Electron-Rich Bi Nanosheets Promote CO2•- Formation for High-Performance and pH-Universal Electrocatalytic CO2 Reduction

Electrochemical CO2 reduction reaction (CO2RR) to chemical fuels such as formate offers a promising pathway to carbon-neutral future, but its practical application is largely inhibited by the lack of effective activation of CO2 molecules and pH-universal feasibility. Here, we report an electronic structure manipulation strategy to electron-rich Bi nanosheets, where electrons transfer from Cu donor to Bi acceptor in bimetallic Cu-Bi, enabling CO2RR towards formate with concurrent high activity, selectivity and stability in pH-universal (acidic, neutral and alkaline) electrolytes. Combined in situ Raman spectra and computational calculations unravel that electron-rich Bi promotes CO2 center dot- formation to activate CO2 molecules, and enhance the adsorption strength of *OCHO intermediate with an up-shifted p-band center, thus leading to its superior activity and selectivity of formate. Further integration of the robust electron-rich Bi nanosheets into III-V-based photovoltaic solar cell results in an unassisted artificial leaf with a high solar-to-formate (STF) efficiency of 13.7 %.

Automated summary

In this study, an electronic structure manipulation strategy was employed to electron-rich Bi nanosheets, enabling CO2RR towards formate with high activity, selectivity, and stability in pH-universal electrolytes. The mechanism was unravelled by in situ Raman spectra and computational calculations, revealing the promotion of CO2 activation and enhanced adsorption of *OCHO intermediate by electron-rich Bi. Integration of the electron-rich Bi nanosheets with III-V-based photovoltaic solar cell resulted in an unassisted artificial leaf with a high solar-to-formate efficiency of 13.7%.