Robust Zn-deposited Cu foil catalysts for stable syngas production from electrochemical CO2 reduction

Electrochemical CO 2 reduction to syngas driven by renewable energy offers a sustainable alternative to conventional fossil-fuel-based processes, while maintaining a stable H 2 /CO ratio under the inherently fluctuating potentials remains a substantial challenge. In this study, a series of supported Zn catalysts are fabricated by electrodepositing Zn onto Cu foil substrates, with a systematic investigation into the effects of deposition current density (−5 to −20 mA/cm 2 ) and deposition time (10 to 20 min) on catalyst structure and performance. Characterization results reveal that, with increasing deposition parameters, Zn species evolve from discrete nanoplates into an interwoven network of wrinkled structures, accompanied by decreased work function and charge transfer resistance. The synthesized catalysts exhibit a favorable balance in activity toward the electrochemical CO 2 reduction reaction (eCO 2 RR) and hydrogen evolution reaction (HER), thereby enabling highly tunable syngas production with H 2 /CO ratios ranging from 0.5 to 5.4. Notably, the Cu-Zn catalysts demonstrate remarkable stability in syngas composition, maintaining a nearly constant H 2 /CO ratio across a wide potential window of −1.11 to −1.41 V vs. reversible hydrogen electrode (RHE). Furthermore, the Cu-Zn-10–10 catalyst exhibits excellent durability under fluctuating voltage conditions over 24 h, highlighting its potential for seamless integration with intermittent green electricity. In-situ attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) and density functional theory (DFT) calculations indicate that the Cu-Zn bimetallic sites moderately enhance *CO adsorption, inhibiting its rapid desorption. Moreover, the energy barriers of eCO 2 RR and HER show little variation with potential, which collectively ensure the stability of the H 2 /CO ratio within the range of −1.11 to −1.41 V vs. RHE.