Controlled Electrodeposition of Photoelectrochemically Active Amorphous MoS_x Cocatalyst on Sb₂Se₃ Photocathode

Amorphous molybdenum sulfide (a-MoSx) is a promising hydrogen evolution catalyst owing to its low cost and high activity. A simple electrodeposition method (cyclic voltammetry) allows uniform formation of a-MoSx films on conductive surfaces. However, the morphology of a-MoSx deposited on a TiO2/Sb2Se3 photocathode could be modulated by varying the starting potential. The cathodically initiated a-MoSx showed conformal filmlike morphology, whereas anodic initiation induced inhomogeneous particulate deposition. The filmlike morphology of a-MoSx was subjected to catalyst activation, which improved the photocurrent density and reduced the charge-transfer resistance at the semiconductor/electrolyte interface, as compared to that of its particulate counterpart. X-ray photoelectron spectroscopy confirmed that different chemical states of a-MoSx (photoelectrochemically active sites) were developed on the basis of the electrodeposited a-MoSx morphology. The research provides an effective approach for uniformly depositing cost-effective a-MoSx on nanostructured photoelectrodes, for photoelectrochemical water splitting.