Graphite Oxide Loaded With Metal Sulfide (co <sub> 9 </ Sub> S <sub> 8 </ Sub>, Of Cus) Preparation And Electrochemical Properties

Graphite,with long electrochemical stability,has obstacles in technological applications owning to its hydrophobic and oil-phobic nature.We produced graphite oxide by heavily oxygenation of the pristine graphite,which presented as a potential nano-filler.Combined with materials with good electrochemical performance,i.e.metal sulfide,the graphite-based composites will be an attractive candidate for supercapacitor electrodes.In this work,GO loaded cobalt sulfide(Co₉S₈/GO) was fabricated via discrepant sulfide precursors;the effects of reaction parameters(solvents and dispersants) and synthetic routes (solvethermal and reflux) on the morphology and texture of as-obtained products were considered.A series of products with different loading levels were synthesized to probe its relationship with dispersiblity.Co₉S₈/GO(molar ratio:Co₉S₈/GO = 3:1) prepared by reflux at 160℃in ethylene glycol,with COCl₂.2H₂O,thiourea and urea as cobalt,sulfur source and dispersant,has a uniform particle size(5 nm),good dispersiblity and the most effective loading level.The possible mechanism for the formation of as-obtained samples was discussed.Based on the experiment above,CuS/GO was fabricated;the difference between CuS (with copper at a higher valence state) and Co₉S₈(with cobalt at a relative low valence state) was considered.CuS/GO(molar ration:CuS/GO = 2:1) prepared by hydrothermal method at 140℃in ethylene glycol,with CuCl₂.2H₂O,CS₂ and ethylenediamine as copper,sulfur source and sulfur ligand,exhibits a hexagonal morphology with particle size of 50～200nm and good dispersiblity.The possible mechanism was discussed.The electrochemical properties of the obtained products were studied by cyclic voltammetry(CV),electrochemical impedance spectroscopy measurement(EIS) and galvanostatic charge-discharge tests.According to area of CV curves,Co₉S₈/GO(with the loading level:Co₉S₈/GO = 3:1,molar ratio,synthesized by reflux method) and CuS/GO(with the loading level:CuS/GO = 2:1,molar ratio,synthesized by hydrothermal method) gained the highest specific capacitance(689.36 and 183.3 F/g) compared with their counterparts, which retained 79.9%and 76.9%of initial capacitance after 500 cycles in the galvanostatic charge-discharge measurements,respectively.This result consists well with the proposed mechanism.