Electrocatalytic Conversion of Methane to Ethanol via Promoted <sup>•</sup>OH Generation in Aqueous Electrolyte
Ang Li, Huiying Qiu, Zhaohui Wang, Yanzhi Sun, Yang Tang, Pingyu Wan, Haomin Jiang, Yongmei Chen
Abstract
Converting methane (CH 4 ), 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 Cu 2 O/CuO for electrochemical conversion of methane into ethanol (CH 3 CH 2 OH). Density functional theory calculations demonstrated that the Cu 2 O/CuO interface enables efficient CH 4 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 CH 4 is converted to CH 3 CH 2 OH by reaction with active oxygen species ( • OH radicals) electrogenerated in situ through the water oxidation reaction over Cu 2 O/CuO on the anode. Under the optimized conditions, a Faraday efficiency (FE) of 21.1% and a production rate of 126.7 μmol g cat –1 h –1 at ambient pressure for CH 3 CH 2 OH 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 g cat –1 h –1 with an FE of 69.2% was obtained due to the higher solubility of CH 4 in aqueous solution.