Cooperative Interfacial and Electrolyte Engineering in Au@Cu₂O Core@Shell Nanocatalysts for Efficient CO₂ Reduction...

Developing advanced catalytic systems for efficient electrochemical CO₂ reduction (e-CO₂RR) at industrially relevant current densities under environmentally benign conditions remains challenging. Herein, we report Au@Cu₂O (n) core@shell nanocatalysts with outstanding e-CO₂RR performance at -200 mA cm^-2 in near-neutral media, where the Cu₂O shell thickness is tuned by adjusting Au seed solution volume (n mL). In 1.0 M KHCO₃, the thin-shelled Au@Cu₂O (n = 5) nanocatalyst achieves an exceptional Faradaic efficiency (FE_C2+: 50.6 ± 3.3%) and a cathodic energy efficiency (EE_C2+: 29.1 ± 1.3%) for C₂₊ products, outperforming its thicker counterparts (e.g., Au@Cu₂O (n = 2); FE_C2+: 19.6 ± 2.7%, EE_C2+: 8.9 ± 0.9%) and individual control components. This enhanced performance stems from a strong core@shell electron transfer effect that modulates copper oxidation state (OS_Cu) and preserves the core@shell architecture. Intriguingly, iodide addition triggers divergent, shell-thickness-dependent effects. Iodide modulates both structural reconstruction and OS_Cu of the Au@Cu₂O (n = 2) nanocatalyst, boosting C₂₊ product selectivity (S_C2+) fourfold. Conversely, iodide disrupts the pre-existing, highly favorable core@shell electronic interactions of the Au@Cu₂O (n = 5) nanocatalyst, driving OS_Cu away from the favorable regime and thereby suppressing S_C2+. These findings underscore the importance of cooperatively engineering interfacial electronic properties and electrolyte microenvironments for efficient e-CO₂RR at circumneutral pH.