Wang and Hu adopted a mild

hydrothermal process to synthesize hydrous ruthenium oxide tin oxide

composites ((Ru-Sn)O2∙nH2O) a maximum specific capacitance of 830 Fg-1

was observed for pristine Ru06Sn04O2n H2O electrode [103] An incipient

wetness method was used for preparation of Sb doped SnO2 xerogel

impregnated with RuO2 nanocrystallites by Wu et al [104] a specific

capacitance of 15 Fg-1 was obtained with 14 wt RuO2 loading A mild

hydrothermal process is applied by Yuan et al to synthesize hydrous

rutheniumndashtin binary oxides (Ru07Sn03O2middotnH2O) the symmetric

supercapacitor can operate with a high upper cell voltage limit of 145 V in

1 M KOH electrolyte with maximum specific capacitance of 160 Fg-1 and


19

stability with 852 of the initial capacitance over consecutive 1000 cycle

numbers [105] A composite SnO2-RuO2 supercapacitor electrode was

synthesized by cyclic voltammetric plating of RuO2 onto a porous and

highly conductive Sb (6 mol) doped SnO2 particulate substrate that

possessed a large surface area (75 m2g) a specific capacitance of 930 Fg-1

for the RuO2 component was observed [106]

31 Orientation and Purpose of Dissertation

Supercapacitors have the potential to emerge as promising energy

storage technology with an acceptable capacity and long cycle life The

performance of the supercapacitor is highly dependent on the active

electrode material involved in its fabrication that must have

characteristics such as high surface area as well as highly reversible redox

reaction The main electrode materials for supercapacitors are porous

activated carbon (AC) transition metal oxides conducting polymers

mixed metal oxides or their composites Moreover a relatively high-

frequency response is an essential requirement for supercapacitor

delivering pulse power which should be achieved by reducing the

equivalent series resistance (ESR) Accordingly developing and designing

active materials as well as electrodes meeting the above requirements

becomes an interesting subject for many electrochemists In addition it is

possible to obtain high working voltage and high energy density of

supercapacitors by choosing a proper electrode material Both increase of

the working voltage and high energy density of the metal oxide electrode

result in a significant increase of the overall energy density of the

supercapacitors

Although amorphous hydrous RuO2 is the most promising electrode

material for supercapacitors high cost and scarcity of Ru precursors made

researchers to find possible alternatives for RuO2 electrodes for

commercial applications Another approach developed is to combine RuO2


20

with second electrode material to form composite electrode and thus to

minimize the uses of Ru precursors The SnO2 is selected as second

electrode material in order to form the tin oxide-ruthenium oxide (SnO2-

RuO2) composite This is because SnO2 has the same rutile structure as

RuO2 It was observed that the addition of SnO2 into RuO2 matrix increases

the effective surface area and electrochemical stability of net composite

electrode The addition of SnO2 into RuO2 increases the utilization

efficiency of RuO2 All these properties of SnO2 are favorable for formation

of composite electrode with good supercapacitive properties by using

fewer amounts of Ru precursors This will also reduce the cost so it is

useful for the commercial application Recently there has been an increase

interest in nanocrystalline materials where the physical properties are

different from the bulk materials There are two approaches for making

nanocrystalline materials physical methods and chemical methods As

considering the drawbacks of physical methods like expensive need of

sophisticated instrumentation etc chemical methods are more useful as

they are simple and inexpensive

This work is concerned with the development of supercapacitor

electrodes of SnO2-RuO2 composite thin films by simple chemical methods

Among various other deposition methods CBD and SILAR methods have

many advantages over physical method These deposition methods result

