Regulating the interfacial water structure by tensile strain to boost electrochemical semi-hydrogenation of alkynes

Abstract

Electrochemical semi-hydrogenation (ECSH) of alkynes to produce alkenes is an ideal alternative to traditional thermal semi-hydrogenation (TSH) and yet is limited by low conversion yield and product selectivity. Here, we report a new strategy to tune the activity and selectivity of ECSH by regulating the interfacial water structure. The obtained PdCu icosahedrons deliver a greatly enhanced conversion rate and 98.5% alkene selectivity at 96.5% conversion, as well as sustaining about 100 h continuous test. Tensile strain originating from an icosahedral twinned structure is proved to facilitate the formation of an interfacial water structure, especially K⁺ ion hydrated water (K·H₂O) and 2-coordinated hydrogen-bonded water (2-HB·H₂O). We also decode the mysterious role of an interfacial water structure in ECSH performance, in which K·H₂O speeds up water splitting to produce H_ads which in turn accelerates ECSH conversion, and 2-HB·H₂O improves alkene selectivity. The findings provide insights into the tuning of the interfacial water structure in electrocatalyst design in proton-coupled hydrogenation from the viewpoint of lattice strain.