Systematic study of iridium-based catalysts derived from Ir4(CO)12, capable to perform the ORR and HOR

Abstract

In this work, we used Ir4(CO)12 as precursor compound in order to obtain different Ir-based materials by two different thermal processes: pyrolysis and thermolysis. All materials were studied as catalysts for the ORR and HOR in the absence and presence of contaminants (methanol and carbon monoxide, respectively). These studies indicate that only two catalysts performed the ORR in the presence of methanol, since most of them present activity for the methanol oxidation reaction, due to the presence of Ir° particles. However, all synthesized materials performed the HOR even in the presence of CO in different concentrations. Some catalysts, were also evaluated directly as cathodes and anodes in a single PEM Fuel Cell even using a H2/CO mixture gas as fuel, corroborating its acceptable performance compared with commercial platinum catalyst, which are easily deactivated by traces of CO. The products were characterized structural and morphologically by different analytical techniques. The results show that hydrogen atmosphere stimulates the decarbonylation process of the precursor and produces metallic-iridium nanoparticles with a different chemistry nature compared with the materials obtained in nitrogen. In general, results show that these Ir-based materials are a good alternative to be used as both cathodes/anodes in a PEMFC.