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 Cu₃Se₂ 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 3d-Se 4p 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 C₄ and H₂ byproducts. This work positions van der Waals Cu₃Se₂ as a robust platform for selective ethylene production.