Bismuth Silicate Catalyst for Efficient Electrocatalytic CO₂ Reduction and Electrolyte-Free Formic Acid Production

The rising atmospheric CO₂ levels pose significant environmental challenges. Electrocatalytic CO₂ reduction offers a promising approach for converting CO₂ into valuable chemicals such as formate or formic acid. However, the development of efficient electrocatalysts, a deeper mechanistic understanding, and the minimization of energy consumption during product purification remain critical challenges to practical carbon utilization. Here, layered Bi₂SiO₅ is designed as a pre-catalyst, which undergoes electrochemical reconstruction into a Bi@Bi₂O₂CO₃ composite. The catalyst achieves a Faradaic efficiency for formate of 95.8% at -1.06 V and maintains over 90% across a wide potential range, outperforming Bi₂O₂CO₃ and Bi. In situ characterizations reveal that Bi₂SiO₅ converts to Bi₂O₂CO₃ through anion exchange, followed by partial reduction to form Bi@Bi₂O₂CO₃. Charge redistribution at the interface facilitates the proton-coupled electron transfer of ^*CO₂ and desorption of ^*HCOOH, thereby enhancing formate production, as supported by theoretical calculations. Furthermore, integrating the catalyst into an electrolytic cell containing solid-state electrolytes enables the continuous production of electrolyte-free formic acid, simplifying product separation and purification. This work provides insights for the development of practical carbon utilization.