This document describes the validation of a high throughput electrochemical gas sensing screening system. Uniform thin film samples of YSZ and WO3 were developed and characterization using reflectometry and XRD confirmed their relative uniformity. Single and multielectrode cell tests were conducted on the samples at 600°C, showing their ability to detect different concentrations of NO gas. The system was able to conduct combinatorial screening of electrochemical gas sensors and validate the use of a planar sensor array design. Future work involves further optimizing the system.

1. Validation of High Throughput
Electrochemical Gas Sensing
Screening System
ZixuanWang
November 17, 2014

2. Background
Harsh combustion environment - 800 °C
Accurate and selective to target gas

3. High Throughput Methodology
Subatomic difference affect large scale
Not feasible to individually test material
High throughput synthesis and
characterization methods

4. High Throughput Methodology
• Normalize affect of distance on the
potential

5. Development of Uniform Standard Sample
Single Cell

6. Surface Mechanisms
e-
NO  N2 O2-  O2
O2- O2-
Sensors and Actuators B 121 (2007) 652-663

7. Reflectometry Results - YSZ
• Results confirm relative
uniformity of sample
(1.8% difference)

8. XRD Results - YSZ
YSZ Post Anneal XRD Uniformity
• XRD analysis using Jade
• YSZ Cubic:
– (111): 29.675°
– (200): 34.398°
• Confirm identical phases
(1,4) 29.745
(2,4) 29.836 34.848
(3,4) 29.876 34.859
1600
1400
1200
1000
800
600
400
200
0
25 30 35 40 45
(1,4)
(2,4)
(3,4)

9. Reflectometry Results – WO3
• Confirms relative uniformity
(2.5% difference)
• Evidence some parts of the
plate that are slightly thicker
or thinner

10. XRD Results – Post Annealed WO3
• XRD analysis using Jade
• WO3 monoclinic:
– (002): 23.118°
– (020): 23.582°
– (200): 24.365°
• Confirm identical phases
with phase shifts present
4000
3500
3000
2500
2000
1500
1000
500
0
WO3 Post Anneal XRD Uniformity
22.5 23 23.5 24 24.5 25
Intensity
2θ
(1,4)
(2,4)
(3,4)
(1,4) 23.143 23.653 24.362
(2,4) 23.140 23.671 24.397
(3,4) 23.127 23.641 24.377

11. Reflectometry Results - WO3-YSZ
• Sputtering conditions:
same
• YSZ held constant
• Confirms relative
uniformity (4.3%
difference)

12. XRD Results – WO3-YSZ Post-annealed
W M(000) WO3 monoclinic:
(002): 23.118°
(020): 23.582°
(200): 24.365°
YSZ Cubic:
(111): 29.675°
(200): 34.398°
W M(020)
W M(200)
Y C(200)

13. Electrochemical Cell Setup
30
electrode
probes
Gas inlet
Sample
stage

14. Single Electrochemical Cell Tests
140
160
180
200
220
240
260
1
8
15
22
29
36
43
50
57
64
71
78
85
92
99
106
113
120
127
134
141
148
155
162
169
176
183
190
197
204
211
218
Potential (mV)
Time (min)
EMF Response of WO3/YSZ/Pt Cell at 600 C
481 ppm NO
926 ppm NO
2083 ppm NO
481 ppm NO
926 ppm NO
2083 ppm NO
2083 ppm NO

15. Electrochemical Cell Tests
30
20
10
0
180
175
170
165
160
SENSOR RESPONSE
0 500 1000 1500 2000 2500
Change in Potential (ΔmV)
Potential (mV)
NO Concentration (ppm)
Potential Change in Potential

16. Multielectrode Cell Tests
200
180
160
140
120
100
80
60
40
20
0
EMF Response of WO3/YSZ/Pt Cell at 600 C
0 10 20 30 40 50
Response (mV)
Time (min)
164 ppm NO
246 ppm NO
328 ppm NO

17. Conclusions
• Designed planar sensor array
– Use for combinatorial screening of electrochemical
gas sensors
• Confirm deposition uniformity
– Reflectometry: thickness
– XRD: phases
• Cell potential
– Changes valid use of planar sensor design

18. Future Work
• Create multielectrode with increased surface
area/perimeter of the electrodes
• Normalize potential to distance of electrodes
• Create multielectrode with different
composition gradient

19. Acknowledgements
• National Science Foundation (NSF)
• University of South Carolina – College of
Engineering and Computing
• Strategic Approaches to the Generation of
Electricity (SAGE)
• Principal investigators: Dr. Jochen Lauterbach
and Dr. Jason Hattrick-Simpers
• Graduate mentor: Ben Ruiz-Yi