LAUSR

Electrochemical reduction of CO2 (CO2RR) to value-added chemicals is an effective way to harvest renewable energy and utilize carbon dioxide. However, the CO2RR's electrocatalysts suffer from insufficient activity and selectivity due to the limitation of CO2 activation. In this work, a Ni-doped Bi nanosheet (Ni@Bi-NS) electrocatalyst is synthesized for the electrochemical reduction of CO2 to HCOOH. Physicochemical characterization methods are extensively used to investigate the composition and structure of the materials. Electrochemical results reveal that for the HCOOH product, the obtained Ni@Bi-NS exhibits an equivalent current density of 51.12 mA cm -2 at -1.10 V, which is much higher than the pure Bi-NS (18.00 mA cm-2 at -1.10 V). A high Faradaic efficiency of HCOOH over 92.0% is achieved in a wide potential range from -0.80 to -1.10 V, and particularly, the highest efficiency of 98.4% is achieved at -0.90 V. Both experimental and theoretical results reveal that the superior activity and selectivity are attributed to the doping effect of Ni on the Bi nanosheet. The density functional theory calculation reveals that upon doping, the charge is transferred from Ni to the adjacent Bi atoms, which shifts the p-orbital electronic density states towards the Fermi level. The resultant strong orbital hybridization between Bi and the π* orbitals of CO2 facilitates the formation of *OCHO intermediates and favors its activation. This work provides an effective strategy to develop active and selective electrocatalysts for the CO2RR by modulating the electronic density state.