Photocatalytic coatings via thermal spraying: a mini-review

Abstract

Light-driven functional coatings present an enabling technology of major importance in the successful, effective, and efficient exploitation of materials for energy and environmental-related problems of modern-day society. Photocatalyst coatings are traditionally obtained through physical/chemical vapor deposition or sol-gel related techniques. All these processes have certain disadvantages such as high environmental footprint, low adhesion to the substrate, poor mechanical properties, which makes them less suitable for upscaling to pilot and industrial applications. Thermal spraying is nowadays a well-established technique that offers all the prerequisites for obtaining mechanically-resistant and highly efficient photocatalytic coatings, on practically all types of substrates (metals, polymers, ceramics) bearing a wide area of geometries. Even if thick coatings are usually obtained through the thermal spraying method, the inherent nanopatterning of the surface generated through impact and plastic deformation of the feedstock material with the substrate generates the high surface area required for an efficient photocatalysis process. This mini-review presents some of the most important research results in the application of thermal spraying for achieving photocatalytic coatings. All the major techniques related to thermal spraying are considered, starting with flame spraying and moving on to newly developed techniques, such as high velocity oxy-fuel spraying, plasma spraying and cold gas spraying.