A New Low-Temperature Electrochemical Hydrocarbon and NOx Sensor.

Praveen Sekhar,Ajit Khosla,Shyam Aravamudhan,Zachary Moore

doi:10.3390/s17122759

Abstract

In this article, a new investigation on a low-temperature electrochemical hydrocarbon and NOx sensor is presented. Based on the mixed-potential-based sensing scheme, the sensor is constructed using platinum and metal oxide electrodes, along with an Yttria-Stabilized Zirconia (YSZ)/Strontium Titanate (SrTiO3) thin-film electrolyte. Unlike traditional mixed-potential sensors which operate at higher temperatures (>400 °C), this potentiometric sensor operates at 200 °C with dominant hydrocarbon (HC) and NOx response in the open-circuit and biased modes, respectively. The possible low-temperature operation of the sensor is speculated to be primarily due to the enhanced oxygen ion conductivity of the electrolyte, which may be attributed to the space charge effect, epitaxial strain, and atomic reconstruction at the interface of the YSZ/STO thin film. The response and recovery time for the NOx sensor are found to be 7 s and 8 s, respectively. The sensor exhibited stable response even after 120 days of testing, with an 11.4% decrease in HC response and a 3.3% decrease in NOx response.

Highlights

Electrochemical gas sensors [1,2,3,4,5,6] offer a portable, selective, sensitive, rapid, and compact solution to detect analytes for various applications including clean coal power plants, automotive emissions, hydrogen safety, air quality, and breathe analysis to identify chronic disorders
Inspired by the available literature, we have investigated the use of nanoscale heterostructures of Yttria-Stabilized Zirconia (YSZ)/STO in the design of a mixed-potential gas sensor
A mixed-potential-based electrochemical gas sensor that can be operated at low temperatures (200 ◦ C) was reported

Summary

Introduction

Electrochemical gas sensors [1,2,3,4,5,6] offer a portable, selective, sensitive, rapid, and compact solution to detect analytes for various applications including clean coal power plants, automotive emissions, hydrogen safety, air quality, and breathe analysis to identify chronic disorders. Mixed-potential electrochemical sensors fabricated using well-established commercial manufacturing methods present a promising avenue to enable the widespread utilization of gas sensors. These devices are fundamentally simple and robust, owing to their close relationship to the ubiquitous automotive Lambda sensor. The mixed-potential sensors develop a non-Nernstian potential due to differences in the redox kinetics of various gas species at each electrode/electrolyte gas interface in the presence of oxygen [8,9,10,11]. The difference in the steady-state redox reaction rates between the fast and slow electrodes gives rise to the measured mixed-potential response. A stable sensor design incorporates dense electrodes and a porous electrolyte, using a high-temperature ceramic co-fire (HTCC)

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Conclusion