Development of TiO₂-SiO₂ Photocatalysts Having a Microhoneycomb Structure by the Ice Templating Method

Immobilization of TiO₂-based photocatalysts usually suffers from lowered surface area and mass transfer limitation compared with their suspended counterpart. In this work, TiO₂-SiO₂ monolithic photocatalysts having straight macropores, called microhoneycombs, were synthesized. The obtained samples had straight macropores with a diameter in the range of 15-40 μm formed by walls having a thickness up to 5 μm. The samples also contain micropores and small mesopores inside their walls, which contribute to high surface areas of more than 500 m² g^-1. Synthesized photocatalysts were tested in a continuous flow system using the decolorization of methylene blue as a model reaction. It was found that the unique morphology of the samples can be used to promote the uniform distribution of the target fluid while reducing the pressure drop across the photocatalyst to less than a hundredth compared with a packed bed system. In addition, calcination at 600-800 °C improved the strength and photocatalytic activity of the monoliths while preserving the high surface area of the samples.