in pinhole free uniform films Since the basic building blocks are ions

instead of atoms also the preparative parameters are easily controllable

These methods can be used for the large area deposition

It is possible to deposit SnO2-RuO2 composite thin films by varying

different preparative parameters such as suitable metal ion sources pH

deposition time temperature etc The X-ray diffraction (XRD) technique

will be used for the phase identification and crystallite size determination

The chemical bonding in the present material will be studied by fourier


21

transform infrared spectroscopy (FT-IR) and fourier transform Raman

spectroscopy (FT-Raman) Surface morphology of the films will be studied

using scanning electron microscopy (SEM) The compositional study will

be carried out by energy-dispersive X-ray analysis (EDAX) technique

Surface wettability of the film will be studied by measuring the water

contact angle

The supercapacitive properties of the SnO2-RuO2 composite films

will be studied by cyclic voltammetry (CV) using Potentiostat forming a

electrochemical cell comprising platinum as a counter electrode saturated

calomel electrode (SCE) as a reference electrode in a suitable electrolyte

The effect of electrolyte concentration thickness of electrode scan rate

and number of cycles on the performance of supercapacitor electrode will

be studied The charge-discharge mechanism will be studied using

chronopotentiometry and the parameters such as specific energy and

specific power will be calculated The electrochemical impedance

spectroscopic (EIS) study will be carried out to measure ESR of the formed

material Further the effect of surface treatments such as air annealing

ultrasonic weltering and anodization on the supercapacitive properties of

SnO2-RuO2 composite films will be studied

The present study will be performed to prepare SnO2-RuO2

composite films by minimal uses of Ru precursors The simple and

inexpensive SILAR and CBD methods will be used for fabrication SnO2-

RuO2 composite film The supercapacitive behavior of composite films will

be studied for supercapacitor application


22

References

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[2] A K Shukla S Sampath K Vijaymohanan Current Sci 79 (2000) 1656

[3] M Winter and R J Brodd Chem Rev 104 (2004) 4245

[4] J R Miller and P Simon The Electrochem Soc Interface Spring 2008

[5] A Chu and P Braatz J Power Sources 112 (2002) 236

[6] B E Conway Electrochemical Supercapacitors Scientific Fundamentals

and Technological Applications Kluwer-Plenum New York 1999

[7] R Kotz and M Carlen Electrochim Acta 45 (2002) 2483

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[9] M Anderman J Power Sources 127 (2004) 2

[10] Z Y Pan X J Liu S Y Zhang G J Shen L G Zhang Z H Lu J Z Liu J Phys

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[11] Y Wu H Yan P Yang Chem Eur J 8 (2002) 1260

[12] J Hu T W Odom C M Lieber Acc Chem Res 32 (1999) 435

[13] P C Ohara J R Heath W M Gelbart Angew Chem Int Ed Engl 36 (1997)

1078

[14] Y Q Zhu W K Hsu H W Kroto D R M Walton Chem Commun 21 (2001)

2184

[15] J Hu M Ouyang P Yang C M Lieber Nature 399 (1999) 48

[16] X Duan Y Huang Y Cui J Wang C M Lieber Nature 409 (2001) 66


23

[17] J F Colomer G Bister I Willems Z Konya A Fonseca G Van Tendeloo J B

Nagy Chem Commun 14 (1999) 1343

[18] C N R Rao Pure Appl Chem 69 (1997) 199

[19] Z Jarzebski and J Marton J Electrochem Soc Rev and News 123 (1976)

199C

[20] W Choi K Sung K Kim J Cho and et al J Mater Sci Lett 16 (1997) 1551

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[22] M Batzill and U Diebold Progress in Surface Science 79 (2005) 47

[23] R Summitt J A Marley N F Borrelli J Phys Chem Solids 25 (1964) 1465

[24] N Amin T Isaka A Yamada M Konagai Sol Ene Mater Solar Cells 67

(2001) 195

[25] S Seal and S Shukla J Met 54 (2002) 35

[26] S Mishra C Ghanshyam N Ram S Singh R P Bajpai R K Bedi Bull Mater

Sci 25 (2002) 231

[27] C Xu G Xu Y Liu X Zhao G Wang Scripta Mater 46 (2002) 789

[28] J Kappler A Tomescu N Barsan V Weimar Thin Solid Films 391 (2001)

