In situ engineering 3D conductive core-shell nano-networks and electronic structure of bismuth alloy nanosheets for efficient electrocatalytic CO2 reduction

The electrocatalytic carbon dioxide reduction reaction (CO2RR) to obtain valuable formic acid (HCOOH) with high Faradaic efficiency (>90%) and large current density (>150 mA cm(-2)) in H-type cells is extremely challenging due to the carbon dioxide (CO2) mass transfer limitation. This study reports an excellent electrocatalyst for the CO2RR based on the in-situ construction of three-dimensional (3D) porous networked core-shell nanowire structures on copper (Cu) foam. The core-shell structure comprises a Cu nanowire (NW) core and an antimony-bismuth (Sb-Bi) alloy shell (Cu@SbxBiy NWs/Cu). The as-prepared Cu@SbxBiy NWs/Cu exhibits a high current density of 171.3 mA cm(-2) along with 92% Faradaic efficiency of HCOOH (FEHCOOH), which is superior to most reported studies in terms of high current density. Theoretical research has shown that introducing Sb upshifts the electron states of Bi close to the Fermi level, allowing more advantageous adsorption of the *OCHO intermediate onto Sb-Bi interfaces than Bi surfaces, thereby accelerating the CO2RR. Furthermore, Sb0.1Bi1 has stronger bond energy than pure Bi, favoring the stability of the catalyst during the reaction. Additionally, the formation of the Sb0.1Bi1 alloy and 3D conductive core-shell nano-networks is more conducive to fast electron transfer and exposure of more active sites in the reaction process, obtaining better catalytic activity. This study provides valuable insights into the design of highly active Bi-based catalysts for energy conversion.