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

Abstract

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 firstprinciples 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.4Li + 3CO 2 →2Li 2 CO 3 + C During discharge, this reaction generates Li2CO3 and C via the CO2 reduction reaction (Li-CO2RR); during charging, it proceeds through the decomposition of Li2CO3 (Li-CO2ER), releasing CO2. 11 However, the inherent insulating nature and thermodynamic stability of Li2CO3 result in a high decomposition barrier and sluggish kinetics, leading to major challenges including large charge-discharge overpotentials, low energy efficiency, and poor cycling stability. 6,12,13 As the primary