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Improving O_2 production of WO_3 photoanodes with IrO_2 in acidic aqueous electrolyte

Spurgeon, Joshua M. and Velazquez, Jesus M. and McDowell, Matthew T. (2014) Improving O_2 production of WO_3 photoanodes with IrO_2 in acidic aqueous electrolyte. Physical Chemistry Chemical Physics, 16 (8). pp. 3623-3631. ISSN 1463-9076.

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WO_3 is a promising candidate for a photoanode material in an acidic electrolyte, in which it is more stable than most metal oxides, but kinetic limitations combined with the large driving force available in the WO_3 valence band for water oxidation make competing reactions such as the oxidation of the acid counterion a more favorable reaction. The incorporation of an oxygen evolving catalyst (OEC) on the WO_3 surface can improve the kinetics for water oxidation and increase the branching ratio for O_2 production. Ir-based OECs were attached to WO_3 photoanodes by a variety of methods including sintering from metal salts, sputtering, drop-casting of particles, and electrodeposition to analyze how attachment strategies can affect photoelectrochemical oxygen production at WO_3 photoanodes in 1 M H_2SO_4. High surface coverage of catalyst on the semiconductor was necessary to ensure that most minority-carrier holes contributed to water oxidation through an active catalyst site rather than a side-reaction through the WO_3/electrolyte interface. Sputtering of IrO_2 layers on WO_3 did not detrimentally affect the energy-conversion behavior of the photoanode and improved the O_2 yield at 1.2 V vs. RHE from ~0% for bare WO_3 to 50–70% for a thin, optically transparent catalyst layer to nearly 100% for thick, opaque catalyst layers. Measurements with a fast one-electron redox couple indicated ohmic behavior at the IrO_2/WO_3 junction, which provided a shunt pathway for electrocatalytic IrO_2 behavior with the WO_3 photoanode under reverse bias. Although other OECs were tested, only IrO_2 displayed extended stability under the anodic operating conditions in acid as determined by XPS.

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Additional Information:© 2014 the Owner Societies. Received 31 Dec 2013, Accepted 10 Jan 2014, First published online 10 Jan 2014. This material is based upon work performed by the Joint Center for Artificial Photosynthesis, a DOE Energy Innovation Hub, supported through the Office of Science of the U.S. Department of Energy under Award Number DE-SC0004993. XPS data were collected at the Molecular Materials Research Center of the Beckman Institute of the California Institute of Technology.
Funding AgencyGrant Number
Department of Energy (DOE)DE-SC0004993
Issue or Number:8
Record Number:CaltechAUTHORS:20140128-073407483
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Official Citation:Spurgeon, J. M., Velazquez, J. M., & McDowell, M. T. (2014). Improving O2 production of WO3 photoanodes with IrO2 in acidic aqueous electrolyte. Physical Chemistry Chemical Physics, 16(8), 3623-3631. doi: 10.1039/c3cp55527e
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:43528
Deposited By: Tony Diaz
Deposited On:31 Jan 2014 16:33
Last Modified:03 Oct 2019 06:08

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