TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Method: Removal of the portion of the iron from the deposited catalyst nanoparticles comprises leaching the portion of the iron from the catalyst nanoparticles, lowering a pH of the solvent, or applying an electrical potential to the solvent, to alter solubility condition of the iron in the solvent. Formation of the colloidal suspension comprises mixing a platinum-containing halogen and an iron-containing halogen in the solvent. Portion(s) of the deposited catalyst nanoparticles are porous after the iron removal. Preferred Properties: The catalyst nanoparticles have a standard deviation of particle sizes of less than or equal to0.5 nm after the iron removal. Preferred Composition: The platinum constitutes greater than or equal to50 mole% of the catalyst nanoparticles in the colloidal suspension. EXAMPLE - A supported catalyst was prepared by mixing iron chloride hexahydrate (0.58 g), dihydrogen hexachloroplatinate solution (1 g), and ethylene glycol (200 g), for 15 minutes to form glycol mixture having platinum to iron (Pt-Fe) molar ratio of 1:1. Sodium hydroxide solution (2.5 wt.% sodium hydroxide in ethylene glycol, 48 g) was added drop-wise to increase the pH and have opaque-white color when pH reached 10-11 and transparent yellow when pH reached 11-12. The resulting mixture was stirred for 2 hours at room temperature, and was heated in oil bath at 190degreesC for 3-5 hours with nitrogen purging. The resulting colloidal suspension had a transparent, dark brown color. The colloidal suspension (242 g) was added to a sheared support particle containing carbon black support particles (0.95 g) and ethylene glycol (25 g). Nitric acid (5 ml) was incrementally added to the combined colloidal suspension while stirring to reduce pH to 4-5. The combined colloidal suspension was then stirred overnight to cause the catalyst nanoparticles to deposit on the support particles, and to alter the stability of the iron. Then, nitric acid (10 ml) was incrementally added while stirring for 1 hour to further alter the stability of the iron, causing additional portions of the iron to leach from the deposited catalyst nanoparticles. The combined colloidal suspension was filtered and washed with deionized water. The resulting wet catalyst cake was dried overnight at 110degreesC under vacuum. The composition of the resulting supported catalyst was 30 wt.% platinum. The supported catalyst was used to prepare catalyst ink by combining supported catalyst (1 g), water (4 g), and 10% perfluorosulfonic acid/polytetrafluoroethylene copolymer (4 g). The mixture was sheared at 30000 rpm for 5 minutes, heated to 100degreesF for 30 minutes, and cooled. The catalyst ink was used to form a catalyst-coated gas diffusion layer of a fuel cell membrane electrode assembly (MEA). A potentiodynamic polarization scans for the MEA showed that the supported catalyst had good catalytic properties.