Study of the oxygen reduction and hydrogen oxidation reactions on RhIrRu-based catalysts

Abstract

In this work, we have used a mixture of three carbonyl cluster compounds [Rh6(CO)16, Ir4(CO)12 and Ru3(CO)12] in order to obtain two new RhIrRu-based catalytic materials by pyrolysis in different atmospheres: neutral (N2) and reductive (H2). The products were structurally characterized by different analytical techniques. The results show that the hydrogen atmosphere favors the decarbonylation process of the precursors. The tri-metallic materials were also electrochemically characterized by rotating disk electrode measurements. These studies indicate that the new catalysts can perform the oxygen reduction reaction (ORR) even in the presence of methanol, and the hydrogen oxidation reaction (HOR) even in the presence of carbon monoxide. The polarization curves are similar in the absence and presence of such proton exchange membrane (PEM) fuel cell contaminants, an important advantage over commercial platinum catalysts, which are easily deactivated by small concentrations of these species. The kinetic parameters of the catalysts, such as Tafel slope (b), exchange current density (jo) and charge transfer coefficient (α), were calculated for both reactions, as well. The results show that the new materials are good potential candidates to be evaluated as both cathodes and anodes in PEM fuel cells.