(349f) Dynamic Photo-Electrochemical Interface for Solar Fuels

Semiconductor photoelectrochemistry (PEC) is a promising route for sustainable production of clean H₂ fuel vis solar water splitting However, scalable implementation of high-efficiency PEC device is plagued by their limited stability. For decades, stability has remained one of the most significant but least understood topics in the field. Herein, I will introduce our efforts at Caltech to establish fundamental understanding over material corrosion and photoelectrode stability, for several technologically important semiconductors (InP, GaAs and GaInP) used as H₂-evolving photocathodes. Comprehensive insights are achieved by leveraging delicate experiment design as well as correlative measurements of electrochemistry, material dissolution as well as evolving surface conditions. Overall, three key concepts regarding stability are emphasized: (a) kinetic stabilization by surface catalysis, (b) Fermi level pinning by surface non-stoichiometry, and (c) structural integrity of multi-layer architectures in solar-fuel devices. Together, this advanced understanding reveals the dynamic nature of photo-electrochemical interface, whereas the electrochemical stability and physical stability of photoelectrodes need to be considered separately.