Taylor D. Bell Department of Chemistry Telephone: (314...

Taylor D. Bell Department of Chemistry Telephone: (314) 283-2493 University of Missouri—Columbia Email: [email protected] 105 Chemistry Building 601 S. College Avenue Shane E. Moore Columbia, MO 65211 Telephone: (309) 838-8122 USA Email: [email protected] Dr. Rainer Glaser, Associate Editor April 12, 2015 321 Chemistry Building 601 S. College Avenue Columbia, Missouri 65211 Re: REVISED

Synthesis of an Improved TiO2 Co-catalyst for the Breakdown of Organic Materials

By: Taylor Bell and Shane Moore Dear Dr. Glaser: Thank you for your communication that contained the peer reviews of our original manuscript. We have made changes in response to the reviewers’ comments and these are described in the following. Major Revisions [M.1] Emphasis increased on the requirements of water vapor for reaction to occur. [M.2] Emphasis increased on the ability of hydroxyl radicals to react blindly with most organic compounds. [M.3] Figure and scheme titles fixed in order to avoid confusion with numbering. Response to Reviewer 1 [A.1] Cover letter is no longer present, but in future use, it will be corrected. [B.1] Deleted “of the analysis”. [C.1] Changed to heading 1, but left in line with text, according to JOC format. [C.2-4] In JOC there is not a requirement for a reference to the graphical abstract nor label or title. [C.5] Overlapping in graphical abstract was not apparent to us. [C.6] Arrow movement is described later on in the paper as a movement of the positive hole (red) and the negative excited electron (blue). [C.7] Red and blue are used throughout our paper to delineate positive and negative respectively.

[D.1] Return removed. [D.2] Fixed “chemists” [D.3] changed to “The use of photocatalyst” [D.4] added comma [D.5] Sentence 8; “Photocatalysis is the use of light waves to accelerate a chemical reaction.” [D.6] Revised by changing “waves” to “energy” [D.7] Changed to Scheme 1 [D.8] Added space [D.9] Reference added to avoid infringement [D.10-11] Text overlapping with picture fixed. [D.12] Subscript fixed. [D.13] Reduced the number of uses of OH radicals. [D.14] Black line was present if tracking changes was left on. Removed. [D.15] Subscript fixed [D.16] Scheme 2 fixed. Color scheme was kept consistent throughout so feel it unnecessary to change. [D.17] This is referring to the entire paper where we report the function and results of our photocatalyst. [D.18] Changed to “our evidence shows” [E.1] Heading changed. [E.2] Sub heading helps to avoid confusion. [E.3] comma added [E.3] Added a comma [E.4] Changed “drop by drop” to dropwise [E.5] Added a comma [E.6] Revised first sentence to specify g-C3N4 had to be made separately at first clarifying what was occurring. [E.7] Calcination techniques are found in the supplemental information. Added phrase saying “these techniques can be found in supplemental information” to advise readers. [E.8] Revised to “this aqueous solution…” [E.9] Changed to “and” [E.10] Changed to “The two materials synthesized” [E.11] Added period [E.12] Deleted the extra “and then for” [E.13] Deleted the extra “(“. Also revised so that items in parentheses were more accurate.

[E.14] Added “for” and a comma [F.1] Already in heading format [F.2] Put it on next page [F.3] Added comma [F.4] For the purposes of this assignment, footnotes were not to be used so we included it as an end not. In future communications with JOC we will be sure to follow the correct format. [F.5] Made the Table bigger to fix irradiation [F.6] Added reverences to show what was being described. [F.7] Made both graphite carbon nitrides not capitalized [F.8] Removed actually [F.9] Added comma [F.10] X axis title is now present, and a y axis title can be inferred from the type of spectra being shown, that being said, a y axis title would be beneficial but they are relative absorbances and adding a scale to a table that we did not create would be difficult and probably incorrect. [F.11] Titles in the key are consistent with the rest of the paper. [F.12] A more careful review of the spectra would show that our photocatalyst increased its wavelength range over that of g-Mn/Ti, although g-Mn/Ti shows increased absorbance for some of the wavelengths, our photocatalyst has a greater range so it can be excited by visible light more often. [F.13] Removed. [F.14] Added a comparison sentence. [F.15] made clear that TiO2 is represented to Ti. [F.16] Sentence fixed. [F.17] Title added [F.18] Fixed title. [F.19] Names referred to previously. [F.20] Added sentence to show that because the comparison compounds are TiO2 and g-Ce/Ti and they show their specific photoluminescence patterns, the decreased photoluminescence is a sign of increased charge separation and therefore better photocatalytic activity as seen in Table 1. [F.21] Added period [F.22] Changed to more specific synthesis of hydroxyl radicals [F.23] Changed “Scheme 4” to “Scheme 3” [F.24] Turned it into two sentences instead of one long one. [F.25] Changed “so close” to close enough and then revised following sentences to make it sound better. [F.26-27] Reformatted the entire sentence to make it clear and make sense

