CdS‐Enhanced Ethanol Selectivity in Electrocatalytic CO2 Reduction at Sulfide‐Derived Cu−Cd

Abstract The development of Cu‐based catalysts for the electrochemical CO 2 reduction reaction (eCO 2 RR) is of major interest for generating commercially important C 2 liquid products such as ethanol. Cu is exclusive among the eCO 2 RR metallic catalysts in that it facilitates the formation of a range of highly reduced C 2 products, with a reasonable total faradaic efficiency but poor product selectivity. Here, a series of new sulfide‐derived copper‐cadmium catalysts (SD‐Cu x Cd y ) was developed. An excellent faradaic efficiency of around 32 % but with a relatively low current density of 0.6 mA cm −2 for ethanol was obtained using the SD‐CuCd 2 catalyst at the relatively low overpotential of 0.89 V in a CO 2 ‐saturated aqueous 0.10 m KHCO 3 solution with an H‐cell. The current density increased by an order of magnitude under similar conditions using a flow cell where the mass transport rate for CO 2 was greatly enhanced. Ex situ spectroscopic and microscopic, and voltammetric investigations pointed to the role of abundant phase boundaries between CdS and Cu + /Cu sites in the SD‐CuCd 2 catalyst in enhancing the selectivity and efficiency of ethanol formation at low potentials.