Homonuclear transition-metal dimers embedded monolayer C2N as promising anchoring and electrocatalytic materials for lithium-sulfur battery: First-principles calculations

• The adsorption energies of transition-metal dimers embedded monolayer C 2 N (TM 2 @C 2 N) for Li 2 S n clusters are moderate. • Metallization occurs in the TM 2 @C 2 N systems originating from the TM-3 d orbital. • The small free energy of sulfur reduction reaction on the TM 2 @C 2 N systems accelerate the charge-discharge reaction. • The decomposition energy barrier of the electrochemical conversions on the TM 2 @C 2 N systems is quite small. The practical applications of lithium-sulfur (Li-S) batteries are greatly impeded by several bottlenecks, such as the dissolution of lithium polysulfides (LiPSs) and the poor conversion efficiency during discharging/charging processes. To handle these issues, we construct homonuclear transition-metal dimers embedded in monolayer C 2 N (TM 2 @C 2 N, TM = Cu, V, Co, Fe, and Ni) structures and comprehensively explore their potential as anchoring and electrocatalytic materials in Li-S battery by using first-principles calculations. It is found that the TM 2 @C 2 N have excellent anchoring ability for LiPSs with moderate adsorption energy, which can effectively suppress the shuttle effect. The introduction of TM dimer in monolayer C 2 N can reduce the free energy of sulfur reduction reaction to 1.22−1.46 eV and decrease the decomposition energy barriers of electrochemical conversions to 0.82−1.29 eV, which makes the high activity to the catalytic conversion and the enhanced catalytic conversion efficiency in the discharging/charging processes. This work not only reveals that the TM 2 @C 2 N can serve as electrocatalysts to facilitate the adsorption for LiPSs and the catalytic conversion of the high-performance Li-S battery, but also provides a guidance for the homonuclear dual-atom catalysts design in Li-S battery.