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'O4 (M, M' = Al, Ga, In) photoelectrocatalysts, notable for their distinct spinel- and delafossite-like structures. These novel materials are derived from a pseudobinary CuMO2-based solid solution. Specifically, the delafossite-like CuAlInO4 and CuGaInO4 manifest a trigonal superstructure within the R3‾m space group, defined by structural motifs comprising [InO6] octahedra, [CuO5] hexahedra, and [AlO5] or [GaO5] 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'O4 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 CuGaInO4 photocathode stands out due to its notably elevated carrier density and reduced resistance for carrier transport, distinguishing it from CuAlGaO4 and CuAlInO4. Consequently, it exhibits superior photoelectrochemical activity. CuGaInO4, serving as an unadorned photocathode, demonstrates a noteworthy photocurrent density of 8.6 μA/cm2 under 0.61VRHE and 102.05 μA/cm2 at 0.15 VRHE. Moreover, it achieves a peak incident photon-to-current efficiency of approximately 1.86 % at 0.61 VRHE under a 480 nm wavelength.