Hi,
There are several methods for coating PM ta a converter, you first need to clarify what the substrate is and if you have a carrier phase on the concverter or if you want a powder catalyst to attach to the converter structure. If you have a powder catalyst you may bind that to the substrate e.g. by using a phase transition such as boemite to gamma-alumina. If you already have a carrier phase such as gamma-alumina on the substrate, you can impregnate the carrier phase with a solution of a Rh-salt; please keep in mind e.g. Cl is a catalyst poison, therefore a nitrate salt is preferred.
In both cases a calcination to a minimum of 500C is advisable. Hope this helps.