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The novel Sm 1-x Ce x FeO 3-d (x = 0, 0.01, 0.05) (SCF) perovskites with and without 1 wt% of Pt nanoparticles (NPs) were investigated for carbon monoxide and ethylene oxidation in the temperature range of 25-350°C. All perovskites were predominantly ionic conductors, with ionic conductivities two orders of magnitude higher than the electronic contribution. Furthermore, the cerium doping increases the ionic conductivity of these materials at high temperatures. The bare SCF perovskites possessed catalytic activity for both reactions; however the Pt-supported catalysts had 50-100°C lower light-off temperatures than the corresponding perovskites. More significantly, the enhancement in the catalytic activity of the Pt/SCF family with respect to other Pt-supported catalysts was shown by the lower activation energies, which were 25.7 kJ/mol over Pt/Sm 0.95 Ce 0.05 FeO 3-d and 18.3 kJ/mol over Pt/Sm 0.99 Ce 0.01 FeO 3-d for CO and ethylene oxidation, respectively. The corresponding activation energies for Pt NPs supported on conventional cAl 2 O 3 were 57.1 and 32 kJ/mol, and on ionically conductive yttria-stabilized zirconia (YSZ) were 35.8 and 22 kJ/mol for CO and C 2 H 4 oxidation, respectively. The increased activity was attributed to the high ionic conductivity (O 2-) of the perovskite supports at 100-400°C that facilitates the spontaneous backspillover of O 2-promoters from the lattice to the gas-exposed Pt nanoparticle surface. The promoters alter the adsorption strength of reactants similar to the electrochemical promotion mechanism observed under polarization.