Direct carbonate electroreduction on a dynamic Bi2O2CO3 cathode via a synergistic adsorption-reduction-replenishment cycle

A pulsed-potential strategy enables in-situ construction of a reactive carbonate layer on Bi 2 O 2 CO 3 . • In situ Raman reveals higher surface carbonate concentration on Bi 2 O 2 CO 3 than on metallic Bi. • An adsorption–reduction–replenishment cycle is sustained by reversible phase transformation between Bi 2 O 2 CO 3 and Bi. • Direct carbonate-to-formate conversion achieves 24.3% faradaic efficiency and stable operation over 150 h. • DFT calculations show Bi 2 O 2 CO 3 favors carbonate adsorption while adjacent Bi sites promote formate desorption. Direct electroreduction of carbonate (CO 3 2− ) to value-added chemicals presents a promising yet underexplored pathway toward closed carbon cycles, primarily due to the intrinsic stability of carbonate and its weak affinity for conventional electrode surfaces. Here, we overcome these barriers through a pulsed-potential strategy that enables the in-situ construction and dynamic preservation of a reactive carbonate layer on a bismuth oxycarbonate (Bi 2 O 2 CO 3 ) cathode. In situ Raman spectroscopy reveals a significantly enhanced surface carbonate concentration on Bi 2 O 2 CO 3 compared to metallic Bi under cathodic polarization. A synergistic adsorption-reduction-replenishment cycle is sustained under pulsed potentials (0 V RHE for adsorption and −0.5 V RHE for reduction), driven by the dynamic interconversion between reactive adsorbed carbonate and stabilizing structural carbonate within the lattice, coupled with the reversible phase transformation between Bi 2 O 2 CO 3 and Bi. This approach enables direct carbonate-to-formate conversion with a Faradaic efficiency of 24.1% (a 40-fold advance over the state-of-the-art FE of ∼0.6%) and long-time operation exceeding 150 h. First-principles calculations reveal the molecular origin of this synergy: the Bi 2 O 2 CO 3 surface thermodynamically favors carbonate adsorption (ΔG ads  = −2.14 eV), while adjacent metallic Bi sites facilitate formate desorption (ΔG des  = 0.82 eV). This work establishes a direct carbonate electroreduction route and presents a general paradigm for managing anionic reactants through dynamic interfacial engineering. Download: Download high-res image (221KB) Download: Download full-size image