Identifying a Langmuir–Hinshelwood Hydrogenation Mechanism to Design a Bimetallic AgPd Catalyst for Electrochemical Acetylene‐to‐Ethylene Conversion

The intensified hydrogen evolution reaction (HER) competition is an elusive obstacle for the practical application of electrocatalytic acetylene (C 2 H 2 ) hydrogenation (EAH) for petroleum‐independent ethylene (C 2 H 4 ) formation. Fundamentally, ambiguous mechanistic insight severely hinders the rational design of efficient catalysts, leaving the identification of Eley–Rideal (E–R) or Langmuir–Hinshelwood (L–H) mechanisms as intrinsic challenges. Here, the L–H pathway is proven to be the predominant route, which is regarded as the principle for catalyst design. Consequently, a bimetallic AgPd alloy (AgPd NPs) is predicted and proven to be a promising catalyst. Accordingly, the AgPd NPs deliver a C 2 H 4 partial current density of 0.47 A cm −2 and a turnover frequency (TOF) of 8.27 s −1 (1.66‐fold vs. the Ag counterpart under equal conditions). In situ spectroscopic characterizations unveil that the Pd dopants could not only induce *H transfer to free sites to increase C 2 H 2 mass transfer, but also optimize the match degree of surface *H and *C 2 H 2 . *H migration‐enabled transport modulation could efficiently enhance the turnover process, simultaneously promoting C 2 H 4 formation while inhibiting HER competition.