A PdO/Ce1-xPdxO2-delta catalyst containing surface PdOx (x = 1-2) species and Ce1-xPdxO2-delta solid solution was prepared by a solution combustion method. It was found that the surface PdOx species could be removed by nitric acid treatment. Also, partial Pd4+ cations in the CeO2 lattice migrated to the surface to form surface PdOx species after high temperature calcination (500 degrees C). The catalyst was tested for catalytic CO and CH4 oxidation. For CO oxidation, the specific reaction rate of the surface PdOx species (673.4 mu mol(CO)g(Pd)(-1)s(-1)) was 249 times as high as that of the Ce1-xPdxO2-delta solid solution (2.7 mu mol(CO)g(Pd)(-1)s(-1)), due to the fact that the surface PdOx species provided CO chemisorption sites. While for CH4 oxidation, the specific reaction rate of the Ce1-xPdxO2-delta solid solution (7.5 mu mol(CH4)g(Pd)(-1)s(-1)) was higher than that of the PdO/Ce1-xPdxO2-delta catalyst (2.8 mu mol(CH4)g(Pd)(-1)s(-1)), due to the covered Ce1-xPdxO2-delta surface by surface PdOx species. (C) 2012 Elsevier B.V. All rights reserved.