The Study on Nickel Cobalt Compound@Nickel Molybdate Core-Shell Structure Applied to Supercapacitor and Electrocatalytic Oxygen Evolution Reaction

• Main Authors: CHIU, KUAN-LIN, 邱冠霖
• Other Authors: LU, YIN-LIN
• Format: Others
• Language: zh-TW
• Published: 2019
• Online Access: http://ndltd.ncl.edu.tw/handle/gad94n

碩士 === 國立臺北科技大學 === 化學工程與生物科技系化學工程碩士班 === 107 === Nickel cobalt sulfide has been widely used in the field of supercapacitor owing to its high conductivity and its multiple oxidation states. Higher electrochemical performance can be achieved by the combination of nickel cobalt sulfide with the core-shell hollow structure. Many researches about nickel cobalt sulfide with a core-shell hollow structure have been reported, and they were often used as the electrodes for supercapacitor. The application for the electrocatalyst for water splitting, which has the same requirements as supercapacitors, were rarely discussed. If one can explore nickel cobalt sulfide with core-shell hollow structure into these two fields, it can not only greatly enhance the applications of this material, but also acts as a bridge to connect this two fields. This research has successfully synthesized the nickel cobalt compoud@nickel molybdate with a core-shell hollow structure on nickel foam by combination of two facile methods, hydrothermal and calcination, and we applied this material to supercapacitor and eletrocatalyst for oxygen evolution reaction. The walls of nickel cobalt compound nanotubes are composed of interconnected nickel molybdate nanosheets. The nanotubes can accelerate electrons transfer rate, and the nanosheets can enhance the stability of nickel cobalt compoud@nickel molybdate . When evaluated as the electrode for supercapacitor, the nickel cobalt sulfide@nickel molybdate exhibits ultrahigh specific capacitance of 17.75 F cm-2 at a current density of 10 mA cm-2. Even at high current density of 50 mA cm-2, nickel cobalt compound@nickel molybdate still possess the specific capacitance of 10.88 F cm-2. When assembly with activated carbon to form asymmetry supercapacitor, it has an energy density of 5.28 Wh kg-1 in a power density of 328.86 W kg-1, and possess an energy density of 1.21 Wh kg-1 in a power density of 2302.01 W kg-1. The results showed that the nickel cobalt compound@nickel molybdate is better than nickel cobalt sulfide in the field of energy storage device. When nickel cobalt compound@nickel molybdate evaluated as the electrocatalyst for oxygen evolution reaction, nickel cobalt compound@nickel molybdate has to applied higher overpotential of 1.567 V vs. RHE to achieve 0.12 A cm-2 current density, While nickel cobalt sulfide only needs 1.553 V. Nickel cobalt sulfide has a tafel slope of 86.1 mV dec-1, which is lower than nickel cobalt compound@nickel molybdate. It means that when a material is suitable for energy storage device, it is not definitely suitable for electrocatalyst for oxygen evolution reaction.