Efficient electrocatalytic conversion of carbon dioxide in a low-resistance pressurized alkaline electrolyzer

Abstract

Electrochemical carbon dioxide conversion offers a means to utilize carbon dioxide and simultaneously store excess renewable energy. To be economical, industrial carbon dioxide electroreduction systems require high energy efficiencies to minimize electrical input. To this end, these systems need high product selectivity at low cell voltages and industrially viable current densities. Here, a liquid phase flow cell electrolyzer using a silver catalyst for carbon dioxide conversion to carbon monoxide is reported. Significant improvements in cell efficiency are demonstrated through the synergistic combination of three factors: minimal electrode spacing (0.25 mm flow field), pressurization (50 bar), and alkalinity (5 M KOH). Diminished electrode spacings reduce ohmic losses, pressurization increases carbon monoxide selectivities, and alkaline conditions improve reaction kinetics. The combination of these three factors enables an uncorrected full cell energy efficiency of 67% at 202 mA/cm2, the highest reported above 150 mA/cm2. This system maintains a competitive energy efficiency of 47% at a high current density of 941 mA/cm2.