CO2 Electroreduction to Methane at Production Rates Exceeding 100 mA/cm2

The electrochemical reduction of CO 2 to methane is a promising method to store intermittent renewable energy. Previous research reporting high methane selectivity has relied on H-cells, and total current densities have therefore resided below 50 mA/cm 2, insufficient for industrial applications. Here, we increase the methane production rate by modifying the system so that it functions efficiently in a flow cell configuration. We investigate the impact of the local environment on methane selectivity in flow cells by tuning the choice of electrolyte cation, catalyst thickness, and local pH. We achieve a methane selectivity of 48% ± 4% with a partial current density of 120 ± 10 mA/cm 2, representing a cathodic energy efficiency of 23%. We showcase a stable operation for 14 h.