Slot-Die Process of a Sol–Gel Photocatalytic Porous Coating for Large-Area Fabrication of Functional Architectural Glass

Abstract

The slot-die process is an appealing technology for the fabrication of coatings on large-area substrates. However, its application on the production of photocatalytic coatings based on sol–gel formulations remains virtually unexplored. Thus, assessing the suitable formulation of the sol and operational parameters that allow one to yield high-efficacy photocatalyst coatings is a current challenge. This work aims to analyze the transferability of titania sol formulation optimized for dip-coating processes to slot-die technology. In this sense, firstly, the sol formulation is optimized by analyzing the influence of several types of surfactants on the microstructural features and photoactivity of TiO2 coatings’ growth on glass substrates. All formulations rendered a meaningful porosity and nanoscopic anatase crystallites (11–15 nm) with optical band gap values close to the expectation (3.25–3.31 eV). Accordingly, the performance of the photocatalytic dye degradation was closely related to the porosity and crystallite size led by each titania sol, and no meaningful differences were found between the results provided by the coatings developed by dip-coating and the slot-die method, which demonstrates the capability of the latter for its application on a large-scale fabrication of photocatalytic coatings.