Electronic Modulation of Bismuth by g-C3N4 Constructs Electron-Enriched Active Sites for Accelerated CO2 Electroreduction to Formate

Electrochemical reduction of CO₂ (ECO₂RR) to formate represents a promising approach to achieving carbon neutrality, yet it faces significant challenges due to the low adsorption efficiency of the CO₂ intermediates. In this study, we developed a highly dispersed electron-rich Bi metal catalyst, utilizing low-cost g-C₃N₄ as a nonmetallic support and electron donor. This design created a conductive network and a multielectron environment around the Bi atoms that facilitated dynamic interfacial charge transfer from g-C₃N₄ to Bi, thus enhancing the catalytic efficiency of active sites. The assembly catalyst exhibited a formate selectivity of over 90% within a wide potential window and maintained stable catalytic activity in simulated seawater solutions. In situ Raman spectroscopy and DFT calculations indicated that the incorporation of the nonmetallic support shifted the Bi-p band center to more negative values while increasing Bader charge transfer between Bi and *OCHO intermediates. This indicated enhanced adsorption of the *OCHO intermediate by electron-rich Bi, thus improving the selectivity and activity for formate production.