Exploring the photoelectrocatalytic performance of spinel- and delafossite-like CuMM’O4 (M, M’ = Al, Ga, In) obtained from pseudobinary CuMO2-based solid solution

In this study, the focus revolves around the synthesis, characterization, and subsequent evaluation of CuMM’O 4 (M, M’ = Al, Ga, In) photoelectrocatalysts, notable for their distinct spinel- and delafossite-like structures. These novel materials are derived from a pseudobinary CuMO 2 -based solid solution. Specifically, the delafossite-like CuAlInO 4 and CuGaInO 4 manifest a trigonal superstructure within the R 3 ‾ m $R\bar{3}m$ space group, defined by structural motifs comprising [InO 6 ] octahedra, [CuO 5 ] hexahedra, and [AlO 5 ] or [GaO 5 ] hexahedra. This study spans a comprehensive analysis encompassing optical properties, electrical characteristics, electronic structure, and the ensuing photoelectrochemical performancer. This exploration integrates experimental analyses and density functional theory calculations to discern the intricacies of these materials. The assessed CuMM’O 4 samples display favorable optical traits and band-edge positions conducive to facilitating visible-light-driven photoelectrochemical water-splitting. Among the evaluated samples, the delafossite-like CuGaInO 4 photocathode stands out due to its notably elevated carrier density and reduced resistance for carrier transport, distinguishing it from CuAlGaO 4 and CuAlInO 4 . Consequently, it exhibits superior photoelectrochemical activity. CuGaInO 4 , serving as an unadorned photocathode, demonstrates a noteworthy photocurrent density of 8.6 μA/cm 2 under 0.61V RHE and 102.05 μA/cm 2 at 0.15 V RHE . Moreover, it achieves a peak incident photon-to-current efficiency of approximately 1.86 % at 0.61 V RHE under a 480 nm wavelength.