186

[29] G Korotcenkov V Macsanov V Tolstoy V Brinzari J Schwank G Faglia

Sens Actuators B 96 (2003) 602

[30] Y Wang H Zeng J Y Lee Ad Mater 18 (2006) 645

[31] Z W Pan Z R Dai Z L Wang Science 291 (2001) 1947


24

[32] J Hu Y Bando Q Liu D Golberg Adv Funct Mater 13 (2003) 493

[33] K Murakami I Yagi S Kaneko J Am Ceram Soc 79 (1996) 2557

[34] N G Deshpande J C Vyas R Sharma Thin Solid Films 516 (2008) 8587

[35] Y C Her J Y Wu Y R Lin S Y Tsai Appl Phy Lett 89 (2006) 043115

[36] httpWikipediacomruthenium (IV) oxide

[37] S Bhaskar P S Dobal S B Majumder R S Katiyar J Appl Phys 89 (2001)

2987

[38] C S Hsieh D S Tsai R S Chen Y S Huang Appl Phys Lett 85 (2004)

3860

[39] H Liu E Iglesia J Phys Chem B 109 (2005) 2155

[40] W J Long R M Stroud K E Swider-Lyons D R Rolison J Phys Chem B

104 (2000) 9772

[41] D R Rolison P L Hagans K E Swider J W Long Langmuir 15 (1999) 774

[42] V D Patake C D Lokhande App Surf Sci 254 (2008) 2820

[43] T P Gujar V R Shinde C D Lokhande W Kim K Jung O S Joo

Electrochem Commun 9 (2007) 504

[44] H Ma C Liu J Liao Y Su X Xue W Xing J Mol Cat A 247 (2006) 7

[45] L Armelao D Barreca B Moraru J Non-Cryst Solid 316 (2003) 364

[46] I Zhitomirsky and L Gal-Or Mat Lett 31 (1997) 155

[47] I Zhitomirsky Mat Lett 33 (1998) 305

[48] C C Hu M Liu K Chang J Power Sources 163 (2007) 1126


25

[49] J J Jow H J Lee H R Chen M S Wu T Y Wei Electrochim Acta 52

(2007) 2625

[50] N L Wu Mater Chem Phys 75 (2002) 6

[51] K R Prasad N Miura Electrochem Commun 6 (2004) 849

[52] R S Mane J Chang D Hama B N Pawar T Ganesh B W Cho J Lee S Han

Curr Appl Phys 9 (2009) 87

[53] M Wu L Zhang D Wang C Xiao S Zhang J Power Sources 175 (2008)

669

[54] S Hwang and S Hyun J Power Sources 172 (2007) 451

[55] M Jayalakshmi N Venugopal K P Raja M Mohan Rao J Power Sources

158 (2006) 1538

[56] Z Hu Y Xie Y Wang L Mo Y Yang Z Zhang Mater Chem Phys 114

(2009) 990

[57] M Jayalakshmi M M Rao N Venugopal K Kim J Power Sources 166

(2007) 578

[58] S Trasatti and G Buzzanca J Electroanal Chem 29 (1971) A1

[59] B E Conway J Electrochem Soc 125 (1978) 1471

[60] J P Zheng P J Cygan T R Jow J Electrochem Soc 142 (1995) 2699

[61] W Lee R S Mane V V Todkar S Lee O Egorova W Chae S Han

Electrochem Sol State Lett 10 (2007) A225

[62] H Kim and K Kim Electrochem Sol State Lett 4 (2001) A62

[63] J H Jang A Kato K Machida K Naoi J Electrochem Soc 153 (2006) A321


26

[64] Y Zheng H Y Ding M L Zhang Thin solid films 516 (2008) 7381

[65] B O Park C D Lokhande H S Park K D Jung O S Joo J Power Sources

134 (2004) 148

[66] Q L Fang D A Evans S L Roberson J P Zheng J Electrochem Soc 148

(2001) A833

[67] K H Chang and C C Hu J Electrochem Soc 151 (2004) A958

[68] Y Lin N Zhao W Nie X Ji J Phys Chem C 112 (2008) 16219

[69] D Susanti D S Tsai Y S Huang A Korotcov W H Chung J Phys Chem C

111 (2007) 9530

[70] V Subramanian S C Hall P H Smith B Rambabu Solid State Ionic 175

(2004) 511

[71] O Barbieri M Hahn A Foelske R Kotz J Electrochem Soc153 (2006)

