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Enhanced stability of silicon for photoelectrochemical water oxidation through self-healing enabled by an alkaline protective electrolyte

Fu, Harold J. and Moreno-Hernandez, Ivan A. and Buabthong, Pakpoom and Papadantonakis, Kimberly M. and Brunschwig, Bruce S. and Lewis, Nathan S. (2020) Enhanced stability of silicon for photoelectrochemical water oxidation through self-healing enabled by an alkaline protective electrolyte. Energy and Environmental Science, 13 (11). pp. 4132-4141. ISSN 1754-5692. https://resolver.caltech.edu/CaltechAUTHORS:20201016-131847563

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Abstract

Alkaline electrolytes impede the corrosion of Si photoanodes under positive potentials and/or illumination, due to the formation of a SiO_x layer that etches 2–3 orders of magnitude more slowly than Si. Hence during water oxidation under illumination, pinholes in protection layers on Si photoanodes result in the local formation of a protective, stabilizing passive oxide on the Si surface. However, operation under natural diurnal insolation cycles additionally requires protection strategies that minimize the dark corrosive etching rate of Si at pinholes. We show herein that addition of [Fe(CN)₆]³⁻ to 1.0 M KOH(aq) results in a self-healing process that extends the lifetime to >280 h of an np⁺-Si(100) photoanode patterned with an array of Ni catalyst islands operated under simulated day/night cycles. The self-healing [Fe(CN)₆]³⁻ additive caused the exposed Si(100) surface to etch >180 times slower than the Si etch rate in 1.0 M KOH(aq) alone. No appreciable difference in etch rate or facet preference was observed between Si(100) and Si(111) surfaces in 1.0 M KOH(aq) with [Fe(CN)₆]³⁻, indicating that the surface conformally oxidized before Si dissolved. The presence of [Fe(CN)₆]³⁻ minimally impacted the faradaic efficiency or overpotential of p⁺-Si/Ni electrodes for the oxygen-evolution reaction.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1039/d0ee02250kDOIArticle
ORCID:
AuthorORCID
Fu, Harold J.0000-0001-9738-209X
Moreno-Hernandez, Ivan A.0000-0001-6461-9214
Buabthong, Pakpoom0000-0001-5538-138X
Papadantonakis, Kimberly M.0000-0002-9900-5500
Brunschwig, Bruce S.0000-0002-6135-6727
Lewis, Nathan S.0000-0001-5245-0538
Additional Information:© Royal Society of Chemistry 2020. Submitted 16 Jul 2020; Accepted 06 Oct 2020; First published 06 Oct 2020. This work was supported through the Office of Science of the U.S. Department of Energy (DOE) under award no. DE-SC0004993 to the Joint Center for Artificial Photosynthesis, a DOE Energy Innovation Hub. Research was in part carried out at the Molecular Materials Resource Center of the Beckman Institute. We thank M. H. Richter for assistance in automating day/night cycles. There are no conflicts to declare.
Group:JCAP
Funders:
Funding AgencyGrant Number
Department of Energy (DOE)DE-SC0004993
Issue or Number:11
Record Number:CaltechAUTHORS:20201016-131847563
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20201016-131847563
Official Citation:Enhanced stability of silicon for photoelectrochemical water oxidation through self-healing enabled by an alkaline protective electrolyte. Energy Environ. Sci., 2020, 13, 4132-4141; doi: 10.1039/d0ee02250k
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:106114
Collection:CaltechAUTHORS
Deposited By: George Porter
Deposited On:16 Oct 2020 21:30
Last Modified:16 Nov 2020 21:46

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