Gas-Proton Microenvironment Modulation for Enhanced CO2-to-Formate Electroreduction.

Precise control of interfacial water structure is essential for suppressing side reactions and enabling selective CO2 electroreduction at industrial current densities. Here, we synthesize a series of bismuth-based catalysts with spatially encoded superhydrophilic-superhydrophobic nanodomains by partially embedding polyvinylidene fluoride (PVDF) into Bi nanoparticles. This strategy creates interfacial polarity patterns that stabilize *OCHO intermediates while suppressing hydrogen and CO evolution. Compared to the PVDF-free control, the optimized Bi-PVDF catalyst exhibits significantly enhanced formate partial current density, Faradaic efficiency (FE), and long-term stability. It achieves > 90% FE at -200 mA cm-2 for 50 h and maintains high selectivity up to -700 mA cm-2. Operando spectroscopy and multiscale simulations reveal that the dual-wettability interface modulates local hydration and charge distribution, promoting selective intermediate formation while kinetically suppressing side pathways. By addressing the longstanding challenge of coupled gas-proton transport, this work offers a mechanism-driven and scalable strategy to construct interfacial microenvironments for high-rate, selective CO2 electroreduction.