(303j) Double-Inverse-Opal Structured Assemblies of Titania-Based Photocatalytic Particles Towards Continuous Water Purification Process

Photocatalytic decomposition of organic pollutants without using chemical agents is a sustainable way for water purification. Nano–micron sized particulate photocatalysts are commonly employed for an efficient photocatalytic reaction. However, such photocatalytic particles need to be separated from products after the reactions completed, suggesting its limited application to batch reactions. Photocatalytic particles immobilized on supports (e.g., inert inorganic particles or aerogels) or substrates can be easily separated and collected after the reaction, but it decreases the effective surface area of photocatalytic particles. To immobilize or confine the photocatalytic particles without losing their effective surface area, we previously reported the double-inverse-opal (DIO) structured photocatalysts that consist of an inverse-opal silica frame enclosing photocatalytic titania particles in its voids [1]. The voids in the silica frame connected with each other through the interconnecting pores. DIOs exhibited higher photocatalytic activity than the assemblies of titania particles immobilized by a silica frame without voids. This indicated that interconnecting pores have an important role for the reaction.

In this study, photocatalytic activities of DIOs which have ordered or disordered structures were examined. Fabrication of DIOs proceeds by following steps: (i) polymer coating on photocatalytic particles, (ii) self-assembly of polymer-coated particles and infiltration of silica skeleton, and (iii) heat treatment to create voids by removing polymer layers. Monodisperse or polydisperse particles were prepared for the templates for DIOs with different regularity. The ordered DIOs exhibited higher photocatalytic activity, suggesting the importance of regularity of voids to ensure connecting them to each other.

Reference:

[1] H. Namigata et al., Materials, 14, 28 (2021).