Dual Spatial and Electronic Regulation in van der Waals Cu₃Se₂ Nanosheets for Electrocatalytic Acetylene Semi‐Hydrogenation

Copper‐based catalysts are promising for electrocatalytic acetylene semi‐hydrogenation to sustainable ethylene production, yet conventional catalysts suffer from a dilemma: contiguous Cu ensembles induce C─C coupling, while isolated Cu atoms on electronegative supports cause over‐polarization and competing hydrogen evolution reaction, limiting selectivity and Faradaic efficiency (FE) of ethylene. Here, we report atomically thin two‐dimensional van der Waals Cu 3 Se 2 nanosheets featuring a unique Cu─Se coordination that enables simultaneous spatial confinement and electronic modulation of Cu sites. The catalyst delivers a FE ethylene over 90% at a current density of 502 mA cm −2 and maintains >90% FE for 25 h at 200 mA cm −2 , outperforming commercial and advanced Cu‐based catalysts. Mechanistic studies show that Cu 3 d ‐Se 4 p orbital hybridization tailors the density of states and d ‐band center, facilitating π ‐orbital activation of acetylene, boosting active hydrogen utilization, and reducing the hydrogenation barrier. Simultaneously, it raises energy barriers for C─C coupling and H * recombination, suppressing C 4 and H 2 byproducts. This work positions van der Waals Cu 3 Se 2 as a robust platform for selective ethylene production.