A review on plasma electrolytic oxidation coatings for organic pollutant degradation: How to prepare them and what to expect of them?

Powdered photocatalysts have been extensively investigated for the decontamination of various pollutants. In spite of the superior photocatalytic performance mediated by powdered photocatalytic materials, the major strides in the production of photoactive coatings are a crucial issue since they open up a world of industrial opportunities for photocatalysis. Plasma electrolytic oxidation is a promising technique, which is capable of fabricating ceramic coatings with controllable porous structure at a low cost, simple and easy operation, high metallurgical bonding strength to the substrate, and the possibility of the coating formation on complex geometry or large size substrates. This review is aimed at summarizing the fundamental aspects of the PEO process together with the effects in the photocatalytic activity of the multiple parameters of the PEO process such as the electrolyte and additive, deposition time, as well as electrical parameters based on the chemical composition of substrate. The role of duplex treatment in photocatalytic activity improvement is also summarized. Furthermore, to compare the performance of photocatalytic systems, photocatalytic coating efficiency (PCE) was proposed. In overall, this review offers a distillate of the available information on PEO coatings, which can influence the design and creation of more effective materials and impulse their real-world application.