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Monolayer iron oxide grown on porous platinum sensing layers of carbon monoxide sensors
Linköping University, Department of Physics, Chemistry and Biology, Applied Sensor Science. Linköping University, The Institute of Technology.
KTH Royal Institute of Technology, Material Physics, Kista, Sweden.
KTH Royal Institute of Technology, Material Physics, Kista, Sweden.
KTH Royal Institute of Technology, Material Physics, Kista, Sweden.
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2015 (English)Manuscript (preprint) (Other academic)
Abstract [en]

Mono-layer iron oxide has been deposited through e-beam evaporation on a silica supported poly-crystalline platinum (Pt) model catalyst and its CO oxidation characteristics obtained from mass spectrometry measurements under various CO and O2 concentrations (ranging from 100 to 900 ppm and 3 to 7 %, respectively) as well as at different temperatures (ranging from 130 to 220 °C) and compared to the CO oxidation on corresponding non-coated Pt samples. Fabricating the model system as a Metal Oxide Semiconductor (MOS) structure from 4H-SiC with a top layer of SiO2 (as the support material) and a thin, discontinuous polycrystalline Pt film as the metal (the active catalyst material) also provided the possibility to investigate whether changes in catalyst surface conditions could be electronically monitored through the changes in capacitance they induce across the MOS structure.

A low-temperature shift in the activity to CO oxidation for the iron oxide modified compared to bare Pt catalysts similar to what has previously been reported on single-crystalline Pt was found also for the near-realistic MOS model catalyst. This low-temperature shift was furthermore reflected in the electrical measurements, strongly indicating a correlation between the MOS capacitance and the CO oxidation characteristics, both in the case of iron oxide coated and non-coated Pt samples. By monitoring the MOS capacitance during more than 200 hours of continuous operation and analyzing the iron oxide coated samples by photo electron spectroscopy it could also be concluded that the iron oxide coated model catalyst seemingly retains its CO oxidation characteristics and chemical/compositional integrity over time. These findings might not only point to the applicability of iron oxide modified Pt in practical applications but may also open up new possibilities regarding the utilization of MOS model systems in studying and understanding as well as tailor CO oxidation (and other) catalysts and/or gas sensors for specific applications.

Place, publisher, year, edition, pages
2015.
Keyword [en]
Silicon carbide, MAX phase, Physical vapor deposition, High temperature
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:liu:diva-113762OAI: oai:DiVA.org:liu-113762DiVA: diva2:784570
Available from: 2015-01-30 Created: 2015-01-30 Last updated: 2015-01-30Bibliographically approved
In thesis
1. Functional Nanostructures for Gas Sensors
Open this publication in new window or tab >>Functional Nanostructures for Gas Sensors
2015 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

This research focuses on three main topics within the aims of FUNMAT, which are:

  1. Ohmic contacts to high-temperature chemical gas sensors.
  2. Studies of catalytic monolayers on active gate metal in SiC-based gas sensors.
  3. Investigating potential sensing properties of the nanoscale material MXene.

Within the first research topic, we study the growth of Ohmic contacts to 4H-SiC for high temperature and corrosive environment applications, being a need in chemical gas sensors e.g. for automotive industry. For this purpose, common commercially-synthesized contacts are not suitable, due to either the presence of low-melting point elements or rapid oxidation. Improving the previously reported growth methods, designing durable oxygen-barrier capping layers, and synthesizing new contact-materials are our main focuses.

For the second research topic, we investigate the improvement of the sensing performance of platinum-based sensing layers in silicon carbide field-effect gas sensors, which have many industrial applications. This project started with modification of field-effect-based metal oxide semiconductor CO sensors by the synthesis of one monolayer iron oxide on the platinum sensing layers of the sensors. Monolayer metal oxides have been reported to enhance the catalytic properties of platinum which is a promising result to be used in improving the performance of gas sensors.

And finally, the third research topic covers studies of newly synthesized materials to be explored for any potential sensing property. Our focus is on metal carbide nano-sheets known as MXene phases and to study their  gas adsorption properties. Due to several uninvestigated features of newly synthesized materials, ab.initio. theoretical studies are of importance.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2015. 52 p.
Series
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 1705
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-113763 (URN)978-91-7519-133-1 (ISBN)
Presentation
2015-02-20, Planck, Fysikhuset, Campus Valla, Linköpings universitet, Linköping, 10:15 (English)
Opponent
Supervisors
Available from: 2015-01-30 Created: 2015-01-30 Last updated: 2015-01-30Bibliographically approved

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Fashandi, HosseinEriksson, JohanEklund, PerLloyd Spetz, AnitaAndersson, Mike

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