TECHNOLOGY FOCUS - CHEMICAL ENGINEERING - Preferred Arrangement: The visible light responsive photocatalyst is arranged at the surface of an inorganic material layer of organic material layer and thus self-assembling film containing the photocatalyst is formed. The inorganic material layer or organic material layer has groove portion at the surface. The inorganic material layer consists of metal and/or ceramics. The visible light responsive photocatalyst is covered by the surface of a laminate having sequential lamination of electroconductive layer, proton conductive layer and electroconductive layer. Water is reduced in the electroconductive layer of surface side of the laminate and proton is oxidized in the electroconductive layer of the backside of the laminate. The electroconductive layers are supplied with electricity. Platinum and/or transition metal oxide are arranged at inner or outer side of the electroconductive layer of backside. Several laminates are arranged along lamination direction, and the flow path is provided between two laminates. The electroconductive layer consists of carbon particles, carbon porous material and/or carbon fiber. The proton conductive layer contains polymer and/or oxide. The proton conductive layer and/or electroconductive layer are (semi)-transparent.    TECHNOLOGY FOCUS - IMAGING AND COMMUNICATION - Preferred Light Source: The visible light source is sunlight, lamp, light emitting diode and/or semiconductor laser.    TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Solution: The sacrificial reagent-containing aqueous solution contains sacrificial reagent in water. The sacrificial reagent generates ion(s) chosen from hydroxide ion, sulfite ion, sulfide ion and silver ion.Preferred Photocatalyst: The visible light responsive photocatalyst contains tantalum nitride (Ta3N5), metal oxide chosen from strontium-titanium oxide (SrTiO3), silver-tantalum oxide (AgTaO3), silver-niobium oxide (AgNbO3), indium-tantalum oxide (InTaO4), indium-niobium oxide (InNbO4), and bismuth-vanadium oxide (BiVO4) doped with nitrogen sulfur, chromium and/or antimony, zinc sulfide optionally doped with copper and/or nickel, oxide chosen from gallium oxide, indium oxide, zinc oxide, silver oxide and sodium oxide, sulfide chosen from gallium sulfide, indium sulfide, zinc sulfide, silver sulfide and sodium sulfide, and/or gallium oxide-indium oxide (Ga2O3-In2O3) solid solution. The mean diameter of the photocatalyst is 0.01-50 microns. The photocatalyst supports the co-catalyst(s) chosen from platinum, nickel oxide, ruthenium oxide and iridium oxide, or microparticles exhibiting gold plasmon absorption and/or microparticles exhibiting silver plasmon absorption.