Evaluation of Colloidal Pd and Pd-alloys as Anode Electrocatalysts for Direct Borohydride Fuel Cells Applications

Abstract

Borohydride oxidation on supported Pd and Pd-alloy nano-electrocatalysts (Pd, Pd-Ir, Pd-Ni, Pd-Au, and Pd-Ag) prepared by a modified Bonneman method has been investigated using cyclic voltammetry (CV), rotating disk electrode (RDE) voltammetry, and single fuel cell test station. Electrochemical parameters, such as Tafel slopes, exchange current densities, oxidation peak potentials, and fuel cell performance, have been determined. The electrochemical parameters impact on the cell performance is considered as important as that of the operating conditions. The influences of temperature, and fuel and oxidant flow rates, on the fuel cell performance were also evaluated. The current density of the borohydride fuel cell increases with increase in temperature for all investigated electrocatalysts. The increase in current density with increase in fuel flow rate was not as high as expected within the investigated flow rate range. This is in a good agreement with RDE results. A fuel cell employing Pd-Ir as the anode catalyst and operated at a cell voltage of 0.5 V, can give a current density of 50 mA cm n2 at 298 K, while the same catalyst and at same cell voltage can give 110 mA cm n2 at 333 K.