[F.28] Overlapping fixed. [F.29] Color scheme is consistent and therefore assumed to be clear. [F.30] Reference to scheme in text helps to clarify what is happening. [F.31] removed more or less [F.32] added an is [F.33] Changed sentence [F.34] Revised last sentence [G.1] “In our contribution” is consistent with current style of research presentation. [G.2] Specified by saying “ a more electron donating species”. [G.3] Reworded the name of photocatalyst. [I.1] After careful review of references, no glaring mistakes seemed present. [J.1] removed period. [J.2] Title added. [J.3] overlapping fixed. [J.4] clarity added to show which photocatalyst is ours. [J.5] Revised clarity on air and water pollution. [M.1] Response to Reviewer 2 [1.1] Though 3rd person is not desirable, sometimes it is necessary in this assignment to help delineate between the data from our reference paper and the data of the comparison materials. [1.2] Many grammatical errors fixed. [1.3] A figure of the catalytic activity would be a great addition but the figures provided in our reference paper were very complex and they were not included because their interpretation is not entirely clear. [1.4] Again, a morphology figure would be fantastic to absolutely confirm our structure, but our reference paper did not provide any morphology figure so we did not provide one either. [1.5] Though toluene was our pollutant in our experiment, the hydroxyl radical formation and eventual reaction with a compound is rather non-specific and this fact was emphasized to avoid any confusion. [M.2] Response to Reviewer 3 [1.1] Numbering and referencing of schemes fixed [M.3] [1.2] The graphs were enlarged and a discussion of the actual contents would be beneficial but the paper we chose did not go into much detail about their experimental methods and we are definitely not experts on XPS. In future communications we would become more familiar with the standard XPS methods.

[Minor issues] All grammatical and typographical errors were fixed. We hope these changes will suffice for publication in JOC and look forward to your response. With best regards, Taylor and Shane

Taylor Bell Shane Moore

1


Taylor D. Bell, Shane E. Moore

Department of Chemistry, University of Missouri-Columbia, Missouri 65201

Email: [email protected]; [email protected]


2

Abstract: Photocatalysts have been shown to photo-oxidize organic molecules. This is

done through an OH radical at the electron hole site. Charge separation is difficult in

homogenous catalysts so catalysts with better separation properties are being sought after.

We have created a co-catalyst containing manganese modified carbon nitride on TiO2

with ceria on the surface with manganese in the 3+ oxidation state and cerium in the 3+

and 4+ oxidation states. Our compound was found to have an increased rate of

degradation of toluene. This was determined to be the effect of better charge separation

in our co-catalyst because of the inclusion of the manganese species as well as an

increased number of active sites. This result was compared to that of TiO2 and TiO2 with

carbon nitride and ceria on the surface showing that the manganese is in-fact the

important component of our co-catalyst.


3

Introduction

With the growing number of people on earth, our ecological footprint increases

each day. The need for ways to remove pollution dumped into the environment has

chemists looking for cleaner methods. Solar energy has long been an area of interest due

to its mass availability and versatile nature. Solar energy can be used for the generation

of heat, the generation of steam to produce electricity, the direct conversion of sunlight to

electricity through solar panels, the production of biofuels, and the use of photocatalyst.1

Solar energy is a very inexpensive alternative to fossil fuels in developing

countries. Additionally, with renewable energy sources projected to increase their market

share substantially, the economic advantages of developing new and better uses for solar

energy are lucrative.2 One area of major interest is photocatalysis. Photocatalysis is the

use of light energy to accelerate a chemical reaction.3 The most important function of

photocatalysis to our society is the production of renewable energy.

