Transition metal phosphide of nickel and cobalt-modified Zn0.5Cd0.5S for efficient photocatalytic hydrogen evolution with visible light irradiation

Abstract

Transition metal phosphides (TMPs), as an environmentally friendly non-noble metal cocatalyst, play a key role in promoting photocatalytic hydrogen evolution. In this work, three metal phosphating compounds (NiCoP, Ni₂P, and Co₂P) were synthesized by solvothermal method using red phosphorus as a phosphorus source. The three kinds of co-catalysts were individually loaded onto Zn_0.5Cd_0.5S by physical agitation method to form binary nanocomposites (ZnCdS/TMPs). The results showed that the three composite photocatalysts all showed excellent HER performance in the Na₂S/Na₂SO₃ sacrifice solution. Among them, the hydrogen production rate of ZnCdS/NiCoP-5% reached 64 μmol at 5 h, which was significantly higher than that of pure Zn_0.5Cd_0.5S, ZnCdS/Ni₂P-5%, and ZnCdS/Co₂P-5%. According to the results of various characterization techniques, NiCoP nanoparticles provide more active sites for Zn_0.5Cd_0.5S and the composite photocatalytic materials exhibit excellent hydrogen evolution performance. Moreover, the Schottky barrier between Zn_0.5Cd_0.5S and NiCoP nanoparticles effectively enhances the charge separation rate, thus promoting the improvement of photocatalytic hydrogen evolution. Therefore, low-cost transition metal phosphide as a cocatalyst has broad prospects in the field of photocatalysis.