Hierarchical fabrication of hollow CoP nanocages coated with ZnInS thin layer: Highly efficient noble-metal-free photocatalyst for hydrogen evolution.

The directional synthesis of transition metal phosphides was considered to be an effective strategy to solve the overdependence of noble metals on photocatalytic hydrogen evolution (PHE) reactions. Inspiringly, this work reported a facile method for constructing hollow CoP nanocages (CoP NCGs) that derived from ZIF-67 by calcining and phosphiding procedure in nitrogen atmosphere to act as non-noble metal cocatalysts. Followed with further coating thin-layered ZnInS (ZIS) on the surface of CoP NCGs through a hydrothermal reaction, the hierarchical robust CoP/ZnInS nanocages (CoP/ZIS NCGs) were then delicately fabricated as efficient photocatalysts for PHE reactions. The uniquely hollow structure of CoP NCGs largely diffused the photogenerated chargers that induced from ZIS and the closely interfacial contact significantly promoted the separation and transfer of electrons from ZIS to CoP according to density functional theory (DFT) calculation, synergistically resulting in an efficient hydrogen generation performance. PHE results showed that an efficient H evolution rate of 7.93 mmol/g/h over 10% CoP/ZIS NCGs was achieved, about 10 times higher than that of pristine ZnInS. More importantly, the hierarchically hollow CoP/ZIS NCGs exhibited ascendant PHE activity in comparison with that of 1% noble metal (Pt, Au, Ag) loaded ZnInS with superior sustainability, all indicating the efficient and stable photocatalysts of CoP/ZIS NCGs for PHE reactions.