Sulfur vacancies and a Ni2P co-catalyst synergistically boost the photocatalytic H2 evolution of Zn0.5Cd0.5S

Abstract

Improving the separation efficiency of photo-generated electron–hole pair is a key issue in the field of photocatalytic hydrogen production. In this work, we successfully improved the efficiency of photo-generated carrier separation using the synergistic action of sulfur (S) vacancies and a Ni₂P co-catalyst. Vs-Zn_0.5Cd_0.5S (Vs-ZCS) with S vacancies was designed and constructed, and Vs-ZCS/Ni₂P photocatalysts were prepared with non-precious metal Ni₂P as a co-catalyst. Among all the produced materials, Vs-ZCS/Ni₂P-5% has a photocatalytic characteristic of 40.81 mmol g⁻¹ h⁻¹, which is 7.88, 3.08 and 3.75 times greater than those of ZCS (5.18 mmol g⁻¹ h⁻¹), Vs-ZCS (13.25 mmol g⁻¹ h⁻¹) and ZCS/Ni₂P-5% (10.88 mmol g⁻¹ h⁻¹), respectively. The results of transient photo-current, electrochemical impedance spectroscopy, photoluminescence and time-resolved fluorescence show that the synergistic effect of S vacancies and Ni₂P significantly promotes the separation and transfer efficiency of photo-generated carriers, as well as the photocatalytic hydrogen production reaction. Superoxide radicals and electrons are the active species for photocatalytic hydrogen generation, which is confirmed by active species capture tests and EPR. This study presents an innovative approach for developing photocatalysts with low cost and good catalytic performance.