Selective proton-coupled electron transfer engineering between CuxIny alloy and polyoxometalate medium for efficient CO2 electroreduction to CO

Polyoxometalates (POMs) are promising electrolyte additives to promote the electrocatalytic CO₂ reduction reaction (ECO₂RR) at the electrode/electrolyte interface, but the pure metal electrode’s severe oxidation caused by POM’s proton-coupled electron transfer (PCET) characteristic remains unfavorable for ECO₂RR. Herein, three new Cu_xIn_y alloys with different element ratios (1:1, 2:3, and 1:3) were prepared by the one-step reduction method. The effects of PCET behavior between the as-prepared alloys and a Keggin-type POM (PV₂MoW₉) on ECO₂RR performance were explored. Among prepared alloys, Cu₁In₃ shows the highest Faradic efficiency of CO (FE_CO) of 95.3% at −0.25 V (vs. RHE) in POM medium. The experimental results suggest greatly enhanced reaction kinetics in the presence of PV₂MoW₉. In-situ surface enhanced Raman data reveal the highly affected performance of ECO₂RR by the sequential PCET behavior between PV₂MoW₉ and Cu_xIn_y alloy. As a “sacrificial agent”, the initially generated In₂O₃ assists in segregating Cu atoms on the alloy surface, thereby promoting the process ECO₂RR → CO. From the perspective of electrode-electrolyte interaction, this work proposes a new strategy to adjust the ECO₂RR reaction pathway through rational design of alloy element composition.