Designing Cu-Based Tandem Catalysts for CO2 Electroreduction Based on Mass Transport of CO Intermediate

Electrochemical reduction of CO2 to high-value hydrocarbons and oxygenates is an attractive technique to store intermittent renewable energy. Diverse catalysts are capable of catalyzing the CO2 to CO conversion, while further reduction of CO occurs almost exclusively on Cu. Monocomponent Cu catalysts suffer from the high overpotential and low Faradaic efficiency of hydrocarbons and oxygenates. Combining CO2 to CO conversion on Au, Ag, single-atom catalysts, etc., with CO reduction on Cu is a promising strategy to achieve high selectivity and a high formation rate of highly reduced products. Numerous tandem catalysts have been developed based on this idea, and the mass transport of a CO intermediate from a CO-formation catalyst to Cu is the key factor that needs to be considered in the design of tandem catalysts. Rational analysis of the different modes of CO mass transport in the reported designs is needed for further development of tandem catalysts for CO2 reduction. In this review, we elucidate how the spatial distribution of the CO-formation catalyst and Cu determines the mode of CO mass transport and consequently affects the utilization efficiency and reduction rate of the CO intermediate. We also discuss the challenges and perspectives in understanding the interaction between the CO-formation catalyst and Cu and improving their catalytic performance in the CO2 tandem reduction.