Photocatalytic Decomposition of N2O over TiO2/g-C3N4 Photocatalysts Heterojunction

Significance Statement

Due to the considerable increase of concentration of nitrous oxide in the atmosphere resulting mostly from anthropological effects, scientists have faced the challenges of lowering the effects of nitrous oxide on environment as it is regarded as a greenhouse gas contributing to global warming and also ozone layer depletion.

Decomposing nitrous oxide by a photocatalytical process under ultraviolet irradiation can certainly offer solutions to this issue. A semiconductor such as titanium dioxide shows photocatalytic activity and can be used as a photocatalyst. However, its large band gap and quick electron-hole recombination limits its photoactivity.

Another semiconductor, graphitic carbon nitride also exhibits photocatalytic activity. They have also been studied to provide support as photocatalytic materials. However, their morphological property and abrupt electron-hole recombination limits their potential in photocatalytical processes. In order to limit the electron-hole recombination phenomenon which occurs in both discussed photocatalysts, generation of heterojunction in the semiconductor or changes in their morphologies could serve as a means for achieving this.

In a recent article published in Applied Surface Science, Kamila Koči and colleagues prepared different mixing ratios of titania and graphitic carbon nitride photocatalyst for decomposition of nitrous oxide under ultraviolet irradiation at wavelengths of 254 nm (UVC) and 365 nm (UVA).

They prepared mixing ratios of 1:2, 1:4 and 1:6 with respect to titania and graphitic carbon nitride photocatalyst nanocomposite by means of mechanical mixing in water suspension before the calcination took place. All fabricated nanocomposites were characterized by several experimental techniques and their decomposition effect on nitrous oxide under photocatalyst was observed with an 8 W Hg irradiation lamp.

Results from all the characterization techniques show the successful deposition of titania on the graphitic carbon nitride surface for all the prepared nanocomposite photocatalysts following the generation of heterojunction in all of them.

Their photocatalytic decomposition rate on nitrous oxide was also investigated for 14 hours. They discovered all the tested nanocomposites had comparable photocatalytic activity under ultraviolet irradiation at wavelength of 254 nm. However, under wavelength of 365 nm, the highest decomposition rate for nitrous oxide conversion was observed with titania and graphitic carbon nitride in mixing ratio 1 to 2.The decomposition process at both wavelengths increased as the time progressed.

All photocatalyst nanocomposites were compared with a commercial photocatalyst, Evonik P25 and exhibited higher photocatalytic activity. They also observed, with the aid of kinetic constants evaluation, that increase in proportion of graphitic carbon nitride resulted in decrease in photocatalytic activity. At longer wavelength, the composite titania/graphitic carbon nitride in ratio of 1:2 had the highest photocurrent generation as a result of the created heterojunction, which limits the electron-hole recombination phenomenon.

The research team was able to develop a photocatalyst which converts one of the potential greenhouse gases, nitrous oxide into non-hazardous gases of nitrogen and oxygen respectively.

Photocatalytic Decomposition of N2O over TiO2/g-C3N4 Photocatalysts Heterojunction - Advances in Engineering

About The Author

Kamila Kočí is a professor at the Institute of Environmental Technology of the VŠB – Technical University of Ostrava, Czech Republic. She received her diploma in the University of Chemistry and Technology in Prague. After working in industry and secondary school for 15 years, she returned to academia in 2008. She obtained her Ph.D. degree in 2009 at VŠB-Technical University of Ostrava.

Her research topics are heterogeneous photocatalysis in gaseous and liquid phases, physico-chemical properties of nanostructured photocatalysts, kinetics and mechanisms of photochemical reaction and chemical engineering. She has published more than 35 papers in peer-reviewed journal. She also is a reviewer for more than 20 scientific journal and several national and international funding agencies.

About The Author

Jana Kupková is a researcher assistant at the Nanotechnology Centre in VŠB-Technical University of Ostrava, Czech Republic. She received her BS and MS degrees in the field of Chemical and Physical Methods of Material Testing from the VŠB- Technical University of Ostrava in 2008 and 2010, respectively. She received her Ph.D. degree in Materials Science and Engineering from the same university in 2015.

