Tailoring preparation, structure and photocatalytic activity of layer-by-layer films for degradation of different target molecules

• Less is more: LbL films with less photocatalyst may have higher activity.
• Adsorption of dyes and NH3 restricts their penetration in the LbL film.
• LbL films could be devised that selectively degrade specific molecules.
• LbL film activity in photoelectrochemical water splitting increases with number of layer pairs.

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.

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