A2049

[72] Y Y Liang H L Li X G Zhang J Power Sources 173 (2007) 599

[73] Y Q Zhao G Q Zhang H L Li Solid State Ionics 177 (2006) 1335

[74] W Sugimoto K Yokoshima Y Murakami Y Takasu Electrochim Acta 52

(2006) 1742

[75] C C Hu M J Liu K H Chang Electrochim Acta 53 (2008) 2679

[76] A Devadas S Baranton T W Napporn C Coutanceau Accepted

Manuscript doi101016jjpowsour201011149

[77] H Kim J H Kim K B Kim Electrochem Sol State Lett 8 (2005) A369

[78] Y Sato K Yomogida T Nanaumi K Kobayakawa Y Ohsawa M Kawai


27

Electrochem Sol State Lett 3 (2000) 113

[79] V Panic T Vidakovic S Gojkovic A Dekanski S Milonjic B Nikolic

Electrochim Acta 48 (2003) 3805

[80] X Liu T A Huber M C Kopac P G Pickup Electrochim Acta 54 (2009)

7141

[81] F Pico E Morales J A Fernandez T A Centeno J Ibanez R M Rojas J M

Amarilla J M Rojo Electrochim Acta 54 (2009) 2239

[82] W Yong-gang and Z Xiao-gang Electrochim Acta 49 (2004) 1957

[83] K H Chang and C C Hu Electrochim Acta 52 (2006) 1749

[84] Y Liu W Zhao X Zhang Electrochim Acta 53 (2008) 3296

[85] F Pico J Ibanez T A Centeno C Pecharroman R M Rojas J M Amarilla J

M Rojo Electrochim Acta 51 (2006) 4693

[86] J Zang S J Bao C M Li H Bian X Cui Q Bao C Q Sun J Guo K Lian J

Phys Chem C 112 (2008) 14843

[87] L M Huang H Z Lin T C Wen A Gopalan Electrochim Acta 52 (2006)

1058

[88] S Trasatti (Ed) Electrodes of Conductive Metallic Oxides PartsAampB

Elsevier Amsterdam 1980 eg

[89] S M Lin and T C Wen J Electrochem Soc 140 (1993) 2265

[90] T C Wen and C C Hu J Electrochem Soc 139 (1992) 2158

[91] A I Onuchukwu and S Trasatti J Appl Electrochem 21 (1991) 858

[92] Ch Comninellis and G P Vercesi J Appl Electrochem 21 (1991) 136

[93] T Minami Mater Res Soc Bull 25 (2000) 38


28

[94] C Terrier J P Chatelon J A Roger Thin Solid Films 295 (1997) 95

[95] Y S He J C Campbell R C Murphy M F Arendt J S Swinnea J

Electerochem Soc 143 (1996) 32

[96] J Gaudet A C Tavares S Trasatti D Guay Chem Mater 17 (2005) 1570

[97] R Hutchings K Miiller R Kotz S Stucki J Mater Sci 19 (1984) 3987

[98] D T Shieh and B J Hwang Electrochim Acta 38 (1993) 2239

[99] B V Tilak K Tari C L Hoover J Electrochem Soc 135 (1988) 1386

[100] S Yanqun and T Dian J Wuhan Uni Tech Mater Sci Ed 22 (2007) 626

[101] C C Hu C C Wang K H Chang Electrochim Acta 52 (2007) 2691

[102] H K Kim S H Choi Y S Yoon S Y Chang Y W Ok T Y Seong Thin Solid

Films 475 (2005) 54

[103] C C Wang and C C Hu Electrochim Acta 50 (2005) 2573

[104] N L Wu S L Kuo M H Lee J Power Sources 104 (2002) 62

[105] C Yuan H Dou B Gao L Su X Zhang J Sol State Electrochem 12 (2008)