Her research interests include study of clay minerals, preparation and characterization of the new forms of ceramic materials based on the natural or modified clay minerals, further the preparation and characterization of new nanocomposites prepared especially from modified clay minerals. She has been working in the field of the X-ray powder diffraction phase analysis since 2012. She has experience in measurement, characterization and phase identification of inorganic materials, especially rocks and clay minerals, further ceramic materials, composites, catalysis etc.

About The Author

Prof. Piotr Kustrowski received his PhD at the Jagiellonian University in Krakow in 2000. After habilitation in 2007 at this university he established his own research group. In 2012 he was appointed as head of Chemical Technology Department. From 2016 he is a dean of Faculty of Chemistry at the Jagiellonian University.

In his scientific activity he specializes in understanding relationships between structural, textural and surface properties of porous materials (such as mesoporous silicas, carbons or natural and synthetic clays) and their activity in adsorption and catalytic applications. He develops new functional materials for environment protection (removal of cationic and anionic contaminants from waste water, elimination of nitrogen oxides and volatile organic compounds from air) and technological processes (catalysts for e.g. dehydrogenation of alkane, aldol and Knoevenagel condensation, biodiesel production). His current publication record includes about 130 original papers and chapters published in various journals and books related to catalysis and chemistry of materials.

About The Author

Petr Praus obtained his MSc in Technology of Silicates at Institute of Chemical Technology Prague (1987) and PhD in Analytical Chemistry at University of Pardubice (1996). He worked in analytical laboratories of several industrial companies. Since 2002 he has been working at VŠB-Technical University of Ostrava.

Since 2013 he has been a full professor in the field of Material Science and Engineering. During last several years he has been working as a head of the Department of Chemistry, senior researcher and Vice-rector for Research and Development. He has been teaching analytical chemistry and related subjects. His research has been focused on the synthesis, characterization and applications of nanocomposite materials.

About The Author

Martin Reli is a junior researcher at the Institute of Environmental Technology of the VŠB–Technical University of Ostrava, Czech Republic. He received his PhD degree from the VŠB –Technical University of Ostrava in 2013. The topic of his PhD thesis was “Materials based on TiO2 modified by metals for photocatalytic reduction of carbon dioxide”.

His current field of interest are photocatalytical reactions in gas and liquid phase with possible environmental impact. Especially photocatalytic reduction of carbon dioxide, photocatalytic decomposition of nitrous oxide, nitric oxide and ammonia. He is also interested in advanced oxidation processes (AOPs) utilized for degradation of organic compounds (styrene, acetone, xylene, toluene) from waste gases.

About The Author

Marcel Šihor is a Doctoral student at the Department of Physical Chemistry and Theory of Technological Processes VŠB-Technical University of Ostrava, Czech Republic. He received his BC degrees in Chemistry and Technology of Environment and MS degrees in Chemical Engineering Protection from VŠB-Technical University of Ostrava the 2011 and 2013, respectively. He attended a foreign internship at National Taiwan University and the University of Oulu, led by professors J. C.S. Wu and M. Huuhtanen, respectively.

From 2013 he works and studies Ph.D. in the Laboratory of heterogeneous photocatalysis as a doctoral researcher at the Institute of Environmental Technology (IET), VŠB-Technical University of Ostrava, with a research project dealing with the Photocatalytic decomposition of nitrous oxide in the gas phase.

About The Author

Ivana Troppová is a Junior researcher at the Institute of Environmental Technologies of the VŠB-Technical University of Ostrava, Czech Republic from 2015. She received her MS degree and PhD degree in Environmental Engineering and Environmental Protection in Industry from the VŠB-Technical University of Ostrava in 2007 and 2011, respectively. After PhD degree she worked as a Junior researcher at the Centre of Environmental Technologies of the VŠB-Technical University of Ostrava.

From 2012 to 2015 she worked as a Post-doc researcher at the Department of Physical Chemistry, Faculty of Chemical Technology at the University of Pardubice. Her current research interests include in environmental catalysis, adsorption on solids, extraction by supercritical and pressurized fluids – its utilization for unconventional preparation of nanostructured metal oxides, preparation and characterization of various macroscopic forms of nanostructured metal oxides and she has experience with adsorption equipment and device for determining the specific surface area.

Reference

Kočí, K., Reli, M., Troppová, I., Šihor, M., Kupková, J., Kustrowski, P., Praus, P. Photocatalytic Decomposition of N2O over TiO2/g-C3N4 Photocatalysts HeterojunctionApplied Surface Science 396 (2017) 1685–1695.

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