Oxygen vacancies induced special CO2 adsorption modes on Bi2MoO6 for highly selective conversion to CH4

Search for suitable photocatalysts with ultrahigh selective generation of CH4 from CO2 is a great challenge in artificial photocatalysis. Herein, effective CO2 photoconversion to CH4 with high selectivity up to 96.7% is achieved over oxygen-deficient Bi2MoO6 under visible-light. Various characterizations and DFT calculations indicated that well-designed oxygen vacancies (OVs) on the {001} surface of Bi2MoO6 can not only enhance light harvesting and e−-/h+ separation, but favor CO2 adsorption in a special bidentate carbonate mode, which thermodynamically supports the further hydrogenation of intermediate *CO to generate CH4. Based on the in-situ infrared spectroscopy analysis, the CO2 adsorption modes and reaction intermediates of two pathways over Bi2MoO6 with or without OVs were figured out. The reasonable photocatalytic mechanism for highly selective conversion to CH4 was also proposed. This work provides new insights to the role of OVs in selective CO2 photoconversion, and paves ways to design efficient CH4 evolution systems.