Photocatalytic thin films composed of titanium dioxide and poly(styrene sulfonate) with hierarchical porosity and high transparency were prepared by the layer-by-layer self-assembly method. The influence of preparation conditions on the structure and photocatalytic activity of the films was investigated. It was found there is no need to reach adsorption equilibrium during layer deposition. Using very short deposition times, films with better transparency and higher activity for methylene blue photo-oxidation were obtained. Diffusion limitations due to strong adsorption of dye molecules and ammonia to the polyelectrolyte were revealed. These results indicate that films could be devised to selectively degrade specific target molecules in a mixture. The films were deposited on a three-dimensional carbon substrate and successfully demonstrated in a photoelectrochemical water splitting experiment. (C) 2014 Elsevier B.V. All rights reserved.