NOVELTY - Population of platinum-copper nanoparticles comprises (a) a particle interior comprising platinum and copper, and (b) a surface layer comprising platinum surrounding the particle interior, where the nanoparticles have an average particle size of 10-500 nm, as determined by scanning electron microscopy.    USE - The population of platinum-copper nanoparticles is useful: in an electrode which is useful in a fuel cell and a metal-air battery (all claimed); and as electrocatalysts for the oxidation of small molecule organic compounds including alcohols e.g. methanol and ethanol and oxidation of carboxylic acids e.g. formic acid.    ADVANTAGE - The population of platinum-copper nanoparticles exhibits: a platinum electrochemical surface area of at least 10 m2 platinum/g of platinum; an oxygen reduction ICP-MS-determined, internal resistance-corrected (IR-corrected), mass activity at 0.9 V(reversible hydrogen electrode(RHE)) of at least 0.2 A/mg of platinum, measured at 25 degrees C and 100 kPa oxygen in 0.1 M of perchloric acid; an oxygen reduction platinum-surface area-based, IR-corrected, specific activity at 0.9 V(RHE) of at least 750 mu A/cm2 of platinum, measured at 25 degrees C and 100 kPa oxygen in 0.1 M perchloric acid; less than a 30% reduction in platinum electrochemical surface area following 10000 cycles between a potential of 0.6-1.1 V(RHE) in oxygen-saturated 0.1 M perchloric acid at 25 degrees C; less than a 50% reduction in oxygen reduction ICP-MS determined, IR-corrected, mass activity at 0.9 V(RHE), measured at 25 degrees C and 100 kPa oxygen, following 10000 cycles between a potential of 0.6-1.1 V(RHE) in oxygen-saturated 0.1 M perchloric acid at 25 degrees C (claimed); and improved stability and/or sustained or improved catalytic activity.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for:    (1) an electrode comprising the nanoparticles disposed on a conductive substrate;    (2) a fuel cell comprising an anode, a cathode and an electrolyte membrane disposed between the anode and the cathode, where at least one of the anode and the cathode comprises the electrode;    (3) a metal-air battery comprising a metal or metal-containing anode, a cathode, and an electrolyte dispose between the anode and the cathode, where the cathode comprises the electrode; and    (4) producing a platinum-copper catalyst comprising (a) galvanically depositing platinum on a porous copper support at greater than 5 degrees C to form a platinum-copper precursor catalyst, and (b) conditioning the platinum-copper precursor catalyst to form the platinum-copper catalyst.