Hierarchical TiO₂ Layers Prepared by Plasma Jets

Heterogeneous photocatalysis of TiO₂ is one of the most efficient advanced oxidation processes for water and air purification. Here, we prepared hierarchical TiO₂ layers (Spikelets) by hollow-cathode discharge sputtering and tested their photocatalytic performance in the abatement of inorganic (NO, NO₂) and organic (4-chlorophenol) pollutant dispersed in air and water, respectively. The structural-textural properties of the photocatalysts were determined via variety of physico-chemical techniques (XRD, Raman spectroscopy, SEM, FE-SEM. DF-TEM, EDAX and DC measurements). The photocatalysis was carried out under conditions similar to real environment conditions. Although the abatement of NO and NO₂ was comparable with that of industrial benchmark Aeroxide^® TiO₂ P25, the formation of harmful nitrous acid (HONO) product on the Spikelet TiO₂ layers was suppressed. Similarly, in the decontamination of water by organics, the mineralization of 4-chlorophenol on Spikelet layers was interestingly the same, although their reaction rate constant was three-times lower. The possible explanation may be the more than half-magnitude order higher external quantum efficacy (EQE) compared to that of the reference TiO₂ P25 layer. Therefore, such favorable kinetics and reaction selectivity, together with feasible scale-up, make the hierarchical TiO₂ layers very promising photocatalyst which can be used for environmental remediation.