Articles written in Journal of Chemical Sciences

    • Insight into 1:1 complexes of H2O with NF3 and CF2Cl2: a quantum chemical approach


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      The competition of hydrogen, halogen and pnicogen bonding to the stability of the atmospheric complexes is interesting, especially where the molecules by the most abundant greenhouse effect in the atmosphere are subject of interest. In the present work, we have computationally studied the addition of H2O to the NF3 and C2FCl2 molecules to reveal the electronic and structural features of the NF3-H2O and CF2Cl2-H2O complexes through DFT, MP2 and CCSD (T) methods. The interaction energies, geometry and electronic properties including charge transfer, energy gap, NEDA and AIM analyses of all the complexes werecalculated to discuss the nature and strength of intermolecular interactions. The results indicate that the role of halogen bonding is more obvious than that of hydrogen and pnicogen bonding, and compared with the NF3,CF2Cl2 is more effectively stabilized by the H2O molecules

    • Comparative study of various preparation methods of metal-free N and S Co-doped porous graphene as an ORR catalyst in alkaline solution


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      In this work, various methods (chemical vapor deposition (CVD), hydrothermal, and pyrolysis)have been applied for preparing sulfur–nitrogen co-doped porous graphene. Afterwards, the electrochemical behavior of the samples prepared through different techniques was investigated for oxygen reduction reaction(ORR). The prepared heteroatoms-doped electro-catalysts were thoroughly characterized by X-ray diffraction, Raman spectroscopy, N2 adsorption-desorption, field emission scanning electron microscopy, and X-rayphotoelectron spectroscopy techniques. The results showed that co-doping of S and N into porous graphene significantly enhanced the ORR performance. The obtained results showed that the efficiency trend of preparation methods on the ORR performance followed as pyrolysis > CVD > hydrothermal. In addition, the electron transfer numbers in these methods at optimal conditions were 4.1, 3.4, and 2.6, respectively. Among different preparation techniques, pyrolysis as a post-synthesis doping technique has exhibited the most efficient ORR process, in which electron transfer follows the 4e pathway. Moreover, the catalyst prepared bythe pyrolysis method has an onset potential of 0.93V which is very close to the conventional Pt/C 20 wt.%(0.99 V) electro-catalysts because of surface doping and better control over the final product. Finally, themicrobial fuel cell test showed a high peak power density of 30.94 mW m-2 for the optimal sample, which isclose to the Pt/C 20 wt.% (38.63 mW m--2) cathodes, because of the synergistic effect of N and S co-dopedcarbon structure.

      Synthesis and characterization of heteroatom co-doped graphenes using CVD, Pyrolysis and hydrothermal techniques are reported and their electrochemical behaviors evaluated. The results represent the high dependence of ORR activity of the prepared electrocatalysts to the synthesis method and the electrocatalyst via pyrolysis method shows high selectivity for the 4e- reduction.

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