NOVELTY - Composition (I) for use in an electrochemical or catalytic application, comprises nanoparticles (106) with a metal or metal oxide core and an oxide shell, water and ion-conducting polymer.    USE - (I) is useful in the electrochemical and catalytic application. (I) is useful to form electrode and assembly for the fuel cell (all claimed), where the electrode is: gas and liquid diffusion electrode; and useful in electrochemical devices comprising direct methanol fuel cells, direct formic acid fuel cells, hydrogen fuel cells and alkaline fuel cells. (I) is useful e.g. to form an ink, which is useful to make anode and cathode electrodes and catalyst.    ADVANTAGE - (I) is platinum free, hence cost effective. (I) exhibits improved catalytic activity relative to larger particles with comparable material compositions and improve tolerance to anodic reactants that permeate that fuel cell membrane. (I) enhances physical contact between the electrode and the fuel cell membrane, and promotes ionic conductivity at the electrode-membrane interface. (I) is capable of ionic networking throughout the ink composition to create a substantially structurally coherent mass without significantly impacting the reactivity of a substantial number of the nanoparticles.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for:    (1) an electrode comprising an electron-conducting support (102) treated with (I);    (2) an assembly for a fuel cell comprising an ion-exchange membrane that in use separates a negative electrode and a positive electrode, where the membrane is treated with (I);    (3) a method of making a fuel cell comprising bringing together: at least one electrode and an ion-exchange membrane; and the assembly and electrode; and    (4) a fuel cell comprising at least one electrode or the assembly.    DESCRIPTION OF DRAWING(S) - The figure shows a cross-section of a direct oxidation fuel cell anode or cathode electrode.    Fuel cell cathode electrode (101)    Electron-conducting support (102)    Catalyst layer (103)    Carbon fibers (104)    Nanoparticles. (106)