Delafossite CuFeO2 Photocathodes for Photoelectrochemical Water Splitting: Fundamental Properties, Synthesis, and Modification Strategies

Abstract

Delafossite CuFeO2 couples an earth-abundant composition with a 1.3-1.7 eV band gap that straddles the hydrogenevolution potential, positioning it as a leading p-type photocathode. Yet photocurrents rarely exceed 15 % of the theoretical 15 mAcm -2 ceiling because small-polaron transport and Fermi-level pinning limit carrier collection. This Review maps how modern synthesis-from equilibrium powders to non-equilibrium thin-film growth-controls phase purity, point defects and interfacial energetics, and surveys bulk-doping, nanostructuring, heterojunction and cocatalyst strategies aimed at relieving those intrinsic bottlenecks. We conclude by outlining quantitative design rules and pressing research priorities for pushing CuFeO2 beyond the 10 mAcm -2 milestone and into deployable PEC architectures. This approach not only guides the development of CuFeO2 photocathodes but also offers a new design paradigm for other similar materials in photoelectrochemical applications.