Oleylamine-Assisted Construction of Bi-Bi2O2CO3 Heterojunction With a Self-Release-Replenishing Mars-van Krevelen-Type Mechanism for Efficient CO2 Electroreduction.

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.