A novel APPJ system used to simulate the effect of ozone and visible light on enhancing the catalytic activity of nano-Co3O4 for dye removal at neutral pH

In this paper, the design of a novel atmospheric pressure plasma jet (APPJ) reactor, and the effects of ozone and light on enhancing the catalytic activity of Co3O4 for methyl orange (MO) degradation are reported. The preliminary discharge characteristics of the APPJ were investigated and the fabricated Co3O4 nanoparticles (NPs) were characterized by x-ray diffraction (XRD), the scanning electron microscope (SEM) and the transmission electron microscope (TEM). The experimental results showed that the average diameter of fabricated Co3O4 NPs was approximately 40 nm, and the Ar/O-2 plasma emitted strong light in the region of 600-800 nm, fitting the band gap energy (2.25 eV) of the fabricated Co3O4 NPs. Catalytic data suggested that the combination of the nanosized Co3O4 catalyst, ozone and the visible light from the Ar/O-2 plasma was sufficient to degrade MO molecules effectively. The simulated degradation rate constant (k alpha) of the Co3O4 NPs catalyst/visible light/ozone was 0.1 min(-1), approximately 50 and 1.5 times of those achieved in the photocatalytic and plasma processes, respectively.