Fabrication And Electrochemistry Properties Of Transition Metal Oxides/sulfides And Composites

During the burning of Coal and fossil fuels a huge quantity of pollutant is produced and discharged in the air which leads to more environmental problems, therefore many researchers pay much attention to this phenomenon and also to the process of power consumption transfers and power recycle. Considering the system of power transformation,pesudocapacitor has been widely used as a large potential development, they have a higher power density comparing to the battery and also a large energy density than double electrode layer supercapacitor. The transition oxides/sulfides with an excellent electrochemical performance have been fabricated using an electro chemical reaction.First of all, the samples of cobalt hydroxide with nano lamellar structure were prepared by traditional hydrothermal method, an ion exchange reaction between the cobalt and the sulfur sodium was then produced in the solution. A reaction between the cobalt hydroxide nanometer pieces and the sulfur sodium hydride has taken place and the hydrogen sulfide cobalt slices were then produced and kept the layer structure of cobalt oxide nanometer precursor. Large number of active site and functional groups were found on the surface of the sulfide cobalt nanometer pieces after the ion exchange reactions, and therefore making new compound with other nanomaterials groups will be easy due to the huge number of these actives sites. The combination between the sulfide cobalt nanometer pieces and the reduced graphene oxide, not only increase the contact area with the electrolyte, but also improve the conductivity of the material and the efficiency of the charge transfer, which played a positive role on improving its electrochemical performance. Due to the dual function of pseudocapacitors electrode material and double electrode layer supercapacitors electrode material, CoS/rGO got the specific capacity of 772.7 F·g-1 with current density of 5 mA·cm-2 in electrochemical performance test, which means that CoS/rGO has great potential in the super capacitor application.The reductive graphite oxide was attached on the surface of nickel foam three dimensional network structures by a soaking method; the precursor used was prepared by the etching nickel foam using the hydrochloride. Nickel hydroxide has grown on the nickel foam substrate; then an ion exchange reaction occurred in the NaHS solution. Nickel sulfide nanopieces kept the nanometer crisscrossed lamella structure of the nickel hydroxide precursor, and finally Ni3S2/rGO composite material was then prepared.Although the lamellar morphology structure of nickel sulfide was affected by the coating graphene, however this later prevents the nanometer layers to fall during the process of charging and discharging deformation. Composite materials showed excellent electrochemical performance in electrochemical tests compared with pure nickel sulfide material (The specific capacity of Ni3S2/rGO was 1133.33 F·g-1 at a current density of 15 mA·cm-2). The purpose of this process is improving the dispersion and conductive properties of the two-dimensional material by growing onto substrate and therefore improving their electrochemical performance.