Photocatalytic methane activation by dual reaction sites co-modified WO3

Abstract

Methane (CH4) upgrading into liquid oxygenates under mild conditions is of great significance to sustainable energy and clean environment, whilst holds great challenges of achieving superior activity and selectivity. Herein, tungsten oxide (WO3) modified with palladium (Pd) nanoparticles and oxygen vacancies (OVs) was employed as dual reaction sites to drive CH4 conversion with O2 at room temperature. Optimized Pd0.5-def-WO3 photocatalyst enables almost 33 times improvement in oxygenates production compared with WO3, with a yield of 7018 μmol·g–1·h–1, and a high selectivity of 81% towards primary products (CH3OH and CH3OOH), which is superior to most of the previous reported. In-situ XPS spectra proved Pd nanoparticles were the hole acceptors based on the shift of Pd3d to high binding energy under light irradiation. The in-situ solid-state EPR spectra demonstrate an enhancement of OVs signal which proves the role of OVs as the electron acceptors. Consequently, efficient charge separation has been achieved, contributing to the superior activity and selectivity for CH4 conversion.