Crystalline CdS/Amorphous Cd(OH)2 Composite for Electrochemical CO2 Reduction to CO in a Wide Potential Window.

Electrochemical CO2 reduction is a promising method for converting atmospheric CO2 into valuable low‐carbon chemicals. In this study, a crystalline cadmium sulfide/amorphous cadmium hydroxide composite was successfully deposited on the carbon paper substrate surface by in‐situ chemical bath deposition (named as c‐CdS/a‐Cd(OH)2/CP electrodes) for the efficient electrochemical CO2 reduction to produce CO. The c‐CdS/a‐Cd(OH)2/CP electrode exhibited high CO Faradaic efficiencies (>90 %) under a wide potential window of 1.0 V, with the highest value reaching ~100 % at the applied potential ranging from −2.16 V to −2.46 V vs. ferrocene/ferrocenium (Fc/Fc+), superior to the crystalline counterpart c‐CdS/CP and c‐CdS/c‐Cd(OH)2@CP electrodes. Meanwhile, the CO partial current density reached up to 154.7 mA cm−2 at −2.76 V vs. Fc/Fc+ on the c‐CdS/a‐Cd(OH)2/CP electrode. The excellent performance of this electrode was mainly ascribed to its special three‐dimensional structure and the introduction of a‐Cd(OH)2. These structures could provide more active sites, accelerate the charge transfer, and enhance adsorption of *COOH intermediates, thereby improving the CO selectivity. Moreover, the electrolytes consisting of 1‐butyl‐3‐methylimidazolium tetrafluoroborate and acetonitrile also enhanced the reaction kinetics of electrochemical CO2 reduction to CO. [ABSTRACT FROM AUTHOR]