Novel active pigments for photocatalytic coatings

A recent study describes the preparation of TiO2–based hollow microspheres by spray drying and their use as active pigments for photocatalytic coatings.

A laboratory.
It was demonstrated that the glass transition temperature of the final crosslinked network could be controlled by the addition of a monoallylated monomer. Image source: kwanchaift - (symbol image).

The use of TiO2 nanoparticles in organic-based photocatalytic coatings imposes several challenges: poor activity under visible light, binder photo-degradation, need for UV activation and toxicity concerns. Here we present a scalable two-step synthesis route to prepare TiO2-based hollow microspheres (HoS) as alternative photocatalyst to commercial TiO2 nanoparticles.

The hollow microspheres of TiO2 or WO3-doped TiO2 (3 mol% WO3) were synthesised via template-assisted spray-drying followed by calcination. The structure and composition of the powders were characterised and their photocatalytic performance is assessed using methylene blue photo-degradation under UV irradiation as model reaction. XRD analysis revealed the presence of anatase and TiO2(B) phases, indicating the heterostructured nature of the samples. The results of the dye photo-degradation tests confirmed the photocatalytic functionality of the TiO2-based HoS. Moreover, the introduction of WO3 (TiO2/WO3 HoS) lead to an enhancement of the performance, approaching that of commercial (Aeroxide P25, ~21 nm) nanoparticles.

Coatings tested towards pollutant abatement under UV light

The most active TiO2/WO3 HoS were incorporated into an acrylic formulation and the resulting coatings tested towards pollutant abatement under UV light. A coating containing P25 nanoparticles underwent an activation process where binder degradation lead to increased TiO2 exposure and a rise in catalytic activity but possibly at the expense of coating stability. By contrast TiO2/WO3 HoS-acrylic coatings exhibited catalytic activity similar to the initial activity of P25 containing coatings, but did not cause the same partial binder photo-degradation.

The study has been published in Progress in Organic Coatings, Volume 160, November 2021.

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