Oleylamine-Assisted Construction of Bi-Bi₂O₂CO₃ Heterojunction With a Self-Release-Replenishing Mars-van...

Bismuth-based catalysts for the electrochemical CO₂ reduction (CO₂RR) to formate have been extensively developed, yet the limited mass transport of gaseous CO₂ remains a sspersistent challenge. Herein, we report a novel Bi-Bi₂O₂CO₃ heterojunction electrocatalyst (Bi-BOC-OLA) constructed via an oleylamine-assisted strategy and disclose a new self-release-replenishing Mars-van Krevelen-type mechanism that alleviates this constraint. Oleylamine-induced expansion of [Bi₂O₂]²⁺ layers enables the Bi₂O₂CO₃ lattice in Bi-BOC-OLA to function as an in situ carbon reservoir that continuously supplies carbon-oxygen intermediates to active Bi centers. External CO₂ replenishes lattice vacancies, creating an energy-efficient cycle that reduces reliance on gaseous CO₂ transport. Consequently, Bi-BOC-OLA achieves a formate Faradaic efficiency of 97%, a record partial current density of -1.4 A cm^-2 and stable operation for 160 h at -400 mA cm^-2. This work reveals how dynamic lattice participation in Bi-Bi₂O₂CO₃ heterojunctions enables high-rate CO₂-to-formate conversion and provides a new mechanistic basis for the design of Bi-based CO₂RR catalysts.