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Preparation and electrochemical performance of nitrogen-enriched activated carbon derived from silkworm pupae waste
(2019-01-01)
Sattayarut, Vichuda
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Chanthad, Chalathorn
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Khemthong, Pongtanawat
;
Kuboon, Sanchai
;
Wanchaem, Thanthamrong
In this study, nitrogen-enriched activated carbon from silkworm pupae waste (P-AC) was successfully prepared and its electrochemical performances in aqueous and organic electrolytes were investigated. Silkworm pupae waste is beneficial because it is a nitrogen-enriched, inexpensive, and locally available material. The preparation process includes hydrothermal treatment of the silkworm pupae waste at 200 °C, and chemical activation using zinc chloride at activation temperatures of 700, 800 and 900 °C (P700, P800, and P900, respectively). The nitrogen content in the P-ACs was approximately 3.8-6.4 at%, decreasing with activation temperature, while the surface area was approximately 1062-1267 m2 g-1, increasing with activation temperature. Compared to a commercial AC, the P-ACs show higher nitrogen content but lower surface area. Furthermore, the P800 exhibited superior specific capacitance (154.6 and 91.6 F g-1 in aqueous and organic electrolytes) compared to a commercial AC despite possessing smaller surface area. The high nitrogen content enhanced the pseudocapacitance and improved the electrical conductivity of the P-ACs. These properties were confirmed by relatively low series and charge transfer resistances, a capacity retention higher than 88% at a current density of 0.5 A g-1 and excellent cycling stability demonstrated by maintaining 97.6% of its capacitance after 3000 cycles. These results demonstrate that silkworm pupae waste is a viable source of nitrogen-enriched AC for application in supercapacitors.
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Piezoelectric-Induced Triboelectric Hybrid Nanogenerators Based on the ZnO Nanowire Layer Decorated on the Au/polydimethylsiloxane-Al Structure for Enhanced Triboelectric Performance
(2018-02-21)
Jirayupat, Chaiyanut
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Wongwiriyapan, Winadda
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Kasamechonchung, Panita
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Wutikhun, Tuksadon
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Tantisantisom, Kittipong
Here, we demonstrate a novel device structure design to enhance the electrical conversion output of a triboelectric device through the piezoelectric effect called as the piezo-induced triboelectric (PIT) device. By utilizing the piezopotential of ZnO nanowires embedded into the polydimethylsiloxane (PDMS) layer attached on the top electrode of the conventional triboelectric device (Au/PDMS-Al), the PIT device exhibits an output power density of 50 μW/cm2, which is larger than that of the conventional triboelectric device by up to 100 folds under the external applied force of 8.5 N. We found that the effect of the external piezopotential on the top Au electrode of the triboelectric device not only enhances the electron transfer from the Al electrode to PDMS but also boosts the internal built-in potential of the triboelectric device through an external electric field of the piezoelectric layer. Furthermore, 100 light-emitting diodes (LEDs) could be lighted up via the PIT device, whereas the conventional device could illuminate less than 20 LED bulbs. Thus, our results highlight that the enhancement of the triboelectric output can be achieved by using a PIT device structure, which enables us to develop hybrid nanogenerators for various self-power electronics such as wearable and mobile devices.
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Facile synthesis of hybrid manganese oxide and multiwalled carbon nanotube by two-step electrodeposition for supercapacitor electrode
(2017-01-01)
Wanchaem, Thanthamrong
;
Rattanamai, Songsak
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Dulyaseree, Paweena
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Khanchaitit, Paisan
;
Wongwiriyapan, Winadda
This work presents a facile synthesis of hybrid manganese oxide and multiwalled carbon nanotube (MnO<inf>x</inf>/MWCNT) by two-step electrodeposition technique for supercapacitor electrode application. Firstly, MWCNT was deposited onto SS304 substrate by electrophoretic deposition at a constant voltage of 7 V for 5 min. MWCNT solution was prepared using sodium dodecylbenzenesulfonate (SBDS) as a surfactant. Next, MnO<inf>x</inf> was deposited onto the pre-deposited MWCNT/SS304 substrate by galvanostatic electrodeposition using 0.1 M manganese sulfate (MnSO<inf>4</inf>) solution as a precursor. The electrodeposition condition was set at a constant current of 1 mA/cm2 for 5-15 min. Nanosheet array of MnO<inf>x</inf> was formed uniformly on MWCNT. At the deposition time of 10 min, the thickness of MnO<inf>x</inf> nanosheet was approximately 40 nm. Hybrid MnO<inf>x</inf>/MWCNT was characterized its electrochemical properties by cyclic voltammetry, galvanostatic charge-discharge, and electrochemical Impedance spectroscopy. Hybrid MnO<inf>x</inf>/MWCNT shows an improved specific capacitance of 267.03 F·g-1 with a series resistance of 5.17 Ω, surpassing electrode material with only MnO<inf>x</inf> or MWCNT. The high specific capacitance would be ascribed to the integration of MWCNT and MnO<inf>x</inf> functions. MWCNT may act as a platform for MnO<inf>x</inf> deposition, resulting in an increase in electrochemically active surface area of MnO<inf>x</inf>. The obtained results indicate that this two-step electrodeposition method allows tailor-made hybrid materials with nanoscale control without using harsh and toxic chemicals or high synthesis temperature.

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