Molecular electrocatalysts can mediate fast, selective CO reduction in a flow cell.

Practical electrochemical carbon dioxide (CO) conversion requires a catalyst capable of mediating the efficient formation of a single product with high selectivity at high current densities. Solid-state electrocatalysts achieve the CO reduction reaction (CORR) at current densities ≥ 150 milliamperes per square centimeter (mA/cm), but maintaining high selectivities at high current densities and efficiencies remains a challenge. Molecular CORR catalysts can be designed to achieve high selectivities and low overpotentials but only at current densities irrelevant to commercial operation. We show here that cobalt phthalocyanine, a widely available molecular catalyst, can mediate CO to CO formation in a zero-gap membrane flow reactor with selectivities > 95% at 150 mA/cm The revelation that molecular catalysts can work efficiently under these operating conditions illuminates a distinct approach for optimizing CORR catalysts and electrolyzers.