Highly Selectively Methane Photooxidation to CH₃OH and HCHO over an Integrated Fe₂O₃/WO₃ Heterojunction Greatly Promoted by Iron(III) Chloride

Realizing highly selective and efficient CH4 conversion to CH3OH and HCHO can bring about both energy and environmental benefits and is of great significance for social development. Herein, an integrated Fe2O3/WO3 heterojunction was established and used for CH4 photooxidation to CH3OH and HCHO at ambient temperature. Under optimized experimental conditions, a high CH3OH + HCHO yield of 15.3 mmol g–1 h–1 was achieved with a high selectivity of 97.3%, outperforming most of the current reports so far as we know. This improved catalytic performance could be attributed to the synergy between the Fe2O3/WO3 heterojunction and FeCl3 in solution. Fe3+ served as the electron acceptor and Fenton reactant and together with the formed heterojunction effectively improved carrier separation and ·OH generation. ·OH induced in situ formation of ·Cl. The formed ·Cl then activated CH4 and produced chlorine-containing intermediates CH3Cl/CH2Cl2, which ultimately resulted in the formation of CH3OH and HCHO through CH3Cl/CH2Cl2 hydrolysis and effectively avoided overoxidation. This work demonstrated an effective strategy of converting CH4 to CH3OH and HCHO without peroxidation.