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

Journal Article (Journal Article)

Alkaline electrolytes impede the corrosion of Si photoanodes under positive potentials and/or illumination, due to the formation of a SiOx 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.

Full Text

Duke Authors

Cited Authors

  • Fu, HJ; Moreno-Hernandez, IA; Buabthong, P; Papadantonakis, KM; Brunschwig, BS; Lewis, NS

Published Date

  • November 1, 2020

Published In

Volume / Issue

  • 13 / 11

Start / End Page

  • 4132 - 4141

Electronic International Standard Serial Number (EISSN)

  • 1754-5706

International Standard Serial Number (ISSN)

  • 1754-5692

Digital Object Identifier (DOI)

  • 10.1039/d0ee02250k

Citation Source

  • Scopus