NOVELTY - Membrane electrode structure comprises: a photocatalyst-molecule-loaded ion-conductive membrane (10); a photocatalyst molecule (16) chemically bonded to the photocatalyst-molecule-loaded ion-conductive membrane; and a metal nanostructure fixed on or near the surface of the photocatalyst-molecule-loaded ion-conductive membrane proximate to the photocatalyst molecule.    USE - The membrane electrode structure is useful in: a membrane electrode assembly of a fuel cell; and a non-fuel-cell application which is hydrogen generation.    ADVANTAGE - The membrane electrode structure: utilizes the membrane material which is substantially not electron-conducting (claimed); reduces the required amounts of metal while achieving improved performance to the fuel cell; reduces metal usage by nanoscale engineering of the membrane-metal interface; and utilizes the ion-conductive membrane which is capable of withstanding the relatively high temperatures of an operating fuel cell.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for preparing the membrane electrode structure, comprising: loading an ion-conductive membrane with a photocatalyst to form a photocatalyst-molecule-loaded ion-conductive membrane; immersing the photocatalyst-molecule-loaded ion-conductive membrane in a reaction solution comprising a metal ion precursor and an electron donor; illuminating the photocatalyst-molecule-loaded ion-conductive membrane with light of a wavelength to produce an excited photocatalyst molecule; reacting the excited photocatalyst molecule with the electron donor and the metal ion precursor to form a reduced metal atom proximate to the excited photocatalyst molecule; and combining many reduced metal atoms to form a metal nanoparticle (12) fixed on or near the surface of the photocatalyst-loaded ion-conductive membrane.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic in side view of the surface region of the loaded membrane, showing photocatalyst molecules loaded within some pores of the ionomer membrane, where a metal nanodendrite has been grown proximate to the photocatalyst at the entrance of one pore.    Photocatalyst-loaded ion-conductive membrane (10)    Metal nanoparticles (12)    Pores (14,18,20)    Photocatalyst molecule (16)