W Single-Atom Catalyst for CH4 Photooxidation in Water Vapor.

Abstract

Solar-driven high-efficiency and direct conversion of methane into high-value-added liquid oxygenates against overoxidation remains a great challenge. Herein, facile and mass fabrication of low-cost tungsten single-atom photocatalysts is achieved by directly calcining urea and sodium tungstate under atmosphere (W-SA-PCN-m, urea amount m= 7.5, 15, 30, and 150g). The single-atom photocatalysts can manage H2 O2 in situ generation and decomposition into ·OH, thus achieving highly efficient CH4 photooxidation in water vapor under mild conditions. Systematic investigations demonstrate that integration of multifunctions of methane activation, H2 O2 generation, and decomposition into one photocatalyst can dramatically promote methane conversion to C1 oxygenates with a yield as high as 4956 µmol gcat -1 , superior to that of the most reported non-precious photocatalysts. Liquid-solid phase transition can induce the products to facilely switch infrom HCOOH to CH3 OH by pulling the catalyst above water with CH3 OH/HCOOH ratio from 10% (in H2 O) to 80% (above H2 O).