Preparation And Eletrochemical Properities Of Nanodiamond Based Electrode Material

Nanodiamond, as a kind of functional materials, has both properties of diamond and nanomaterials. On the one hand, nanodiamond has high mechanical strength, thermal and chemical stability, so it can stably work in a strong corrosive solution, poisonous or high potential environments for a long time. These properties make it has potential to be a kind of good electrode material. On the other hand, as a kind of nanomaterials nanodiamond has large surface areas and high surface activity. So it has the potential to be a new catalyst support material.The electrochemical properties of nanodiamond powder electrode were studied by cyclic voltammetry. The results showed that nanodiamond powder electrode was electrochemically stable in KCl electrolytes, its potential window was 2.2 V and background current in magnitude was 1×10-6 A. The electrode reaction was quasi-reversible and diffusion-controlled in ferricyanide–ferrocyanide redox couple solution.The electrochemical properties of nanodiamond powder electrode toward nitrite oxidation were also studied with cyclic voltammetry and Tafel curves. The detection limit was 1.2×10^-4 mol/L. Coating nanodiamond with Titania could improve the electrochemical activity of nanodiamond. Cycled vacuum-feeding chemical vapour deposition was utiltzed to coat nanodiamond with titanium from gaseous TiCl₄ and H₂, and then an oxidation treatment was carried out in the air. Titania coating was obtained on the surface of nanodiamond particles. The structure and the morphology of the TiO2/ND were characterized by Raman spectrum and Transmission Electron Microscopy. Anatase coated nanodiamond powder electrode could catalyse the oxidation of nitrite, and improve the detection limit to 5.5×10^-7 mol/L.Nanodiamond powder with average particle sizes of 5 and 100 nm (ND5 and ND100) were modified with Pt nanoparticles by electrodeposition from 1.1 mmol/L H2PtCl6+0.5 mol/L H₂SO₄ aqueous solution for 1200 s under -0.2 V. The structure and morphology of the composite were characterized by Field Emission-Scanning Electron Microscope and X-ray Diffraction. The results showed that Pt nanoparticles with particle sizes of 10 nm were well-dispersed on the facet surfaces of nanodiamond particles. The electrooxidation of methanol on Pt-modified nanodiamond powders was investigated by cyclic voltammetry, which indicated its good electrocatalytic activity. Compared with ND100, ND5 modified with Pt nanoparticles exhibited better electrocatalytic activity on the same deposition conditions.Pt-modified nanodiamond was prepared by a microwave heating polyol method. The structure and morphology of the composite were characterized by Transmission Electron Microscopy and X-ray Diffraction. It was found that the Pt nanoparticles were small and uniform in size, and highly dispersed on nanodiamond supports. The mean size of the Pt particles was 3⁵ nm, which is smaller than that obtained by electrodeposition. The Pt-modified nanodiamond exhibited good electrocatalytic activity for methanol electrooxidation. Compared with Pt/ND100 and Pt/ND250, Pt/ND5 with same Pt loading exhibited a much higher electrocatalytic activity for methanol electrooxidation.