TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Composition: The nanoparticles are tin-doped indium oxide, fluorine-doped tin oxide, antimony-tin oxide, gallium-zinc oxide, indium-zinc oxide, copper-aluminum oxide, fluorine-doped zinc oxide and/or aluminum zinc oxide nanoparticles, preferably tin-doped indium oxide nanoparticles. The support substrate comprises conductive material, transparent conducting oxide, planar transparent conducting oxide, or tin-doped indium oxide, fluorine-doped tin oxide, antimony-tin oxide, gallium-zinc oxide, indium-zinc oxide, copper-aluminum oxide, fluorine-doped zinc oxide and/or aluminum-zinc oxide. The catalyst is ruthenium, osmium or iridium catalyst. The catalyst is of formula: L1-M(-L3)-L2 (I), (aqua-2,2'-bipyridine-2,2':6',2"-terpyridine) ruthenium cation, (aqua-2,2'-bipyrimidine-2,2':6',2"-terpyridine) ruthenium cation or (aqua-2,2'-bipyrazine-2,2':6',2"-terpyridine) ruthenium cation, or chosen from 18 cations e.g. (2,2'-bipyridyl-N-((6-((dimethylamino)methyl)pyridin-2-yl)methyl)-N,N-dimethylamine) ruthenium cation, ((3'-(phosphonomethyl)-1,1'-biphenyl-3-yl)methylphosphonic acid-1-methyl-2-(6-(1-methyl-3a,7a-dihydro-1H-benzimidazol-2-yl)pyridin-2-yl)-1H-benzimidazole) ruthenium cation, (2,2'-bipyridine-2,2':6',2"-terpyridine) ruthenium cation, (2,2'-bipyrimidine-2,2':6',2"-terpyridine) ruthenium cation and (2,2'-bipyridine-1-methyl-2-(6-(1-methyl-3a,7a-dihydro-1H-benzimidazol-2-yl)pyridin-2-yl)-1H-benzimidazole) ruthenium cation, or transition metal complex comprising at least one phosphonate-derivatized ligand chosen from 4,4'-diphosphonato-2,2'-bipyridine and 4,4'-methylenediphosphonato-2,2'-bipyridine.M=ruthenium, osmium, iridium, iron, cobalt or nickel;L1=bidentate ligand, preferably 2,2'-bipyridyl (bpy), 2,2'-bipyrimidyl (bpm), 2,2'-bipyrazinyl (bpz), acetylacetonyl, P2-bpy, 2,6-bis(1-methylbenzimidazol-2-yl)pyridinyl (mebim-py), 2-(2,3-dihydro-1H-imidazol-1-yl)pyrazinyl or 2,6-bis(1-methylbenzimidazol-2-yl)pyrazinyl;L2=tridentate ligand, preferably 2,2':6',2"-terpyridiyl, 2,6-bis((dimethylamino)methyl)pyridinyl or 2,6-bis(1-methylbenzimidazol-2-yl)pyridinyl;andL3=monodentate ligand.Preferred Properties: The average diameter of nanoparticles is 80 nm or less, preferably 40 nm or less. The total surface area of electrode is 1-10000 times, preferably 1-5000 times more than the total surface coverage of electrode containing same material which is not in form of nanoparticles. Preferred Process: The transition metal catalyst is absorbed to surface of nanoparticles. The electrode is prepared by annealing support substrate with nanoparticles under atmosphere of mixed gas containing hydrogen (1-3 vol.%) and inert gas chosen from helium, argon and nitrogen, preferably nitrogen. The nanoparticle film having thickness of 5o-100 microns is exposed to solution of transition metal catalyst, and polymer is added to suspension of nanoparticles.    TECHNOLOGY FOCUS - POLYMERS - Preferred Composition: The electrode further comprises dye compound on surface of nanoparticles. The dye compound comprises chromophore chosen from carboxylic acid substituent, phosphonic acid substituent and silane substituent, preferably monomer, oligomer or polymer of porphyrin, pyrene, perylene, coumarin, rhodamine, buckminsterfullerene, thiophene, ruthenium polypyridyl complex, ferrocene and/or methyl viologen.