This study investigates the nitrogen (N)-doped sumanene (SUMA) molecule's catalytic behavior for the four-electron oxygen reduction reaction (ORR) process. Accordingly, the N atom is doped at three different positions on the SUMA molecule to obtain the pyrrolic, pyridinic, and graphitic SUMA. The free energy value for the individual reaction processes in the four-electron reduction reaction shows high exothermicity and feasibility for the N-doped SUMA molecules.Moreover, the free energy for the entire four-electron reduction reaction lies well below the value of O 2 reduction into two water (H 2 O) molecules -474.71 kJ/mol.The N-doped SUMA molecules exhibit stronger adsorption energy despite being metal-free. The physisorption of the final product (H 2 O molecule) over the SUMA molecules suggests the possibility of regeneration of the catalyst, thereby controlling catalytic poisoning. Specifically, the graphitic SUMA shows a prominent catalytic behavior due to a lower highest occupied molecular orbital-lowest unoccupied molecular orbital energy gap, which arises due to the increased charge density of the carbon atoms present near the graphitic N site. Besides, doping carbon-based materials with N at the central benzene ring significantly enhances their catalytic efficiency due to localized π-orbitals. Overall, the results reveal that N-doped SUMA molecules are a promising metal-free catalyst for ORR activity.

Using the first-principle calculations, we have investigated the chemical properties of small lithium clusters adsorbed on Stone−Wales defected graphene (SW-GN) sheet. The DFT study shows that the Li clusters orient above the defect region in the SW-GN sheet. A single SW defect could accommodate a maximum of four Li atoms. The interaction energy shows that the presence of the SW defect in the graphene sheet enhances the interaction between the SW-GN sheet and Li clusters. As the cluster size increases, the interaction between the defective sheet and Li clusters increases. The interaction energy and cohesive energy per Li atom show a decrease in energy value as the Li cluster size increases, and this result is substantiated with adsorption capacity value. The charge transfer indicates that SW defected graphene acts as an electron acceptor while the clusters behave as donors. The DOS plot indicates that the adsorption of Li clusters has influenced a change in the electronic property of the bare SW graphene sheet, thereby shifting the Fermi level to the conduction band. From all the above results, we infer that SW defected graphene proves to be a prospective anode material by reducing the clustering of Li atoms, thereby hindering dendrite formation. Further improvement in the anodic material could be established through an increase in the defect ratio in the graphene sheet.

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