d–π Conjugation-Driven Electronic Structure Engineering: Stabilizing Critical Intermediates on AuCu₁/PPy for CO₂ Electroreduction

The electrochemical carbon dioxide reduction reaction (CO₂RR) offers a route to store renewable electricity as value-added chemicals. However, designing electrocatalysts with high selectivity and stability remains a significant challenge. Here, an elaborate catalyst, AuCu₁ supported on polypyrrole (defined as AuCu₁/PPy), synthesized via an electrodeposition-galvanic replacement reaction, featuring d–π conjugation, demonstrates exceptional performance for CO₂-to-CO conversion. With atomically isolated Cu sites confirmed by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and X-ray absorption spectroscopy, the AuCu₁/PPy catalyst modulates both electronic configuration and spatial immobilization of Au active sites, yielding 99.16% CO faradaic efficiency (FE) with sustained stability over 30 h at −0.6 V versus the reversible hydrogen electrode (RHE), representing 1.83-fold and 8.57-fold improvements in FE and stability compared to the control catalyst Au/PPy. In situ Raman experiments and density functional theory calculations reveal that isolated Cu promotes uniform Au growth, further modulating and stabilizing the *CO₂^–/*COOH intermediate adsorption via d–π conjugation. Concurrently, the delocalized electronic structure enhances charge transfer, lowering activation barriers for *CO formation by 58%. Critically, d–π conjugation regulates electronic and geometric structures of Au nanoparticles, reducing the energy barrier to superior selectivity and durability. This work constructs a metal-coupled polymer electrocatalyst to decipher the mechanistic role of d–π conjugation in the CO₂RR, which may provide new insights for the rational design of advanced catalysts.