Ampere-level electroconversion of acetylene towards polymer grade ethylene via Pd-H mediated non-spillover hydrogenation

Electroconversion of acetylene towards polymer-grade ethylene (EAE) is recognized as a promising substitution for thermo-catalytic route. The excessive active-hydrogen supplies a high current density induces the conspicuous hydrogen evolution, reducing the ethylene Faradaic efficiency (FE). Here, we develop a Cu-Pd single atom alloy (SAA) catalyst, achieving a 90.5% FE with a large ethylene partial current density of -1.16 A cm -2 , and maintain stability for 110 h at -0.2 A cm -2 in the flow-cell system. In membrane electrode assembly, Cu-Pd SAA delivers a 90.1% ethylene FE and ~100 % conversion at -2.5 A (-0.1 A cm -2 ), along with 500 h stability for crude ethylene purification. Combined in-situ spectroscopy and DFT calculation reveal that the catalyst facilitates the direct hydrogenation of acetylene via Pd-H species rather than hydrogen spillover. This mechanism concurrently lowers the EAE energy barrier and suppresses the hydrogen evolution reaction. This work provides insights for designing high-efficiency electrocatalysts for hydrogenation electrosynthesis.

Ethylene (C 2 H 4 ), as an essential building block for producing commodity chemicals, mainly stems from petroleum cracking 1-4 . The development of acetylene (C 2 H 2 ) production derived from coal or methane provide a feasible route, that is acetylene hydrogenation to ethylene, to preclude oil dependence 5-8 . At present, industrial hydrogenation of acetylene to ethylene still depends on thermo-catalytic process (TAE), which demands extensive energy consumption and excess high-purity hydrogen 9-11 . In this case, intensive carbon emissions and high cost is inevitable. As an emerging technology in recent years, electro-conversion of acetylene towards ethylene (EAE) powered by renewable energy has been recognized as a promising replacement to TAE 12-16 . A fundamental issue in making EAE profitable is to maintain remarkable ethylene selectivity at high current density 10 . However, the high current density will lead to severe hydrogen evolution and low ethylene selectivity, especially at ampere level 17,18 . In these regards, there is a pressing need to design efficient electrocatalysts for achieving high ethylene selectivity and ampere-level current density simultaneously.