Making Solar Hydrogen: A Review of the Challenges and Strategies of Synthesizing CuFeO Photocathodes for Photoelectrochemical Water Splitting.

Delafossite CuFeO has emerged as a promising earth-abundant p-type photocathode for solar fuel generation due to its stability in aqueous conditions and its favorable light absorption characteristics. However, practical photocurrent generation in CuFeO has consistently fallen short of its theoretical potential. This limitation is attributed primarily to suboptimal practical visible light absorption, resulting in diminished incident photon-to-current conversion efficiency (IPCE). Challenges related to charge separation and transport, originating from low acceptor density and inherent low conductivity, further contribute to the reported suboptimal performance of delafossite CuFeO. Thus, the present review comprehensively documents the latest advancements in the field of CuFeO photocathode research, with a particular emphasis on strategies to overcome the challenges currently being faced and on the illustration of pathways that may lead to the enhancement of critical performance parameters such as photocurrents, photovoltage, and fill factor.