TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Processes: The method further includes washing mixture with distilled water to remove excess base after contacting Ce(NO3)3 and base, resulting in mixture with neutral pH. The method further includes dispersing mixture in a liquid containing water or hydrophilic solvent, such as alcohol, ketone, and/or N,N-dimethylformamide. Mixture is converted into composition containing porous CeO2 nanoparticles by dehydrating the mixture by a hydrothermal method using autoclave at 160-200 degrees C, preferably 160 degrees C for 12-24 hours preferably 12 hours. Mixture is converted into composition containing porous CeO2 nanoparticles by calcination at 200-600 degrees C, preferably 300 degrees C. The method further includes dispersing active component in porous CeO2 nanoparticles. Preferred Compositions: Base is sodium hydroxide (NaOH) and/or potassium hydroxide (KOH), preferably NaOH. Ratio Ce(NO3)3:base is 1:80-1:200, preferably 1:120. Nanoparticles contain mixture of CeO2 and cerium hydroxide (Ce(OH)3). Active component contains noble metal, metal oxide, bi-metal, and/or triple-metal, such as ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir), platinum (Pt), gold (Au), mercury (Hg), rhenium (Re), silver (Ag), and/or copper (Cu). Metal oxide is copper(II) oxide (CuO), nickel(II) oxide (NiO), and/or cobalt oxide (Co3O4). Bi-metal is PtPd and/or AuPd. Triple-metal is CoNiPt and/or CuPdAu. The 1st catalyst is CeO2-zirconia (ZrO2), CeO2-titania (TiO2), and/or CeO2-cadmium sulfide (CdS). Preferred Conditions: Reaction pressure is 1-1.5 atm. Reaction temperature is 100 degrees C. Preferred Parameters: Nanoparticles have average length of 40-80 nm and average diameter of 5-8 nm. Nanoparticles are rod-shaped. Nanoparticles are non-porous. Porous CeO2 nanoparticles have larger oxygen vacancy concentration than that of non-porous CeO2 nanoparticles. Porous CeO2 nanoparticles have specific surface area of 95-150 m2/g, specific surface area of 141 m2/g, oxygen storage capacity of 700-900 mu mol O2/g, preferably 900 mu mol O2/g, and specific surface Ce3+ ratio of 9-33%, preferably 33%.