The carbon balance during high-rate CO ₂ reduction in flow electrolyzers was rigorously analyzed, showing that CO ₂ consumption should be taken into account for evaluating catalytic selectivity of gas products.

Electrochemical CO₂ reduction (CO₂R) is an attractive option for storing renewable electricity and for the sustainable production of valuable chemicals and fuels. In this roadmap, we review recent progress in fundamental understanding, catalyst development, and in engineering and scale-up. We discuss the outstanding challenges towards commercialization of electrochemical CO₂R technology: energy efficiencies, selectivities, low current densities, and stability. We highlight the opportunities in establishing rigorous standards for benchmarking performance, advances in in operando characterization, the discovery of new materials towards high value products, the investigation of phenomena across multiple-length scales and the application of data science towards doing so. We hope that this collective perspective sparks new research activities that ultimately bring us a step closer towards establishing a low- or zero-emission carbon cycle.

In this work, the highly selective and stable electrocatalytic reduction of CO2 to CO on nanostructured Ag electrocatalysts is presented. The Ag electrocatalysts are synthesized by the electroreduction of Ag2CO3 formed by in-situ anodic-etching of Ag foil in a KHCO3 electrolyte. After 3 min of this etching treatment, the Ag2CO3-derived nanostructured Ag electrocatalysts are capable of producing CO with up to 92% Faradaic efficiency at an overpotential as low as 290 mV, which surpasses all the reported Ag catalysts at identical conditions to date. In addition, the anodic-etched Ag retained ~90% catalytic selectivity in the electroreduction of CO2 to CO for more than 100 hours. The Ag2CO3-derived Ag is able to facilitate the activation of CO2 via reducing the activation energy barrier of the initial electron transfer and provide an increased number of active sites, resulting in the dramatically improved catalytic activity for the reduction of CO2 to CO.