1 / 35

Analyzing the Properties of IrOx Derived Electrochemical Sensors

Analyzing the Properties of IrOx Derived Electrochemical Sensors.

avalon
Download Presentation

Analyzing the Properties of IrOx Derived Electrochemical Sensors

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Analyzing the Properties of IrOx Derived Electrochemical Sensors Brandon JohnsonUniversity Of California, IrvineDepartment of Electrical Engineering and Computer ScienceMentor: Dr. Marc MadouUniversity Of California, IrvineChancellor's Professor Department of Mechanical and Aerospace Engineering

  2. Electrochemistry Background How does electrochemical sensing work? Snoswell, David Robert Evan. The Influence of Surface Heterogeneity and Solution Composition on the Colloid Stability of SiO2 and TiO2 Dispersions, Australian Digital Thesis Program, 2003.

  3. Why Are We Even Interested? • Glass pH electrodes have their short commings • Extremely fragile • Relatively slow response times • Short lifetime • Cannot be used in certain media • Alkaline • HF • Organic Solutions

  4. Science Looks Into Metal Oxides • Various Metal Oxides tested • Sb2O3 • Widely used for acid based titrations or solutions containing HF. However potential drift makes this unsuitable for pH measurements. • Bi2O3 • Used in pH measurements for KOH • PtO2, IrO2, RuO2, OsO2, TaO5, RhO2, TiO2, SnO2 • IrO2 held the most promise Sheng Yao, Min Wang, and Marc Madou. A pH Electrode Based on Melt-Oxidized Iridium Oxide, Journal of The Electrochemical Society, 148 (4) H29-H36 (2001)

  5. Methods of Creating IrOx • Electrochemical growth • Electrodeposition • Sputtered Coating • Thermal method • Printing Method • Lithium Carbonate (Li2CO3) melt bath

  6. Initial Claims Regarding these IrOx Sensors • Extremely consistent Eo regardless of storage medium

  7. Initial Claims Regarding these IrOx Sensors • Super fast response times

  8. Initial Claims Regarding these IrOx Sensors • Consistent and stable readings across a variety of pH’s

  9. Initial Claims Regarding these IrOx Sensors

  10. Initial Claims Regarding these IrOx Sensors • Additionally these sensors claimed to be stable in 4M HCL or a 5M H2SO4 solution • Claimed to have excellent mechanical stability

  11. The Problem • These results were not corroborated in industry for some time.

  12. Initial Results Results in a buffer of pH 8

  13. Initial Results Results in a buffer of pH 3

  14. Initial Results Analysis of Nernstian Slope

  15. Initial Results Analysis of Nernstian Slope

  16. Initial Results • So far the slopes look good but the Eo has an almost 200mV deviation between the probes • The response times are extremely slow

  17. Off to the SEM

  18. Off to the SEM

  19. Off to the SEM

  20. Off to the SEM

  21. Off to the SEM

  22. Significance of the BSE Results • The IrOx was not uniform • Was there a polymer coating? • Was there damage done to the probe? • Was there some sort of residue from being in the pH buffer solution?

  23. The Answer • The required break-in period • Conversion of the Li8IrO6 to an unknown structure • Additionally hydration plays a major role in the ability of the IrOx sensors to respond rapidly and correctly Chrisanti, Santi. A pH Electrode Based on Melt-Oxidized Iridium Oxide, A Thesis Presented in Partial Fulfillment of the Requirement for the Degree Master of Science in the Graduate School of The Ohio State University, 2003.

  24. Results Example response time of a non-hydrated probe after the initial break-in period

  25. Results Example response time of a hydrated probe after the initial break-in period

  26. Results Extrapolated slopes of 4 hydrated probes, post break-in

  27. Results

  28. Results Probe stability and response results across a variety of pH buffers

  29. Results Response time for a pH jump from pH 2 to pH 5.5

  30. Results Response time for a pH jump from pH 2 to pH 3.5

  31. Results Response time for a standard glass bulb working electrode

  32. Results Results from a test in H2S04

  33. Results An interesting result regarding mechanical stability

  34. Significance • Consistencies with original publications • Response times consistent with original publications • Stability in a wide range of pH buffers also confirmed • Discrepancies with original publications • Break-in period • Necessity of hydration • Possibly the stability in a H2S04 solution • Consistency of the Eo

  35. Acknowledgements • Mentor: Dr. Marc Madou • Lab Team: Kelvin Cheung, Jim Zoval, Horacio Kido, Chunlie (Peggy) Wang, Rabih Zaouk, Benjamin Park, Francesc Jornet, and Kuosheng Ma • IM-SURE: Said Shokair, Jerry McMillan, Goran Matijasevic • National Science Foundation (NSF)

More Related