1645

[106] S L Kuo and N L Wu Electrochem Sol State Lett 6 (2003) A85


2

11 General

111 Need of Supercapacitor

The growing demand of energy sources in recent few years has

become the concern topic for researchers due to the lack of renewable

energy sources The use of fossil fuels for energy production is also a

burning issue regarding the worldrsquos ecology and economical concern

Global warming fuel dependency and pollution are few examples to divert

from fuel-based economy to electricity-based civilization Some

conventional sources of energy are solar energy wind energy etc but this

energy production is highly depending on natural phenomena and we do

not have control over these phenomenarsquos Therefore there is immense

need to develop energy storage devices to store the generated energy for

future use In this aspect the electrochemical power sources are emerged

as the new sources for store and production of electrical energy The

electrochemical power sources are more efficient than the fuel-based

system because they provide clean energy which is necessary demand

according to environmental issues

Electrical energy storage is required in many applications such as

telecommunication devices cell phones standby power systems and

electric hybrid vehicles [1] Many applications are demanding local storage

or local generation of electrical energy Therefore there is a strong need of

development of improved methods for storing energy when it is available

and retrieving when it is needed The electrochemical power sources

include batteries fuel cells and supercapacitors The electrical energy

storage in these sources is according to fundamentally in two different

ways [2]

a) Indirectly in batteries as potentially available chemical energy

required Faradic oxidation and reduction of the electroactive

reagents to release charges that can perform electrical work


3































4





V

QC = (11)




d

KAC = (12)




2

CV2

1E =

(13)


given by [5]

ESR4

VP

2

times

= (14)








5

















6










to dispose











consumer electronic










7






























8


(RuO2) Thin Films


















9



















heating












10






373 K [35]













11































12































13































14































15































16































17














achieved [87]











and studied






18































19

























supercapacitors






20































21






contact angle




















22

References












Chem B 101 (1997) 9703




1078


2184




23





199C






(2001) 195



Sci 25 (2002) 231



186






24







2987


3860



104 (2000) 9772











25


(2007) 2625






669



158 (2006) 1538


(2009) 990


(2007) 578









26



134 (2004) 148


(2001) A833




111 (2007) 9530


(2004) 511


A2049




(2006) 1742







27





7141









Phys Chem C 112 (2008) 14843


1058









28











Films 475 (2005) 54




1645



3































4





V

QC = (11)




d

KAC = (12)




2

CV2

1E =

(13)


given by [5]

ESR4

VP

2

times

= (14)








5

















6










to dispose











consumer electronic










7






























8


(RuO2) Thin Films


















9



















heating












10






373 K [35]













11































12































13































14































15































16































17














achieved [87]











and studied






18































19

























supercapacitors






20































21






contact angle




















22

References












Chem B 101 (1997) 9703




1078


2184




23





199C






(2001) 195



Sci 25 (2002) 231



186






24







2987


3860



104 (2000) 9772











25


(2007) 2625






669



158 (2006) 1538


(2009) 990


(2007) 578









26



134 (2004) 148


(2001) A833




111 (2007) 9530


(2004) 511


A2049




(2006) 1742







27





7141









Phys Chem C 112 (2008) 14843


1058









28











Films 475 (2005) 54




1645



4





V

QC = (11)




d

KAC = (12)




2

CV2

1E =

(13)


given by [5]

ESR4

VP

2

times

= (14)








5

















6










to dispose











consumer electronic










7






























8


(RuO2) Thin Films


















9



















heating












10






373 K [35]













11































12































13































14































15































16































17














achieved [87]











and studied






18































19

























supercapacitors






20































21






contact angle




















22

References












Chem B 101 (1997) 9703




1078


2184




23





199C






(2001) 195



Sci 25 (2002) 231



186






24







2987


3860



104 (2000) 9772











25


(2007) 2625






669



158 (2006) 1538


(2009) 990


(2007) 578









26



134 (2004) 148


(2001) A833




111 (2007) 9530


(2004) 511


A2049




(2006) 1742







27





7141









Phys Chem C 112 (2008) 14843


1058









28











Films 475 (2005) 54




1645



5

















6










to dispose











consumer electronic










7






























8


(RuO2) Thin Films


















9



















heating












10






373 K [35]













11































12































13































14































15































16































17














achieved [87]











and studied






18































19

























supercapacitors






20































21






contact angle




















22

References












Chem B 101 (1997) 9703




1078


2184




23





199C






(2001) 195



Sci 25 (2002) 231



186






24







2987


3860



104 (2000) 9772











25


(2007) 2625






669



158 (2006) 1538


(2009) 990


(2007) 578









26



134 (2004) 148


(2001) A833




111 (2007) 9530


(2004) 511


A2049




(2006) 1742







27





7141









Phys Chem C 112 (2008) 14843


1058









28











Films 475 (2005) 54




1645



6










to dispose











consumer electronic










7






























8


(RuO2) Thin Films


















9



















heating












10






373 K [35]













11































12































13































14































15































16































17














achieved [87]











and studied






18































19

























supercapacitors






20































21






contact angle




















22

References












Chem B 101 (1997) 9703




1078


2184




23





199C






(2001) 195



Sci 25 (2002) 231



186






24







2987


3860



104 (2000) 9772











25


(2007) 2625






669



158 (2006) 1538


(2009) 990


(2007) 578









26



134 (2004) 148


(2001) A833




111 (2007) 9530


(2004) 511


A2049




(2006) 1742







27





7141









Phys Chem C 112 (2008) 14843


1058









28











Films 475 (2005) 54




1645



7






























8


(RuO2) Thin Films


















9



















heating












10






373 K [35]













11































12































13































14































15































16































17














achieved [87]











and studied






18































19

























supercapacitors






20































21






contact angle




















22

References












Chem B 101 (1997) 9703




1078


2184




23





199C






(2001) 195



Sci 25 (2002) 231



186






24







2987


3860



104 (2000) 9772











25


(2007) 2625






669



158 (2006) 1538


(2009) 990


(2007) 578









26



134 (2004) 148


(2001) A833




111 (2007) 9530


(2004) 511


A2049




(2006) 1742







27





7141









Phys Chem C 112 (2008) 14843


1058









28











Films 475 (2005) 54




1645



8


(RuO2) Thin Films


















9



















heating












10






373 K [35]













11































12































13































14































15































16































17














achieved [87]











and studied






18































19

























supercapacitors






20































21






contact angle




















22

References












Chem B 101 (1997) 9703




1078


2184




23





199C






(2001) 195



Sci 25 (2002) 231



186






24







2987


3860



104 (2000) 9772











25


(2007) 2625






669



158 (2006) 1538


(2009) 990


(2007) 578









26



134 (2004) 148


(2001) A833




111 (2007) 9530


(2004) 511


A2049




(2006) 1742







27





7141









Phys Chem C 112 (2008) 14843


1058









28











Films 475 (2005) 54




1645



9



















heating












10






373 K [35]













11































12































13































14































15































16































17














achieved [87]











and studied






18































19

























supercapacitors






20































21






contact angle




















22

References












Chem B 101 (1997) 9703




1078


2184




23





199C






(2001) 195



Sci 25 (2002) 231



186






24







2987


3860



104 (2000) 9772











25


(2007) 2625






669



158 (2006) 1538


(2009) 990


(2007) 578









26



134 (2004) 148


(2001) A833




111 (2007) 9530


(2004) 511


A2049




(2006) 1742







27





7141









Phys Chem C 112 (2008) 14843


1058









28











Films 475 (2005) 54




1645



10






373 K [35]













11































12































13































14































15































16































17














achieved [87]











and studied






18































19

























supercapacitors






20































21






contact angle




















22

References












Chem B 101 (1997) 9703




1078


2184




23





199C






(2001) 195



Sci 25 (2002) 231



186






24







2987


3860



104 (2000) 9772











25


(2007) 2625






669



158 (2006) 1538


(2009) 990


(2007) 578









26



134 (2004) 148


(2001) A833




111 (2007) 9530


(2004) 511


A2049




(2006) 1742







27





7141









Phys Chem C 112 (2008) 14843


1058









28











Films 475 (2005) 54




1645



11































12































13































14































15































16































17














achieved [87]











