analyzing the properties of irox derived electrochemical sensors
DESCRIPTION
Analyzing the Properties of IrOx Derived Electrochemical Sensors. - PowerPoint PPT PresentationTRANSCRIPT
Brandon JohnsonUniversity Of California, Irvine
Department of Electrical Engineering and Computer Science
Mentor: Dr. Marc MadouUniversity Of California, Irvine
Chancellor's Professor Department of Mechanical and Aerospace Engineering
Analyzing the Properties of IrOx Analyzing the Properties of IrOx Derived Electrochemical SensorsDerived Electrochemical Sensors
Electrochemistry BackgroundElectrochemistry BackgroundHow 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.
Why Are We Even Interested?Why Are We Even Interested? Glass pH electrodes have their short commingsGlass pH electrodes have their short commings
Extremely fragileExtremely fragileRelatively slow response timesRelatively slow response timesShort lifetimeShort lifetimeCannot be used in certain mediaCannot be used in certain media
AlkalineAlkalineHFHFOrganic SolutionsOrganic Solutions
Science Looks Into Metal OxidesScience Looks Into Metal Oxides
Various Metal Oxides testedVarious Metal Oxides tested SbSb22OO33
Widely used for acid based titrations or solutions containing Widely used for acid based titrations or solutions containing HF. However potential drift makes this unsuitable for pH HF. However potential drift makes this unsuitable for pH measurements.measurements.
BiBi22OO33
Used in pH measurements for KOHUsed in pH measurements for KOH PtOPtO22, IrO, IrO22, RuO, RuO22, OsO, OsO22, TaO, TaO55, RhO, RhO22, TiO, TiO22, SnO, SnO22
IrOIrO2 2 held the most promiseheld 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)
Methods of Creating IrOxMethods of Creating IrOxElectrochemical growthElectrochemical growthElectrodepositionElectrodepositionSputtered CoatingSputtered CoatingThermal methodThermal methodPrinting MethodPrinting MethodLithium Carbonate (LiLithium Carbonate (Li22COCO33) melt bath) melt bath
Initial Claims Regarding these IrOx SensorsInitial Claims Regarding these IrOx Sensors
Extremely consistent EExtremely consistent Eoo regardless of storage medium regardless of storage medium
Initial Claims Regarding these IrOx SensorsInitial Claims Regarding these IrOx Sensors Super fast response timesSuper fast response times
Initial Claims Regarding these IrOx SensorsInitial Claims Regarding these IrOx Sensors Consistent and stable readings across a variety Consistent and stable readings across a variety
of pH’sof pH’s
Initial Claims Regarding these IrOx SensorsInitial Claims Regarding these IrOx Sensors
Initial Claims Regarding these IrOx SensorsInitial Claims Regarding these IrOx Sensors
Additionally these sensors claimed to be stable Additionally these sensors claimed to be stable in 4M HCL or a 5M Hin 4M HCL or a 5M H22SOSO4 4 solutionsolution
Claimed to have excellent mechanical stabilityClaimed to have excellent mechanical stability
The ProblemThe ProblemThese results were not corroborated in These results were not corroborated in
industry for some time.industry for some time.
Initial ResultsInitial Results
1.50E-01
2.00E-01
2.50E-01
3.00E-01
3.50E-01
0 200 400 600 800 1000
Probe 2Probe 4Probe 5Probe 6Probe 7
Results in a buffer of pH 8
5.20E-01
5.40E-01
5.60E-01
5.80E-01
6.00E-01
6.20E-01
6.40E-01
6.60E-01
6.80E-01
0 500 1000 1500 2000 2500
Probe 2Probe 4Probe 5Probe 6Probe 7Working
Initial ResultsInitial ResultsResults in a buffer of pH 3
-400
-200
0
200
400
600
800
1000
0 2 4 6 8 10 12 14
WorkingProbe-B4Probe-B5Probe-B6Probe-B7Probe-K1Probe-K2Probe-K3
Initial ResultsInitial ResultsAnalysis of Nernstian Slope
pH Working Probe-B4 Probe-B5 Probe-B6 Probe-B7 Probe-K1 Probe-K2 Probe-K3
0 720.5 766.417 806.083 833.583 656.944 737.996 753.7
2 354 600 648 686 720 553 620 633
3 295 536 579 616 656 494 544 556
6.01 116 380 413 446 480 379 353 370
8.12 -15 227 279 317 360 273 234 229
10.04 130 188 219 271 165 137 146
11.06 110 89.5 86.8
12.08 -239 57.5 30.8 34.9
slope 60.0417 60.25 59.2083 60.0417 56.7917 51.9722 58.9778 60.35
Initial ResultsInitial Results
Analysis of Nernstian Slope
So far the slopes look good but the ESo far the slopes look good but the Eo o has has an almost 200mV deviation between the an almost 200mV deviation between the probesprobes
The response times are extremely slowThe response times are extremely slow
Initial ResultsInitial Results
Off to the SEMOff to the SEM
Off to the SEMOff to the SEM
Off to the SEMOff to the SEM
Off to the SEMOff to the SEM
Off to the SEMOff to the SEM
Significance of the BSE ResultsSignificance of the BSE ResultsThe IrOx was not uniformThe IrOx was not uniform
Was there a polymer coating?Was there a polymer coating?Was there damage done to the probe?Was there damage done to the probe?Was there some sort of residue from being in Was there some sort of residue from being in
the pH buffer solution?the pH buffer solution?
