Electrochemical CO2 reduction to syngas on copper mesh electrode: Alloying strategy for tuning syngas composition

Electrochemical CO2 reduction to synthetic fuels and commodity chemicals using renewable energy offers a promising approach to mitigate CO2 emissions and alleviate energy crisis. Copper-based catalysts show potential for electrochemical CO2 reduction applications, while they face the key challenges of high potential, sluggish kinetics, and poor selectivity. In this work, Cu-Zn, Cu-Co, Cu-Cd, and Cu-In bimetallic catalysts are synthesized via the electrodeposition method for electrochemical CO2 reduction to syngas with adjustable CO/H2 ratios. The bimetallic catalysts are characterized using various techniques to reveal their crystalline structures, morphologies, and elemental compositions. The structure-property-activity relationships of these catalysts are investigated to identify optimal candidates for electrochemical CO2 reduction applications. The findings reveal that the bare Cu mesh catalyst exhibits poor CO2 reduction activity, and the products are dominated by hydrogen evolution reaction (HER). The bimetallic catalysts exhibit improved CO2 reduction performance, with the Cu-Zn and Cu-Cd catalysts showing excellent activity, and the CO/H2 ratio in syngas can be tuned over a wide range by adjusting the applied potential. The Cu-Zn and Cu-Cd catalysts demonstrate outstanding performance with Faradic efficiencies of ∼90 % and ∼80 % towards syngas production with CO/H2 ratios of ∼2.0 and ∼1.5 at −0.81 and −1.01 V vs. RHE, respectively, making the produced syngas suitable for various industrial applications. Stability tests over 450 min show that the Cu-Zn and Cu-Cd catalysts maintain stable catalytic activity, syngas selectivity and CO/H2 ratio, making them robust candidates for syngas production. The results will provide valuable insights into the design of robust catalysts for electrochemical CO2 reduction, offering a promising path toward sustainable syngas production.