| Summary: | 碩士 === 國立高雄應用科技大學 === 化學工程系碩士班 === 96 === Nickel hydroxide (Ni(OH)2) powder is synthesized by co-precipitation method and is deposited onto the stainless steel (SS) substrate by electrophoretic deposition (EPD) and dip coating, respectively. Electrochemical performances and capacitive properties of the deposited Ni(OH)2 electrode after annealing at different temperatures for different lengths of time is investigated by cyclic voltammetry (CV). In addition, nickel oxide/carbon fiber (NiO/VGCF) and nickel oxide/carbon nanotube (NiO/CNT) composite electrodes are fabricated by EPD in order to enhance the capacitive behavior of the pure NiO electrode.
Surface morphology of the synthesized Ni(OH)2 powder is platelet-like shape structure observed by SEM. Annealing temperature influences both the crystal structure and the specific surface area of the synthesized Ni(OH)2. XRD results show that the Ni(OH)2 converts into NiO after annealing at temperature higher than 300 ℃ due to the removal of water from Ni(OH)2. BET analysis indicates that Ni(OH)2 powder after annealing at 300 ℃ has the highest specific-surface area compared with other annealing temperatures.
An electrode after annealing at 300 ℃ has better capacitive behavior due to the conversion of Ni(OH)2 to NiO. The oxidation and reduction peaks during CV scan appear at 0.45 V and 0.35 V versus Ag/AgCl reference electrode, respectively. Specific capacitance of an electrode after annealing at 300 ℃ is found to be about 140 Fg-1 at a scan rate of 10 mVs-1.
The XRD and SEM results indicate that NiO particles are coated on the surface of carbon nanofiber/nanotube by EPD. The high conductivity of VGCF facilitates the redox reactions of NiO in 0.45 V (oxidation) and in 0.35 V (reduction), and therefore, promotes effectively the nickel oxide in the capacitance characteristics.
Compared with NiO electrode, the specific capacitances of NiO/VGCF and NiO/CNT composite electrodes are increased by 30 Fg-1 and 10 Fg-1, respectively in scan rate of 10 mVs-1. The results show that VGCF and CNT can improve the capacitive behavior of the composite electrode effectively.
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