Strong Dipole–Dipole Interaction Promotes Electrocatalytic Acetylene Semihydrogenation over Symmetric Organo-Electrocatalysts

Unveiling the intrinsic interaction between organo-electrocatalysts and reactants is crucial for understanding the catalytic mechanism and designing high-activity catalysts, but it faces daunting challenges. Herein, we report the strong dipole–dipole interaction between fluorobenzoic acids and acetylene. The operando spectroscopic studies, electrochemical analyses and theoretical simulations together prove that high symmetry of fluorobenzoic acid increases dipole magnitude and further strengthens total dipole moment with acetylene. The induced strong dipole–dipole interaction linearly reduces the energy barrier of acetylene adsorption on fluorobenzoic acid and effectively activates acetylene by polarizing the C≡C bond and redistributing the electron density of O^– sites in carboxylate anion. As a result, the highly symmetric 2,4,6-trifluorobenzoic acid affords a large ethylene partial current density of 242 mA/cm² and an ethylene Faradaic efficiency of 94.5% at –0.9 V versus the reversible hydrogen electrode (RHE) under pure acetylene atmosphere, considerably surpassing the asymmetric fluorobenzoic acid analogues. This work not only provides profound understanding on the interaction between reactants and catalysts but also guides the rational design of high-performance organo-electrocatalysts.