Oxygen Reduction on electrochemical Ti/TiO2 electrodes modified by Pt doping

AVALLE, L.B., FILIPPIN F.A., SANTOS E.

Nice, Fancia

Congreso; 61st Annual Meeting of International Society of Electrochemistry; 2010

International Society of Electrochemistry

<!-- @page { margin: 0.79in } P { margin-bottom: 0.08in } --> Platinum particles dispersed on TiO2 matrix presents higher catalytic activity toward oxygen reduction reaction (ORR) compared to metallic substrates [1]. The present work studies the electrocatalytic activity for ORR of Ti/TiO2 electrodes modified by platinum doping. Different amounts of Pt were electrodeposited on pulished Ti from 1x10-2 M H2PtCl6 in 0.1 M HCl. Then the oxide film was formed up to different final formation potentials (Vform) by potentiodynamic sweep (scan rate=0.05 Vs-1, supporting electrolytes: 10mM HClO4 - pH=2, 10mM KClO4 - pH=7 and 10mM KOH - pH=12). Cyclic Voltametry (CV), Electrochemical Impedance Spectroscopy (EIS) and Current Transient (CT) techniques were employed to measure kinetic parameters such as heterogeneous rate constant (k) and cathodic transfer coefficient (α) for modified and unmodified electrodes. In previous papers, the donor concentration (ND) and flat band potential (Vfb) of unmodified material were determined in the dark and under illumination [2]. These parameters are highly dependent on platinum concentration and oxide thickness. The EIS response of doped oxide displayed two time constants which values were calculated using an equivalent circuit with two RC elements connected in parallel. At constant Pt concentration, the increment in pH increased the number of electrons participating in the OOR. This behaviour was associated to the pH-dependent distribution of TiO2 surface acid-base groups and the energy states generated by Pt doping. 1- L. Timperman, Y.J. Feng, W. Vogel, N. Alonso-Vante. Electrochimica Acta, in press. 2- F.Y. Oliva, L.B. Avalle, E. Santos, O.R. Camara. Journal of Photochemistry and Photobiology A: Chemistry, 146 (2002) 175.