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

CO 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 CO. However, the low efficiency and poor reversibility of Li-CO evolution significantly impede the applications of Li-CO batteries. Herein, first-principles calculations were employed to investigate the 21 MMNC dual-atom catalysts and explore the catalytic mechanism for the Li-CO evolution reaction. Among these dual-atom catalysts, the MoMoNC shows the highest adsorption interaction with CO 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-CO discharging process was limited by the rate-determining reactions involving *Li + CO → *LiCO and *LiCO + Li + e → *CO + LiCO, 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 MoMoNC active site. Furthermore, the MoMoNC active site shows a lower energy barrier for the decomposition of *LiCO than the pure graphene, which reveals the MoMoNC active site with excellent CO 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-CO evolution mechanisms and guides the design of advanced dual-atom catalysts for highly reversible Li-CO batteries.