NOVELTY - Hybrid continuous and closed photo and thermochemical water splitting cycle method (M1), comprises e.g.: receiving solar radiation; using only the quantum portion of solar spectrum in photoreactor for simultaneous production of hydrogen and ammonium sulfate via photochemical oxidation of aqueous ammonium sulfite solution; reacting ammonium sulfate with at least one metal oxide to produce ammonium, metal sulfate and water, and metal sulfate to produce ammonium, metal pyrosulfate and water; and using solar thermal radiation for simultaneous production of oxygen, metal oxide and sulfur dioxide.    USE - The method is useful for hybrid continuous and closed photo and thermochemical water splitting for producing hydrogen and oxygen (all claimed).    ADVANTAGE - The method utilizes the full solar spectrum, and thus allows the cycle to reach potentially a higher overall efficiency, when compared to conventional purely thermochemical water splitting cycles.    DETAILED DESCRIPTION - Hybrid continuous and closed photo and thermochemical water splitting cycle method (M1), comprises: receiving a solar radiation; using only the quantum portion of a solar spectrum in a photoreactor for the simultaneous production of hydrogen and ammonium sulfate via photochemical oxidation of aqueous ammonium sulfite solution; reacting the ammonium sulfate with at least one metal oxide comprising zinc oxide, magnesium oxide, calcium oxide, barium oxide, ferric oxide, cobalt(III) oxide, nickel oxide, manganese oxide, cuprous oxide or lead oxide to produce ammonium, metal sulfate and water, and a metal sulfate comprising potassium sulfate, rubidium sulfate or cesium sulfate to produce ammonium, metal pyrosulfate and water, where the ratio of metal oxide or metal sulfate to ammonium sulfate is maintained at 1.5-1; using the solar thermal radiation for the simultaneous production of oxygen, metal oxide and sulfur dioxide based on one of the decomposition of metal sulfate and decomposition of metal pyrosulfate, where the heating rate is maintained at 5-500 degrees C/minute; adding water to react with the ammonia and sulfur dioxide for the production of ammonium sulfite to close the hybrid photo/thermal water splitting cycles; supplying the regenerated ammonium sulfite to the photo-reactor; and repeating the steps starting with the hydrogen production step. The method implements a closed water splitting cycle, where only the water is consumed by the closed water splitting cycle. INDEPENDENT CLAIMS are also included for:    (1) a metal sulfate-ammonia cycle method (M2) for producing hydrogen and oxygen from a continuous and closed system, comprising: feeding a 1 M aqueous tetraammine sulfite solution into a photocatalytic reactor or electrochemical reactor to oxidize the aqueous tetraamine sulfite into aqueous diammine sulfate and reduce water to hydrogen; mixing the resulting aqueous diammine sulfate with metal oxide to form a slurry, where the ratio of metal oxide to ammonium sulfate is maintained at 1.5-1; heating the slurry of aqueous diammonium sulfate and metal oxide in the low temperature reactor to produce a gaseous mixture of ammonia and hydrogen and metal sulfate; heating solid zinc sulfate at a high temperature reactor to produce a gaseous mixture of sulfur dioxide and oxygen and solid zinc oxide, where the heating rate is maintained at 5-50 degrees C/minute; recycling zinc oxide back to mix with aqueous diammonium sulfate solution to a slurry that is be fed into a low temperature reactor; mixing the gaseous mixture of sulfur dioxide and oxygen with ammonia and water in an absorber to separate oxygen from aqueous diammonium sulfite solution to produce oxygen; and recycling the ammonium sulfite back to the photoreactor to close the water splitting cycle to produce both gaseous hydrogen and gaseous oxygen as the only products output from the continuous and closed zinc sulfate-ammonia cycle, where the method implements a closed water splitting cycle, and only the water is consumed by the closed water splitting cycle; and    (2) metal pyrosulfite-ammonia hybrid continuous and closed photo and thermo-chemical water splitting cycle method (M3) comprising: receiving a solar radiation; using the solar radiation for the production of hydrogen in a photoreactor via photochemical oxidation of aqueous ammonium sulfite solution to produce hydrogen; using the solar radiation for the production of oxygen including introducing a metal sulfate (potassium sulfate, rubidium sulfate or cesium sulfate) to convert ammonium sulfate into metal pyrosulfate (potassium pyrosulfate, rubidium pyrosulfate or cesium pyrosulfate), where the ratio of metal oxide or metal sulfate to ammonium sulfate is maintained at 1.5-1; decomposing the metal pyrosulfate for the production of oxygen, where the heating rate is maintained at 5-50 degrees C/minute; and supplying the regenerated ammonium sulfite to the photo reactor, where the method implements a closed water splitting cycle, and only the water is consumed by the closed water splitting cycle.    DESCRIPTION OF DRAWING(S) - The figure illustrates a process flow diagram of the hybrid photo/thermal-chemical water splitting cycle.