Synergistic effects of b4c and zno nanomaterials as electrodes for supercapacitors

Official URL: https://risc01.sabanciuniv.edu/record=b2767354_(Table of contents)

Boron carbide (B4C) is one of the world’s hardest bulk materials with excellent stability in extreme chemical and thermal conditions. Despite its discovery in the 19th century and numerous studies since 1930s, its atomic structure, electronic properties and electrochemical behavior are yet one of the most debated topics among chemists, physicists and materials scientists. The difficulty in distinguishing the absolute accurate atomic positions with common characterization techniques is mainly due to the very close similarity of the scattering cross-sections of 11B and 12C, and the point defects formed within the crystal which affects the atomic arrangements and the charge densities in the elementary cells. Similarly, significant efforts have been devoted to reveal the unique electronic, optical, structural and magnetic properties of zinc oxide (ZnO) which is an n-type semiconductor and has been used in various applications including energy storage devices, particularly supercapacitors (SCs). The development of efficient and long-life electrodes from sustainable materials for SCs is of the utmost importance to satisfy the increasing energy demands. In this Ph.D. dissertation, B4C and ZnO were selected as electrodes for SCs due to their interesting defective properties that contribute to the enhanced capacitive performances by modifying their electronic and atomic structure. First, modified sol-gel synthesis of B4C nanostructures from aqueous solutions of B and C sources was described. The pure B4C phase was obtained by the heat treatment at temperatures ≤1500 ℃ which is lower than the conventional sintering temperatures (≥ 2000 ℃). Then, extensive thermal and microstructural characterizations were carried out to reveal the crystal structure, lattice parameters, mean particle size, and the microstructure of the synthesized B4C powders. Complementary X- and Q-band EPR analyses of defect centers in B4C and ZnO were performed to reveal the effects of intrinsic defects on the electrochemical performance of the SCs. The synthesized B4C and ZnO were v assembled in a custom-made all-in-one supercapacitor device, and their synergistic effects on the electrochemical performance was investigated by CV, EIS, and GCPL techniques.