ELECTROCHEMICAL CELL ELECTROCATALYST

An electrocatalyst includes a conglomerate of platinum atoms forming an amorphous nanoparticle structure having at least about 40% of highly undercoordinated surface atoms with fewer than 6 adjacent atoms on its surface; and a passivating crust including catalytically active monoatomic adsorbed oxygen atoms such that at least 50% of the amorphous nanoparticle structure has oxygen coverage, the amorphous nanoparticle structure having a diameter of up to 3 nm.