Enhancing Photocatalytic Activity of ZnO Nanoparticles in a Circulating Fluidized Bed with Plasma Jets

Abstract

In this work, zinc oxide (ZnO) nanoparticles were modified in a circulating fluidized bed through argon and hydrogen (Ar-H) alternative-current (AC) arc plasma, which shows the characteristics of non-equilibrium and equilibrium plasma at the same time. In addition, a circulating fluidized bed with two plasma jets was used for cyclic processing. The catalytic degradation performance on Rhodamine B (Rh B) by Ar-H plasma modified ZnO and pure ZnO was tested in aqueous media to identify the significant role of hydrogen atoms in Rh B degradation mechanism. Meanwhile, the effects of plasma treatment time on the morphology, size and photocatalytic performance of ZnO were also investigated. The results demonstrated that ZnO after 20 minutes-treatment by Ar-H plasma showed Rh B photocatalytic degradation rate is ten times greater than that of pure ZnO, and the reaction follows a first-kinetics for the Rh B degradation process. Furthermore, the photocatalyst cycle experiment curve exhibited that the modified ZnO still displays optimum photocatalytic activity after five cycles of experiment. The improvement of photocatalytic activity and luminescence performance attributes to the significant increase of the surface area, and the introduction of hydrogen atoms on the surface also could enhance the time of carrier existence where the hydrogen atoms act as shallow donors.

Effectual visible light photocatalytic reduction of para-nitro phenol using reduced graphene oxide and ZnO composite

“…The benefits of utilising the one dimensional (1D) nanostructures like nanorods can provide a higher surface area to volume ratio and enable efficient carrier transport in comparison with zero and other dimensional nanostructures due to the decreased boundaries, surface defects and structural disorders 18 . However, utilisation of ZnO in photocatalysis exhibits some disadvantages namely, (i) particle aggregation during photocatalysis activity that restrains the activity of ZnO on a large scale, (ii) the restriction of ZnO usage in the visible region because of its wide band gap, (iii) the expeditious recombination of charge recombination of the photo generated electron–hole pairs 19 , 20 . Further, the wide band gap restricts the catalytic activity due to the low light absorption, to conquer this issue the band gap of ZnO can be tuned by ion doping or coupling with different semiconductors, deposition metals and non-metals, defect Engineering and co-catalyst will regulate the band gap energy 21 , 22 .…”