Highly selective aerobic oxidation of methane to methanol over gold decorated zinc oxide via photocatalysis

Abstract

Photodriven CH₄ conversion has been regarded as a promising green strategy for fabrication of value-added commodity chemicals, in particular methanol. However, due to the incomplete transformation of intermediates or the overoxidation of products, a good selectivity of methanol is hard to achieve. Here, we present a highly selective transformation of methane to methanol using gold modified zinc oxide as a photocatalyst under full light spectrum irradiation at atmospheric temperature. The selectivity of methanol can reach 99.1% with a productivity of 1371 μmol g⁻¹. Fine tuning the loading amount of gold nanoparticles (0.75 wt%) and inputting an appropriate light energy are the pivotal factors for selectivity improvement. Besides, in contrast to the reported photocatalytic aerobic CH₄ oxidation on gold modified zinc oxide, we find that both oxygen and water, rather than only molecular oxygen, provide the O-source for methanol formation. This result is verified through ¹⁸O-isotope tests (¹⁸O₂ and H₂¹⁸O), leading to a disparate mechanism.