In situ revealing C–C coupling behavior for CO₂ electroreduction on tensile strain Pt^δ+–Cu^δ+ dual sites

Engineering the desired dual metal sites to realize C–C coupling of CO₂ is of great importance for the practical applications of CO₂ electroreduction reaction (CER). Herein, an efficient strategy for constructing heterogeneous Pt^δ+–Cu^δ+ dual sites to strengthen the generation and coupling of *CO and *CHO (or *COH) during CER process is presented in this work. The radii-larger Pt not only stabilizes the Cu^δ+ but also induces a tensile strain in Pt^δ+–Cu^δ+ dual sites. The obtained Pt^δ+–Cu^δ+ dual sites achieve a total Faradaic efficiency and current density of C₂ products with 70.9% and 586.9 mA·cm⁻² at – 1.20 V (vs. RHE), which is higher than that of Cu^δ+ single site (55.4%, 286.9 mA·cm⁻²). The in situ attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) reveals that the Pt^δ+–Cu^δ+ dual sites can promote the generation of C₁ intermediates (such as *CO, *COOH, *COH, and *CHO) and C–C coupling. Additional in situ surface-enhanced Raman spectra demonstrate that Pt^δ+–Cu^δ+ dual sites can induce the generation of the high-frequency peak for *CO_atop, thus accelerating the C–C coupling. This work provides a promising avenue for stabilizing and enhancing the performance of Cu^δ+ sites toward CER.