Synthesis and characterization of direct Z-scheme Bi2MoO6/ZnIn2S4 composite photocatalyst with enhanced photocatalytic oxidation of NO under visible light

In the work, the direct Z-scheme Bi2MoO6/ZnIn2S4 (BMO + x%–ZIS; x = 2, 4, 6, 8, 10) composite semiconductor photocatalysts were successfully constructed by using a simple wet impregnation method. Then the oxidation of NO (~400 ppm) with H2O2 solution injected (0.0075 mL min−1) was used to estimate their photocatalytic performances under visible light. The results indicate that BMO + x%–ZIS composites exhibit enhanced photocatalytic activity, wherein the BMO + 6%–ZIS composite possesses the highest photocatalytic activity (84.94%). The enhanced photocatalytic performance is ascribed to the low rate of recombination of photogenerated electrons and holes and the production and participation of active radical species as confirmed by PL spectra and trapping experiment as well as fluorescence spectra. The existence of H2O2 is also essential in the improvement of the photocatalytic efficiency via production of more active species. The photocatalytic product in the PCO of NO is NO3−, which was detected by ion chromatography. In addition, the mechanism of PCO of NO was discussed detailedly. The results indicate that ·OH plays an important role, but the effect of ·O2− is also crucial in the experiment of PCO of NO system.