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

Abstract

The intensified hydrogen evolution reaction (HER) competition is an elusive obstacle for the practical application of electrocatalytic acetylene (C2H2) hydrogenation (EAH) for petroleum-independent ethylene (C2H4) 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 C2H4 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 C2H2 mass transfer, but also optimize the match degree of surface *H and *C2H2. *H migration-enabled transport modulation could efficiently enhance the turnover process, simultaneously promoting C2H4 formation while inhibiting HER competition.