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Structural, morphological, optical, and electrochemical properties of Zn-doped CeO2/rGO nanocomposites
(2025-04-01)
Utara, Songkot
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Salidkul, Nuchjaree
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Karaphun, Attaphol
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Sonsupap, Somchai
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Chanlek, Narong
Metal-doped cerium oxide has recently attracted the interest of researchers worldwide because of its various applications in different fields such as supercapacitors, high-sensitivity electrodes or photocatalytic. Metal-doped cerium oxide can be improved utilizing a variety of metals and composites with enhanced conductivity, which advances materials science in semiconductor processing. In this study, undoped and Zn-doped CeO<inf>2</inf> nanoparticles at 5, 10, 15, and 20 at.% were reacted with reduced graphene oxide (rGO) using a hydrothermal method. They were heated at 150 °C for 12 h and then processed in an ultrasonic reactor (20 kHz) at 25 ± 1 °C. Their structural, morphological, elemental, optical, and electrochemical properties were systematically characterized. The calculated average crystallite sizes of CeO<inf>2</inf> peaks ranged from 4.60 ± 0.2 to 12.0 ± 0.4 nm. These samples exhibited a single CeO<inf>2</inf> phase corresponding to a face-centered cubic structure, except for 20 at.% Zn-doped CeO<inf>2</inf>/rGO, which presented a ZnO phase. The samples had lower band gap values than expected for undoped CeO<inf>2</inf> nanoparticles, higher valence states due to their Ce3+/Ce4+ ratios, and a large surface area, 242 m2/g, due to Zn-doping in CeO<inf>2</inf> samples. The highest specific capacitance values achieved were 88.49 F/g at 5 mV/s and 134.01 F/g at 0.5 A/g for undoped CeO<inf>2</inf>/rGO. Zn-doping resulted in decreased capacitive behavior with specific capacitance values in the range of 70.78–81.00 F/g at 5 mV/s and 79.24–101.43 F/g at 0.5 A/g. This study for synthesizing Zn/CeO<inf>2</inf>/rGO ternary nanocomposites produced materials with improved band gaps, valence states of Ce3+/Ce4+ ratios, and greater surface area for improved electrocatalytic performance.
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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
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Karaphun, Attaphol
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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−1 at current density of 0.5 A g−1. 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−1 at current density of 0.5 A g−1. 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−1 at current density of 3 A g−1. This hybrid energy-storage device indicated specific energy density (E<inf>sp</inf>) of 11.09 W h kg−1 and specific power density (P<inf>sp</inf>) of 2.67 kW kg−1, 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
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Phrompet, Chaiwat
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Maneesai, Keerati
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Karaphun, Attaphol
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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.

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