CO2 electroreduction to ratio-tunable syngas with Cu-In-Ag electrodes: from electronic structure regulation to mechanistic understanding

Abstract

Syngas production via green electricity-driven reduction of CO2 (CO2RR) and hydrogen evolution reaction (HER) represents a promising strategy, where ternary metal catalysts have been widely utilized to mediate the competing CO2RR and HER processes. However, the intrinsic mechanism by which electronic structure modulation in ternary metal catalysts governs syngas selectivity remains elusive. Herein, we present a series of ternary Cu-In-Ag catalysts, fabricated via a facile coprecipitation method, for syngas production with tunable H2/CO ratio and high current density. Interestingly, the H2/CO ratio could be precisely tuned from 0.19 to 1.05 through either tailoring the metal composition of the Cu-In-Ag ternary catalyst or adjusting the applied potential. Moreover, combined analysis of X-ray absorption fine structure spectrum (XAFS), in situ attenuated total reflection surface-enhanced infrared absorption spectroscopy (in situ ATR-SEIRAS) and density functional theory (DFT) calculations demonstrates that Ag incorporation triggers electron redistribution in the Cu-In-Ag catalyst: Ag prompt In to donate electrons to Cu, generating electron-rich Cu sites, which enhances CO2 activation, facilitates CO desorption and increases the energy barrier for *H formation, thereby achieving a balance between CO2RR and HER. This work establishes a novel design paradigm for ternary metal catalysts through electronic structure modulation toward sustainable and green syngas production from CO2 electroreduction.