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Title: Understanding the Oxygen Evolution Reaction Mechanism on CoO x using Operando Ambient-Pressure X-ray Photoelectron Spectroscopy

Abstract

Photoelectrochemical water splitting is a promising approach for renewable production of hydrogen from solar energy and requires interfacing advanced water-splitting catalysts with semiconductors. Understanding the mechanism of function of such electrocatalysts at the atomic scale and under realistic working conditions is a challenging, yet important, task for advancing efficient and stable function. This is particularly true for the case of oxygen evolution catalysts and, here, we study a highly active Co 3O 4/Co(OH) 2 biphasic electrocatalyst on Si by means of operando ambient-pressure X-ray photoelectron spectroscopy performed at the solid/liquid electrified interface. Spectral simulation and multiplet fitting reveal that the catalyst undergoes chemical-structural transformations as a function of the applied anodic potential, with complete conversion of the Co(OH) 2 and partial conversion of the spinel Co 3O 4 phases to CoO(OH) under precatalytic electrochemical conditions. Furthermore, we observe new spectral features in both Co 2p and O 1s core-level regions to emerge under oxygen evolution reaction conditions on CoO(OH). The operando photoelectron spectra support assignment of these newly observed features to highly active Co 4+ centers under catalytic conditions. Comparison of these results to those from a pure phase spinel Co 3O 4 catalyst supports this interpretation and reveals thatmore » the presence of Co(OH) 2 enhances catalytic activity by promoting transformations to CoO(OH). The direct investigation of electrified interfaces presented in this work can be extended to different materials under realistic catalytic conditions, thereby providing a powerful tool for mechanism discovery and an enabling capability for catalyst design.« less

Authors:
 [1];  [2]; ORCiD logo [3];  [3];  [2]; ORCiD logo [2]; ORCiD logo [2]; ORCiD logo [2]
  1. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Helmholtz-Zentrum Berlin fur Materialien und Energie GmbH, Berlin (Germany)
  2. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  3. IOM-CNR, Trieste (Italy)
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES)
OSTI Identifier:
1379905
Grant/Contract Number:  
AC02-05CH11231
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Journal of the American Chemical Society
Additional Journal Information:
Journal Volume: 139; Journal Issue: 26; Journal ID: ISSN 0002-7863
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; water splitting; cobalt oxide photoelectrocatalysts; operando spectroscopy; ambient pressure XPS; oxygen evolution reaction mechanism

Citation Formats

Favaro, Marco, Yang, Jinhui, Nappini, Silvia, Magnano, Elena, Toma, Francesca M., Crumlin, Ethan J., Yano, Junko, and Sharp, Ian D. Understanding the Oxygen Evolution Reaction Mechanism on CoOx using Operando Ambient-Pressure X-ray Photoelectron Spectroscopy. United States: N. p., 2017. Web. doi:10.1021/jacs.7b03211.
Favaro, Marco, Yang, Jinhui, Nappini, Silvia, Magnano, Elena, Toma, Francesca M., Crumlin, Ethan J., Yano, Junko, & Sharp, Ian D. Understanding the Oxygen Evolution Reaction Mechanism on CoOx using Operando Ambient-Pressure X-ray Photoelectron Spectroscopy. United States. https://doi.org/10.1021/jacs.7b03211
Favaro, Marco, Yang, Jinhui, Nappini, Silvia, Magnano, Elena, Toma, Francesca M., Crumlin, Ethan J., Yano, Junko, and Sharp, Ian D. Fri . "Understanding the Oxygen Evolution Reaction Mechanism on CoOx using Operando Ambient-Pressure X-ray Photoelectron Spectroscopy". United States. https://doi.org/10.1021/jacs.7b03211. https://www.osti.gov/servlets/purl/1379905.
@article{osti_1379905,
title = {Understanding the Oxygen Evolution Reaction Mechanism on CoOx using Operando Ambient-Pressure X-ray Photoelectron Spectroscopy},
author = {Favaro, Marco and Yang, Jinhui and Nappini, Silvia and Magnano, Elena and Toma, Francesca M. and Crumlin, Ethan J. and Yano, Junko and Sharp, Ian D.},
abstractNote = {Photoelectrochemical water splitting is a promising approach for renewable production of hydrogen from solar energy and requires interfacing advanced water-splitting catalysts with semiconductors. Understanding the mechanism of function of such electrocatalysts at the atomic scale and under realistic working conditions is a challenging, yet important, task for advancing efficient and stable function. This is particularly true for the case of oxygen evolution catalysts and, here, we study a highly active Co3O4/Co(OH)2 biphasic electrocatalyst on Si by means of operando ambient-pressure X-ray photoelectron spectroscopy performed at the solid/liquid electrified interface. Spectral simulation and multiplet fitting reveal that the catalyst undergoes chemical-structural transformations as a function of the applied anodic potential, with complete conversion of the Co(OH)2 and partial conversion of the spinel Co3O4 phases to CoO(OH) under precatalytic electrochemical conditions. Furthermore, we observe new spectral features in both Co 2p and O 1s core-level regions to emerge under oxygen evolution reaction conditions on CoO(OH). The operando photoelectron spectra support assignment of these newly observed features to highly active Co4+ centers under catalytic conditions. Comparison of these results to those from a pure phase spinel Co3O4 catalyst supports this interpretation and reveals that the presence of Co(OH)2 enhances catalytic activity by promoting transformations to CoO(OH). The direct investigation of electrified interfaces presented in this work can be extended to different materials under realistic catalytic conditions, thereby providing a powerful tool for mechanism discovery and an enabling capability for catalyst design.},
doi = {10.1021/jacs.7b03211},
url = {https://www.osti.gov/biblio/1379905}, journal = {Journal of the American Chemical Society},
issn = {0002-7863},
number = 26,
volume = 139,
place = {United States},
year = {2017},
month = {6}
}

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