When Rh/Al2O3 is heated under air it makes rhodium-aluminate type solid solution. Literature says it is reversible and it would be more easily reversible under H2. When it is used as TWC catalysts, at high temperature O2 and H2 both are possible at a time, then how fast RhAl2O4 phase formation and deformation can be? Does anyone have an idea about Rh dispersion or oxidation state changes at lean and rich perturbations?