Copper-Bridge-Enhanced p‑Band Center Modulation of Carbon–Bismuth Heterojunction for CO2 Electroreduction

Bismuth-based catalysts have advanced CO2 electroreduction to formic acid, but their intrinsic electronic structure remains a key obstacle to achieving a high catalytic performance. Herein, a copper bridge strategy is proposed to enhance electronic modulation effects in bismuth/carbon composites. Density functional theory calculations prove the novel p–d–p hybrid orbitals on the carbon–copper–bismuth heterojunction structure (Bi-Cu/HMCS) could stabilize the HCOO* intermediate and lower the thermodynamic barrier from CO2 to formic acid. With the rapid electron-supplying effect of “copper bridge”, the faradaic efficiency of formate reaches 100% (±2%) at a low overpotential of 500 mV and remains above 90% within a wide potential range. Using a solid-state electrolyte device, pure 0.6 M HCOOH is produced at a stable current density of 100 mA cm–2 within 7.5 h, boasting an impressive energy efficiency of 53.8%. This work offers a new strategy for optimizing electronic structure of metal/carbon composite electrocatalysts.