Photocatalysis uses solar energy for electron excitation in materials that allow for

electron dissociation and charge carrier diffusion.4 Electron dissociation occurs when

electrons get excited to their next energy level, creating electron “holes” where they left.4

Charge carrier diffusion is then used to separate the electrons further so that they can be

used for reducing agents and their holes can be used as oxidizing agents.4 Oxidative and

reductive materials can then be applied to areas such as turning water and fuel to H2,

biomasses to fuel, and environmental factors such as NOx and CO2 reduction (Scheme

1).5


4

Scheme 1. Uses of Photocatalysts6

Scheme 2. Photocatalytic Formation of OH radical by TiO2

Although new ways of clean fuel synthesis from water splitting to form H2 and biofuel

synthesis are being created, existing pollutants still need to be removed from the

environment. 7 Previous groups have reported on the ability of TiO2 to break down

organic materials by the formation of OH radicals.8 Scheme 2 shows how the OH


5

radicals are created by one electron forming a lone pair filling in the created hole by TiO2

leaving the extra one by itself. These are then used for oxidation of many compounds,

like BPA, that is found in municipal water sources and is toxic to people. 9

Here we report the results of using TiO2 doped with CeO2 and a manganese

enhanced graphene C3N4 (g-Mn/CeTi) to degrade organic materials, in this case toluene.

Our evidence shows that the ceria and Mn g-C3N4 will enhance TiO2 by separating the

charge distribution quicker and therefore increasing the efficiency of the photocatalyst.

The electron separation creates charge holes in the co-catalyst that can then create OH

radicals that sit in these holes.10 OH radicals are able to degrade organic materials by

photo-oxidation. In our experiment we use toluene as a viable organic material to be

oxidized.

Materials and Methods

Preparation of Catalyst

Materials were all made using the micro emulsion technique. CeO2-TiO2 was

first made using a previously obtained TiO2 sample. A CeO2 aqueous solution was used

for the micro emulsion. After 30 minutes of agitation, a stoichiometric quantity of

tetramethylammonium hydroxide was introduced by a similar micro emulsion technique.

Titanium tetraisopropoxide was then introduced to the previous micro emulsion

dropwise. The resulting mixture was then stirred for 24 hours, centrifuged, rinsed with

methanol, and dried for 12 hours. After drying, heat ramping was used (2 ̊C min-1) to

500 ̊C.

For g-C3N4 modified with Mn production, g-C3N4 had to be first made separately

by calcination techniques of melamine at 580 ̊C which can be found in supplemental

information. This aqueous solution was then mixed with an aqueous solution of


6

dissolved manganese (II) chloride tetrahydrate and stirred for 1 hour at room temperature.

Then it was centrifuged, washed, and dried at 60 ̊C.

The two materials synthesized were then combined using an impregnation method

by suspending the appropriate amounts of g-C3N4 or g-C3N4-MnOxOHy in methanol and

sonicating for 1 hour. The sample was then dried at 110 ̊C for 24 hours to get the

finished products of the g-C3N4/TiO2, g-C3N4/CeO2-TiO2, g-C3N4-MnOxOHy/TiO2, and

g-C3N4-MnOxOHy/TiO2-CeO2 composite sites.

Photocatalytic Measurements

A continuous flow annular photo reactor was used in the gas-phase photo

oxidation of toluene. Activity and selectivity for the gas-phase photo-oxidation were

tested with 40 mg of the photocatalytic material as a thin layer coating on a Pyrex tube.

The corresponding amount of catalyst was then mixed with 1 ml ethanol and painted on

the tube before allowing to dry. Gas-phase toluene was then pumped through the tube at

100-700 ppmv, first for 6 hours in the dark and then for 24 hours under irradiation by

four UV lamps symmetrically positioned around the photo reactor. Concentrations of

reactants and products were analyzed during the process using online gas

chromatography equipped with HP-PLOT-Q/HP-Innowax columns and TCD (for CO2

measurements) / FID (for organic measurements) detectors. This allowed for calculations

of not only the concentrations, but also the rates.

Results and Discussion

A ternary photocatalyst was created which contained Mn modified carbon nitride,

TiO2, and ceria. This was characterized by XRD and XPS and discussion of these

methods can be found in Figures S1, S2, and S3. Figure S1 shows that our TiO2 is solely


7

in the anatase form. This is important to allow for reproducibility and consistent

comparison between the different photocatalysts. Figure S2 determined that the

oxidation state of Cerium was either 3+ or 4+. Furthermore, the BET surface area was

determined as well as the band gap and is contained in Table 1.

