Electrocatalytic CO2 Reduction to Fuels: Progress and Opportunities

Standard practices are necessary for accurate assessment of catalytic performance for CO2 reduction. Catalyst design efforts aimed at improving the activity of Cu for CO2 reduction have been largely unsuccessful. Opportunities remain for modifying Cu through formation of surface alloys. For practical application of CO2 reduction, transition to gas-fed systems is necessary. Increasing fundamental understanding of surface chemistry will continue to aid the development of efficient CO2 reduction systems. The electrochemical reduction of CO2 remains an appealing option for storing renewable energy in a chemical form. In this review, we assess progress in designing catalysts that convert CO2 to high energy density products. We explain how reaction data can be reported to reflect the intrinsic properties of the catalyst. This analysis shows that limited advances have been made in improving the performance of Cu. We suggest that opportunities remain using bimetallic catalysts that are resistant to dealloying. While aqueous systems are instrumental to developing our understanding of this chemistry, gas-fed systems that operate at high current densities must be developed. Although obstacles remain for practical application of CO2 reduction, advances in fundamental understanding made over the years give reason for optimism. The electrochemical reduction of CO2 remains an appealing option for storing renewable energy in a chemical form. In this review, we assess progress in designing catalysts that convert CO2 to high energy density products. We explain how reaction data can be reported to reflect the intrinsic properties of the catalyst. This analysis shows that limited advances have been made in improving the performance of Cu. We suggest that opportunities remain using bimetallic catalysts that are resistant to dealloying. While aqueous systems are instrumental to developing our understanding of this chemistry, gas-fed systems that operate at high current densities must be developed. Although obstacles remain for practical application of CO2 reduction, advances in fundamental understanding made over the years give reason for optimism. the fraction of total charge used in a specific Faradaic process (to produce a certain product). for reaction to occur, reactants must be transported to and products transported from the catalyst surface. When surface reaction rates become sufficiently high, overall measured rates will be influenced by these transport processes, masking the intrinsic kinetic behavior of the catalyst surface. Under conditions of mass transport limitations, the conditions in the electrolyte (pH, concentration of CO2) near the catalyst surface will differ significantly from the bulk solution. defined by the Tafel equation that relates applied potential and current density,η = a + b log (j), where η is the overpotential or the difference between the electrode potential and the standard potential, a is the exchange current density, b is the Tafel slope, and j is the current density. The Tafel slope quantifies the sensitivity of the current density to the applied potential. In principle, experimentally observed Tafel slopes can be compared with theoretically derived slopes based on a microkinetic model. the number of molecules of a specified product made per catalytic site per unit time. TOFs generally depend on electrode potential, reactant concentration, temperature, etc.