Optimization of light response and electron redistribution of active sites by structuring CoS2/MoS2/Ni3S2 heterojunction for highly efficient photo-assisted oxygen evolution

Highly efficient photoelectrocatalysts become one of the current research hotspots for overall water splitting, the design of heterojunctions with a wide response range to sunlight and efficient separation and migration of photogenerated carriers is challenging. Herein, a nanorod CoS2/MoS2/Ni3S2 photoelectrocatalyst with heterojunction is prepared by a one-step hydrothermal method. Under simulated solar irradiation, CoS2/MoS2/Ni3S2 exhibits excellent photoelectrocatalytic activity for OER, with overpotential of 166 mV and the cell voltage of 1.464 V at 10 mA cm-2, and the catalytic performance exhibited a slight decline after 12 hours of stable operation. In addition the STH efficiency reaches 6.6 %. Experiments and DFT calculations demonstrate that CoS2 as a photoactive layer optimizes the light absorption properties of catalyst. Additionally, MoS2 as a co-catalyst modulates the d-band centers and the electronic structure of Co active site, reducing the energy barrier of the ratedetermining step. Meanwhile, the II-type heterojunction formed by CoS2 and MoS2 can effectively promote the separation and migration of photo-generated carriers, which further enhances the photoelectrocatalytic OER performance. This work provides a novel insight to design photoelectrocatalysts with transition metal sulfide heterojunction for overall water splitting.