Interfacial Water Activation via Reconstruction-Induced Sites for pH-Universal Electroreduction of CO2.

Renewable electricity-driven electroreduction of CO2 into formate represents one of the most commercially attractive routes for carbon valorization, yet Bi-based catalysts often suffer from unstable surface states under reaction conditions. Here, we exploit this intrinsic instability to construct an interfacial Cs/Cl dual-modified Bi nanoflower catalyst via an in situ electrochemical surface reconstruction strategy, which delivers high formate selectivity across a broad pH window, including acidic, neutral, and alkaline media. In situ spectroscopic analysis and theoretical calculations reveal that Cs/Cl dual-modification fundamentally serves as synergistic sites by reconfiguring the interfacial electronic environment, accelerating water dissociation, and stabilizing *OCHO intermediates, thereby steering the reaction pathway toward formate. Furthermore, pairing CO2 reduction with methanol oxidation in a two-electrode configuration enables the simultaneous electrosynthesis of formate at both electrodes under low cell voltages, offering a dual-value coproduction strategy for carbon utilization and biomass upgrading. This work establishes interfacial water activation via reconstruction-induced dual-sites as a powerful design principle for next-generation CO2 reduction electrocatalysts.