Metal oxides are promising compounds for water-splitting systems toward hydrogen production. One of the most important methods to prepare nanosized metal oxides is the decomposition of metal complexes. Herein, different Mn oxides from the decomposition of beta-cyclodextrin-Mn complex in different calcined temperatures were studied by scanning electron microscopy, thermal gravimetric analysis, X-ray diffraction and a few electrochemical methods. Using scanning electron microscopy, we propose a mechanism to answer to the question that how is Mn oxide formed by the decomposition of beta-cyclodextrin-Mn complex. In the next step, usual chemometric methods, principal component analysis (PCA) and multivariate curve resolution-alternating least squares (MCR-ALS), were used to not only determine the number of components and data visualization, but also examine the square wave voltammograms of obtained Mn oxides from the decomposition of beta-cyclodextrin-Mn complex. Water-oxidizing activities of the compounds under the presence of photo produced Ru(bpy)(3)(3+) were also considered. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.