Post on 30-Aug-2019
transcript
S1
Reversible thermal-responsive electrochemical energy storage
based on smart LDH@P(NIPAM-co-SPMA) films
Yibo Dou, Ting Pan, Awu Zhou, Simin Xu, Xiaoxi Liu, Jingbin Han, Min Wei,*
David G. Evans and Xue Duan
State Key Laboratory of Chemical Resource Engineering, Beijing University of
Chemical Technology, Beijing 100029, P. R. China
CORRESPONDING AUTHOR FOOTNOTE
Corresponding author. Phone: +86-10-64412131. Fax: +86-10-64425385. E-mail:
weimin@mail.buct.edu.cn.
Experimental Section
Synthesis of LDH nanoplatelets array on Ni foil substrate: The LDH
nanoplatelets array was synthesized by a homogeneous hydrothermal method.[1]
Typically, Ni(NO3)2·6H2O (15 mmol), Al(NO3)2·9H2O (5 mmol), NH4F (20 mmol)
and Ni(NH2)2 (50 mmol) were dissolved in 100 ml of water, and was transferred into
a Teflon-lined stainless steel autoclave. A piece of clean Ni foil (2 cm×6 cm,
thickness: 60 µm) was then immersed into the solution. The autoclave was sealed
and maintained at 110 C for 8 h. After the reaction, the LDH nanoplatelets array was
observed on both sides of Ni foil. Subsequently, the Ni foil was washed thoroughly to
remove the surface deposited material, followed by coating with a thin layer of
Electronic Supplementary Material (ESI) for Chemical CommunicationsThis journal is © The Royal Society of Chemistry 2013
S2
electrochemically inert and nonconductive poly(methyl methacrylate) (PMMA) via a
cast-coating technique. Finally, the substrate was dried at 100 C for 5 min.
Synthesis of P(NIPAM-co-SPMA) polymer: The P(NIPAM-co-SPMA) polymer
was synthesized via free radical dispersion polymerization according to the reported
method.[2,3]
Typically, N-isopropylacrylamide (NIPAM; 4.343 g),
2-acrylamido-2-methyl propane sulfonicacid (SPMA; 2.011 g), N,N-methylenebis
(acrylamide) (0.082 g) and sodium dodecyl sulfate (0.050 g) were dissolved in 250 ml
of deionized water with vigorous stirring at 72 °C in nitrogen atmosphere. A
potassium persulfate solution (0.218 g, 50 ml) was added and stirred for 5 h under
nitrogen. The reaction mixture was centrifuged and washed three times with deionized
water, and then filtrated using a membrane filter (1.2 μm, Millipore) to remove any
unreacted monomer and other impurities. The obtained P(NIPAM-co-SPMA) polymer
was then exhaustively dialyzed against deionized water (changing the dialysate twice
daily for a week).
Fabrication of highly-arrayed LDH@P(NIPAM-co-SPMA) and
LDH@P(SPMA) electrode: A thin coating of P(NIPAM-co-SPMA) polymer or
P(SPMA) polymer was deposited onto the surface of LDH nanoplatelets array by dip
coating method.[4]
The prepared LDH film on Ni foil was immersed into the
P(NIPAM-co-SPMA) or P(SPMA) solution by the use of the Deposition Robots
(Riegler & Kirstein GmbH). The Ni foil was placed vertically in the solution for 5
min, followed by withdrawing the substrate out of the solution with a ascent velocity
of 0.05 cm/min. The resulting film were dried in air for 15 min. The whole process
Electronic Supplementary Material (ESI) for Chemical CommunicationsThis journal is © The Royal Society of Chemistry 2013
S3
(immersion, withdrawing, drying) was repeated 10 times. In order to enable the
P(NIPAM-co-SPMA) or P(SPMA) polymer to stick to the LDH surface tightly, the
obtained LDH@P(NIPAM-co-SPMA) film was thermally cross-linked by the
following process:[5,6]
the film was placed in a sealed container purged with N2 for 15
min, which was then slowly heated to 85 °C (approximately 1 h ramping time) and
sustained for 2 h.
Fabrication of pristine P(NIPAM-co-SPMA) planar film: The planar film of
P(NIPAM-co-SPMA) was fabricated by applying the spin-coating procedure.[7]
The
P(NIPAM-co-SPMA) solution was spin-coated onto a Ni substrate (60 s per cycle,
1500 rpm, 5 cycles). The films were dried at room temperature after each spin-coating
process. Finally, the substrates coated with pristine P(NIPAM-co-SPMA) planar film
were obtained for control experiment.
Fabrication of randomly-stacked LDH/P(NIPAM-co-SPMA) electrode: the
LDH@P(NIPAM-co-SPMA) film was scratched from the Ni foil substrate to give a
comparison study with their well-aligned array counterpart. The working electrode
was prepared as follows: 2 mg of the scratched material was first mixed with
polytetrafluoroethylene (PTFT) (LDH@P(NIPAM-co-SPMA):PTFT=50:1, w/w) and
then was dispersed in ethanol; the suspension was drop-dried onto a Ni foam (1.6
cm2) at 80 °C overnight. The foam was pressed at 5 MPa before measurement.
