A Four-Electrode Mixed-Potential Sensor Array for Simultaneous Decoding of Hazardous Multi-Gas Mixtures

The development of sensors is necessary to provide controls to work with harmful gases required in many industrial processes and scientific endeavors. However, industrial growth especially in agriculture, power generation and transportation industries has become a major source of air pollution resulting in ozone depletion, eutrophication, smog and global warming.1, 2 As a result, the goalpost for sensor requirements is constantly changing due to increasingly tighter regulations on pollutants.3 Despite significant advancements, the need for fast, durable and highly selective sensors for monitoring air pollutants in various applications is constantly increasing. This is further complicated in environments where multiple gases with varying toxicity are present due to cross-sensitivity towards non-target chemical species within a given environment. Mixed-potential sensors, whose sensitivity depends on the kinetics of electrochemical reactions at the electrode-electrolyte interface, are shown to have higher sensitivity and durability towards a variety of gases although cross-sensitivity towards non-target gases remains a challenge.4 Recently mixed potential sensor arrays coupled with modeling have been evaluated for addressing this issue.5 Previously our group studied the role of varying bias currents of 0, -1.5, -3.5 and -6 µA on an Au|YSZ|Pt sensor that was exposed to different target gases such as NH3, NO, NO2, and C3H6, and analyzed the results through a Bayesian model where two and three gas mixtures were successfully decoded with increased selectivity.6 We recently tested a total of four mixed potential sensors connected in series where the four SEs, one AuPd, two La0.8Sr0.2CrO3 and another In doped SnO2, all with varying selectivity and sensitivity towards target gases such as NO, NO2, NH3 and C3H8, and decoded gas mixtures containing two and three analyte gases with less than 3% error in predicting the absolute concentration values of individual gases present in the mixture using a Bayesian algorithm.7, 8 In this presentation, we will discuss our latest results using a four electrode single platform mixed potential sensor array towards decoding two and three gas mixtures. The four electrodes of choice where a Pt quasi-reference electrode, one AuPd and two La0.8Sr0.2CrO3 electrodes (Figure 1). The target gases utilized in this work are NO, NO2, NH3 and C3H8. We will also elaborate results obtained with our sensors in a simulated poultry house environment for tracking ammonia concentrations in the presence of hydrocarbons such as ethane and propane. References 1. Shaddick, G.; Thomas, M. L.; Amini, H.; Broday, D.; Cohen, A.; Frostad, J.; Green, A.; Gumy, S.; Liu, Y.; Martin, R. V.; Pruss-Ustun, A.; Simpson, D.; van Donkelaar, A.; Brauer, M., Data Integration for the Assessment of Population Exposure to Ambient Air Pollution for Global Burden of Disease Assessment. Environmental Science & Technology 2018, 52 (16), 9069-9078. 2. Ramaiyan, K. P.; Mukundan, R., Electrochemical Sensors for Air Quality Monitoring. The Electrochemical Society Interface 2019, 28 (3), 59-63. 3. Farrauto, R. J.; Deeba, M.; Alerasool, S., Gasoline automobile catalysis and its historical journey to cleaner air. Nature Catalysis 2019, 2 (7), 603-613. 4. Miura, N.; Sato, T.; Anggraini, S. A.; Ikeda, H.; Zhuiykov, S., A review of mixed-potential type zirconia-based gas sensors. Ionics 2014, 20 (7), 901-925. 5. Tsui, L.-k.; Benavidez, A.; Palanisamy, P.; Evans, L.; Garzon, F., Automatic signal decoding and sensor stability of a 3-electrode mixed-potential sensor for NOx/NH3 quantification. Electrochimica Acta 2018, 283, 141-148. 6. Tsitron, J.; Kreller, C. R.; Sekhar, P. K.; Mukundan, R.; Garzon, F. H.; Brosha, E. L.; Morozov, A. V., Bayesian decoding of the ammonia response of a zirconia-based mixed-potential sensor in the presence of hydrocarbon interference. Sensors and Actuators B: Chemical 2014, 192, 283-293. 7. Javed, U.; Ramaiyan, K. P.; Kreller, C. R.; Brosha, E. L.; Mukundan, R.; Morozov, A. V., Using sensor arrays to decode NOx/NH3/C3H8 gas mixtures for automotive exhaust monitoring. Sensors and Actuators B: Chemical 2018, 264, 110-118. 8. Ramaiyan, K. P.; Kreller, C. R.; Brosha, E. L.; Mukundan, R.; Javed, U.; Morozov, A. V., Quantitative Decoding of Complex Gas Mixtures Using Mixed-Potential Sensor Arrays. ECS Transactions 2016, 75 (16), 107-111. Figure 1