Orbital Coupling‐Engineered Coordination‐Unsaturated CuAg Nanochains Drives Spontaneous Electrocatalytic Acetylene Semihydrogenation and Zn‐C 2 H 2 Batteries

Abstract Electrocatalytic semihydrogenation of acetylene (C 2 H 2 ) offers a mild and sustainable pathway for ethylene production, yet it faces critical challenges including competitive C─C coupling for 1,3‐butadiene due to insufficient proton supply and hydrogen evolution under high current densities. To address these limitations, we design a coordination‐unsaturated CuAg bimetallic catalyst with cross‐linked nanochains (Cu 0.5 Ag CNCs), which synergistically regulates proton dynamics, maintaining high activity from 0.1 to 0.6 A cm −2 and achieving an ethylene Faradaic efficiency of 95.1% at 0.5 A cm −2 . Mechanistic studies reveal that the introduction of Cu makes the d‐band center in Cu 0.5 Ag CNCs upshift toward the Fermi level, strengthening orbital coupling with C 2 H 2 and creating a high *H demand surface. In situ spectroscopic and density functional theory analyses demonstrate that coordination‐unsaturated Cu‐Ag interfacial sites promote spontaneous C 2 H 2 hydrogenation, especially bypassing formation barriers of *C 2 H 2 and *C 2 H 3 . This thermodynamic superiority originates from sufficient proton supply and exothermic *H consumption for C 2 H 2 hydrogenation. Furthermore, the catalyst enables a Zn‐C 2 H 2 battery with a power density of 2.12 mW cm −2 , showcasing dual functionality in electrosynthesis and energy storage. Our work establishes a paradigm for coordination unsaturated bimetallic catalyst design through orbital coupling engineering, providing atomic‐level insights into proton‐mediated reaction control for sustainable chemical manufacturing.