Scalable Routes to Functional Materials: Photocatalytic, TCO and Anti-Soiling Coatings

The search for efficient materials for sustainable infrastructure is a key challenge to address the global environmental crisis. Sunlight-activated coatings, particularly those produced from scalable technologies, are sought in the glass industry for applications in self-cleaning windows. Current research involves developing processes towards sustainable and inexpensive functional materials including photocatalysts, anti-soiling coatings, transparent conducting oxides (TCOs) and photoelectrochemical films on float glass. For example, we have been developing sustainable upscaled routes to TCO materials from precursors containing earth abundant elements (titanium, aluminium, zinc) with equivalent or better figures of merit to existing TCOs. Our method uses aerosol assisted chemical vapour deposition (AACVD) to develop large scale coatings. Compared to conventional CVD, the AACVD method uses aerosol droplets to transport precursors, with the aid of an inert carrier gases. Therefore, in AACVD volatility is no longer crucial and this allows for a wider choice of precursors being available for use and can lead to high quality films at low cost.<br/><br/>Recent work has also investigated a range of bismuth-based materials for a number of applications. For example, adherent coatings of phenethylammonium bismuth iodide have been deposited via AACVD. The film morphology was found to depend on the deposition conditions and substrates, resulting in different optical properties to those reported from their spin-coated counterparts. Bismuth oxyhalides, BiOX (X = Cl, Br, and I), are of interest in a range of applications including photoelectrochemical (PEC) sensing, pollutant degradation and water splitting, with particular focus as emerging materials in photocatalytic applications. We recently reported visible-light-active iodide-doped BiOBr thin films fabricated via AACVD. The impact of dopant concentration on the structural, morphological, and optical properties was studied and the photocatalytic properties of films were evaluated. An optimized material was identified as containing 2.7 atom% iodide dopant. We have also synthesised BiOI and ZnO heterojunction materials. It was found that the BiOI/ZnO structure was far less active towards PEC water oxidation, while the ZnO/BiOI heterojunction showed a significant enhancement in activity compared with its parent materials. The ZnO/BiOI heterojunction, with a 120 nm thick ZnO film, exhibited the best PEC performance through studying the influence of the ZnO film thickness and deposition temperature.<br/><br/>AACVD has also been used to develop thin films of other functional materials, including processes towards sustainable and inexpensive anti-soiling coating on float glass and photocatalytic films.<br/><br/>References:<br/>1. Wang, M.; Carmalt, C. J., <i>ACS Appl. Energy Mater.</i> 2022, 5, 5434.<br/>2. Marchand, P.; Hassan, I. A.; Parkin, I. P.; Carmalt, C. J., <i>Dalton Trans.</i>, 2013,<b>42</b>, 9406.<br/>3. Wang, M.; Sanchez-Perez, C.; Habib, F.; Blunt, M. O.; Carmalt, C. J., <i>Chem. - Eur. J.</i>, 2021, <b>27</b>, 9406.<br/>4. <i>Wang, M.; Quesada-Cabrera, R.; Sathasivam, S.; Blunt, M. O.; Borowiec, J.; Carmalt, C. J., </i>ACS Applied Materials & Interfaces<i> <b>Article ASAP</b>, DOI: 10.1021/acsami.3c11525.</i><br/><i>5. </i>Wang, M.; Kafizas, A.; Sathasivam, S.; Blunt, M. O.; Moss, B. Gonzalez-Carrero, S.; Carmalt, C. J., <i>Applied Catalysis B: Environmental</i>, 2023, 331, 122657.