Tandem effect at snowflake-like cuprous sulphide interfaces for highly selective conversion of carbon dioxide to formate by electrochemical reduction

Electrochemical carbon dioxide reduction (ECR) is a commercially promising technology to resolve the energy dilemma and accomplish carbon recycling. Herein, a novel electrocatalyst has been investigated to produce formate (HCOOH) highly selectively during ECR by loading SnO 2 @C onto cuprous sulphide (Cu 2 S) to form a triplet effect at the interface. Snowflake-like Cu 2 S significantly enhances the local concentration of carbon dioxide (CO 2 ) and promotes the binding of CO 2 with SnO 2 , and the addition of carbon spheres enhances the electron transport, which is beneficial to the conversion of CO 2 to HCOOH products. The snowflake-like Cu 2 S loaded with 1 wt% SnO 2 @C had an HCOOH Faraday Efficiency of 88% at −1.0 V ( vs. Reversible Hydrogen Electrode, RHE), and the current density for CO 2 reduction was stabilized at 15.6 mA cm −2 , which was much higher than the HCOOH Faraday efficiency (FE) of 31.0% for pure Cu 2 S accompanied by a CO 2 reduction current density of 3.9 mA cm −2 . Combined investigations using in-situ Fourier transform infrared spectroscopy (FT-IR) with in-situ Raman spectra reveal that the active species is Cu + . Cu 2 S/1%SnO 2 @C can effectively promote the adsorption and activation of carbonate and inhibit the production of CO intermediates. The corresponding density functional theory (DFT) demonstrates that Cu 2 S/1%SnO 2 @C can well stabilize the HCOO* intermediate during the ECR process. The interaction between Cu 2 S and SnO 2 @C adjusts the surface electronic distribution and accelerates electron transfer, which efficiently improves CO 2 -to-HCOOH conversion. The result obtained from this work provides a simple and efficient electrocatalyst to enhance the HCOOH selectivity of ECR.