Delafossite-type CuGaO2 particulate photocathode synthesized via molten salt method for efficient and stable solar water splitting

Abstract

With the growing demand for renewable energy, photoelectrochemical (PEC) water splitting has emerged as a promising method for hydrogen production. CuGaO₂ is a highly attractive photocathode material due to its positive onset potential, high photovoltage, and ability to absorb visible light via valence band engineering. However, most CuGaO₂ materials suffer from poor crystallinity and oxygen vacancies, which hinder PEC performance. In this study, we synthesized micron-sized prism-shaped CuGaO₂ (MP-CGO) using a novel molten salt method. The MP-CGO photocathode achieved a photocurrent density of 1.2 mA cm⁻² with stability over 6 h, surpassing the performance of materials prepared by hydrothermal methods. This improvement is attributed to enhanced crystallinity and the elimination of defects, which increase carrier concentration, accelerate charge transport, and improve onset potential. Furthermore, MP-CGO, when loaded with Pt cocatalysts, efficiently facilitated hydrogen production. These findings lay a strong foundation for the development of CuGaO₂-based and ternary oxide photocathodes.