Table 1. Reaction Rate of Toluene Photo-oxidation and other Properties of Various

Photocatalysts11,12

Catalyst

BET Surface

Area (m2 g-1)

Band Gap (eV)

Irradia- tion

[Tol.]in (M m-3)

[Tol.]out (M m-3) Rate

g-Mn/CeTia 100.4 2.96 100% 6.69x10-3 5.9x10-3 8.5x10-10 mol s-1 m-2

TiO2 277 3.20 --- 0.0075 0.0055 0.00027 mol m-3 min-1

g/CeTib 101 2.94 --- 700 ppm --- 6.2x10-10 mol s-1 m-2

ag-Mn/CeTi: graphitic carbon nitride on TiO2 with manganese and ceria co-catalyst. bg/CeTi: graphitic carbon nitride on TiO2 with ceria co-catalyst.

Looking at the surface area and band gap differences, one would likely assume that

g/CeTi would work slightly better for the photo-oxidation of toluene than the g-Mn/CeTi.

A slightly decreased band gap would indicate better excitation by visible light. To

determine which photocatalyst is better excited by visible light, UV-vis spectra were

taken can be seen in Figure 1.


8

Figure 1. UV-vis spectra g-Mn/CeTi, Ti, and g/CeTi.

The UV-vis spectra shows that our new photocatalyst, marginally increases the

wavelength of absorption compared to just TiO2, represented by Ti. The spectra also

show that our g-Mn/CeTi co-catalyst has increased absorption over the g/CeTi and TiO2

in the ranges of 250nm to 350nm. Although others are able to absorb in more of the UV

light spectrum, the g-Mn/CeTi absorbs more of the visible light.

After characterization we went on to test the photocatalytic properties of our

compound. We found the rate of toluene degradation to be 8.5x10-10 mol s-1 m-2 which

was higher than that of TiO2 and g/CeTi. If just the UV-vis spectra and the band gap

were considered, it would be assumed that our photocatalyst was not better than the other

g/CeTi since there was not much difference between our co-catalyst and g/CeTi, so we

decided to look at the photoluminescence spectra to determine the amount of

recombination that was occurring.


9

Figure 2. Photoluminescence spectra of various photocatalysts including g-Mn/CeTi,

g/CeTi, and Ti.

From Figure 2 we can see that our co-catalyst is showing decreased

photoluminescence, which is indicative of decreased electron-hole recombination. This

leads us to believe that our new co-catalyst is better at separating charges and avoiding

recombination. Though some good photocatalysts may show high photoluminescence,

here with comparison to TiO2 and graphitic carbon nitride, we can see that our

photocatalyst has decreased photoluminescence, which leads us to believe that there is

better charge separation and therefor better activity. This better handling of charges,

especially holes, allows for increased ability to react for the OH radicals which are the

true reactive species in the degradation of toluene and other organic molecules.


10

Degradation of organic molecules by photo-oxidation is a non-selective process

that involves hydroxyl radicals. These are formed on the surface of the photocatalyst at

the electron hole. Our photocatalyst has increased charge-handling capabilities as was

indicated by the photoluminescence spectra. We determined that it has two different

active sites where the hydroxyl radicals can occur as is illustrated in Scheme 4. Scheme

4 is a two dimensional representation of the attack of toluene. Although the holes seem

close enough that the hydroxyl radicals would interact, due to the three dimensional

structure, the hydroxyl radicals are separated enough to increase the rate of the reaction

as demonstrated.

Scheme 3. OH Radical Formation and Attack of Toluene


11

Scheme 4. Photo-oxidation of BPA by Hydroxyl Radicals9

The mechanism for the photo-oxidation of organic molecules has been studied but

it appears that it is the random attacks by hydroxyl radicals that eventually lead to the

complete mineralization of the molecule to CO2 and H2O. This is shown in Scheme 4

with BPA being the organic molecule that is being degraded. The complete degradation

consists of many cross-reactions with hydroxyl radicals and self attacks that eventually


12

breaks it down to CO2. Although this may not be as effective in air because it needs to be

in the presence of water, this is a very good strategy for the removal of water pollutants

because of their confined volume. With high enough water vapor concentrations in the

air the photocatalyst can be effective. There could be alterations made to allow air to be

more easily cleaned by confining the air and forcing the different products to react with

each other. The biggest importance is that a more effective photocatalyst with multiple

reactive sites has been created which will allow for quicker degradation of organic

materials.

