Regulating the Electronic Structure of Bismuth Nanosheets by Titanium Doping to Boost CO2 Electroreduction and Zn–CO2 Batteries

The electrochemical carbon dioxide reduction reaction (E-CO₂ RR) to formate is a promising strategy for mitigating greenhouse gas emissions and addressing the global energy crisis. Developing low-cost and environmentally friendly electrocatalysts with high selectivity and industrial current densities for formate production is an ideal but challenging goal in the field of electrocatalysis. Herein, novel titanium-doped bismuth nanosheets (TiBi NSs) with enhanced E-CO₂ RR performance are synthesized through one-step electrochemical reduction of bismuth titanate (Bi₄ Ti₃ O₁₂ ). We comprehensively evaluated TiBi NSs using in situ Raman spectra, finite element method, and density functional theory. The results indicate that the ultrathin nanosheet structure of TiBi NSs can accelerate mass transfer, while the electron-rich properties can accelerate the production of *CO₂ ^- and enhance the adsorption strength of *OCHO intermediate. The TiBi NSs deliver a high formate Faradaic efficiency (FE_formate ) of 96.3% and a formate production rate of 4032 µmol h^-1 cm^-2 at -1.01 V versus RHE. An ultra-high current density of -338.3 mA cm^-2 is achieved at -1.25 versus RHE, and simultaneously FE_formate still reaches more than 90%. Furthermore, the rechargeable Zn-CO₂ battery using TiBi NSs as a cathode catalyst achieves a maximum power density of 1.05 mW cm^-2 and excellent charging/discharging stability of 27 h.