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 1H NMR with regard to their behavior toward reduction treatments under H2. 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.