Conclusion

We are able to report that by adding CeO2 and a manganese doped graphene-C3N4

to the surface of TiO2 we speed up the photo-oxidation of toluene. Instead of increasing

the spectrum that the photocatalysis could absorb we found that it increases the rate by

having a more electron donating species to separate charge, and therefore create electron

holes. Characterization of the compound by XRD and XPS showed us that the Mn

species acts as a strong cationic species when incorporated with the g-C3N4 surface

allowing for long lasting electron holes. Oxidation of OH by the Mn species will create

OH radicals that are able to degrade toluene.

Our results show that modification of TiO2 by ceria and manganese doped

graphene carbon nitrides is an effective way for the degradation of organic pollutants.

Furthermore we’ve shown how adding inorganic materials like manganese we can create

more and longer lasting electron holes that can oxidizes species like OH effectively. OH

radical formation is important for many reactions like BPA and NOx degradation. The

application of this quicker acting co-catalyst can be wide spread among photo-oxidation

reactions.


13

Supplemental Material Available: The appendix contains a more detailed description

of the preparation of our photocatalyst as well as more information of the process used to

test our photo catalyst. XPS and XRD spectra are also contained in the supplemental

material. This material is available free of charge via the Internet at http://pubs.acs.org.

References

(1) About: Solar Energy. http://www.seia.org/about/solar-energy (accessed April 13,

2015)

(2) Renewables to Surpass Gas by 2016 in the Global Power Mix.

http://www.iea.org/newsroomandevents/pressreleases/2013/june/renewables-to-surpass-

gas-by-2016-in-the-global-power-mix.html (Accessed April 12, 2015).

(3) Photocatalysis. Merriam Webster, Eleven [Online]; Merriam-Webster Incorporated,

Posted Online 2015. http://www.merriam-

webster.com/medical/photocatalysis?show=0&t=1419648098 (accessed April 12, 2015)

(4) Linic, S. Christopher, P.; Ingram, D. B. Plasmonic-metal Nanostructures for Efficient

Conversion of Solar to Chemical Energy. Nat. Mater. 2011, 10, 911-921.

(5) Basic Functions Of Photocatalyst. http://www.tipe.com.cn/library/kb2503.htm

(Accessed April 12, 2015).

(6) What is microalgae. http://www.febico.com/en/page/What-is-Microalgae/FL-1-

Microalgae.html (Accessed April 10, 2015)


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(7) Xu, C.; Yang, W.; Guo, Q.; Dai, D.; Chen, M.; Yang, X. Molecular Hydrogen

Formation from Photocatalysis of Methanol on Anatase-TiO2(101). J. Am. Chem. Soc.

2014, 136, 602-605.

(8) Wagner, V.; Jenkin, M. E.; Saunders, S. M.; Stanton J.; Wirtz, K.; Pilling, M. J.

Modelling of the Photooxidation of Toluene: Conceptual Ideas for Validating Detailed

Mechanism. Atmos. Chem. Phys. 2003, 3, 89-106.

(9) Sin, J.; Lam, S.; Mohamed, A. R.; Lee, K. Degrading Endocrine Disrupting

Chemicals from Wastewater by TiO2 Photocatalysis: A Review. Int. J. Photoenergy

2012, Article ID 185159, 23 pages (doi:10.1155/2012/185159).

(10) Lawless, D.; Serpone, N.; Meisel, D. Role of OH Radicals and Trapped Holes in

Photocatalysis. A Pulse Radiolysis Study. J. Phys. Chem. 1991, 95, 5166-5170.

(11) Kim, S. B.; Hong, S. C. Kinetic Study for Photocatalytic Degradation of Volatile

Organic Compounds in Air Using Thin Film TiO2 Photocatalyst. App. Catal. B. 2002,

35, 305-315.

(12) Munoz-Batista, M. J.; Fernandez-Garcia, M.; Kubacka, A. Promotion of CeO2-TiO2

Photoactivity by g-C3N4: Ultraviolet and visible light elimination of toluene. App. Catal.

B. 2015, 164, 261-270.


S1

Supporting Information


Taylor D. Bell, Shane E. Moore

Department of Chemistry, University of Missouri-Columbia, Missouri 65201

Email: [email protected]; [email protected]


S2

Table of Contents

Preparation of Co-catalyst………………………………………………….. S3

Photocatalytic Experimental Details ………………………………………. S4

XRD Spectroscopy of Co-catalyst…………………………………………. S5

XPS Spectroscopy of Co-catalyst………………………………………….. S6

Bibliography…………………………………………………….…………. S8


S3

Preparation of Catalyst

Original materials were prepared using the micro emulsion technique with n-

Heptane as an organic media, Triton X-100 as a surfactant, and hexanol as a cosurfactant.

