Defects influence photocatalytic NOCM product selectivity by controlling photogenerative carriers

Abstract

Photocatalytic Non-oxidative coupling of methane (NOCM) is a green method to convert methane into high value-added products such as ethane and ethylene by using photogenerated electron-holes. Compared with oxidative coupling of methane (OCM), besides C2 products, H2 is also produced in NOCM process. However, the effect of the photogenerative carriers on the yield and selectivity of photocatalytic NOCM products is still unclear. We tested Au1-ZnO/TiO2 synthesized by NaBH4 reduction and photodeposition in a flowing gas reactor at atmospheric pressure without external heat source. The Au1-ZnO/TiO2-N sample showed a superior C2H6 yield of 0.015 mmol/h accompanied by a small amount of H2 production (1.32 μmol/h). Meanwhile, Au1-ZnO/TiO2-p120 sample shows much higher H2 yield (0.012 mmol/h) and a lower C2H6 yield (4.96 μmol/h). Through varies characterizations, we demonstrated that the selectivity of C2H6 and H2 are highly related to photogenerative carriers. We propose that defects affect the degree of peroxidation in photocatalytic NOCM by controlling the concentration of photogenerated holes.