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Title: Selective CO Production by Photoelectrochemical Methane Oxidation on TiO 2

Abstract

The inertness of the C–H bond in CH 4 poses significant challenges to selective CH 4 oxidation, which often proceeds all the way to CO 2 once activated. Selective oxidation of CH 4 to high-value industrial chemicals such as CO or CH 3OH remains a challenge. Presently, the main methods to activate CH 4 oxidation include thermochemical, electrochemical, and photocatalytic reactions. Of them, photocatalytic reactions hold great promise for practical applications but have been poorly studied. Existing demonstrations of photocatalytic CH 4 oxidation exhibit limited control over the product selectivity, with CO 2 as the most common product. The yield of CO or other hydrocarbons is too low to be of any practical value. In this work, we show that highly selective production of CO by CH4 oxidation can be achieved by a photoelectrochemical (PEC) approach. Under our experimental conditions, the highest yield for CO production was 81.9%. The substrate we used was TiO 2 grown by atomic layer deposition (ALD), which features high concentrations of Ti 3+ species. The selectivity toward CO was found to be highly sensitive to the substrate types, with significantly lower yield on P25 or commercial anatase TiO 2 substrates. Moreover, our results revealed thatmore » the selectivity toward CO also depends on the applied potentials. Based on the experimental results, we proposed a reaction mechanism that involves synergistic effects by adjacent Ti sites on TiO 2. Spectroscopic characterization and computational studies provide critical evidence to support the mechanism. Furthermore, the synergistic effect was found to parallel heterogeneous CO 2 reduction mechanisms. Our results not only present a new route to selective CH 4 oxidation, but also highlight the importance of mechanistic understandings in advancing heterogeneous catalysis.« less

Authors:
 [1];  [1];  [2]; ORCiD logo [1];  [3]; ORCiD logo [1];  [3]; ORCiD logo [1];  [1]; ORCiD logo [3]; ORCiD logo [1]; ORCiD logo [2]; ORCiD logo [1]
  1. Boston College, Chestnut Hill, MA (United States)
  2. Univ. of California, Riverside, CA (United States)
  3. Yale Univ., New Haven, CT (United States)
Publication Date:
Research Org.:
Yale Univ., New Haven, CT (United States); Univ. of California, Riverside, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1498722
Grant/Contract Number:  
[FG02-05ER15646; AC02-05CH11231]
Resource Type:
Accepted Manuscript
Journal Name:
ACS Central Science
Additional Journal Information:
[ Journal Volume: 4; Journal Issue: 5]; Journal ID: ISSN 2374-7943
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Li, Wei, He, Da, Hu, Guoxiang, Li, Xiang, Banerjee, Gourab, Li, Jingyi, Lee, Shin Hee, Dong, Qi, Gao, Tianyue, Brudvig, Gary W., Waegele, Matthias M., Jiang, De-en, and Wang, Dunwei. Selective CO Production by Photoelectrochemical Methane Oxidation on TiO2. United States: N. p., 2018. Web. doi:10.1021/acscentsci.8b00130.
Li, Wei, He, Da, Hu, Guoxiang, Li, Xiang, Banerjee, Gourab, Li, Jingyi, Lee, Shin Hee, Dong, Qi, Gao, Tianyue, Brudvig, Gary W., Waegele, Matthias M., Jiang, De-en, & Wang, Dunwei. Selective CO Production by Photoelectrochemical Methane Oxidation on TiO2. United States. doi:10.1021/acscentsci.8b00130.
Li, Wei, He, Da, Hu, Guoxiang, Li, Xiang, Banerjee, Gourab, Li, Jingyi, Lee, Shin Hee, Dong, Qi, Gao, Tianyue, Brudvig, Gary W., Waegele, Matthias M., Jiang, De-en, and Wang, Dunwei. Mon . "Selective CO Production by Photoelectrochemical Methane Oxidation on TiO2". United States. doi:10.1021/acscentsci.8b00130. https://www.osti.gov/servlets/purl/1498722.
@article{osti_1498722,
title = {Selective CO Production by Photoelectrochemical Methane Oxidation on TiO2},
author = {Li, Wei and He, Da and Hu, Guoxiang and Li, Xiang and Banerjee, Gourab and Li, Jingyi and Lee, Shin Hee and Dong, Qi and Gao, Tianyue and Brudvig, Gary W. and Waegele, Matthias M. and Jiang, De-en and Wang, Dunwei},
abstractNote = {The inertness of the C–H bond in CH4 poses significant challenges to selective CH4 oxidation, which often proceeds all the way to CO2 once activated. Selective oxidation of CH4 to high-value industrial chemicals such as CO or CH3OH remains a challenge. Presently, the main methods to activate CH4 oxidation include thermochemical, electrochemical, and photocatalytic reactions. Of them, photocatalytic reactions hold great promise for practical applications but have been poorly studied. Existing demonstrations of photocatalytic CH4 oxidation exhibit limited control over the product selectivity, with CO2 as the most common product. The yield of CO or other hydrocarbons is too low to be of any practical value. In this work, we show that highly selective production of CO by CH4 oxidation can be achieved by a photoelectrochemical (PEC) approach. Under our experimental conditions, the highest yield for CO production was 81.9%. The substrate we used was TiO2 grown by atomic layer deposition (ALD), which features high concentrations of Ti3+ species. The selectivity toward CO was found to be highly sensitive to the substrate types, with significantly lower yield on P25 or commercial anatase TiO2 substrates. Moreover, our results revealed that the selectivity toward CO also depends on the applied potentials. Based on the experimental results, we proposed a reaction mechanism that involves synergistic effects by adjacent Ti sites on TiO2. Spectroscopic characterization and computational studies provide critical evidence to support the mechanism. Furthermore, the synergistic effect was found to parallel heterogeneous CO2 reduction mechanisms. Our results not only present a new route to selective CH4 oxidation, but also highlight the importance of mechanistic understandings in advancing heterogeneous catalysis.},
doi = {10.1021/acscentsci.8b00130},
journal = {ACS Central Science},
number = [5],
volume = [4],
place = {United States},
year = {2018},
month = {4}
}

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Figures / Tables:

Figure 1 Figure 1: (a) Schematic illustration of selective CH4 oxidation to CO on a TiO2 photoelectrode, starting with charge separation between O2− and Ti4+ to produce −•O−Ti3+ upon illumination. The separation of the redox half reactions permitted us to focus on CH4 oxidation. (b) Dependence of the CO efficiency and selectivitymore » on the applied potentials (left axis, efficiency, %; right axis, selectivity of CO over all carbonaceous products, %). PEC bulk electrolysis was conducted on ALD TiO2 in CH4-saturated 1.0 M NaOH electrolyte at the corresponding applied potentials.« less

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Works referencing / citing this record:

Atomically Thin 2D Transition Metal Oxides: Structural Reconstruction, Interaction with Substrates, and Potential Applications
journal, October 2018

  • Yang, Tong; Song, Ting Ting; Callsen, Martin
  • Advanced Materials Interfaces, Vol. 6, Issue 1
  • DOI: 10.1002/admi.201801160

    Figures/Tables have been extracted from DOE-funded journal article accepted manuscripts.