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.