and studied






18































19

























supercapacitors






20































21






contact angle




















22

References












Chem B 101 (1997) 9703




1078


2184




23





199C






(2001) 195



Sci 25 (2002) 231



186






24







2987


3860



104 (2000) 9772











25


(2007) 2625






669



158 (2006) 1538


(2009) 990


(2007) 578









26



134 (2004) 148


(2001) A833




111 (2007) 9530


(2004) 511


A2049




(2006) 1742







27





7141









Phys Chem C 112 (2008) 14843


1058









28











Films 475 (2005) 54




1645



12































13































14































15































16































17














achieved [87]











and studied






18































19

























supercapacitors






20































21






contact angle




















22

References












Chem B 101 (1997) 9703




1078


2184




23





199C






(2001) 195



Sci 25 (2002) 231



186






24







2987


3860



104 (2000) 9772











25


(2007) 2625






669



158 (2006) 1538


(2009) 990


(2007) 578









26



134 (2004) 148


(2001) A833




111 (2007) 9530


(2004) 511


A2049




(2006) 1742







27





7141









Phys Chem C 112 (2008) 14843


1058









28











Films 475 (2005) 54




1645



13































14































15































16































17














achieved [87]











and studied






18































19

























supercapacitors






20































21






contact angle




















22

References












Chem B 101 (1997) 9703




1078


2184




23





199C






(2001) 195



Sci 25 (2002) 231



186






24







2987


3860



104 (2000) 9772











25


(2007) 2625






669



158 (2006) 1538


(2009) 990


(2007) 578









26



134 (2004) 148


(2001) A833




111 (2007) 9530


(2004) 511


A2049




(2006) 1742







27





7141









Phys Chem C 112 (2008) 14843


1058









28











Films 475 (2005) 54




1645



14































15































16































17














achieved [87]











and studied






18































19

























supercapacitors






20































21






contact angle




















22

References












Chem B 101 (1997) 9703




1078


2184




23





199C






(2001) 195



Sci 25 (2002) 231



186






24







2987


3860



104 (2000) 9772











25


(2007) 2625






669



158 (2006) 1538


(2009) 990


(2007) 578









26



134 (2004) 148


(2001) A833




111 (2007) 9530


(2004) 511


A2049




(2006) 1742







27





7141









Phys Chem C 112 (2008) 14843


1058









28











Films 475 (2005) 54




1645



15































16































17














achieved [87]











and studied






18































19

























supercapacitors






20































21






contact angle




















22

References












Chem B 101 (1997) 9703




1078


2184




23





199C






(2001) 195



Sci 25 (2002) 231



186






24







2987


3860



104 (2000) 9772











25


(2007) 2625






669



158 (2006) 1538


(2009) 990


(2007) 578









26



134 (2004) 148


(2001) A833




111 (2007) 9530


(2004) 511


A2049




(2006) 1742







27





7141









Phys Chem C 112 (2008) 14843


1058









28











Films 475 (2005) 54




1645



16































17














achieved [87]











and studied






18































19

























supercapacitors






20































21






contact angle




















22

References












Chem B 101 (1997) 9703




1078


2184




23





199C






(2001) 195



Sci 25 (2002) 231



186






24







2987


3860



104 (2000) 9772











25


(2007) 2625






669



158 (2006) 1538


(2009) 990


(2007) 578









26



134 (2004) 148


(2001) A833




111 (2007) 9530


(2004) 511


A2049




(2006) 1742







27





7141









Phys Chem C 112 (2008) 14843


1058









28











Films 475 (2005) 54




1645



17














achieved [87]











