Unraveling the Role of Interfacial Water Structure in Electrochemical Semihydrogenation of Alkynes

Electrochemical semihydrogenation (ECSH) of alkynes to alkenes is an ideal alternative to traditional thermal semihydrogenation, and yet is limited by low conversion yield and product selectivity. Here, we offer an insight into the catalyst design from the viewpoint of an interfacial water structure toward highly active and selective ECSH. In situ Raman spectroscopy measurements combined with theoretical calculations reveal that the structure of interfacial water on Pd nanosheets can be altered by Fe doping toward trihedrally coordinated water and dangling O–H water, which in turn boosts the activity and selectivity in ECSH. Remarkably, the PdFe nanosheets can sustain continuous 264 h of electrolysis with 100-fold amplified amount of alkynes production in a flow cell. We also demonstrate the incomparable superiority for ECSH of alkynes to alkenes in terms of performance, energy, and cost.