Research to Business
Offer: 673

Better gas sensor technology with MOFs

The use of metal-organic frameworks in gas analysis in combustion furnaces reduces the cross-sensitivity of metal oxide gas sensors to humidity.

The MOF coating on the zinc oxide (ZnO) prevents the exchange of water between the atmosphere and the ZnO/MOF interface. If the sensor is exposed to fewer humidity fluctuations, the quality of the gas analysis rises. (Image: Institute of Functional Interf

The continuous analysis of gases in combustion furnaces serves as the basis for controlling the combustion. Semiconducting metal oxide gas sensors (MOGs) are used for this purpose. However, the analysis is strongly influenced by the presence of water steam, the so-called water cross-sensitivity.

State of the art

Since the water is registered as gas by the MOG itself, measurements of the gas concentrations are often very inaccurate. On the one hand, the water comes from the environment (air humidity), on the other hand the water is generated by the interaction of the analyzed gases with the metal oxide. Gas analysis in the exhaust air of combustion processes is made more difficult by the fact that the combustion process itself produces water as a reaction product, which additionally increases the air humidity.

Due to the complexity of the entire system, water cross-sensitivity is still a major challenge in the field of MOG technology. There are no known technical solutions to make the sensor less dependent on water. Only on the software side can cross-sensitivity be counteracted during data interpretation.

Technology

Scientists from the Institute for Functional Interfaces (IFG) at KIT have developed an extension for MOGs in cooperation with the Karlsruhe University of Applied Sciences that effectively reduces water cross-sensitivity. The principle: metal-organic frameworks (MOFs), which function as highly porous molecular storage devices, are deposited directly on the semiconductor material of the sensor. The MOFs act as diffusion barriers for the water molecules, while other gas molecules pass through the porous layer almost unhindered. The water formed at the oxide – MOF interface as a result of the chemical conversion of the gases is prevented by the MOF layer from diffusing through the MOF into the external atmosphere. This results in water steam saturation at the boundary, which ensures a stable humidity level.

Advantages

With the saturation occurring, fluctuations in relative humidity outside the sensor no longer have any influence on the measurement. MOFs significantly increase the accuracy and quality of gas analyses. This results in higher control reliability for combustion furnaces.

Options for companies

The positive effect of the MOFs has been proven in series of experiments. KIT is looking for partners for the further development and use of MOFs in gas sensor technology for combustion furnaces.

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Your contact person for this offer

Dagmar Vössing, Karlsruhe Institute of Technology (KIT)
Head of Technology Transfer, Innovation and Relations Management (IRM)
Phone: +49 721 608-25582

Email: dagmar.voessing@kit.edu

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