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Author: search.filters.author.Tuichai, WattanaSubject: search.filters.subject.Reduced graphene oxide

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    Ag nanomaterials deposited reduced graphene oxide nanocomposite as an advanced hybrid electrode material for Asymmetric Supercapacitor device
    (2020-12-30)
    Tuichai, Wattana
    ;
    Karaphun, Attaphol
    ;
    Ruttanapun, Chesta
    Asymmetric Supercapacitor (ASC) was effectively fabricated using CR 2032-coin cell based on the positive electrode of the hybrid Ag@rGO nanocomposite and the negative electrode of reduced Graphene Oxide (rGO) material with polyvinyl alcohol (PVA)/6 M KOH electrolyte. The Ag@rGO nanocomposite was prepared through a seed-mediated growing process by a 10 wt% of Ag nanomaterials deposits in suspension rGO 90 wt% which presented a specific capacitance value of 65.9 F g<sup>−1</sup> at current density of 0.5 A g<sup>−1</sup>. Moreover, the rGO electrode with a 5 mg/mL concentration was synthesized by the modified Hummers’ method and revealed a high specific capacitance value of 317.3 F g<sup>−1</sup> at current density of 0.5 A g<sup>−1</sup>. Interestingly, the ASC assembly of Ag@rGO//rGO hybrid energy-storage device provided a wide voltage window of 0.0–1.4 V and showed a specific capacitance (C<inf>sc</inf>) value of 44.17 F g<sup>−1</sup> at current density of 3 A g<sup>−1</sup>. This hybrid energy-storage device indicated specific energy density (E<inf>sp</inf>) of 11.09 W h kg<sup>−1</sup> and specific power density (P<inf>sp</inf>) of 2.67 kW kg<sup>−1</sup>, respectively. It also showed a good cycle stability of 81.5%. The capacitance retention finished at 500 cycles.
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    Effect of grain boundary interfaces on electrochemical and thermoelectric properties of a Bi2Te3/reduced graphene oxide composites
    (2020-08-01)
    Thongsamrit, Wannisa
    ;
    Phrompet, Chaiwat
    ;
    Maneesai, Keerati
    ;
    Karaphun, Attaphol
    ;
    Tuichai, Wattana
    The electrochemical and enhanced thermoelectric properties of pristine Bi<inf>2</inf>Te<inf>3</inf> and Bi<inf>2</inf>Te<inf>3</inf>/reduced graphene oxide (Bi<inf>2</inf>Te<inf>3</inf> + rGO) composites at 1%, 3% and 5% levels of rGO were synthesized via a simple ultrasonic method. The X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), UV–vis spectrometry (UV–vis) and their electrochemical and thermoelectric properties were measured. The ultrasonic method succeeded in producing rGO nanosheets composited with Bi<inf>2</inf>Te<inf>3</inf> forming grain boundary interfaces of rGO with Bi<inf>2</inf>Te<inf>3</inf>. The resulting samples displayed a continuous network structure of rGO nanosheets in Bi<inf>2</inf>Te<inf>3</inf> + rGO composites for electrons in the conduction band of the Bi<inf>2</inf>Te<inf>3</inf> structure. Electrons were transferred to rGO nanosheets at the interface, contributing electron charge carriers in Bi<inf>2</inf>Te<inf>3</inf> + rGO composites. This indicates band alignment between Bi<inf>2</inf>Te<inf>3</inf> and rGO nanosheets. The Bi<inf>2</inf>Te<inf>3</inf> + rGO composites exhibited an increasing storage charge mechanism of electrical double layer capacitors with greater rGO contents. The Bi<inf>2</inf>Te<inf>3</inf> + rGO composites displayed negative a Seebeck coefficient for thermoelectric materials. The highest ZT value was 0.17 in the bulk 1% Bi<inf>2</inf>Te<inf>3</inf> + rGO composite. Improved electrochemical and thermoelectric properties of the Bi<inf>2</inf>Te<inf>3</inf> + rGO 1% composite resulted from the interaction of the grain boundary interfaces of rGO nanosheets with pristine Bi<inf>2</inf>Te<inf>3</inf> following the model of band alignment between Bi<inf>2</inf>Te<inf>3</inf> and rGO nanosheets.