Efficient photocatalytic hydrogen production from formic acid on inexpensive and stable phosphide/Zn3In2S6 composite photocatalysts under mild conditions

Developing an efficient, stable and low-cost photocatalytic hydrogen production from formic acid is a daunting challenge and has attracted the intense interest of many of researchers. In this paper, we report the synthesis of novel composite photocatalysts (Ni2P/Zn3In2S6 (ZIS6) and MoP/ZIS6) and their catalytic performance for H2 production reaction from formic acid under visible light irradiation, in which Ni2P and MoP were used as cocatalysts to enhance hydrogen generation activity of ZIS6. The photocatalytic hydrogen production rates of the optimized 1.5 wt% Ni2P/ZIS6 (45.73 μmol·h−1) and 0.25 wt% MoP/ZIS6 (92.69 μmol·h−1) were 3.5 times and 7.2 times higher than that of the pure ZIS6 (12.88 μmol·h−1), respectively. The apparent quantum efficiency at wavelength λ = 400 ± 10 nm for the two photocatalysts was about 1.8% and 6.4%, respectively. Significantly, it was found that the remarkable improvement of hydrogen production performance is attributed to the introduction of the phosphide cocatalysts, which can serve as a charge separation center and an active site for photocatalytic hydrogen production from the decomposition of formic acid. The reaction mechanism of photocatalytic hydrogen production from formic acid was also proposed.