Issue 11, 2021

Investigations of the stability of etched or platinized p-InP(100) photocathodes for solar-driven hydrogen evolution in acidic or alkaline aqueous electrolytes

Abstract

The stability of p-InP photocathodes performing the hydrogen-evolution reaction (HER) has been evaluated in contact with either 1.0 M H2SO4(aq) or 1.0 M KOH(aq), with a focus on identifying corrosion mechanisms. Stability for the solar-driven HER was evaluated using p-InP electrodes that were either etched or coated with an electrodeposited Pt catalyst (p-InP/Pt). Variables such as trace O2 were systematically controlled during the measurements. Changes in surface characteristics after exposure to electrochemical conditions as well as electrode dissolution processes were monitored using X-ray photoelectron spectroscopy (XPS) and inductively coupled plasma mass spectrometry (ICP-MS). In either H2SO4 or KOH, etched p-InP photoelectrodes corroded cathodically under illumination, forming metallic In0 at the electrode surface. In contrast, electrodeposition of Pt kinetically stabilized illuminated p-InP photocathodes in both H2SO4 and KOH by inhibiting the cathodic corrosion pathway. Notably, when held at 0 V vs. the reversible hydrogen electrode (RHE) in 1.0 M H2SO4(aq), p-InP/Pt exhibited a stable current density (J) of ∼−18 mA cm−2 for >285 h under simulated 1 Sun illumination. The long-term current density vs. potential (JE) behavior at pH 0 and pH 14 of p-InP/Pt photocathodes correlated with changes in the surface chemistry as well as the dissolution of p-InP. In acidic media, the JE behavior of p-InP/Pt photocathodes remained nearly constant with time, but the surface of a p-InP/Pt electrodes gradually turned P-rich via a slow and continuous leaching of In ions. In alkaline electrolyte, the surface of p-InP/Pt electrodes was passivated by formation of an InOx layer that exhibited negligible dissolution but led to a substantial degradation in the JE characteristics. Consequently, changes in the catalytic kinetics and surface stoichiometry are both important considerations for determining the corrosion chemistry and the long-term operational stability of InP photoelectrodes.

Graphical abstract: Investigations of the stability of etched or platinized p-InP(100) photocathodes for solar-driven hydrogen evolution in acidic or alkaline aqueous electrolytes

Supplementary files

Article information

Article type
Paper
Submitted
09 Sep 2021
Accepted
23 Sep 2021
First published
30 Sep 2021

Energy Environ. Sci., 2021,14, 6007-6020

Investigations of the stability of etched or platinized p-InP(100) photocathodes for solar-driven hydrogen evolution in acidic or alkaline aqueous electrolytes

W. Yu, M. H. Richter, P. Buabthong, I. A. Moreno-Hernandez, C. G. Read, E. Simonoff, B. S. Brunschwig and N. S. Lewis, Energy Environ. Sci., 2021, 14, 6007 DOI: 10.1039/D1EE02809J

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