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

Homonuclear transition-metal dimers embedded in monolayer C2N (TM2@C2N) structures are built and comprehensively explored as potential anchoring and electrocatalytic materials in Li-S battery by using first-principles calculations. The TM2@C2N show excellent anchoring ability for LiPSs with moderate adsorption energy, which can effectively suppress the shuttle effect. The introduction of TM dimer in monolayer C2N reduce the free energy and decrease the decomposition energy barriers of electrochemical conversions, which make 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 TM2@C2N can serve as electrocatalysts to facilitate the adsorption for LiPSs and the catalytic conversion in the high-performance Li-S battery, but also provides a guidance for the homonuclear dual-atom catalysts design in Li-S battery. [Display omitted] •The adsorption energies of transition-metal dimers embedded monolayer C2N (TM2@C2N) for Li2Sn clusters are moderate.•Metallization occurs in the TM2@C2N systems originating from the TM-3d orbital.•The small free energy of sulfur reduction reaction on the TM2@C2N systems accelerate the charge–discharge reaction.•The decomposition energy barrier of the electrochemical conversions on the TM2@C2N 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 C2N (TM2@C2N, 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 TM2@C2N have excellent anchoring ability for LiPSs with moderate adsorption energy, which can effectively suppress the shuttle effect. The introduction of TM dimer in monolayer C2N 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 TM2@C2N can serve as electrocatalysts to faci