CdS enhanced ethanol selectivity in electrocatalytic CO2 reduction at sulphide derived Cu-Cd.

The development of Cu-based catalysts for the electrochemical CO2 reduction reaction (eCO2RR) is of major interest for generating commercially important C2 liquid products such as ethanol. Cu is exclusive among the eCO2RR metallic catalysts in that it facilitates the formation of a range of highly reduced C2 products, with a reasonable total faradaic efficiency but poor product selectivity. We report here the development of a series of new sulphide-derived copper-cadmium catalysts (SD-CuxCdy). An excellent faradaic efficiency of ~32% but with a relatively low current density of -0.6 mA cm-2 for ethanol was obtained using the SD-CuCd2 catalyst at the relatively low overpotential of 0.89 V in a CO2 saturated aqueous 0.10 M KHCO3 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 CO2 was greatly enhanced. Ex situ spectroscopic and microscopic, and voltammetric investigations point to the role of abundant phase boundaries between CdS and Cu+/Cu sites in the SD-CuCd2 catalyst in enhancing the selectivity and efficiency of ethanol formation at low potentials.