Photocatalytic and Gas Sensitive Multiwalled Carbon Nanotube/TiO<sub>2</sub>-ZnO and ZnO-TiO<sub>2</sub> Composites Prepared by Atomic Layer Deposition
László Péter Bakos,
Nóra Justh,
Ulisses Carlo Moura da Silva Bezerra da Costa,
Krisztina László,
János László Lábár,
Tamás Igricz,
Katalin Varga-Josepovits,
Pawel Pasierb,
Elina Färm,
Mikko Ritala,
Markku Leskelä,
Imre Miklós Szilágyi
Affiliations
László Péter Bakos
Department of Inorganic and Analytical Chemistry, Budapest University of Technology and Economics, Szent Gellért tér 4., H-1111 Budapest, Hungary
Nóra Justh
Department of Inorganic and Analytical Chemistry, Budapest University of Technology and Economics, Szent Gellért tér 4., H-1111 Budapest, Hungary
Ulisses Carlo Moura da Silva Bezerra da Costa
Department of Inorganic and Analytical Chemistry, Budapest University of Technology and Economics, Szent Gellért tér 4., H-1111 Budapest, Hungary
Krisztina László
Department of Physical Chemistry and Materials Science, Budapest University of Technology and Economics, P.O. Box 92, H-1521 Budapest, Hungary
János László Lábár
Institute for Technical Physics and Materials Science, Research Centre of Energy, Hungarian Academy of Sciences, Konkoly–Thege út 29–33., H-1121 Budapest, Hungary
Tamás Igricz
Department of Organic Chemistry and Technology, Budapest University of Technology and Economics, Budafoki út 8., H-1111 Budapest, Hungary
Katalin Varga-Josepovits
Department of Atomic Physics, Budapest University of Technology and Economics, Budafoki út 8., H-1111 Budapest, Hungary
Pawel Pasierb
Department of Inorganic Chemistry, AGH University of Science and Technology, Mickiewicza 30., 30-059 Kraków, Poland
Elina Färm
ASM Microchemistry Oy, Pietari Kalmin katu 1F2, FI-00560 Helsinki, Finland
Mikko Ritala
Department of Chemistry, University of Helsinki, P.O. Box 55, FI-00014 Helsinki, Finland
Markku Leskelä
Department of Chemistry, University of Helsinki, P.O. Box 55, FI-00014 Helsinki, Finland
Imre Miklós Szilágyi
Department of Inorganic and Analytical Chemistry, Budapest University of Technology and Economics, Szent Gellért tér 4., H-1111 Budapest, Hungary
TiO2 and ZnO single and multilayers were deposited on hydroxyl functionalized multi-walled carbon nanotubes using atomic layer deposition. The bare carbon nanotubes and the resulting heterostructures were characterized by TG/DTA, Raman, XRD, SEM-EDX, XPS, TEM-EELS-SAED and low temperature nitrogen adsorption techniques, and their photocatalytic and gas sensing activities were also studied. The carbon nanotubes (CNTs) were uniformly covered with anatase TiO2 and wurtzite ZnO layers and with their combinations. In the photocatalytic degradation of methyl orange, the most beneficial structures are those where ZnO is the external layer, both in the case of single and double oxide layer covered CNTs (CNT-ZnO and CNT-TiO2-ZnO). The samples with multilayer oxides (CNT-ZnO-TiO2 and CNT-TiO2-ZnO) have lower catalytic activity due to their larger average densities, and consequently lower surface areas, compared to single oxide layer coated CNTs (CNT-ZnO and CNT-TiO2). In contrast, in gas sensing it is advantageous to have TiO2 as the outer layer. Since ZnO has higher conductivity, its gas sensing signals are lower when reacting with NH3 gas. The double oxide layer samples have higher resistivity, and hence a larger gas sensing response than their single oxide layer counterparts.
