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Converting methane (CH4), the greenhouse gas, into high-value liquid oxygenates by an electrochemical method under mild conditions is a desired technology for establishing an energy- and environment-sustainable society. However, challenges from the competition of the oxygen evolution reaction and selectivity of the desired products still exist. Here we report the catalytic performance of Cu2O/CuO for electrochemical conversion of methane into ethanol (CH3CH2OH). Density functional theory calculations demonstrated that the Cu2O/CuO interface enables efficient CH4 adsorption, which provides an effective pathway for methane utilization under mild conditions. Based on electrochemical studies and electron paramagnetic resonance (EPR) measurement results, it is confirmed that the activated CH4 is converted to CH3CH2OH by reaction with active oxygen species (•OH radicals) electrogenerated in situ through the water oxidation reaction over Cu2O/CuO on the anode. Under the optimized conditions, a Faraday efficiency (FE) of 21.1% and a production rate of 126.7 μmol gcat–1 h–1 at ambient pressure for CH3CH2OH production were obtained, and the FE remained ∼19.0% at 2.2 V cell voltage during 8 h of electrolysis. When the pressure in the bath was lifted to 4.0 bar, the production rate of 441.3 μmol gcat–1 h–1 with an FE of 69.2% was obtained due to the higher solubility of CH4 in aqueous solution.
Li et al. (Tue,) studied this question.