Photoelectrochemical Properties of CuFeO₂ Photocathodes Prepared by Pulsed Laser Deposition

Photoelectrochemical (PEC) water splitting using tandem cell devices offers a promising method for generating green hydrogen from solar energy. Developing suitable semiconductor materials is crucial for the cost-effectiveness and scalability of this technology. CuFeO₂ has gained attention due to its narrow bandgap, positive photocurrent onset potential, and earth-abundant nontoxic composition. However, CuFeO₂ photocathode performance is hindered by weak catalytic activity, Fermi level pinning, bulk defect states, and charge carrier localization. In this work, we employ pulsed laser deposition (PLD) to produce high-purity CuFeO₂ thin films with controlled morphology and crystal structure. We optimize the parameters for the PLD process to produce compact and uniform films, minimizing diffuse optical scattering. By doing so, we can accurately determine the absorption coefficient, as well as the direct and indirect band gaps of the films. Our study provides important insights into the carrier dynamics in CuFeO₂ thin films, including localization in the picosecond and nanosecond time scales. Important electrical properties such as the dielectric constant and the flat-band potential are identified. Surface chemical states are elucidated by detailed X-ray photoelectron spectroscopy analyses. In addition, photoelectrochemical tests show promising potential for these films in water splitting. These findings highlight key properties and improvement opportunities for CuFeO₂ films for photoelectrochemical applications. © 2024 The Authors. Published by American Chemical Society.