Visualizing highly selective electrochemical CO2 reduction on a molecularly dispersed catalyst

Abstract

Electrochemical CO2 reduction driven by renewable electricity provides a promising strategy for the ambient synthesis of CO. While great efforts were being devoted to developing highly efficient catalysts for electrochemical CO2 reduction reactions (CO2RRs), electrode improvement is another important direction for the real-world application of CO2 conversion. Toward a better understanding on the mechanism of the highly selective CO2RR catalyst on the electrode, an in-situ, high-resolution, and high-speed microscale visualization techniques are applied to observe the generation and detachment of the CO2RR products (CO and H2) on the electrode coated with molecularly dispersed electrocatalyst of methoxy group functionalized nickel phthalocyanine (NiPc-OMe MDE). The catalyst exhibits superb selectivity towards CO formation with Faradic efficiency above 98% from −0.56 V to −0.77 V vs. RHE and approaches 100% at −0.65 V vs. RHE. The CO and H2 bubbles are observed in CO2 and Ar atmosphere, which provide direct evidence for the high selectivity of NiPc-OMe MDE. Additionally, the number of reaction regions and their gas production rate increase as the applied cathodic potential increases. The in-situ optical visualization method employed in the electrochemical test system contributes to better electrode design of the CO2 electrolyzer to accelerate the transition from lab-scale investigation to industrialization.