A fuel cell (70) having an anode (72), a cathode (78) and an electrolyte (76) between the anode (72) and the cathode (78) includes a cathode catalyst (80) formed of a plurality of nanoparticles. Each nanoparticle (20) has a plurality of terraces (26) formed of platinum surface atoms (14), and a plurality of edge (28) and corner regions (29) formed of atoms from a second metal (30)—The cathode catalyst may be formed by combining a platinum nanoparticle with a metal salt in a solution. Ions from the second metal react with platinum and replace platinum atoms on the nanoparticle. The second metal atoms at the corner and edge regions of the nanoparticle, as well as at any surface defects, result in a more stable catalyst structure. In some embodiments, the fuel cell (70) is a proton exchange membrane fuel cell and the nanoparticles are tetrahedron-shaped. In some embodiments, the fuel cell (70) is a phosphoric acid fuel cell and the nanoparticles are cubic-shaped.