Preparation Of Pt/Graphene Nanocomposite Electrode And Its Electrocatalytic Performance For Methanol Oxidation

Direct methanol fuel cell is one of the most popular projects in the field of fuel cells in recent years, which has advantages of high energy density, low operating temperature, start fast and so on. However, its commercial development is severely restricted by the high cost, low activity and poor stability of the Pt catalyst. Therefore, the developments of economic and efficient catalysts become an important topic of direct methanol fuel cell research. The thesis studies the preparation of Pt/graphene nanocomposite electrode and its electrocatalytic performance for methanol oxidation, which specifically includes:1. The Pt/graphene nanocomposite was prepared by ultrasonic method with the non-toxic ascorbic acid as reducing agent within one-step process. The structure and morphologies of the obtained catalysts were characterized by ultraviolet visible absorption spectrum, X-ray diffraction and scanning electron microscopy. The results showed that Pt nanoparticles were successfully assembled and well distributed on the surface of graphene sheets.2. The Pt/graphene nanocomposite was coating on the surface of glassy carbon electrode and the electrocatalysis properties of modified electrode for methanol oxidation in acid solution were characterized by cyclic voltammetry, chronoamperometry, chronocoulometry and electrochemical impedance spectroscopy. The modified electrode of Pt nanoparticles undoped with graphene was fabricated for comparison. The electrochemical results indicated that the anodic oxidation of electrode is controlled by diffusion process and Pt/graphene has significantly higher electrocatalytic activity, long-term stability more excellent charge transport performance for methanol oxidation reaction compared to Pt. Chronocoulometry was used by controlling step potential to determine the diffusion coefficient of methanol in sulfuric acid which was 1.37×10-9 cm2/s at 298 K, as well as the forward rate constants(fk) at different potentials.