Because of their many advantages, graphene and graphene-based materials are used in supercapacitor electrodes. The main limitation of these electrodes is their low quantum capacitance, which is a direct result of the shortage of states near the Fermi level. Using first-principles density functional theory calculations, this report explored the quantum capacitances of Si-, S-, and P-doped graphenes and the same materials codoped with nitrogen. The findings imply that using phosphorus- and nitrogen-doped graphenes as electrode materials for supercapacitors could be a worthwhile strategy. Quantum capacitance calculations confirmed the greater advantage of some codoped graphenes compared with doped and pristine graphene.

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Density functional theory B3LYP and Hartree-Fock methods with 6-311??G** basis set were utilized to study the relationship between electronic structure and corrosion inhibition efficiencies of protonated and non-protonated forms of 3-formyl 8-hydroxy quinoline and 5-naphthylazo-8-hydroxyquinoline (5NA8HQ) in acidic media in gas and solvent phase. Quantum chemical parameters including highest molecular orbital energy, lowest unoccupied molecular orbital energy, energy gap (DE g ), the fraction of electrons transferred (DN), and energy change during charge transfer (DE) were calculated. Protonation energy calculations showed that the favorite protonation site of 5NA8HQ is the N12 position, which is confirmed by the result of previously reported experimental investigations. Calculations on the inhibitor/iron system were performed using the B3LYP/6-311??G** method and found that azo nitrogens of 5NA8HQ have better interaction with iron. Also, nuclear quadrupole resonance parameters indicate that azo nitrogens (N11 and N12) are the best sites for interaction with iron.