This invention comprises methods, for typical small nanoparticles, of removing elements distribution heterogeneity in the particle to significantly improve performance. For big nanoparticles, the performance of 3-D architecture made from the segregated nanoparticle could be further improved by increasing the elements distribution heterogeneity with proper post-treatment. Can be used in applications such as fuel cell electric cars, back up power for remote communication tower and other stationary applications.

A method for scaled-up synthesis of PtNi nanoparticles. Synthesizing a Pt nanoparticle catalyst comprises the steps of: synthesizing PtNi nanoparticles, isolating PtNi/substrate nanoparticles, acid leaching the PtNi/substrate, and annealing the leached PtNi/substrate nanoparticles, and forming a Pt-skin on the PtNi/substrate nanoparticles.