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The electron diffusion coefficient at varying porosity has been determined in a series of nanostructured TiO2 films of different initial thicknesses. The porosity was changed by applying different pressures prior to sintering, thereby modifying the internal morphology of the films though not their chemical and surface conditions. A systematic increase of the effective diffusion coefficient was observed as the porosity was decreased, indicating the improvement of the internal connectivity of the network of nanoparticles. The experimental results have been rationalized using percolation theory. First of all, applying a power law dependence, the diffusion coefficient as a function of porosity from different films collapsed in a single master curve. In addition, application of the models of effective medium approximation (EMA) allows us to compare the experimental results with previous data from Monte Carlo simulation. The different data show a similar dependence in agreement with the EMA predictions, indicating that the geometrical effect of electron transport due to variation of porous morphology in TiO2 nanoparticulate networks is well described by the percolation concept. [ABSTRACT FROM AUTHOR]

The design of efficient self-standing hybrid systems for water purification that combines good adsorption properties with high photodegradation ability is highly challenging owing to the difficulty in simultaneously controlling the band structure and porosity of a semiconductor while maintaining its self-standing nature. Here, we report the synthesis of carbon-rich carbon nitride self-standing filters from supramolecular hydrogels composed of melamine and cyanobenzoic acid. The influence of the chemical structure on the properties of the hydrogels and the final films was studied by tuning parameters such as monomer nature, molar ratio, and pyrolysis temperature. Thanks to their ability to combine the adsorption and photodegradation of organic pollutants, the prepared self-standing films showed remarkable activity and stability in flow conditions (>95 % efficiency after 10 consecutive cycles). Additionally, the photocatalytic activity of the films was assessed in the powder form for the hydrogen evolution reaction and photocurrent generation in a photoelectrochemical cell. The reported work opens opportunities for the controlled synthesis of multifunctional filters for water purification and other energy-related and sustainable technologies., (© 2022 Wiley-VCH GmbH.)