▎ 摘　　要

NOVELTY - A graphene oxide solution is prepared, added to mixture of dimethylaminopropyl ethyl carboxamide and ethylenediamine, silica nanoparticles are added, and positively charged graphene oxide is added, centrifuged and dissolved in deionized water, and washed, to obtain graphene oxide/silica nanocomposite particles. The graphene oxide/silica nanocomposite particles are heated, and cooled, to obtain silica coated graphene nanoparticles. The nanoparticles are dissolved in hydrofluoric acid, vacuum filtration is carried out, and washed, to obtain graphene. USE - Preparation of graphene used for electrochemical capacitor (claimed). ADVANTAGE - The electrochemical capacitor formed using graphene has high storage stability. DETAILED DESCRIPTION - Graphite oxide is dispersed in deionized water, and ultrasonically treated, to obtain graphene oxide solution having concentration of 0.5-1 mg/ml. A solution of partially oxidized graphene is taken, and pH is adjusted to 3-6, to obtain negatively charged graphene oxide solution. Another portion of graphene oxide solution is added to dimethylaminopropyl ethyl carboxamide and ethylenediamine, 20-30 mg/ml silica nanoparticles are added, and positively charged graphene oxide is added, mixed, centrifuged and dissolved in deionized water, and washed for 3-10 times, to obtain graphene oxide/silica nanocomposite particles. The nanocomposite particles are placed under an inert atmosphere, heated at 700-900 degrees C and at rate of 15-30 degrees C/minutes for 0.5-2 hours, and cooled to room temperature, to obtain silica coated graphene nanoparticles. The silica coated graphene nanoparticles are mixed with hydrofluoric acid in a ratio of 1 g:0.5-2 ml, stirred, vacuum filtration is carried out, and washed with deionized water to neutral pH, to obtain graphene. INDEPENDENT CLAIMS are included for the following: (1) graphene; and (2) usage method of graphene, which involves using graphene for electrochemical capacitor.