Material characterizations: X-ray diffraction (XRD) patterns were recorded by a
Rigaku XRD-6000 diffractometer, using Cu Kα radiation (λ = 0.15418 nm) at 40 kV,
30 mA. The morphology of films was investigated using a scanning electron
Electronic Supplementary Material (ESI) for Chemical CommunicationsThis journal is © The Royal Society of Chemistry 2013
S4
microscope (SEM; Zeiss SUPRA 55) with the accelerating voltage of 20 KV, a
NanoScope IIIa atomic force microscope (AFM) from Veeco Instruments and a
transmission electron microscopy (TEM; JEOL JEM-2100). X-ray photoelectron
spectroscopy (XPS) measurements were performed using an ESCALAB 250
instrument (Thermo Electron) with Al Kα radiation. The UV-vis absorption spectra
were collected in the range 200700 nm on a Shimadzu U-3000 spectrophotometer,
with the slit width of 1.0 nm. Water contact angle of films was measured using a
sessile drop at three different sites of each film sample using a commercial drop shape
analysis system (DSA100, KRüSS GmbH, Germany). The volume of water droplets
used for measurement is 2 μl. The water contact angle was determined by the average
of at least five measurements. Cyclic voltammetry (CV), electrochemical impedance
spectroscopy (EIS) and galvanostatic (GV) charge-discharge measurements were
performed on a CHI 660C electrochemistry workstation using a three-electrode mode
in 1 M KOH aqueous solution. The highly-arrayed LDH@P(NIPAM-co-SPMA) on
Ni sbustrate or randomly-stacked LDH@P(NIPAM-co-SPMA) on Ni foam was
directly used as the working electrode. The reference and counter electrode were
Hg/HgO and a platinum wire, respectively.
Average specific capacitance value was calculated from the CV curves using the
following equation:
H
L)(
1
LH
V
V
idVVVsm
C (1)
where i is the oxidation or reduction current; s is scanning rate; m denotes the mass of
the active material; VH and VL represent high and low potential limit of the CV tests.
Electronic Supplementary Material (ESI) for Chemical CommunicationsThis journal is © The Royal Society of Chemistry 2013
S5
Specific capacitance was also calculated from the galvanostatic charge-discharge
curves, by the equation:
Vm
tiC
Δ
Δ (2)
where i is the discharge current; Δt is the discharge time; m denotes the mass of the
active material, and ΔV corresponds to the voltage change after a full charge or
discharge process.
Figure 1. XRD patterns of as-prepared NiAl-LDH film on the Ni foil substrate and
the corresponding powdered sample scraped from the substrate (two reflections
denoted with blue triangles originate from the substrate).
Electronic Supplementary Material (ESI) for Chemical CommunicationsThis journal is © The Royal Society of Chemistry 2013
S6
Figure 2. The water contact angle as a function of temperature for the
LDH@P(NIPAM-co-SPMA) film and pristine P(NIPAM-co-SPMA) planar film,
respectively.
Figure 3. The transmittance of P(NIPAM-co-SPMA) solution at 600 nm upon
increasing the temperature from 20 °C to 40 °C (inset: the photographs of
P(NIPAM-co-SPMA) solution at 20 and 40 °C, respectively).
Electronic Supplementary Material (ESI) for Chemical CommunicationsThis journal is © The Royal Society of Chemistry 2013
S7
Figure 4. The reversible variation in water contact angle between 20 and 40 °C for
five consecutive cycles towards the LDH@P(NIPAM-co-SPMA) film, in comparison
with the pristine P(NIPAM-co-SPMA) planar film.
Figure 5. The specific capacitance corresponding to the highly-arrayed
LDH@P(NIPAM-co-SPMA) electrode in the temperature range 2040 °C.
Electronic Supplementary Material (ESI) for Chemical CommunicationsThis journal is © The Royal Society of Chemistry 2013
S8
Figure 6. Temperature-dependent CVs curves in the range 2040 °C for (A) LDH
electrode and (B) LDH@P(SPMA) electrode, respectively.
Figure 7. Galvanostatic discharge curves at a current density of 1 A/g for the
randomly-stacked LDH/P(NIPAM-co-SPMA) electrode in the presence of 1 M KOH
solution in the temperature range 2040 °C.
Electronic Supplementary Material (ESI) for Chemical CommunicationsThis journal is © The Royal Society of Chemistry 2013
S9
Figure 8. Galvanostatic charge-discharge curves at a current density of 1 A/g for the
LDH@P(NIPAM-co-SPMA) switch with normal and bending test in the presence of 1
M KOH solution at 20 to 40 °C, respectively.
Figure 9. The galvanostatic charge-discharge curves at a current density of 1 A/g for
(A) the as-prepared LDH@P(NIPAM-co-SPMA) switch, (B) the switch after storage
for 50 days in the presence of 1 M KOH solution at 20 to 40 °C, respectively.
References:
[1] J. Han, Y. Dou, J. Zhao, M. Wei, D. G. Evans and X. Duan, Small, 2013, 9, 98.
[2] J. Wong, A. Gaharwar, D. Muller-Schulte, D. Bahadur and W. Richtering, J.
Electronic Supplementary Material (ESI) for Chemical CommunicationsThis journal is © The Royal Society of Chemistry 2013
S10
Colloid Interface Sci., 2008, 324, 47.
[3] H. Senff and W. Richtering, Colloid Polym. Sci., 2000, 278, 830.
[4] Y. Zhao, S. He, M. Wei, D. G. Evans and X. Duan, Chem. Commun., 2010, 46,
3031.
[5] J. L. Stair, J. J. Harris and M. L. Bruening, Chem. Mater., 2001, 13, 2641.
[6] L. Mariniello, C. Giosafatto, P. Pierro, A. Sorrentino and R. Porta,
Biomacromolecules, 2010, 11, 2394.
[7] Y. Dou, J. Han, T. Wang, M. Wei, D. G. Evans and X. Duan, J. Mater. Chem.,
2012, 22, 14001.
Electronic Supplementary Material (ESI) for Chemical CommunicationsThis journal is © The Royal Society of Chemistry 2013