The adsorption-structural properties of a diatomite/ nano - TiO2 based photocatalyst for alternative energy generation have been studied depending on the synthesis conditions: samples calcination temperature, pH of titania precipitation, temperature of synthesis, concentration of a titania precursor. Homogeneous hydrolysis with titanium chloride as a precipitation agent and Moldavian diatomite as support material was used to obtain a diatomite surface covered with TiO2. Samples were characterized by means of X-ray powder diffraction, chemical analysis and nitrogen adsorption/desorption measurements. During samples calcination, two mutually opposite processes occur: - increasing of TiO2 crystallinity which leads to an increase in the catalytic activity of the sample and the other - to reduce it by decreasing of the specific surface and pore volume. The diatomite improved the thermal stability of TiO2 crystals in the composite and inhibited the phase transformation of anatase to rutile. All the samples contain anatase phase without any rutile phase even at 8000C. The pH and temperature of the titanium dioxide precipitation have a significant effect on the properties of the composite. An increase in the amount of anatase in the composite leads to a decrease in volume and the effective radius of macropores and to an increase in the specific surface area and the size of the anatase crystallites. The optimal parameters of the composite synthesis were determined, which correspond to the maximum content of anatase while maintaining a high surface area and nanoscale particles size: pH 4.5 and the ambient temperature of synthesis, the calcination temperature was determined to be as 4000C.