Microenvironmental hydrophobicity-regulated evolution of reaction sites for boosting electrochemical CO₂ reduction

Dynamic evolution of reaction sites, prompted by catalyst reconstruction during the CO₂ reduction reaction (CO₂RR), have been demonstrated. However, understanding how the microenvironment of electrode dominates the reconstruction process to maintain sufficient and stable triple-phase interfaces remain a significant challenge. This study proposes the regulation of hydrophobic interfaces of Bi₂O₃ catalysts using polytetrafluoroethylene (PTFE) as a binder, showing an efficient strategy for stable CO₂-to-formate conversion. With an optimized electrode containing a 5 wt% PTFE solution, the prepared electrode exhibits an excellent electrocatalytic activity toward formate selectivity, with the Faradaic efficiency reaching 97.5 ± 0.8 % and a partial current density of −218.2 ± 3.8 mA cm⁻². These hydrophobic interfaces not only enhance the capture of CO₂ molecules, but also regulate the formation of Bi⁰/Bi³⁺ sites as a result of controlling partial reduction of Bi³⁺ during CO₂RR. In-situ spectroscopic analysis and theoretical calculations have revealed that these Bi⁰/Bi³⁺ sites facilitate the adsorption of CO₂ and lower the protonation steps barriers for formate formation, thereby improving the efficiency and stability of CO₂RR.