Differentiated Interfacial Proton Delivery for Durable CO 2 ‐to‐Formate Electrosynthesis

Interfacial ion and water organization critically influence proton‐coupled electrochemical reactions, yet their coupled regulation under high‐rate CO 2 electroreduction remains poorly understood. Here, we construct a mosaic‐and‐gap‐confined poly(dimethylsiloxane)‐modified Bi (Bi‐PDMS) interface that reorganizes the catalyst–electrolyte solvation environment. Atomistic simulations indicate altered near‐surface cation accessibility and a less persistent extended hydrogen‐bond environment, while slow‐growth proton‐transfer calculations show a substantially larger energetic penalty for selected extended proton‐delivery pathways than for local proton transfer to * OCHO. Operando spectroscopy and mass spectrometry measurements further reveal potential‐dependent interfacial water restructuring, suppressed hydrogen evolution, and enhanced formate‐related pathway response. Bi‐PDMS‐30 sustains ∼90% formate Faradaic efficiency (FE) at −0.2 A cm − 2 for ∼200 h with substantially reduced surface‐deposit accumulation. Together, these results support differentiated interfacial proton delivery within a reorganized ion–water environment as a useful framework for selective and durable CO 2 ‐to‐formate electrosynthesis.