NOVELTY - Compositionally modulated nanoparticle catalytic material comprises: shape controlled seed material of first particle shape, disposed in interior of nanoparticle; catalytic material disposed in shell of nanoparticle; and modifier mixed with catalytic material to obtain mixture, in which mixture has second particle shape different from first particle shape, and modifier is configured to modify at least one material property of catalytic material; where shape of compositionally modulated nanoparticle is substantially defined by first particle shape.    USE - As compositionally modulated nanoparticle for use as catalytic material; such as electrocatalyst integrated into cathode of a fuel cell (claimed).    ADVANTAGE - The nanoparticle catalytic material comprises advanced multimetallic nanoscale catalysts that exhibit high activity and improved durability in a fuel cell environment. The catalyst material achieves substantial catalytic improvement for oxygen reduction reaction (ORR) and provides highly active and durable catalytic structures. The catalyst has substantial advantages in that both high conversion rate and long term stability have been demonstrated for conditions of fuel cell environment. After cycling catalyst for 60000 cycles catalyst shows no significant loss of surface area and specific activity is as high at the end of cycling as at beginning. An additional benefit of catalyst technology is that it uses considerably less platinum, thus reduces material cost, while improving catalytic performance and stability. The core/shell Au/FePt nanoparticles are configured with advanced properties for ORR and can be used in fuel cell environment. Compared with FePt/C catalyst systems and commercial Pt/C, core/shell Au/FePt nanoparticles show superior stability with prolonged cycling, while preserving high catalytic activity of Pt-bimetallic alloys. In particular, initial specific activity of Au/FePt/C catalyst is as high as FePt/C. In contrast to FePt/C and Pt/C, no significant loss after potential cycling is observed in surface area and specific activity for Au/FePt/C. After 60000 potential cycles Au/FePt/C system has more than 7 times activity of the Pt/C system and mass activity of Au/FePt/C system is improved by more than an order of magnitude over Pt/C system. The Au core plays significant role in catalyst stabilization mechanism; and Pt atoms disposed proximate surface are electronically altered by subsurface Fe atoms, thus provide high catalytic activity. The Au/FePt3 nanoparticles possess substantially icosahedral shape inherited from Au seeds. The spatial arrangement of surface atoms in icosahedral particle significantly diminishes number of low-coordinated surface sites and increases surface average coordination number compared to cubo-octahedral particles; such as there are 12 atoms with coordination number of 6 on icosohedron versus 24 atoms for cubo-octahedron. Crystal stability is highly dependent on coordination number (number of nearest neighbors) of surface atoms. These low-coordinated atoms are usually considered more vulnerable to oxidation and dissolution in electrochemical environment. Therefore, icasohedral shaped Au/FePt3 nanoparticles would possess higher durability than cubo-octahedral shaped FePt3 nanoparticles.    DETAILED DESCRIPTION - A compositionally modulated nanoparticle catalytic material, comprises: a shape controlled seed material having a first particle shape, and preferentially disposed in an interior portion of the compositionally modulated nanoparticle; a catalytically active material preferentially disposed in a shell portion of the compositionally modulated nanoparticle; and a modifier material mixed with the catalytically active material to obtain a mixture, in which the mixture has a second particle shape different from the first particle shape, and the modifier material is configured to modify at least one material property of the catalytically active material; where the shape of the compositionally modulated nanoparticle is substantially defined by the first particle shape. INDEPENDENT CLAIMS are included for the following:    (1) an electrocatalyst having enhanced catalytic properties and durability in a fuel-cell environment, comprising: a high surface area substrate; several nanoparticles dispersed on the high surface area substrate, where each of several nanoparticles has a substantially icosahedral shape and comprises a core portion comprising a gold nanoparticle, and a platinum-bimetallic shell portion fully encasing the core portion and comprising platinum and a second metal configured to modify both a catalytic durability of the nanoparticle and a catalytic activity of the nanoparticle, where the surface of the bimetallic shell is substantially free of gold; and    (2) method for forming several durable core/shell particles having high catalytic activity, involving: providing an amount of gold nanoparticles; reacting an amount of a platinum precursor to obtain platinum; reacting an amount of an alloying metal precursor to obtain an alloying metal, were the alloying metal is selected to enhance the catalytic activity of the durable core/shell particles; heating a mixture of the platinum, the alloying metal and several gold a nanoparticles; and cooling the mixture to precipitate several nanoparticles, where each of the several nanoparticles comprises a core portion and a shell portion substantially enveloping the core portion, and the platinum and the alloying metal are preferentially disposed in the shell portion.