Supercapacitive performance of NiO Nanospheres Prepared by Electrodeposition-Heat treatment method

Nanostructured nickel oxide (NiO) has received increased interest because of its potential applications in rechargeable alkaline batteries [1], supercapacitors [2] and solar cells [3]. As aresult, different synthesis methods such as chemical precipitation, decomposition, hydrothermal, surfactant template, solid state, solvothermal and sol–gel have been developed for preparation of NiO nanostructures with various shapes and sizes. Furthermore, electrochemical methods (i.e.anodic and cathodic electrodeposition) have been applied for the preparation of nanostructured NiO and demonstrated that electrolytic NiO exhibits better supercapacitive behavior, which can be employed in electrochemical supercapacitors. In this letter, we report NiO ultrafinenanoparticles prepared by galvanostatic deposition (i=0.5 A dm−2) from 0.005 M Ni(NO3)2 bath (T=40C) followed by heat-treatment at 300oC for 3h. The supercapacitive performance of the nanoparticles was evaluated by cyclic voltammetry (CV) and charge-discharge techniques.Fig. 1a shows XRD pattern of the oxide product. The observed peaks in this XRD pattern are fully matched with the corresponding pure cubic-structured crystalline NiO (JCPDS 47-1049, solid lines in Fig. 1a). The SEM image (Fig. 1b) showed the smooth and uniform sphere shapemorphology for NiO. In fact, NiO sample is composed of well–dispersed spheres with the size of about 50 nm (Fig. 1b). The galvanostatic charge-discharge cycling (1000 cycles) was recorded ata current density of 2 A g─1 which the first 20 cycles is presented in Fig. 2. Then, the specificcapacitance was calculated to be 1108 F g─1. As seen in Fig. 2, the specific capacitances of 500th and 1000th discharging cycles were calculated to be 1042 and 998 F g─1, which revealed 94.1% and 90.2% capacity retentions after 500 and 1000 discharging. These results confirmed an excellent cycling stability of NiO nanospheres

کلیدواژه ها:

NiO ، Electrosynthesis ، Nanospheres ، Supercapacitors