The invention relates to a titanium aquo-oxo chloride and to a method for its preparation. The compound is in the form of crystals and has the following composition by weight: 26.91% Ti; 21.36% Cl; and 4.41% H, which corresponds to the formula [Ti.sub.8O.sub.12(H.sub.2O).sub.24]Cl.sub.8.HCl.7H.sub.2O. The method of preparation consists in hydrolyzing TiOCl.sub.2 either in an atmosphere whose moisture content is maintained between 50 and 60%, or by an alkali metal carbonate A.sub.2CO.sub.3, in order to obtain a titanium aquo-oxo chloride. The compound is useful as a semiconductor element of a photovoltaic cell or as a photocatalyst in air or water purification treatments.