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Poster

WEB Towards understanding response generation in conductometric gas sensors

Friday (07.08.2020)
20:41 - 20:41 Poster Room
Part of:
Line-Up:
- Poster *web*Smoothing of additive manufactured parts using ns-pulsed laser source 1 Dipl.-Ing. Florian Kuisat
- Poster TBA -
- Poster *web*Combustion Synthesis of High Entropy Alloys thin films 1 Dr. Anni Wang
- Poster *web*Surface macro-smoothing and micro-structuring of additive manufactured components by using DLIP technique for controlling wetting characteristics 1 Dipl.-Ing. Florian Kuisat
- Poster *web*Influence of embedding materials on heat transfer and ignition transfer time in heterogeneous reactive material system 1 Mostafa Baloochi
- Poster TBA -
- Poster *web*Self reactive joining process with multilayer foils in lap joint configuration 1 Marcus Glaser
- Poster *web*Thermodynamics and kinetics of phase formation in magnetron-sputtered Ni/Al multilayer thin films with nanoscale morphology 1 Sascha Sebastian Riegler
- Poster *web*Femtosecond laser approach to cut Ni/Al reactive foils without ignition of a self-propagation reaction 1 Maria Amelia Martins
- Poster *web*Effect of preparation angle on atom probe tomography of reactive multilayers 1 Christian Schäfer
- Poster *web*Reactive Ni/Al multilayers with 3D Morphologies 1 Konrad Jaekel
- Poster *web*Synchrotron radiation X-ray powder diffraction and magnetometric study of natural and synthetic terms of the stannite-kesterite pseudobinary system in the low temperature regime (5-275 K) 1 Dr. Francesco Di Benedetto
- Poster *web*Coating and Drying of Sodium-Ion-Battery Electrodes 1 Julian Klemens
- Poster *web*Analytical prediction model for Direct Laser Interference Patterning 1 Dr. Bogdan Voisiat
- Poster *web*CFD Analysis of joining processes using reactive multilayers on native surface morphologies of microelectronic substrates 1 Erik Wiss
- Poster *web*Top-Hat profile in Direct Laser Interference Patterning: Is it worth it? 1 Mikhael El-Khoury
- Poster *web*Laser-based (“2D”) surface treatment of lithium-ion battery electrodes to improve the rate capability 1 Jens Sandherr
- Poster *web*Microstructure investigation of superconducting NbN thin films on copper 1 Dipl.-Ing. Ying Li
- Poster TBA -
- Poster *web*Laser functionalized PEEK-based coating systems to minimize friction and wear 1 Dr. Tim Kunze
- Poster *web*Structure and Dynamics in a Layered Na-ion Battery Cathode 1 Euan Bassey
- Poster *web*Electrode-Processing using porous nano-structured Na3V2(PO4)3 (NVP) for Sodium-Ion Batteries 1 Luca Schneider
- Poster TBA -
- Poster *web*Experimental Approach for Phase Diagram determination of Li alloys 1 Joel Fels
- Poster *web*Process Integration of Few-Layer MoS2 into a-Si:H Heterojunction pin-Photodiodes for extended Infrared Detection 1 Charles Otieno Ogolla
- Poster *web*Ti3SiC2- and Ti3AlC2-based ceramics synthesis by spark plasma sintering of preceramic paper 1 Elizaveta Sedanova
- Poster *web*Overheating microstructural study of nickel-based superalloys from turbine blades of aircraft engines 1 Dr. Ana Pastor
- Poster *web*Electrochemical thermodynamics of Lithium Batteries and their materials 1 Prof. Dr. Hans Jürgen Seifert
- Poster *web*Corrosion Analysis of a 316L Stainless Steel Gas Outlet Sealed with a Copper Ring Used in the CO2 Methanation Process 1 Ananya Prechavut
- Poster *web*Self-propagating reaction of structured reactive Al/Ni multilayers 1 Yesenia Sauni
- Poster *web*3D structured electrodes for Li-ion batteries using open porous metal foams as current collector for high energy application 1 Jonas Oehm
- Poster *web*Novel air stable single source precursor for homogeneous crystalline TiS2 thin films 1 Anja Sutorius
- Poster *web*Synthesis of nickel-copper composite with controllable nanostructure through facile solvent control as positive electrode for high-performance supercapacitors 1 Dr. Damin Lee
- Poster *web*Towards understanding response generation in conductometric gas sensors 1 Stefan Kucharski
- Poster Effects of 3D electrode design on high-energy silicon-graphite anode materials 1 Yijing Zheng

Session -F: Functional Materials, Surfaces, and Devices
Belongs to:
Topic X: Poster Session


Conductometric gas sensors (CGS) translate the change in composition of surrounding atmosphere into a measurable electrical response. Their construction is simple: a sensitive layer connecting two electrodes, which makes them inexpensive and easy to fabricate, and therefore one of the most popular gas sensing solutions. Although SnO2, a common sensitive material, shows excellent chemical stability and is currently used for detection of numerous gases, CGS still suffer from limited sensitivity and selectivity, leaving room for research-driven improvement.

The precise mechanism of response generation in these devices largely remains a mystery. Based on phenomenological studies, a model called “the oxygen chemisorption mechanism” was developed, which explains the change in sensor resistance by means of charged oxygen adsorbates altering the Fermi level in the subsurface region of the sensitive layer. Although this model was successfully used to explain some observations, no such oxygen adsorbates have ever been spectroscopically observed under working conditions, including in our own extensive operando studies.

In this work, a summary of multiple experiments showing the lack of direct spectroscopic evidence in support of an oxygen chemisorption mechanism is presented, along with a demonstrated correlation between sensor response and oxygen vacancy formation. NAP-XPS experiments were performed on a working SnO2-based CGS with in situ resistance measurements in different O2 pressures and temperatures. Downward binding energy shifts in the Sn 3d and O 1s emissions accompanied by increased resistance were observed in every instance, indicating both spectroscopic and phenomenological response of the sensor to the increasing pressure of O2. However, the O 1s peak shape, which could indicate formation of oxygen adsorbates, remains unchanged regardless of oxygen pressure, therefore making emergence of such adsorbates unlikely. On the other hand, analysis of the area of Sn and O emissions suggests that the resistance change correlates not only with the binding energy shift, but also the ratio of O to Sn in the analysed subsurface volume, and possibly in the bulk. A description of conductivity as a function of oxygen vacancy concentration, which in turn is a function of surrounding oxygen partial pressure, could revolutionise the way we perceive sensing mechanisms of CGS and result in a more complete picture, eventually leading to the design of new materials.

 

Speaker:
Stefan Kucharski
University College London
Additional Authors:
  • Prof. Chris Blackman
    University College London