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Photocatalytic properties of zinc oxide prepared by thermal degradation of the cellulose template

Wastewater pollution with organic dyes has become one of the leading environmental problems. A non- toxic and environmentally friendly method of wastewater treatment is based on the photocatalytic ability of semiconductors such as zinc oxide (ZnO) [1]. ZnO is an II-IV semiconductor that is characterized by excellent optical, electrical, optoelectric, and photochemical properties and has a wide application in photocatalysis, sensors, solar cells, antimicrobial materials, and more [2]. This work aims to prepare, characterize and investigate the photocatalytic properties of hybrid materials based on: 1) cellulose and zinc oxide (ZnO), and 2) ZnO structures obtained by a polymer templated thermal decomposition of the previously prepared ZnO/cellulose hybrids. We synthesized ZnO on two different cellulose substrates, Sodra Green T and UPM Conifer, using the thermal atomic layer deposition (t-ALD) method. In doing so, we applied standard process conditions for the growth of a 50 nm ZnO film on a silicon substrate. After that, the hybrid materials were calcinated in the programmable furnace to obtain pure ZnO. The samples were characterized using a field emission scanning electron microscope (FE-SEM) and X-ray photoelectron spectroscopy (XPS). In the study of photocatalytic activity of the samples, we used methyl orange (MO) as a model organic pollutant. Changes in the absorbance of the MO solution was monitored using a UV / Vis spectrophotometer. Our results showed that calcinated samples have a larger active surface area as a result of the formation of solid porous tubular structures. Furthermore, ZnO who was synthesized on Sodra Green T cellulose showed a larger amount of reactive surface OH groups, indicating better photocatalytic activities. After calcination of the hybrid materials, the resulting ZnO showed strong photocatalytic activity. Within 80 min there is complete mineralization and decolorization of MO, while before calcination of samples within 240 min there was no discoloration or mineralization of MO. Also, ZnO deposited on Sodra Green T cellulose proved to be a better photocatalyst than ZnO deposited on UPM Conifer cellulose.

photocatalysis, ZnO, ALD

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