Abstract
The use of photocatalytic materials in plasma systems has the potential to enhance the selectivity and yield of desired products. However, the surface interaction between the photocatalyst and plasma is a complex process that is not well understood. This work presents a comprehensive study of the effects of combining titanium dioxide (TiO2) photocatalysts with non-thermal atmospheric pressure nitrogen-oxygen plasmas, which increases the production of ozone and dinitrogen pentoxide (N2O5) while limiting the formation of harmful nitrogen dioxide (NO2) and nitrous oxide (N2O) by products. TiO2 coatings were deposited by magnetron sputtering onto barium titanate (BaTiO3) particulates for use within a packed bed dielectric barrier discharge reactor (DBD). The presence of titanium dioxide can affect the plasma chemistry in the DBD by acting as a sink for atomic oxygen, through photocatalytic formation of superoxide anion radical (O2-), and alteration of the dielectric constant of the BaTiO3 particulates. This work explains the complex interaction of these effects on oxygen and nitrogen plasma chemistry. The effect of the photocatalyst surface properties, gas composition and residence time on the reaction pathways for the formation of ozone and nitrogen oxides (NxOy) were investigated. The photocatalytic activity of titanium dioxide was improved by annealing the coated surface, and was subsequently found to enable the formation of ozone, increase the formation of N2O5 while significantly decreasing the formation of harmful NO2 and N2O with a residence time of 0.011 s
Highlights
Recent years have seen a large emphasis on heterogeneous photo catalysis in the literature due to its potential for environmental and energy related applications [1,2,3,4]
TiO2 coatings were deposited by magnetron sputtering onto BaTiO3 particulates and used in a packed bed dielectric barrier discharge
The photocatalytic activity of the coated particulates was improved by annealing the TiO2, which enabled the formation of the anatase phase
Summary
Recent years have seen a large emphasis on heterogeneous photo catalysis in the literature due to its potential for environmental and energy related applications [1,2,3,4]. Photons with a high enough energy are absorbed by electrons and can cause the electrons to be promoted from the valence band to the conduction band, resulting in the creation of electron hole pairs, which can lead to reduction and oxida tion reactions [6]. TiO2 has three main crystal phases, anatase, rutile and brookite, with anatase being the most photocatalytically active phase [7]. Tailoring of the morphology of the TiO2, either through the use of porous structures [8], or the tailoring of nanoparticle size and shape [9], can increase it’s photocatalytic activity
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