Defect-Engineered Cu-Based Nanomaterials for Efficient CO₂ Reduction over Ultrawide Potential Window

High conversion efficiency over a wide operating potential window is important for the practical application of CO₂ reduction electrocatalysis, yet that remains a huge challenge in differentiating the competing CO₂ reduction and H₂ evolution. Here we introduce point defects (Sn doping) and planar defects (grain boundary) into the Cu substrate. This multidimensional defect integration strategy guides the fabrication of highly diluted SnCu polycrystal, which exhibits high Faradaic efficiencies (>95%) toward CO₂ electroreduction over an ultrawide potential window (ΔE = 1.3 V). The theoretical study indicates that the introduction of Sn doping and grain boundary synergistically provides an optimized electronic effect, which helps suppress H₂ evolution and promotes the hydrogenation of *CO₂.