Influence of precursor salt on metal particle formation in Rh/CeO2 catalysts

Two ceria-supported rhodium samples prepared from two different rhodium precursors (Rh (III) chloride and nitrate) are compared by CO-FTIR, EPR, and H-1 NMR with regard to their behavior toward reduction treatments under H-2. Results of IR and NMR techniques reveal that the presence of chloride ions delays rhodium reduction and favors a higher dispersion of rhodium particles at the catalyst. On the other hand, the onset of metal-support interactions (SMSI effect) upon high temperature reduction is more difficult to be established in the ex-chloride than in the ex-nitrate Rh/CeO2 catalyst. These differences have been ascribed to the presence of Cl- ions at the metal-support interface, which hinders electron exchanges between metal and oxide phases, (C) 2001 Academic Press