Electrooxidation of Methane to Ethanol at Large Current Densities on Conductive Zeolite–CuO–ZrO 2 Composite Catalysts

The electrooxidation of methane (CH4) to directly produce high-value ethanol is an attractive strategy to utilize natural gas; however, the current density for CH4 electrooxidation remains low (<10 mA cm–2) due to the chemical inertness of CH4 and its poor adsorption capacity on catalyst surfaces. Herein, we develop a composite catalyst containing conductive zeolite (ZSM-5), CuO, and ZrO2 for CH4 electrooxidation to ethanol. The abundant pore structure and Lewis acid sites of conductive ZSM-5 significantly enhance the CH4 adsorption capacity of the composite catalyst, achieving a 32-fold improvement over oxide catalysts (CuO–ZrO2). Meanwhile, CuO–ZrO2 exhibits strong CH4 activation capability. Benefiting from the synergistic effect of both active components, the current density for CH4 oxidation to ethanol reaches 60 mA cm–2 in the Na2SO4 electrolyte, with the yield reaching 136.51 mmol gcat–1 h–1. Mechanistic studies indicate that CuO oxidizes water to generate a large quantity of hydroxyl radicals (·OH), which then oxidizes adsorbed CH4 to produce a series of intermediates (*CH3, *OCH2, and *OCH2CH3), while the SO42–-adsorbed ZrO2 effectively stabilizes key intermediates and promotes C–C coupling, creating an efficient electrolyte–catalyst reaction interface. This work presents a strategy for enhancing CH4 adsorption and activation capabilities through composite zeolites and metal oxides.