A method for preparing a carbon-supported, platinum-cobalt alloy, nanoparticle catalyst includes mixing a solution containing, in combination, a platinum precursor, a transition metal precursor consisting of a transition metal that is cobalt, carbon, a stabilizer that is oleyl amine, and a reducing agent that is sodium borohydride to provide carbon-supported, platinum-cobalt alloy nanoparticles, and washing the carbon-supported, platinum-cobalt alloy, nanoparticles using ethanol and distilled water individually or in combination followed by drying at room temperature to obtain dried carbon-supported, platinum-cobalt alloy, nanoparticles; treating the dried carbon-supported, platinum-cobalt alloy, nanoparticles with an acetic acid solution having a concentration ranging from 1-16M to provide acetic acid-treated nanoparticles, and washing the acetic acid-treated nanoparticles using distilled water followed by drying at room temperature to obtain dried acetic acid-treated nanoparticles; and heat treating the dried acetic acid-treated nanoparticles at a temperature ranging from 600 to 1000° C. under a hydrogen-containing atmosphere.