Circular self-cleaning building materials and fabrics using dual doped TiO₂ nanomaterials

Nanostructured titanium dioxide (TiO₂) among other oxides can be used as a prominent photocatalytic nanomaterial with self-cleaning properties. TiO₂ is selected in this research, due to its high photocatalytic activity, high stability and low cost. Metal doping has proved to be a successful approach for enhancing the photocatalytic efficiency of photocatalysts. Photocatalytic products can be applied in the building sector, using both building materials as a matrix, but also in fabrics. In this study undoped and Mn-In, Mn-Cu, In-Ni, Mn-Ni bimetallic doped TiO₂ nanostructures were synthesized using the microwave-assisted hydrothermal method. Decolorization efficiency of applied nanocoatings on fabrics and 3-D printed sustainable blocks made from recycled building materials was studied, both under UV as well as visible light for Methylene Blue (MB), using a self-made depollution and self-cleaning apparatus. Nanocoated samples showed high MB decolorization and great potential in self-cleaning applications. Results showed that the highest MB decolorization for both applications were observed for 0.25 at% Mn-In doped TiO₂. For the application of 3-D printed blocks Mn-In and In-Ni doped TiO₂ showed the highest net MB decolorization, 25.1 and 22.6%, respectively. For the application of nanocoated fabrics, three samples (Mn-In, In-Ni and Mn-Cu doped TiO₂) showed high MB decolorization (58.1, 52.7 and 47.6%, respectively) under indirect sunlight, while under UV light the fabric coated with Mn-In and In-Ni doped TiO₂ showed the highest MB decolorization rate 26.1 and 24.0%, respectively.