Cold spray (P, N, Mo)-TiO₂ photocatalytic coatings: synthesis, microstructural characterization and photocatalytic properties

The (P, N, Mo)-TiO₂ photocatalyst particles were intuitively synthesized using spray the sol-gel method followed by the spray drying method. Imperatively, the (P, N, Mo)-TiO₂ photocatalyst coatings were deposited on aluminum substrate by cold spraying. The (P, N, Mo)-TiO₂ powders were initially prepared by sol-gel method, which exhibited the characteristics of a polygonal particle with a primary particle size of 20 nm and a mean size of 2 μm. The synthesized (P, N, Mo)-TiO₂ powders were agglomerated into spherical particles with a mean size of 5 μm by spray drying method. The agglomerated powders depicted a good flowability, wettability and were suitable for cold spray deposition. The successful (P, N, Mo)-TiO₂ coatings exhibited good interfacial bonding with the substrate, with an average coating thickness of 15 μm. The properties of the synthesized (P, N, Mo)-TiO₂ powders and coatings were analyzed by advanced modern techniques, including XRD, XPS, UV–vis, SEM and TEM. The photocatalytic performance of (P, N, Mo)-TiO₂ coatings were investigated under visible light. Cold sprayed (P, N, Mo)-TiO₂ coatings exhibited excellent photocatalytic activity in MB degradation under visible-light irradiation. The (P, N, Mo)-TiO₂ coating sprayed at 500 °C revealed the highest photodegradation rate of 38% in 4 h. Complementarily, the doping mechanism and photocatalytic mechanism of (P, N, Mo)-TiO₂ coatings were also effectively proposed and discussed. (paper)