The AnswerThe AnswerThe required break-in periodThe required break-in periodConversion of the LiConversion of the Li88IrOIrO66 to an unknown to an unknown
structurestructureAdditionally hydration plays a major role in Additionally hydration plays a major role in
the ability of the IrOx sensors to respond the ability of the IrOx sensors to respond rapidly and correctlyrapidly 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.
ResultsResults
5.50E-01
5.60E-01
5.70E-01
5.80E-01
5.90E-01
6.00E-01
6.10E-01
0 200 400 600 800 1000 1200 1400 1600
Example response time of a non-hydrated probe after the initial break-in period
ResultsResults
4.00E-01
4.20E-01
4.40E-01
4.60E-01
4.80E-01
5.00E-01
5.20E-01
5.40E-01
0 20 40 60 80 100 120
Example response time of a hydrated probe after the initial break-in period
ResultsResults
-100
0
100
200
300
400
500
600
700
800
0 2 4 6 8 10 12 14
Probe-K1 Probe-K5 Probe-K8 Probe-K10
Extrapolated slopes of 4 hydrated probes, post break-in
ResultsResults
pH Probe-K1 Probe-K5 Probe-K8 Probe-K10
0 732.667 650.5 643.833 718.7778
2 609 534 518 590
3 550 478 458 512
6.01 363 298 263 340
8.12 225 180 136 216
10.04 111 83 10 94
11.06 50 34 -50 35
12.08 -18 -43 -116 -34
slope 61.8333 58.25 62.9167 64.38889
ResultsResults
-2.00E-01
-1.00E-01
0.00E+00
1.00E-01
2.00E-01
3.00E-01
4.00E-01
5.00E-01
6.00E-01
7.00E-01
0 200 400 600 800 1000 1200 1400 1600
Probe 1 Probe5 Probe8 Probe10
Probe stability and response results across a variety of pH buffers
ResultsResults
3.50E-01
4.00E-01
4.50E-01
5.00E-01
5.50E-01
6.00E-01
6.50E-01
150 200 250 300 350 400 450
Response time for a pH jump from pH 2 to pH 5.5
ResultsResults
4.00E-01
4.20E-01
4.40E-01
4.60E-01
4.80E-01
5.00E-01
5.20E-01
5.40E-01
55 60 65 70 75
Response time for a pH jump from pH 2 to pH 3.5
ResultsResults
3.20E-01
3.25E-01
3.30E-01
3.35E-01
3.40E-01
3.45E-01
3.50E-01
3.55E-01
3.60E-01
3.65E-01
0 50 100 150 200 250 300
Response time for a standard glass bulb working electrode
ResultsResults
5.75E-01
5.80E-01
5.85E-01
5.90E-01
5.95E-01
6.00E-01
6.05E-01
6.10E-01
6.15E-01
6.20E-01
6.25E-01
0 200 400 600 800 1000 1200 1400 1600
Results from a test in H2S04
ResultsResults
An interesting result regarding mechanical stability
SignificanceSignificanceConsistencies with original publicationsConsistencies with original publications
Response times consistent with original publicationsResponse times consistent with original publications Stability in a wide range of pH buffers also confirmedStability in a wide range of pH buffers also confirmed
Discrepancies with original publicationsDiscrepancies with original publications Break-in period Break-in period Necessity of hydrationNecessity of hydration Possibly the stability in a Possibly the stability in a H2S04 solutionsolution Consistency of the EConsistency of the Eo
AcknowledgementsAcknowledgements Mentor: Dr. Marc MadouMentor: Dr. Marc Madou Lab Team: Kelvin Cheung, Jim Zoval, Horacio Lab Team: Kelvin Cheung, Jim Zoval, Horacio
Kido, Chunlie (Peggy) Wang, Rabih Zaouk, Kido, Chunlie (Peggy) Wang, Rabih Zaouk, Benjamin Park, Francesc Jornet, and Kuosheng Benjamin Park, Francesc Jornet, and Kuosheng MaMa
IM-SURE: Said Shokair, Jerry McMillan, Goran IM-SURE: Said Shokair, Jerry McMillan, Goran MatijasevicMatijasevic
National Science Foundation (NSF)National Science Foundation (NSF)