Study On Application And Performance Of Nanometer Silicon Carbide As Electrode Material

SiC is a typical kind of compound which is combined by covalent bond. It has thecharacteristics of stable chemical performance, high coefficient of thermal conductivity,low coefficient of thermal expansion and good wear-resisting performance. So it iswidely used as abrasives products, refractory materials, semiconductor materials and soon. Micro-nanometer silicon carbide （N-SiC, M-SiC） has the advantages of small sizeparticles, large specific surface area, high surface energy and high surface atomicproportion. So SiC is expected to be used in the areas of electrocatalysis,photoelectrochemistry and electroanalytical chemistry.The electrochemical properties of SiC powder electrode were investigated indifferent pH values of acid, neutral and alkaline support electrolytes. The electrochemicaldynamics process of SiC powder electrode were studied in Na₂SO₄solution includingK₃Fe（CN）₆. The electrochemical dynamics of SiC powder electrode were analyzed inphosphate buffer solution （PBS） containing NO₂^-. And the electrochemical properties ofSiC powder electrodes in solutions including heavy metal lead ion (Pb²⁺) wereresearched. The results indicated that the background currents of SiC powder electrodesin the three kinds of support electrolytes were almost equal and very low. Comparingwith M-SiC powder electrode, N-SiC powder electrode shows wider potential window inneutral solution. The electrochemical reaction of SiC powder electrodes belongs to thequasi-reversiblility reaction in0.01M Fe（CN）₆^3-/4-0.5M Na₂SO₄solution. The peekcurrents intensity are proportional to the square root of the scan rate, which suggests thekinetics process of nano-SiC powder electrode is diffusion-controlled. The resultssuggests clear oxidation effect of NO₂^-appeared at SiC powder electrodes. Comparingwith M-SiC powder electrodes, the initial potential of NO₂^-at N-SiC powder electrodesmoved towards to negative direction, the oxidation peak current of NO₂^-becominglarger, which indicated the N-SiC powder electrodes had larger detection sensitivity.And the limit of detection （LOD） of NO₂^-at N-SiC powder electrodes is610^-8M.The cycle voltampere curve of Pb²⁺at N-SiC powder electrodes showed that thereduction potential of Pb²⁺is-0.5V and the oxidation potential of Pb is-0.3V. The the reduction potential was set to-0.5V. Through differential pulse anodic strippingvoltammetry （DPASV）, the below situation was analyzed. The oxidation peak currentdensity increased when dissolve out time and the concentration of Pb²⁺became larger.The experiments showed the LOD of Pb²⁺on N-SiC powder electrode was4.0510^-5M.N-SiC supported Pt （Pt/N-SiC） catalyst were prepared during the research，and theinfluence of different Pt loading on the catalytic performance was investigated. Theresults showed that Pt/N-SiC catalyst had good catalytic effect in the range of20wt%～49wt%. But the catalytic current would become small with low Pt loading because ofpoor conductivity of N-SiC, which could not play an enough catalytic effect on methanoloxidation. In order to improve the electroconductibility of the catalyst, the two kinds ofconductive agents carbon nano tubes （CNTs） and acetylene black were added. When Ptloading was less than20wt%, the catalytic current became larger （approximately1.1mA）due to the addition of CNTs and acetylene black. And the good catalytic effect dependson less amount of conductive agents. But the conductive agents couldn’t mix uniformlywith the catalyst, which relatively reduced the specific surface area of Pt and thusinfluenced the catalytic performace of the catalyst. After heat treatment in a vacuumenvironment, N-SiC turned into N-GSiC. So the surface of N-SiC was parceled bygraphite of very good conductive properties. The prepared Pt/N-GSiC catalyst usingmicrowave method largely improved the electroconductibility of the catalyst. The Ptsupported on graphite layer could more effectively catalyze the oxidation of methanol.