Potential-dependent activities in interpreting the reaction mechanism of dual-metal atom catalysts for Li-CO2 batteries

Abstract

CO₂ electrochemistry has been considered as a promising cathode reaction for energy storage due to its high theoretical energy density, high electrochemical potential, and ability to fix CO₂. However, the low efficiency and poor reversibility of Li-CO₂ evolution significantly impede the applications of Li-CO₂ batteries. Herein, first-principles calculations were employed to investigate the 21 M₁M₂N₄C dual-atom catalysts and explore the catalytic mechanism for the Li-CO₂ evolution reaction. Among these dual-atom catalysts, the MoMoN₄C shows the highest adsorption interaction with CO₂ due to its high d-center and d-p orbital coupling. The effects of dual-atom sites on the catalytic activities and selectivities were investigated by searching the possible reaction pathways toward the battery-discharging processes in the ether electrolyte with the help of implicit constant electrode potential simulations. The compared results show that the Li-CO₂ discharging process was limited by the rate-determining reactions involving *Li + CO₂ → *LiCO₂ and *LiC₂O₄^@ + Li⁺ + e^- → *CO + Li₂CO₃, and these processes on graphene are relatively sluggish due to the low onset potential range of -2 to -2.36 V vs. SHE. By contrast, The optimized onset potentials of -1.15 to -1.31 V vs. SHE were obtained at the MoMoN₄C active site. Furthermore, the MoMoN₄C active site shows a lower energy barrier for the decomposition of *Li₂CO₃ than the pure graphene, which reveals the MoMoN₄C active site with excellent CO₂ activation ability can reduce the polarization of the discharging reactions and energy barrier for the CO bond cleavage. This work provides deep insight into the Li-CO₂ evolution mechanisms and guides the design of advanced dual-atom catalysts for highly reversible Li-CO₂ batteries.

Keywords: Catalytic activity; Dual-atom catalyst; Implicit solvent; Li-CO(2) battery; Orbital interaction.