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RISS 인기검색어
- 검색키워드
- 저자 : M. Saghafi (검색결과 2 건)
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Zn-Co oxide electrodes with excellent capacitive behavior for using supercapacitor application
M. Saghafi,Sh. Zangeneh 한국물리학회 2019 Current Applied Physics Vol.19 No.6
In the present study, super-capacitive behavior of spinel Zn-Co oxides (with different Zn+2/Co+2 mol ratio) has been thoroughly investigated. The spinel of transition metal oxides with different morphologies has been synthesized with hydrothermal method on Ni foam as substrate layer. The specific capacitance of the Zn-Co oxide electrode prepared at 180 °C for 5 h with different Zn+2/Co+2 mol ratios of 1:0, 2:1, 1:1, 1:2, 0:1 were investigated and measured 405, 842, 726, 1237, 705 F g−1, respectively at 50 mV s−1 scan rate. Zn-Co oxide with Zn+2/Co+2 mol ratio of 1:2 was also synthesized at two different temperatures of 120 and 150 °C for 5 h with the specific capacitance of 1147, 917 F g−1 at 50 mV s−1 scan rate, respectively. Among the obtained data, the sample with Zn+2/Co+2 mol ratio of 1:2 prepared at 180 °C for 5 h possessed highest specific capacitance. The cyclic life of this electrode showed 92% capacitance retention after 1000 cycle of charge-discharge. All results revealed that Zn-Co oxides had excellent supercapacitive properties due to multiple oxidation states and fast ion/ electron transfer at the surface of electrode which could be offered as suitable devices for energy storage applications.
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Longitudinal unzipping of carbon nanotubes and their electrochemical performance in supercapacitors
M. Saghafi,F. Mahboubi,S. Mohajerzadeh,M. Fathi,R. Holze 한국물리학회 2014 Current Applied Physics Vol.14 No.10
The capacitive properties of graphene nanoribbons (GNRs) with different reduction levels were investigated. GNRs have been synthesized through thermal reduction of oxidized GNRs in the temperature range 100e400 C. Oxidized GNRs were synthesized by longitudinal unzipping of multi-walled carbon nanotubes (MWCNTs) by means of chemical treatments. Scanning electron microscopy and transmission electron microscopy observations showed, that the efficient tube unzipping yielded improved effective surface area without any tube annihilation by the unzipping process of MWCNTs. Electrochemical studies indicated that through unzipping of MWCNTs, specific capacitance increased from 8 to 28 F g1 at discharge current density of 0.5 A g1, confirming increased active surface area and increased defect density in the MWCNTs surface. Unzipping of MWCNTs resulted in decreased rate capability of the electrode because of low electrical conductivity due to oxidization during the unzipping process. Thermal reduction of unzipped sample affected both specific capacitance and rate capability of electrodes. The highest specific capacitance of 62 F g1 at discharge current density of 0.5 A g1 was obtained for the sample unzipped and thermally annealed at about 150 C. The amount of oxygen-containing groups was shown to be an important factor influencing the performance of the GNRs. These results make unzipped MWCNTs promising electrode materials for supercapacitor applications.
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