Balancing Dimerization and Hydrogenation Kinetics by Stabilizing Cu⁺ and Tightening H-Bond Network for Electrocatalytic Acetylene Hydrodimerization

The electrocatalytic hydrodimerization of acetylene (EHDA) offers a promising alternative to energy-intensive naphtha steam cracking for producing 1,3-butadiene but faces a formidable challenge due to kinetic imbalance between C–C coupling and hydrogenation. Herein, we balance the dimerization and hydrogenation kinetics of EHDA by stabilizing Cu⁺ and tightening the hydrogen-bond network over citrate anion grafted Cu₂O catalysts (E-CA/Cu₂O). The X-ray absorption fine structure, Cu LMM Auger spectrum, and theoretical simulations corroborate citrate anion modification induces electron transfer from Cu₂O to citrate ions. This stabilizes the active Cu⁺ sites under electrochemical reduction conditions and further lowers the C-C coupling barrier of *C₂H₂ and *C₂H₃ to *C₄H₅. The in situ attenuated total reflection surface-enhanced infrared spectroscopy confirms that the citrate anion also reconstructs the hydrogen-bonding network and reduces the content of isolated water at the electrode-electrolyte interface. The appropriate supply of active *H species effectively promotes the hydrogenation of *C₄H₅ to form 1,3-butadiene rather than competitive acetylene semihydrogenation. As a result, E-CA/Cu₂O catalyst achieves a Faradaic efficiency of 88.0% and a 1,3-butadiene partial current density of 55 mA cm⁻², which is about 3-fold higher than E-Cu₂O. This work will guide the rational design of high-performance catalysts for regulating the kinetics of electrocatalytic acetylene hydrodimerization.