Visualizing the Destabilization of Carbon Intermediates on Pd Alloys: In Situ SERS Insights for Robust and Tunable Syngas Synthesis

Elucidating the “anti-poisoning” mechanism of palladium (Pd) alloy catalysts in the CO2 reduction reaction (CO2RR) has long been impeded by the lack of direct spectroscopic observation of surface intermediates. Herein, by engineering bifunctional Au@AgPd core–shell nanoreactors with a “borrowing SERS” strategy, we bypass the SERS-inactive limitation of Pd and successfully capture the dynamic evolution of key species. Crucially, in situ spectroscopic monitoring reveals a striking adsorption destabilization phenomenon: Ag doping dramatically weakens the binding affinity of carbon intermediates, thereby suppressing the accumulation of poisoning species (*COOH) on the Pd surface. Corroborated by density functional theory and density of states analysis, this effect is attributed to the downward shift of the Pd d-band center, which modulates the adsorption strength of carbon species to a moderate range. Guided by this molecular-level insight, the optimized catalyst achieves precise synthesis of syngas with widely tunable H2/CO ratios (4.04–0.24) and exceptional stability (>60 h), providing a robust paradigm for rationally designing CO-tolerant catalysts.