Defect-Engineered Cu-Based Nanomaterials for Efficient CO 2 Reduction over Ultrawide Potential Window.

High conversion efficiency over a wide operating potential window is important for the practical application of CO 2 reduction electrocatalysis, yet that remains a huge challenge in differentiating the competing CO 2 reduction and H 2 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 CO 2 electroreduction over an ultrawide potential window (Δ E = 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 H 2 evolution and promotes the hydrogenation of *CO 2 .