Photoelectrochemical Water Splitting with p‐Type Metal Oxide Semiconductor Photocathodes

Photoelectrochemical (PEC) water splitting is a promising way to produce clean and sustainable hydrogen fuel. Solar hydrogen production by using p-type metal oxide semiconductor photocathodes has not been studied as extensively as that with n-type metal oxide semiconductor photoanodes and p-type photovoltaic-grade non-oxide semiconductor photocathodes. Copper-based oxide photocathodes show relatively good conductivity, but suffer from instability in aqueous solution under illumination, whereas iron-based metal oxide photocathodes demonstrate more stable PEC performance but have problems in charge separation and transport. Herein, an overview of recent progress in p-type metal oxide-based photocathodes for PEC water reduction is provided. Although these materials have not been fully developed to reach their potential performance, the challenges involved have been identified and strategies to overcome these limitations have been proposed. Future research in this field should address these issues and challenges in addition to the discovery of new materials.