Use of Au/N-TiO2/SiO2 photocatalysts in building materials with NO depolluting activity

Two factors are key in the design of a TiO2 photocatalyst for building materials that meets the requirements for environmental applications: the TiO2 light absorption restricted to UV and its poor adhesion to the substrates. In this work, two strategies of TiO2 modification, nitrogen doping and AuNPs deposition, were combined in order to promote the TiO2 photoactivity under solar radiation. By the other hand, the Au/N-TiO2 photocatalysts were incorporated in a silica sol allowing their application by spray on three different building material substrates (limestone, granite and concrete), where the sol spontaneously produced Au/N-TiO2/SiO2 well-adhered coatings. The samples photoactivity was evaluated by dye degradation tests and NO abatement measurements. The obtained results demonstrated that the AuNPs considerably enhanced the photoactivity of N-TiO2, doubling the amount of NOx removed under UV-visible light. In addition, the role of the substrate and the TiO2/SiO2 ratio of the coating were also investigated. The coatings practically triplicated their depolluting effectiveness on concrete in comparison with their application on limestone. A direct correlation between the TiO2 loading and the photoactivity was observed, increasing NOx abatement by a factor of 1.3 when the Au/N-TiO2 loading of the coating was raised from 10 to 25%. However, the Au presence can induce evident colour modifications of the treated substrates that can limit the product application on certain substrates. (C) 2019 Elsevier Ltd. All rights reserved.