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Catalytic open-circuit passivation by thin metal oxide films of p-Si anodes in aqueous alkaline electrolytes

Fu, Harold J. and Buabthong, Pakpoom and Ifkovits, Zachary Philip and Yu, Weilai and Brunschwig, Bruce S. and Lewis, Nathan S. (2022) Catalytic open-circuit passivation by thin metal oxide films of p-Si anodes in aqueous alkaline electrolytes. Energy and Environmental Science, 15 (1). pp. 334-345. ISSN 1754-5692. doi:10.1039/d1ee03040j.

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Ni and NiOₓ-based protective thin films are shown to catalyze the oxidation of Si in the presence of O₂ in strongly alkaline KOH(aq) even in the absence of illumination. The O₂ in solution drove the open-circuit potential of the electrode to >0.4 V, which is positive of the Si passivation potential. The elevated electrochemical potential of the surface promoted formation of passive oxides on exposed Si regions of Si/Ni electrodes. Catalytic passivation of Si extended the durability of an np⁺-Si(100)/NiOₓ photoanode to >400 h while operating under simulated day/night cycles. In contrast, electrodes without a Ni(Oₓ) layer and/or without O₂ in solution displayed direct etching of the Si and corrosion pitting during non-illuminated, simulated nighttime episodes of day/night cycling. The O₂-derived catalyzed passivation of Si using thin films can be generalized to multiple phases of NiOₓ as well as to materials other than Ni. Relative to operation in aqueous alkaline conditions, decreasing the pH of the electrolyte decreased the dissolution rate of the protective oxide layer formed by the catalyzed passivation process, and consequently increased the durability of the photoanode, but yielded lower photoelectrode fill factors for water oxidation due to the relatively large kinetic overpotentials for the electrocatalyzed oxygen-evolution reaction at near-neutral pH.

Item Type:Article
Related URLs:
URLURL TypeDescription files
Fu, Harold J.0000-0001-9738-209X
Buabthong, Pakpoom0000-0001-5538-138X
Ifkovits, Zachary Philip0000-0003-2538-0794
Yu, Weilai0000-0002-9420-0702
Brunschwig, Bruce S.0000-0002-6135-6727
Lewis, Nathan S.0000-0001-5245-0538
Additional Information:© The Royal Society of Chemistry 2022. Submitted 28 Sep 2021. Accepted 26 Nov 2021. First published 29 Nov 2021. This work was supported through the Office of Science of the U.S. Department of Energy (DOE) under award number DE-SC0004993 to the Joint Center for Artificial Photosynthesis, a DOE Energy Innovation Hub, and under award DE-SC0022087 from the Basic Energy Sciences Office of the DOE. Research was in part performed at the Molecular Materials Resource Center of the Beckman Institute.
Funding AgencyGrant Number
Department of Energy (DOE)DE-SC0004993
Department of Energy (DOE)DE-SC0022087
Issue or Number:1
Record Number:CaltechAUTHORS:20211209-456392000
Persistent URL:
Official Citation:Catalytic open-circuit passivation by thin metal oxide films of p-Si anodes in aqueous alkaline electrolytes. Energy Environ. Sci., 2022, 15, 334-345; DOI:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:112325
Deposited By: George Porter
Deposited On:10 Dec 2021 20:30
Last Modified:21 Jan 2022 18:31

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