MoS2 Catalysts Selectively Achieve High Yield of Liquid Oxygenate from Direct Conversion of Methane via Hydroxyl Radicals

Abstract

Directly converting methane (CH4) into liquid oxygenates (e.g., methanol) can circumvent the cost and engineering limits of natural gas transportation and storage. However, oxygenate yields from CH4 remain low, and sulfur present in natural gas hinders activity in most catalysts. To overcome these barriers, we employ bulk molybdenum disulfide (MoS2), a low-cost, robust catalyst which selectively produces large quantities of liquid oxygenates (>900 µmol/gcat∙hr) from methane in the presence of hydroxyl (OH•) radicals produced from dilute hydrogen peroxide (H2O2) at 75°C. Under realistic reaction conditions, MoS2 partially and reversibly adopts a metastable, more electrically conductive phase (1T’) that can only be observed through in situ structural probes. Herein, we elucidate that redox synergy between H2O2 and MoS2 produces active OH• radical species that selectively transform CH4 to surface methoxy species at the gas-solid liquid interface, leading to the unitary production of liquid oxygenate at a rate competitive with more costly precious metal catalysts, without additional catalyst preparation steps.