Amorphous Interface-Confined Acetylene Semireduction under Industrially Relevant Acetylene-Lean Feeds

Selectively converting gaseous reactants via electrochemistry under industrially relevant lean feeds represents a green and sustainable pathway for gas upgrading and purification, yet achieving high selectivity remains challenging. Conventional catalysts are typically crystalline, with well-exposed active sites where competing reactions can readily occur, for example, parasitic hydrogen evolution and C-C coupling during electrochemical removal of trace acetylene from acetylene-lean streams. Here, we create an interface-confined reaction environment for selective acetylene semireduction into ethylene by introducing an amorphous corona onto crystalline Cu catalysts using electron-withdrawing ligands. The corona, with tunable chemistry and thickness, enriches acetylene near the catalyst surface while stabilizing active sites and key intermediates, thereby regulating reaction pathways. The optimized system achieves near-unity ethylene selectivity with strongly suppressed parasitic reactions, enabling efficient acetylene removal to below 5 ppm for 310 h. These findings establish the amorphous organic corona as a functional catalytic phase rather than merely a molecular ligand modification, and demonstrate its promise as an interface-confined design concept for selective gas electrocatalysis, with broader implications for gas upgrading and purification.