Epitaxial Growth of High‐Energy Copper Facets for Promoting Hydrogen Evolution Reaction

Abstract Copper is known as a conductive metal but an inert catalyst for the hydrogen evolution reaction due to its inappropriate electronic structure. In this work, an active copper catalyst is prepared with high‐energy surfaces by adopting the friction stir welding (FSW) technique. FSW can mix the immiscible Fe and Cu materials homogenously and heat them to a high temperature. Resultantly, α‐Fe transforms into γ‐Fe, and low‐energy γ‐Fe (100) and (110) surfaces induce the epitaxial growth of high‐energy Cu (110) and (100) planes, respectively. After the removal of γ‐Fe by acid etching, the copper electrode exposes high‐energy surface and exhibits excellent acidic HER activity, even being superior to Pt foil at high current densities (>66 mA cm⁻²). Density functional theory calculation reveals that the high‐energy surface favors the adsorption of hydrogen intermediate, thus accelerating the hydrogen evolution reaction. The epitaxial growth induced by FSW opens a new avenue toward engineering high‐performance catalysts. In addition, FSW makes it possible to massively fabricate low‐cost catalyst, which is advantageous to industrial application.