Development of Ir-based and Rh-based catalyst electrodes for PEM fuel cell applications

In this work, we have used Ir4(CO)12 and Rh6(CO)16 as precursors to obtain catalysts by pyrolysis in H2 and by thermolysis in o-dichlorobenzene, respectively. They can perform both the oxygen reduction and the hydrogen oxidation reaction (ORR and HOR, respectively), the latter even in the presence of CO. However, the Iry(H2) catalyst cannot perform the ORR in the presence of methanol. Their evaluation as anodes in a PEMFC, in the absence and presence of CO, was carried out using a Fuel Cell Test System designed and built in our group. The polarization curves showed that the performance of Iry(H2) is not far from that exhibited by platinum with H2; when a H2/0.5% CO mixture was used, the cells with the Iry(H2) or Rhz(o-DCB) electrodes maintained their potential within acceptable values, unlike that with platinum, which completely lost its power. On the other hand, the performance of Ir-based and Rh-based catalysts as cathodes, was less effective than that exhibited by platinum.