and studied






18































19

























supercapacitors






20































21






contact angle




















22

References












Chem B 101 (1997) 9703




1078


2184




23





199C






(2001) 195



Sci 25 (2002) 231



186






24







2987


3860



104 (2000) 9772











25


(2007) 2625






669



158 (2006) 1538


(2009) 990


(2007) 578









26



134 (2004) 148


(2001) A833




111 (2007) 9530


(2004) 511


A2049




(2006) 1742







27





7141









Phys Chem C 112 (2008) 14843


1058









28











Films 475 (2005) 54




1645



18































19

























supercapacitors






20































21






contact angle




















22

References












Chem B 101 (1997) 9703




1078


2184




23





199C






(2001) 195



Sci 25 (2002) 231



186






24







2987


3860



104 (2000) 9772











25


(2007) 2625






669



158 (2006) 1538


(2009) 990


(2007) 578









26



134 (2004) 148


(2001) A833




111 (2007) 9530


(2004) 511


A2049




(2006) 1742







27





7141









Phys Chem C 112 (2008) 14843


1058









28











Films 475 (2005) 54




1645



19

























supercapacitors






20































21






contact angle




















22

References












Chem B 101 (1997) 9703




1078


2184




23





199C






(2001) 195



Sci 25 (2002) 231



186






24







2987


3860



104 (2000) 9772











25


(2007) 2625






669



158 (2006) 1538


(2009) 990


(2007) 578









26



134 (2004) 148


(2001) A833




111 (2007) 9530


(2004) 511


A2049




(2006) 1742







27





7141









Phys Chem C 112 (2008) 14843


1058









28











Films 475 (2005) 54




1645



20































21






contact angle




















22

References












Chem B 101 (1997) 9703




1078


2184




23





199C






(2001) 195



Sci 25 (2002) 231



186






24







2987


3860



104 (2000) 9772











25


(2007) 2625






669



158 (2006) 1538


(2009) 990


(2007) 578









26



134 (2004) 148


(2001) A833




111 (2007) 9530


(2004) 511


A2049




(2006) 1742







27





7141









Phys Chem C 112 (2008) 14843


1058









28











Films 475 (2005) 54




1645



21






contact angle




















22

References












Chem B 101 (1997) 9703




1078


2184




23





199C






(2001) 195



Sci 25 (2002) 231



186






24







2987


3860



104 (2000) 9772











25


(2007) 2625






669



158 (2006) 1538


(2009) 990


(2007) 578









26



134 (2004) 148


(2001) A833




111 (2007) 9530


(2004) 511


A2049




(2006) 1742







27





7141









Phys Chem C 112 (2008) 14843


1058









28











Films 475 (2005) 54




1645



22

References












Chem B 101 (1997) 9703




1078


2184




23





199C






(2001) 195



Sci 25 (2002) 231



186






24







2987


3860



104 (2000) 9772











25


(2007) 2625






669



158 (2006) 1538


(2009) 990


(2007) 578









26



134 (2004) 148


(2001) A833




111 (2007) 9530


(2004) 511


A2049




(2006) 1742







27





7141









Phys Chem C 112 (2008) 14843


1058









28











Films 475 (2005) 54




1645



23





199C






(2001) 195



Sci 25 (2002) 231



186






24







2987


3860



104 (2000) 9772











25


(2007) 2625






669



158 (2006) 1538


(2009) 990


(2007) 578









26



134 (2004) 148


(2001) A833




111 (2007) 9530


(2004) 511


A2049




(2006) 1742







27





7141









Phys Chem C 112 (2008) 14843


1058









28











Films 475 (2005) 54




1645



24







2987


3860



104 (2000) 9772











25


(2007) 2625






669



158 (2006) 1538


(2009) 990


(2007) 578









26



134 (2004) 148


(2001) A833




111 (2007) 9530


(2004) 511


A2049




(2006) 1742







27





7141









Phys Chem C 112 (2008) 14843


1058









28











Films 475 (2005) 54




1645



25


(2007) 2625






669



158 (2006) 1538


(2009) 990


(2007) 578









26



134 (2004) 148


(2001) A833




111 (2007) 9530


(2004) 511


A2049




(2006) 1742







27





7141









Phys Chem C 112 (2008) 14843


1058









28











Films 475 (2005) 54




1645



26



134 (2004) 148


(2001) A833




111 (2007) 9530


(2004) 511


A2049




(2006) 1742







27





7141









Phys Chem C 112 (2008) 14843


1058









28











Films 475 (2005) 54




1645



27





7141









Phys Chem C 112 (2008) 14843


1058









28











Films 475 (2005) 54




1645



28











Films 475 (2005) 54




1645


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