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

The electrooxidation of methane (CH 4 ) to directly produce high-value ethanol is an attractive strategy to utilize natural gas; however, the current density for CH 4 electrooxidation remains low (<10 mA cm –2 ) due to the chemical inertness of CH 4 and its poor adsorption capacity on catalyst surfaces. Herein, we develop a composite catalyst containing conductive zeolite (ZSM-5), CuO, and ZrO 2 for CH 4 electrooxidation to ethanol. The abundant pore structure and Lewis acid sites of conductive ZSM-5 significantly enhance the CH 4 adsorption capacity of the composite catalyst, achieving a 32-fold improvement over oxide catalysts (CuO–ZrO 2 ). Meanwhile, CuO–ZrO 2 exhibits strong CH 4 activation capability. Benefiting from the synergistic effect of both active components, the current density for CH 4 oxidation to ethanol reaches 60 mA cm –2 in the Na 2 SO 4 electrolyte, with the yield reaching 136.51 mmol g cat –1 h –1 . Mechanistic studies indicate that CuO oxidizes water to generate a large quantity of hydroxyl radicals (·OH), which then oxidizes adsorbed CH 4 to produce a series of intermediates (*CH 3, *OCH 2, and *OCH 2 CH 3 ), while the SO 4 2– -adsorbed ZrO 2 effectively stabilizes key intermediates and promotes C–C coupling, creating an efficient electrolyte–catalyst reaction interface. This work presents a strategy for enhancing CH 4 adsorption and activation capabilities through composite zeolites and metal oxides.