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VO 2 NANOSTRUCTURES BASED CHEMORESISTOR FOR LOW POWER ENERGY CONSUMPTION HYDROGEN SENSING

Ms. Aline SIMO Supervisor: Prof Malik Maaza Co-Supervisor: Prof Reginaldt Madjoe iThemba LABS/University of Western Cape. VO 2 NANOSTRUCTURES BASED CHEMORESISTOR FOR LOW POWER ENERGY CONSUMPTION HYDROGEN SENSING. Energy Postgraduate Conference 2013. OUTLINE.

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VO 2 NANOSTRUCTURES BASED CHEMORESISTOR FOR LOW POWER ENERGY CONSUMPTION HYDROGEN SENSING

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  1. Ms. Aline SIMO Supervisor: Prof Malik Maaza Co-Supervisor: Prof ReginaldtMadjoe iThemba LABS/University of Western Cape VO2 NANOSTRUCTURES BASED CHEMORESISTOR FOR LOWPOWER ENERGY CONSUMPTION HYDROGEN SENSING Energy Postgraduate Conference 2013

  2. OUTLINE 1- H2 Gas sensing foresight, Safety & Oxides 2- Gas Sensing Principle 4- VO2 : Mott oxide and Room temperature H2 sensing 5- Conclusions and follow up

  3. H2 GAS SENSING: FORESIGHT US Department of Energy: Hydrogen Posture Plan, www.fchea.org

  4. International Organizations and Associations • European Commission, Directorate for Energy and Transport, “clean Urban Transportation for Europe” http://ec.europa.eu/energy/res/fp6_projects/doc/hydrogen/deliverables/summary.pdf • Green car Congress, “European Commission Adopts 940M Fuel Cells and Hydrogen Joint Technology Initiative,” www.greencarcongress.com/2007/10/european-commis.html • National Hydrogen Association “Key Hydrogen Message” http://www.hydrogenassociation.org/pdf/keyHydrogenMessages.pdf • US Department of Energy, Fuel cells and Infrastructure Technologies: Transition Strategies, by Sig Gronichhttp://www.eere.energy.gov/hydrogenfuelcells/pdfs/transition_wkshp_strategies2.pdf. • US department of Energy, A national vision of America`s Transition to a Hydrogen Economy to 2030 and Beyond, http://www1.eere.energy.gov/hydrogenandfuelcells/pdfs/vision_doc.pdf • HySA initiated by the South African Department of Science and Technology (DST) increase the South African Research in hydrogen and fuel cells , http://www.fuelcelltoday.com • Publications and News • The International Journal for Hydrogen Energy - This site a news service for the hydrogen industry, covering developments in fuel cells, technology, hydrogen supply, storage, projects and regulatory policy. • Sensors & Actuators B: Chemical • Alternative Energy News Hydrogen - This news site links to hydrogen articles across the internet and is updated with several new articles each day • The Hydrogen and Fuel Cell Letter - This monthly newsletter, started in 1986, provides news from across the spectrum from across the hydrogen and fuel cells industry http://www.greencarcongress.com H2 SENSING: FORESIGHT

  5. H2 GAS SAFETY Risk /Safety codes • H2: Wide concentration range of flammability with 4-75% volume compared to gasoline 1-7.6% and wide detonation range (18.3-59% volume vs. 1.1-3.3% for gasoline) • H2: Odorless and leaks not detectable by smell • Ignition of a flammable mixture at small quantity and high diffusivity • H2: reducing dependence on petroleum imports, pollution and greenhouse gas emissions • H2 : is amongst cleanest carrier energy with the highest specific energy offering long term solution being produced from Renewables Energies such as wind-powered electrolysis or solar. Requirements for an Effective Gas Sensor • Sensitivity: Chemical Surface activity • Selectivity: Gas identification • Energy consumption

  6. OXIDES SENSORS: DETECTION LIMT-TEMPERATURE CONSUMPTION

  7. VO2 MOTT OXIDE: ELECTRICAL PROPERTY p* p* 0.7 eV EF d// d// d// p p s s

  8. VO2 MOTT OXIDE: CRYSTALLINE STRUCTURE Monoclinic VO2 with a ~ 0.5753 nm, b ~ 0.4526 nm and c ~ 0.5383 nm, presenting semiconductor behavior at RT. Formation of an electron pair in the monoclinic structure results in semiconductor phase. It can inversely transit to tetragonal rutile and conducting VO2 phase

  9. 1m 20 nm 2 nm VO2 MOTT OXIDE: STRUCTURAL PROPERTY Hydrothermal synthesis ● Nanobelts: 20-150 nm thickness range and a length ≥ 20μm. ● VO2 (A): specific interspacing d(011)~ 0.600 nm.

  10. VO2 SENSING MECHANISM O2- O2 H2 H2 O2- O2- O2- O2- O2 e- e- O2- e- e- O2- O2- e- O2- O2 Potential Barrier x x

  11. SENSING RESPONSE • Different H2 partial pressures equivalent to 140, 90, 50, 14, 0.17 ppm of H2 (N2 carrier): Standard gas sensing BUT at RT. • Average response time are ~840, 890, 1080, 1020, 1050s for 140, 90, 50, 14 and 0.17 ppm of H2 respectively.

  12. SENSITIVITY-RESPONSE TIME Sensitivity: Optimal at 90 ppm of H2 at RT

  13. SELECTIVITY RESPONSE Low detection Limit, High Selectivity H2 comparatively to CO, CO2 at RT, Low Power Consumption. ● For Humidity: idem at RT (background level), ● H2S, NH3, and C2H5OH gases: in progress

  14. CONCLUSIONS AND FOLLOW UP • Synthesis of highly crystalline Pure VO2 • Good response of cyclic gas concentrations activation • Detection limit 0.14ppm of Hydrogen gas at low temperature (low power consumption energy) • Highly selective comparatively to CO and CO2 • Potential application as Mott Infrared Insulator transistor due to its ultrafast synchrotron radiation • Following to test other gases to confirm the selectivity of vanadium dioxide and enhance the working temperature

  15. THANK YOU

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