Light-induced formation of MoOxSy clusters on CdS nanorods as cocatalyst for enhanced hydrogen evolution.

Metal and metal oxide particles are commonly photodeposited on photocatalysts by reduction and oxidation reactions, respectively, consuming charges that are generated under illumination. This study reveals that amorphous MoOxSy clusters can be easily photodeposited at the tips of CdS nanorods (NRs) by in situ photoreduction. The as-prepared MoOxSy-decorated CdS samples were characterized by SEM, TEM, XPS and ICP to determine the composition and possible formation pathways of the amorphous MoOxSy clusters. The MoOxSy-tipped CdS samples exhibited better hydrogen evolution performance than pure CdS under visible-light illumination. The enhanced activity is attributed to the formation of intimate interfacial contact between CdS and the amorphous MoOxSy clusters, which facilitates the charge separation and transfer. Through time-resolved photoluminescence (TRPL) measurements, it was clearly observed that all MoOxSy-decorated CdS samples with different loadings of MoOxSy showed faster PL decay when compared to pure CdS, resulting from the effective trapping of photogenerated electrons by the MoOxSy clusters. Kelvin probe force microscopy (KPFM) was further used to study the surface potentials of pure CdS NRs and MoOxSy-decorated CdS NRs. A higher surface potential on MoOxSy-decorated CdS NRs was observed in the dark, indicating that loading of MoOxSy resulted in a lower surface work function compared to pure CdS NRs. This contributed to the effective electron trapping and separation, which was also reflected by increased photoelectrochemical response. Thus, this study demonstrates the design and facile synthesis of tip-decorated CdS NRs photocatalysts for efficient solar hydrogen production.