Electronegativity-Driven Frontier Orbital Engineering in B-Ti Diatomic Synergy Enables Selective Li₂C₂O₄ Conversion in Li-CO₂ Batteries

As a promising alternative to sluggish Li₂CO₃-based Li-CO₂ electrochemistry, Li₂C₂O₄ offers a favorable 2e⁻ discharge pathway, yet its selective formation and reversible decomposition remain debated. Herein, we propose a nonmetal-metal synergistic catalyst—B-Ti coregulated layered transition metal boride Ti₁₈B₁₈O₉/graphene (B-Ti/TiBOG)—to enable efficient CO₂-to-Li₂C₂O₄ conversion via frontier orbital engineering (FOE). Density functional theory (DFT) and ab initio molecular dynamics (AIMD) simulations reveal that the low electronegativity of B (O > N > C > B) induces asymmetric Ti coordination, driving strong B 2p and Ti 3d orbital hybridization near the Fermi level, and better structural stability, outperforming C/N/O-Ti analogs. Interestingly, this unique FO alignment activates CO₂ by populating its antibonding orbitals through a bidirectional “acceptance-feedback” mechanism to enhance CO₂ adsorption (from −0.19 to −1.05 eV). The B-Ti synergy selectively stabilizes Li₂C₂O₄ nucleation while kinetically suppressing its conversion to Li₂CO₃ (barrier > 0.68 eV). Consequently, the hybrid B-Ti/TiBOG catalyst achieves exceptional bifunctionality, yielding a minimal total overpotential (0.75 V) for CO₂-to-Li₂C₂O₄ cycling—maintained in the tetraethylene glycol dimethyl ether (TEGDME) solvent environments. This work highlights electronegativity-driven FOE in B-Ti diatomic synergy as key for rechargeable Li-CO₂ batteries.