Structure and Properties of Carbon-dispersed Electrocatalysts and of Metal Hydride Alloys
IQSC-USP – São Carlos – Brasil
This presentation will discuss the effects of the structure and electronic properties of nanodispersed electrocatalysts formed by Pt-M/C (M is a 3d or 4d transition metal) and of different Mn oxides on the electrocatalysis of the oxygen reduction (ORR) and hydrogen oxidation (HOR) reactions in acid and alkaline electrolytes. The effects of titanium and platinum addition on the structure and electrochemical properties of MgNiPt (Pt = 1.0, 2.0 and 3.0 at. %) metal hydride alloys processed by mechanical alloying will be also discussed. The physical characterizations of the materials have been made by HRTEM (High resolution transmission electron microscopy), XRD (X-ray diffraction) and in situ XANES (X-ray absorption near edge structure) and EXAFS (extended X-ray absorption fine structure). For the dispersed catalysts, electrochemical investigations have been made with cyclic voltammetry and steady state polarization measurements for the ORR and HOR, which have been carried out by using a rotating ring/disk electrode, with the working electrode formed by a thin layer of the catalysts. Investigations also comprise polymer electrolyte (PEMFC) single cell polarization measurements, with the catalysts forming gas diffusion electrodes and the system supplied with pure oxygen in the cathode and hydrogen, with and without CO, in the anode. In the case of the metal hydride alloys, the electrochemical studies include charge-discharge cycle tests and impedance measurements.