TECHNOLOGY FOCUS - CHEMICAL ENGINEERING - Preferred Method: The photocatalyst is obtained by a calcination process which involves heating a photocatalyst feedstock consisting of copper aluminum oxide (CuAlO2) or a mixture of copper oxide and alumina, at primary calcination temperature of 800-1080 degrees C for 2 hours or more, and heating the photocatalyst feedstock at calcination temperature of 1155 degrees C or more for 2 hours or more. The calcination process involves at least four steps of heating the photocatalyst feedstock. One or more reaction temperature is 210-550 degrees C. Hydrogen and oxygen molecules are separated from the water. The reaction zone has pressure of 1.5-30 atm. Heat is removed. Hydrogen molecules are removed from the reaction zone. Hydrogen molecules are removed from the reaction vessel by continuously flowing water, liquid and/or vapor, into the reaction zone, through the reaction zone and out of the reaction zone. The sunlight is ultraviolet light, visible light, and infrared light. Reaction is carried out using ultraviolet light and/or visible light. The reaction zone is partially contained within a material which is transparent to solar radiation. The reaction zone has a fluidized bed containing the photocatalyst particles. The photocatalyst particles are suspended by a continuous gas flow. The reaction zone has a fixed bed containing the photocatalyst particles. The fixed bed comprises a transparent monolith formed to contain open inner channels for gas flow through monolith. The photocatalyst is attached to the inner channels. The material of the monolith is at least partially transparent to the ultraviolet and visible portions of the solar spectrum. The monolith material partially absorbs the infrared portion of the solar spectrum and is heated. An efficiency of converting light energy into chemical energy is more than 1%, preferably more than 10%. The efficiency for converting solar energy into hydrogen molecules, decreases by less than 10% after photocatalyst is used for photocatalytically generating hydrogen molecules at 210 degrees C for a cumulative time of 200 hours.    TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Component: The reaction zone is substantially free of sulfur-containing compounds and organic compounds. The photocatalyst contains a compound chosen from copper-aluminum oxide (CuAlO2), titania, copper oxide (CuO, Cu2O), nickel oxide, gallium arsenide, gallium phosphide, cadmium selenide, zinc oxide, tungsten oxide, iron oxide, tin oxide, silicon carbide, copper-gallium oxide (CuGaO2), copper-indium oxide (CuInO2) or their mixture. The photocatalyst comprises nanoparticles having average Brunauer Emmett Teller surface area of more than 2 m2/g. The photocatalyst comprises copper-aluminum oxide (CuxAlyOz), where x is 0.95-1.05, y is 0.95-1.05, x+y is 1.95-2.05 and z is x+y-0.05 to x+y+0.05. The photocatalyst is attached to a surface of the reaction vessel. The reaction vessel includes a monolithic structure having channels and a wall containing quartz. The apparatus has reaction chambers having a bundle of quartz tubes and the photocatalyst.