Visible-light-sensitive coatings of graphitic carbon nitride with inherent porosity induced by camphor

Abstract

Graphitic carbon nitride is referred to as a light-sensitive material with a prominent position in photocatalysis. It was shown repeatedly that the interpretation of kinetic data in the photocatalytic ox/redox reactions is not an easy task. The well-developed microporous structure, unlike that of standard heterogeneous catalysis, is not always the necessary feature. A very fine porous structure brings a significant part of the active surface. However, it is not usually available for photons. When hit the surface, they form reactive species that then diffuse deeper into the catalytic particle. However, the process becomes more driven by mass transport and the reaction rate measurement no longer takes place in the kinetic regime. This limitation can be avoided by using light-sensitive materials that offer a sufficiently developed surface, but only to the extent that it is directly accessible to the incident photons. Here, such a type of thin-film catalyst is described, and porogenic camphor is used to create a suitable surface morphology and porosity. The roles of camphor content and additional plasma treatment were experimentally verified. All coatings were described with a battery of techniques with a focus on their structural and morphological properties. The coatings were then employed in a tetracycline oxidation in a slit-type micro-photoreactor. Their performance was compared with chemically identical structures, however, obtained without the porogenic body, and/or the additional plasma treatment. The chosen transformation of tetracycline represents both a suitable model reaction and a process of general relevance in the decontamination of wastewater containing pharmaceuticals.