Weak Acetylene Adsorption Terminated Carbon–Carbon Coupling Kinetics on Silver Electrocatalysts

Abstract

Owing to serious poison of downstream olefin polymerization catalysts from acetylene impurities, selective reduction of acetylene to ethylene is a pivotal process in petrochemical industry. However, during thermocatalytic and electrocatalytic acetylene semihydrogenation, acetylene C–C coupling inevitably occurs on current catalysts. The resultant oligomeric species (particularly long-chain hydrocarbons) block active sites and mass transportation, and eventually decrease catalytic activity and stability. In this work, we report Ag nanowires (NWs) as high-performance electrocatalysts for acetylene semihydrogenation, where the C–C coupling is unprecedentedly suppressed by weakening acetylene adsorption. In pure acetylene, 1,3-butadiene Faradaic efficiency (FE) of Ag NWs is only 2.1%, which is far lower than 41.2% for Cu nanoparticles at −0.2 V versus reversible hydrsogen electrode. Ethylene partial current density of Ag NWs reaches 217 mA/cm2 at 0.85 V, which is considerably higher than those for state-of-the-art Cu-based electrocatalysts. Markedly, no 1,3-butadiene is produced on Ag NWs in a large two-electrode flow cell fed with crude ethylene containing 1 vol % acetylene, presenting thorough termination of acetylene C–C coupling. In situ electrochemical Raman spectroscopy and theoretical investigations reveal that weak acetylene adsorption on Ag surfaces is intrinsically responsible for prohibiting their oligomerization. This work will spark the rapid development of high-performance and stable electrocatalysts for reducing alkynes to olefins.