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 150 g). 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 g_cat ^-1 , superior to that of the most reported non-precious photocatalysts. Liquid-solid phase transition can induce the products to facilely switch in from 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).