Understanding the Stability of Etched or Platinized p-GaInP Photocathodes for Solar-Driven H₂ Evolution

Creators: Yu, Weilai; Young, James L.; Deutsch, Todd G.; Lewis, Nathan S.

Abstract

The long-term stability in acidic or alkaline aqueous electrolytes of p-Ga_(0.52)In_(0.48)P photocathodes, with a band gap of ∼1.8 eV, for the solar-driven hydrogen-evolution reaction (HER) has been evaluated from a thermodynamic, kinetic, and mechanistic perspective. At either pH 0 or pH 14, etched p-GaInP electrodes corroded cathodically under illumination and formed metallic In0 on the photoelectrode surface. In contrast, under the same conditions, electrodeposition of Pt facilitated the HER kinetics and stabilized p-GaInP/Pt photoelectrodes against such cathodic decomposition. When held at 0 V versus the reversible hydrogen electrode, p-GaInP/Pt electrodes in either pH = 0 or pH = 14 exhibited stable current densities (J) of ∼−9 mA cm⁻² for hundreds of hours under simulated 1 sun illumination. During the stability tests, the current density–potential (J–E) characteristics of the p-GaInP/Pt photoelectrodes degraded due to pH-dependent changes in the surface chemistry of the photocathode. This work provides a fundamental understanding of the stability and corrosion mechanisms of p-GaInP photocathodes that constitute a promising top light absorber for tandem solar-fuel generators.

Additional Information

© 2021 American Chemical Society. Received: September 23, 2021; Accepted: November 8, 2021; Published: November 25, 2021. 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 and under award DE-SC0022087 from the Basic Energy Sciences Office of the DOE. Research was in part performed at the Molecular Materials Research Center (MMRC) of the Beckman Institute of the California Institute of Technology. Dr. Nathan Dalleska is thanked for assistance with ICP–MS analysis. Dr. Myles Steiner is thanked for assistance with material fabrication. The authors acknowledge research support from the HydroGEN Advanced Water Splitting Materials Consortium, established as part of the Energy Materials Network under the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Hydrogen and Fuel Cell Technologies Office, under Award Number DE-EE-0008084. This work was authored in part by the National Renewable Energy Laboratory, operated by Alliance for Sustainable Energy, LLC, for the U.S. Department of Energy under Contract Number DE-AC36-08GO28308. The views expressed in the article do not necessarily represent the views of the DOE or the U.S. Government. The U.S. Government retains and the publisher, by accepting the article for publication, acknowledges that the U.S. Government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this work, or allow others to do so, for U.S. Government purposes. \ The authors declare no competing financial interest.

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