Selective oxidation of methane to methanol and methyl hydroperoxide over palladium modified MoO3 photocatalyst under ambient conditions

Abstract

Selective partial oxidation of methane to valuable oxygenated products remains a great challenge, as typically over oxidation of oxygenated products to CO_x is observed. Weak oxidative species on the catalyst surface have a great potential to overcome this limitation. However, weak oxidative species usually have low concentrations and are easily decomposed. Here we report a Pd/MoO₃ photocatalyst which can realize excellent methane oxidation to methanol and methyl hydroperoxide in pure water, under simulated solar light by in situ generated H₂O₂ at room temperature and pressure. The combined selectivity for methanol and methyl hydroperoxide is up to 98.6%, representing a productivity rate of 42.5 μmol g_cat⁻¹ h⁻¹. Further studies on the reaction mechanism indicate that PdO species on the Pd loaded MoO₃ catalyst play an essential role in the suppression of over oxidation. In this case PdO traps the photo-generated electrons, leaving photo-generated holes for decomposition of H₂O₂ into weak oxidative hydroperoxyl radicals which are not involved in the formation of over oxidation products.