Precise Structural Engineering of Bi‐Cu@C Hollow Heterostructures via Component Modulation for Selective CO 2 Electroreduction to Formate

ABSTRACT Bismuth‐copper (Bi‐Cu) bimetallic catalysts show significant promise for electrochemical CO 2 reduction but are often limited by structural simplicity and insufficient synergy between activity, selectivity, and stability. To address this, we developed an ingenious “selective etching‐thermal diffusion” strategy for precisely fabricating heterostructured Bi‐Cu nanoparticles embedded within a hollow carbon matrix (Bi‐Cu@C HS). This approach enables controlled nanoscale structural evolution via component‐regulated phase transformations, yielding tailored architectures from core‐shell to hollow configurations. The optimized Bi‐Cu@C HS catalyst demonstrates exceptional CO 2 ‐to‐formate conversion, achieving a high formate partial current density of 22.5 mA cm −2 with 90% Faradaic efficiency (FE) at −1.16 V vs. RHE. This performance stems from synergistic Bi‐Cu interfacial electronic interactions that accelerate electron transfer and stabilize the key *OCHO intermediate, combined with the hollow architecture maximizing active site accessibility and mass transport. Furthermore, the carbon matrix provides a nanoconfinement effect that suppresses active species leaching and mitigates catalyst poisoning, enabling stable operation for over 11 h with less than 7% activity decay. This work establishes a component‐modulation‐driven paradigm for precise nanoscale structural engineering and offers fundamental insights for designing advanced heterostructured catalysts for sustainable energy conversion.