TECHNOLOGY FOCUS - METALLURGY - Preferred Components: The Pt particles have a diameter of 1 - 3 nm; comprise phosphorus (at least 2, preferably 2 - 50) atom%. Each particle comprises platinum (Pt), ruthenium (Ru) and phosphorus (P). The ratio of Pt and Ru in the particles is Pt40Ru60 - Pt90Ru10. The content of P is 3 - 27 atom% of the total moles of Pt-Ru.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Catalyst: The catalyst (C1) further comprises a carbon support having a specific surface area of 20 - 300 m2/g.Preferred Process: The reducing step is an alcohol reduction or electroless plating step.Preferred Components: The carbon support is at least one selected from carbon black and carbon nanotube. The carbon support is a multi-walled carbon nanotube. The reducing agent is a compound derives from one of phosphinic acid or phosphonic acid. EXAMPLE - Bis(acetylacetonato)platinum(II) (1.69 mmol), tris(acetylacetonato)ruthenium(III) (1.69 mmol) and sodium phosphinate (0.338 mmol) were dissolved into ethylene glycol (300 ml). An ethylene glycol solution (100 ml) into which, Vulcan XC-72R (RTM: carbon support having specific surface area of 254 m2/g) (0.5 g) was dispersed, was added in it. A sulfuric acid solution was added, and the pH value of the solution was adjusted to 3. In a nitrogen gas atmosphere, the solution was stirred and refluxed for 4 hours at 200degreesC, thereby depositing Pt-Ru-P catalyst particulates on the carbon support. Subsequent filtration, washing, and drying gave test Pt-Ru-P catalyst having particle size of 1 - 3 nm. Bis(acetylacetonato)platinum(II) (1.69 mmol) and tris(acetylacetonato)ruthenium(III) (1.69 mmol) were dissolved into ethylene glycol (300 ml). An ethylene glycol solution (100 ml) into which a carbon support (Vulcan XC-72R with the specific surface area of 254 m2/g) (0.5 g) was dispersed, was added in it. A sulfuric acid solution was added, and the pH value of the solution was adjusted to 3. In a nitrogen gas atmosphere, the solution was stirred and refluxed for 4 hours at 200degreesC, thereby depositing Pt-Ru catalyst particulates on the carbon support. Subsequent filtration, washing, and drying gave a comparative Pt-Ru catalyst having particle size of less than or equal to 10 nm.