The main objective of this work is to develop a hybrid water-splitting cycle that employs the photon component of sunlight for production of H-2 and its thermal (i.e. IR) component for generating oxygen. In this paper, (NH4)(2)SO4 thermal decomposition in the presence of Mn3O4, as an oxygen evolving step, was systematically investigated using thermogravimetric/differential thermal analyses (TG/DTA), temperature programmed desorption (TPD) coupled with a mass spectrometer (MS), X-ray Diffraction (XRD), and X-ray Photoelectron Spectroscopy (XPS) techniques. Furthermore, thermolysis of ammonium sulfate, (NH4)(2)SO4, in the presence of Mn3O4 was also investigated by conducting flow reactor experiments. The experimental results obtained indicate that at 200-450 degrees C, (NH4)(2)SO4 decomposes forming NH3 and H2O and sulfur trioxide that in the presence of manganese oxide react to form manganese sulfate, MnSO4. At still higher temperatures (800 similar to 900 degrees C), MnSO4 further decomposed forming SO2 and O-2. Copyright (C) 2010, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights