Regulating p-orbital of metallic bismuth nanosheets via transition-metal oxides enables advanced CO2 electroreduction

The interaction of p-d orbitals can be used to efficiently improve electrocatalytic performance. However, the enhanced mechanism of electrocatalytic CO₂ reduction reaction (eCO₂RR) on main group metals inspired by the p-d orbital interactions is still unclear. Herein, a series of transition-metal oxides (TMOs: Fe₂O₃, Co₃O₄, and NiO) are introduced to metallic bismuth (Bi) nanosheets (NSs), which is proposed as a proof of concept for investigating the effect of introduced TMOs on the eCO₂RR performance for Bi. Based on the results from in-situ Fourier transform infrared (FTIR) spectra and CO₂-temperature programmed deposition (TPD), the TMOs in the Bi/TMOs NSs can enhance the adsorption and/or activation ability of CO₂. Density functional theory (DFT) calculations reveal that the regulated adsorption energy of *OCHO and p-orbital of Bi sites can decrease theoretical overpotentials for both the CO₂-to-*OCHO process and the *OCHO-to-HCOOH process. Moreover, the electron rearrangement that occurred due to the contact between Bi and TMO can also promote electron transport between the catalyst and reactants. Therefore, under the dual positive effect of thermodynamics and kinetics, the Bi sites in Bi/TMO NSs exhibit the maximum catalytic ability, realizing high catalytic activity and selectivity for HCOOH over a wider potential region. In particular, Bi/Fe₂O₃ NSs can present the most significant enhancement effect. It can yield a wide potential region of 500 mV with a high FE_HCOOH (>90%) and achieve a maximum FE_HCOOH of 99.7% (1.11 times that of Bi) at −0.8 V_RHE with the HCOOH partial current density of 12.65 mA cm⁻² (1.86 times that of Bi). This study establishes a relationship between the enhanced performance and the introduced TMOs and provides a practicable and scalable avenue for rationally engineering high-powered electrocatalysts.