A TiO2 sample was first obtained as a first step using titanium tetraisoperoxide as a

precursor. To create CeO2-TiO2, cerium nitrate was introduced in the aqueous phase of

micro emulsion. After 30 minutes of agitation, a stoichiometric quantity of

tetramethylammonium hydroxide (TMAH) to obtain 2.5% of Ce (III) hydroxide was

introduced from the aqueous phase of a similar micro emulsion. After 5 minutes,

titanium tetraisopropoxide was introduced into the mixture with isopropanol (2:3).

Water/(Ti+Ce) and water/ surfactant molar ratios were 110 and 18 for all samples,

respectively. The resulting mixture was then stirred for 24 hours, centrifuged, separated,

and rinsed with methanol and dried at 110 ̊C for 12 hours. After drying, the materials

were subject to a heating ramp (2 ̊C min-1) to 500 ̊C, maintain this temperature for 2

hours.

Graphite carbon nitride (g-C3N4) modified with Mn was synthesized by dissolving

manganese (II) chloride tetrahydrate salt in deionized water to produce a 10mM solution.

Then the salt solution was added to 200mL of a 0.5mg mL-1 uniformly dispersed g-C3N4

aqueous solution that was obtained by previous calcination melamine at 580 ̊C for 4

hours. The mixture was then stirred for 1 hour at room temperature, centrifuged, and

washed with deionized water before being dried at 60 ̊C.

The incipient wetness impregnation method was used to obtain the g-C3N4/TiO2,

g-C3N4/CeO2-TiO2, g-C3N4-MnOxOHy/TiO2, and g-C3N4-MnOxOHy/TiO2-CeO2

composite sites. For this the appropriate amount of g-C3N4 or g-C3N4-MnOxOHy was

suspended in methanol and sonicated for 1 hour, deposited on the corresponding

composite sample and dried at 110 ̊C for 24 hours.


S4

Photocatalytic Experimental Details

A continuous flow annular photo reactor (Panreac) was used in the gas-phase

photo oxidation of toluene. Activity and selectivity for the gas-phase photo oxidation

were tested with 40 mg of the photocatalytic material as a thin layer coating on a Pyrex

tube. The corresponding amount of catalyst was then mixed with 1ml ethanol and

painted on the tube before allowing to dry. Gas-phase toluene was then pumped through

the tube at 100-700 ppmv, first for 6 hours in the dark and then for and then for 24 hours

under irradiation by four UV lamps symmetrically positioned around the photo reactor.

Concentrations of reactants and products were analyzed during the process using online

gas chromatography (Agilent GC 6890) equipped with HP-PLOT-Q/HP-Innowax

columns (0.5/0.32 mm i.d. X 30 m) and TCD (for CO2 measurements) / FID (organic

measurement) detectors.


S5

XRD Spectroscopy for Co-catalyst

The X-ray diffraction pattern is used to show the phase of the TiO2 by comparison

to know patterns. Figure 1 shows that all made samples are found to be in the anatase

phase only.

Figure S1. XRD patterns of the photocatalyst.


S6

XPS Data for Co-Catalyst

XPS data was used to show the relative concentrations of added ceria and g-Mn

clusters. The results in Figure 2 show that there is a low chemical influence of the carbon

nitride in the oxide components especially with interaction of CeTi. We also observe the

bonding stated of Ce-Ti to be Ce(III) and Ce(IV) oxidation states. Figure 3 Shows that

CN species only start to have an effect when the presence of Mn is added. Experimental

fitting was done

Figure S2. XPS Data for Co-catalyst. Mn 2p (A), C 1s (B), and N 1s (C), XPS data and

fitting for g-Mn sample; fitting results for C 1s (D) and N 1s (E) XPS peaks of the g-

Mn/CeTi sample.


S7

Figure S3. C 1s (A) and N 1s (B) XPS spectra for the g, g-Mn, g/Ti, g-Mn/Ti, g/CeTi,

and g-Mn/CeTi samples.


S8

Bibliography

Munoz-Batista, Mario J.; Kubacka, Anna; Fernandez-Garcia, Marcos. Effective

Enhancement of TiO2 Photocatalysis by Synergistic Interaction of Surface Species: From

Promoters to Co-Catalysts. ACS Catal. 2014, 4, 4277-4288.

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