Exploring the Catalytic Role of Mo₂C in Lithium–Nitrogen Batteries

The rechargeable lithium–nitrogen (Li–N2) battery represents a promising strategy for nitrogen fixation and next-generation energy storage systems. However, the strong N≡N triple bond and high ionization energy pose significant challenges for an efficient nitrogen reduction reaction. This study employs density functional theory calculations to evaluate the performance of the Mo2C monolayer as a cathode catalyst for the Li–N2 battery. Results reveal that N2 interacts strongly with the Mo2C surface, significantly activating the N≡N bond and reducing the dissociation energy barrier to 0.379 eV. Crucially, Mo2C exhibits weak and strong adsorption of Li and N atoms, respectively, ensuring that active sites preferentially bond with N without Li poisoning. The calculated low charge/discharge overpotential (<0.62 V) indicates that Mo2C effectively facilitates N2 evolution and reduction reactions. According to the ab initio molecular dynamics simulation, N2 dissociation and Li3N formation can be successfully observed on Mo2C but not on graphene (frequently utilized in Li–O2 and Li–CO2 batteries). This study identifies the primary role of cathode catalysts as promoting the discharge reaction and reversible cycling in the Li–N2 battery, rather than merely reducing overpotential. These findings provide new insights into catalyst design and optimization strategies for enhancing the performance of Li–N2 batteries.