Single-atom versus dual-atom catalysts on β₁₂-borophene for reversible Li-CO₂ batteries: d-d orbital hybridization...

Li-CO₂ batteries have attracted considerable attention due to their dual functions in energy storage and CO₂ utilization. However, their practical application remains hindered by large overpotentials and poor cycling stability. Based on first-principles calculations, this work studied the performance of β₁₂-borophene-supported 3d transition-metal single-atom and dual-atom catalysts (M/β₁₂ and M-M/β₁₂, M = V-Zn) as cathodes for Li-CO₂ batteries. As the atomic number decreases, the d-band center of the catalyst shifts upward toward the Fermi level, enhancing CO₂ adsorption and activation. Dual-atom catalysts (M-M/β₁₂) exhibit superior catalytic performance compared to their single-atom counterparts (M/β₁₂), due to the d-d orbital hybridization between neighboring metal centers. This hybridization optimizes the active-site electronic configuration, enhances CO₂ adsorption/activation, and reduces the reaction overpotential. Notably, V-V/β₁₂ exhibits an ultralow charge-discharge overpotential of 0.48 V and a Li₂CO₃ dissociation barrier of 0.84 eV, displaying exceptional activity. Mechanistic analysis shows that CO₂ undergoes parallel adsorption via C and O atoms at dual-V sites, where extensive d-p orbital hybridization and multicenter electronic coupling activate the CO bond. The electronic synergy from d-d hybridization is key to the enhanced performance of dual-atom catalysts, offering new insights for designing efficient Li-CO₂ battery cathodes.