Dual Active Sites Decorated Tungsten Trioxide for Photocatalytic Methane Oxidation

This study puts forward a dual-active-site mechanism that makes use of nickel-cluster-decorated tungsten oxide catalysts for the efficient oxidation of methane to formaldehyde. Lattice oxygen oxidizes methane following an active site mechanism. Simultaneously, nickel clusters facilitate formaldehyde formation through a radical mechanism.

Abstract

Photocatalytic oxidation of methane to formaldehyde offers an appealing pathway for utilizing the abundant methane resource, nevertheless, suffering from poor formaldehyde formation rate and selectivity. Here, nickel cluster decorated tungsten trioxide of three high surface energy facets is prepared for photocatalytic methane oxidation to formaldehyde with yield rate of 3.27 mmol g⁻¹ h⁻¹, selectivity of 98.2% and turnover number of 20.65. The dual photohole centers of nickel cluster and lattice oxygen both could activate methane for selective formaldehyde formation. The lattice oxygen involves whole methane oxidation process on the catalyst surface based on an active site mechanism, while nickel cluster promotes formation of methyl radical and facilitates a radical mechanism in aqueous phase near the surface. These dual active sites provide an effective strategy to oxidize methane to formaldehyde under photoirradiation with water and oxygen gas.