▎ 摘　　要

NOVELTY - Alloy nanoparticles comprise 5 or more elements. When the alloy nanoparticles are directly supported on a carbon-material support, the carbon-material support which excludes graphene or carbon fiber. USE - Alloy nanoparticles used as aggregate for forming catalyst (all claimed). Uses include but are not limited to hydrogen-producing reaction (HER), hydrogenated reaction, hydrogen-oxidizing reaction, oxygen reductive reaction (ORR), oxygen evolution reactions (OER), nitrogen oxide reductive reaction, carbon monoxide (CO) oxidation reaction, dehydrogenation, exhaust gas purifying catalyst, water electrolysis reaction, and hydrogen fuel battery catalyst. ADVANTAGE - The alloy nanoparticles have excellent catalyst performance, and suppressed catalyst deterioration under high temperature conditions and long-term reactions. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following: (1) aggregate of the alloy nanoparticles, which comprise 98% or more alloy nanoparticles; (2) a catalyst, which comprises the aggregate of the alloy nanoparticles; and (3) manufacture of the alloy nanoparticles, which involves adding and reacting an aqueous solution containing salts of 5 or more elements to a liquid reducing agent and heating to 200-300 degrees C.