Development of Photocatalytic Coatings for Building Materials with Bi₂O₃-ZnO Nanoparticles

Abstract

The aim of this study was to develop versatile coatings that can protect the stone surfaces of Architectural Heritage. Two different 3D media, namely superhydrophobic (SPHB) and hydro-oleophobic (OHB), were utilized as host matrices for nanostructured photocatalysts (Bi2O3-ZnO 8/92). These photocatalysts were sensitive to visible light to enhance their efficiency when exposed to sunlight. To prevent the nanophotocatalyst from clumping together in the 3D media, non-ionic dispersant additives (Tween20, TritonX-100, and Brij35) were incorporated. The optimized suspensions were then applied to various substrates such as sandstone, limestone, and granite. The effectiveness of the coatings was assessed by evaluating the hydrophobicity, oleophobicity, and photocatalytic activity of the coated substrates. The Bi2O3-ZnO photocatalyst exhibited higher activity in the SPHB medium compared to the OHB medium. To simulate real-life conditions, the coated substrates were subjected to accelerated weathering tests to predict their durability. Despite a significant reduction in their thickness, the coatings demonstrated sustained hydrophobic efficiency and self-cleaning capability after the accelerated ageing tests.

Keywords

• built heritage
• coating
• granite
• sandstone
• limestone
• photocatalyst