Manipulation of Electronic Structure in Boron Nitride Nanosheets to Improve Catalytic and Photocatalytic Properties

Hemmati, Amir | 2019

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 52657 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Simchi, Abdolreza
  7. Abstract:
  8. The variety of 2D materials and their wide range of properties, as well as numerous methods to manipulate them, have made this class of materials among prominent candidates for the future of the energy industry. Among the means available to tailor nanomaterials performance for such applications, introducing dopants and the creation of heteroatom-doped structures are of great interest. In this study, mixtures of urea, boric acid, and graphene oxide, as cheap and available precursors, were used to synthesize C-doped h-BN nanosheets. After the implementation of TGA/DSC to select a suitable calcination temperature of 950 C°, the samples were successfully synthesized with relatively precise chemical composition control. FT-IR, Raman, UV-Vis, XRD, FESEM, and EDS characterization techniques were used to investigate the structural evolutions. The results supported that the calcination leads to remarkable elimination of the oxygen-containing groups, detachment of sheets, and the decrease in interplanar spacing. It was also observed that the graphene oxide sheets act as templates for the formation of boron carbonitrides, and by reducing the ratio of graphene oxide to boric acid and urea, morphology changes from a layered to an agglomerated state, while the crystal structure remains turbostratic in both morphologies. The high affinity for boron-nitrogen bond formation indirectly indicated the formation of BN islands coexisting with graphene ones in most samples. The calculated Tauc plots also stated the success of the method used in the modulation of electronic structure and optical energy bandgap. Furthermore, electrochemical measurements of the samples, as electrocatalysts in the hydrogen evolution reaction, showed that the electrocatalytic activity and charge transfer rate increased with increasing boron and nitrogen levels, which decreased afterward. Finally, in the best electrocatalytic performance, the onset potential of 246 mV vs. RHE, overpotential of 395 mV vs. RHE at 10 mAcm-2, and Tafel slope of 42.3 mVdec-1 were measured. Compared to other studies, the small Tafel slope showed a Heirovsky step controlled and the fast kinetics of the reaction at the electrode surface
  9. Keywords:
  10. Doping ; Electrocatalysts ; Hydrogen Evolution Reaction ; Hexagonal Boron Nitride

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