Efficient methane oxidation to oxygenates over etched ZnCr layered double hydroxide nanosheets

Abstract

Direct methane oxidation to valuable oxygenates under mild conditions relies on not only the efficient generation of reactive oxygen species, but also the inhibition of the overoxidation reaction. Here we report that alkali etched ZnCr-layered double hydroxide nanosheets enable direct and selective oxidation of methane to liquid oxygenates using H₂O₂ as the oxidant at 50 °C. With a selectivity of >90%, the maximum yield rates of liquid oxygenates can be achieved as high as 23.4 and 30.7 mmol g⁻¹ h⁻¹ at a methane pressure of 20 and 30 bar, respectively, which are much superior to those of most recently reported catalysts. The enhanced performance can be attributed to the synergistic effect between surface Cr species and etching induced defects, wherein the former can efficiently activate H₂O₂ into reactive oxygen species via a Fenton-like process, and the latter containing unsaturated Zn species and oxygen vacancies facilitate the stabilization of the formed radical intermediates.