Low-Voltage Acidic CO2 Reduction Enabled by a Diaphragm-Based Electrolyzer

Abstract

Large-scale implementation of electrochemical CO2 conversion to value-added products is currently hampered by high electrolyzer cell voltages, resulting in low energy efficiency and high operating costs. Cell voltages are typically well above 3 V and need to be significantly lowered whilst maintaining current densities greater than 200 mA cm−2 to enable energy-efficient CO2 electroreduction. This can be addressed through modification of the resistive components of the device to reduce energy consumption and lower operating costs. Electrodes, electrolyte solutions, and the separator between compartments, provide the largest contributions to the overall cell voltage, therefore decreasing their resistance can lower the electricity input required to drive effective CO2 conversion. Here, by careful analysis and tuning of the various sources of voltage drops within the cell, an optimized diaphragm-based CO2R device is presented, which is able to operate at an industrially relevant current density of 200 mA cm−2 with an |Ecell| as low as 2.89 V, amongst the lowest reported values to date.