Evolutionary mechanism of Ni-ZIF/CdS calcination for efficient photocatalytic hydrogen evolution

Abstract

In this work, we develop Ni/Ni3S2/CdS composite photocatalytic system from annealing of CdS nanosphere coated Ni-ZIF by simple solvothermal method. The Ni/Ni3S2/CdS synthesized after calcination at 700 °C exhibits the best hydrogen evolution performance with an average hydrogen evolution rate of 2104.02 μmol/g/h, which is 152 times higher than that of pure CdS, and external quantum efficiency is 41.9% (λ = 420 nm). Using a series of characterization methods, we revealed that CdS is the photosensitizer, Ni is the catalytic active species, and Ni3S2 formed between Ni and CdS formation plays an important role in charge separation as confirmed by time resolved emission spectroscopy. In addition, the regulation of Ni loading is achieved by changing the annealing time and the molar ratio of Ni salt to CdS. These results demonstrate that Ni/Ni3S2/CdS is a favorable photocatalyst for efficient photocatalytic hydrogen evolution.