Silver-Copper Interfaces: Redefining Co2 Electrocatalysis for Sustainable Syngas Production in Ionic Liquid Electrolyte

Abstract

The CO2 electrochemical reduction has attracted significant attention as an approach to combat climate change and generate economically valuable organic compounds. How to suppress the competing hydrogen evolution reaction is a common challenge in CO2 electroreduction. Copper and its alloys have been acknowledged for their effective catalytic properties in converting CO2 into high-value chemicals. An advanced Ag-Cu/CF catalyst, synthesized via in-situ electroreduction of Ag on a copper foam substrate, has exhibited exceptional performance. In an electrolyte comprising 1-Butyl-3-methylimidazolium tetrafluoroborate ([BMIM]BF4/water/acetonitrile), the catalyst maintained a current density exceeding 180 mA cm-2 and achieved a faradaic efficiency for syngas (CO/H2) production of up to 96% at -2 V vs Ag/AgCl. The high performance was attributed to the role of [BMIM]BF4 as both absorbents and proton donors could stabilize CO2 intermediate with imidazolium cations to form [BMIM]-CO2; the interfaces of Ag-Cu biphasic boundaries are believed to reduce H2 evolution and facilitate the transfer and subsequent reaction of [BMIM]-CO2 complex, in which Ag sites could promote the reduction of CO2 to CO. This investigation provides a fresh perspective on the design of catalytic systems for CO2 electroreduction, emphasizing the strategic importance, composition and structure to enhance the catalyst's selectivity and efficiency in CO/H2 production.

Keywords: Ag-Cu interfaces, CO2 electrochemical reduction, ionic liquid, Syngas