Highly Selective Syngas Production via CO2 Electroreduction on Gas-Induced Surface-Reconstructed Zn Electrodes

Abstract

The generation of syngas through the electrochemical CO2 reduction reaction (eCO2RR) is a compelling approach for reaching carbon neutrality. However, the scarcity of cost-effective and high-performance electrodes makes it difficult to attain a wide range of CO/H2 ratios under high current density conditions. Herein, we report two Zn electrodes (r-ZnO-pc/Zn-CO2 and r-ZnO-pc/Zn-N2) engineered through a facile gas-induced surface reconstruction strategy. This process involved the initial deposition of a ZnO pre-catalyst on Zn foil substrate (ZnO-pc/Zn), followed by its subsequent electrochemical reduction under controlled gas atmospheres (CO2 or N2). By tuning the reduction atmosphere, the morphology and defect concentration of the electrode could be modulated to tailor its catalytic performance for the eCO2RR. Attributed to its thinner nanosheets and abundant defect sites, the CO2-induced r-ZnO-pc/Zn-CO2 electrode exhibited exceptional activity for syngas production in an ionic liquid-based electrolyte. Specifically, it achieved a remarkable Faradaic efficiency for CO of 98.6% at -1.9 V vs. Ag/Ag+. The CO/H2 ratio was also widely tunable from 0.8 to 12.5 across the potential window of -1.7 V to -2.3 V vs. Ag/Ag+, and a high current density of 115.8 mA·cm-2 was attained at the CO/H2 ratio of ~1. Electrochemical characterizations further revealed that the r-ZnO-pc/Zn-CO2 electrode possessed a larger electrochemically active surface area, a faster charge transfer rate, and a stronger binding affinity for the key CO2•- intermediate. These advantageous properties collectively accelerated the eCO2RR kinetics, leading to the significantly enhanced syngas production. This work offers a novel strategy for designing gas-induced surface-reconstructed electrodes, paving a new avenue for high-efficiency syngas synthesis from the eCO2RR.