Modulating the surface state of Cu catalysts by Ga doping enables tunable CO2 electroreduction to syngas over a wide potential window

Abstract

The electrochemical CO₂ reduction reaction (CO₂RR) to produce syngas offers a powerful strategy for achieving 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 the 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 a 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 reaches 1.0, excessive surface hydrophobicity hinders CO₂ reduction but facilitates the hydrogen evolution reaction (HER). Moreover, the Ga-induced modulation of the Cu⁺/Cu²⁺ ratio further exerts a synergistic effect on C₂₊ product selectivity. Additionally, as the Ga doping increases, the *CO binding configuration shifts from linearly bonded to bridge bonded, revealing the reaction pathway. This versatile control of the CO/H₂ ratio in the CO₂RR offers significant opportunities for the direct transformation of CO₂ into syngas.