Modulating Surface State of Cu Catalyst by Ga-doped Enables Tunable CO2 Electroreduction to Syngas over Wide Potential Window

Abstract

Electrochemical CO2 reduction reaction (CO2RR) to syngas offers a powerful strategy for sustainable chemical production. Achieving syngas with tunable CO/H2 ratios within a wide potential window is highly desirable but challenging. Here, by doping Ga into Cu2(OH)2CO3 to engineer interfacial hydrophobicity and electronic structure, we effectively controlled CO and H2 production during CO2 electroreduction. We tuned the CO/H2 ratio from 0.15 to 2.1, achieving maximum 100% syngas production in a wide potential window (-0.6 to -1.8 V vs. RHE). Various characterization techniques, including in situ attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) and in situ electrochemical impedance spectroscopy (EIS), revealed that appropriate Ga doping into Cu2(OH)2CO3 facilitates CO2 mass transfer at the catalyst surface, thereby enhancing CO2RR activity. In contrast, when the Ga doping ratio reached 1.0, excessive surface hydrophobicity hinders CO2 reduction but facilitates hydrogen evolution reaction (HER). Moreover, the Ga-induced modulation of Cu+/Cu2+ ratio further exerts a synergisitic effect on C2+ product selectivity. Additionally, as the Ga doping increased, *CO binding configuration shifted from linearly bonded to bridge-bonded, revealing the reaction pathway. This versatile control of the CO/H2 ratio in CO2RR offers significant opportunities for the direct transformation of CO2 into syngas.