Photocatalytically active coatings for indoor air purification: From SrTiO3 facet engineering to paint applications

Indoor air pollution has emerged as a major public health concern, contributing to symptoms and illnesses collectively known as Sick Building Syndrome (SBS). Conventional air purification technologies often struggle to remove volatile organic compounds (VOCs) at trace levels, emphasizing the need for sustainable, passive mitigation strategies. This thesis explores the development and optimization of strontium titanate (SrTiO₃, STO)–based photocatalysts for indoor air purification, integrating materials design, statistical modeling, and artificial intelligence (AI) approaches.

A data-informed synthesis framework was established by retrospectively applying a neural network to extensive experimental data from hydrothermally synthesized STO. This approach identified key synthesis parameters influencing phase purity and morphology, demonstrating how AI can guide materials discovery.

The photocatalytic oxidation of acetone was systematically investigated using SrTiO₃ with distinct facet exposures: cubic (exclusively {100} facets), {110}-truncated cubes, and {100}-truncated rhombic dodecahedral morphologies. In situ DRIFTS and Time-Resolved Photoluminescence (TRPL) revealed that facet-dependent hydroxylation and charge carrier separation govern the formation and stability of reactive intermediates. A Design of Experiments (DoE) approach further elucidated the effects of external parameters relative humidity and light intensity, confirming superior stability and humidity tolerance for the truncated morphology in the studied conditions.

Building on these insights, Al doping was introduced to tailor STO’s electronic structure and surface reactivity. Structural and spectroscopic analyses confirmed substitutional doping and oxygen vacancy formation, with modified reaction pathways yielding distinct surface-bound intermediates. Doped truncated STO exhibited the most efficient charge separation, but reduced photocatalytic performance in gas-phase photomineralization of acetone.

Finally, STO photocatalysts were embedded into commercial paint formulations to demonstrate proof-of-concept for indoor air purification coatings. Catalyst morphology and drying orientation dictated surface exposure and reactivity, providing key design guidelines for scalable implementation.

Altogether, this work advances the understanding of structure–property–performance relationships in STO photocatalysts, highlighting the potential of facet engineering, doping, and data-driven synthesis toward the development of smart, self-cleaning indoor environments.