Constructing a Stable Built-In Electric Field in Bi/Bi₂Te₃ Nanowires for Electrochemical CO₂ Reduction Reaction

Electrochemically converting carbon dioxide (CO₂) into valuable fuels and renewable chemical feedstocks is considered a highly promising approach to achieve carbon neutrality. In this work, a robust interfacial built-in electric field (BEF) has been successfully designed and created in Bi/Bi₂Te₃ nanowires (NWs). The Bi/Bi₂Te₃ NWs consistently maintain over 90% Faradaic efficiency (FE) within a wide potential range (-0.8 to -1.2 V), with HCOOH selectivity reaching 97.2% at -1.0 V. Moreover, the FE_HCOOH of Bi/Bi₂Te₃ NWs can still reach 94.3% at a current density of 100 mA cm^-2 when it is used as a cathode electrocatalyst in a flow-cell system. Detailed in situ experiments confirm that the presence of interfacial BEF between Bi and Bi/Bi₂Te₃ promotes the formation of *OHCO intermediates, thus facilitating the production of HCOOH species. DFT calculations show that Bi/Bi₂Te₃ NWs increase the formation energies of H* and *COOH while reducing the energy barrier for *OCHO formation, thus achieving a bidirectional optimization of intermediate adsorption. This work provides a feasible scheme for exploring electrocatalytic reaction intermediates by using the BEF strategy.