Selective CH4 reform to methanol through partial oxidation over Bi2O3 at room temperature and pressure

Abstract

Herein, we propose that an efficient CH4 partial photooxidation to methanol depends on appropriate band edge positions in photocatalysts. We demonstrated our hypothesis using Bi2O3 since this semiconductor have a valence band favorable to produce •OH and a conduction band not advantageous to O2•- which is crucial to keep O2 available for •CH3 capture and CH3OH formation. A notably and selective partial photooxidation of methane to methanol was observed under visible light at room temperature and pressure. As a result, the productivity of methanol over Bi2O3 can reach approximately 3771 μmol g−1 h−1 with c.a. 65% selectivity avoiding overoxidation to CO2. Isotope labeling experiment (13CH4) confirmed that methane acts as the carbon source of methanol and ESR measurements proved the •CH3 and •OH generation. Besides, Bi2O3 exhibited good stability after 5 cycles maintaining a high and selective methanol production. These results provide insight into critical photocatalyst properties for the partial photooxidation of methane to methanol.