Enhanced CO Response of NASICON-based Gas Sensors Using Oxide-added Pt Sensing Electrode at Low Temperature Operation

Abstract

NASICON (Na 3 Zr 2 Si 2 PO 12 )-based solid electrolyte-type sensors equipped with various metal oxides (MO)-added Pt sensing electrode (SE, Pt(nMO) (n: MO additive amount in wt%) and Pt counter electrode (CE, Pt) on the same side of the NASICON disc were fabricated and their (Pt(nMO)/Pt sensors) CO-sensing properties were examined at 25-300°C. The Pt(15Bi 2 O 3 )/Pt sensor showed the largest CO response with a change in electromotive force to a positive direction (positive response) at 25°C, while the Pt(15CeO 2 )/Pt sensor showed the largest negative CO response at 25°C. The CO response of the Pt(15CeO 2 )/Pt sensor seems to be determined by mixed potential at the triple phase boundaries (TPBs) containing the electrochemical reactions of CO oxidation and oxygen reduction. X-ray photoelectron spectroscopy of the Pt(15Bi 2 O 3 ) SE before and after exposure to CO indicated a slight reduction of Bi 3+ after the exposure to CO. Therefore, the additional electrochemical reactions containing the reduction of Bi 2 O 3 were anticipated to occur at the TPBs of the Pt(15Bi 2 O 3 ) SE, which resulted in the large positive CO response of the Pt(15Bi 2 O 3 )/Pt sensor. Furthermore, the addition of 15 wt% CeO 2 to Pt CE of the Pt(15Bi 2 O 3 )/Pt sensor largely enhanced the magnitude of CO response and attained relatively excellent CO selectivity against H 2 .

Potentiometric CO sensors using anion-conducting polymer electrolyte: Effects of the kinds of noble metal-loaded metal oxides as sensing-electrode materials on CO-sensing properties

“…The EC(CeO2) sensor showed the largest CO response (ΔECO: ca. 33 mV) among all the EC(MO) sensors, probably because of the relatively large electrocatalytic activity of CO oxidation over CeO2 [26]. However, the response and recovery speeds of the EC(CeO2) sensor were much slower than those of the EC(Bi2O3) sensor.…”

Development of advanced gas-sensing devices based on the microstructural and compositional controls of various promising materials and their different operating mechanism

“…CeO 2 into the Pt-sensing electrode largely responds to CO toward the negative electromotive force and the electrochemical cell assembled with the Bi 2 O 3 /Pt and CeO 2 /Pt electrodes shows the largest CO response among this kind of sensors tested. 122) On the other hand, yttria-stabilized zirconia (YSZ) is very valuable as a solid electrolyte of the electrochemical gas sensors at higher temperatures, 123) and thus we have also developed some kinds of YSZ-based electrochemical gas sensors. Ueda et al have demonstrated that the YSZ-based electrochemical gas sensors with a columnarstructured Pr 0.1 Ce 0.9 O 2 (PCO) electrode fabricated by PLD showed a large toluene response which increased with an increase in the thickness at 500 °C as shown in Fig.…”

PT4 - Challenges for the Development of Toxic Gas Sensors by Employing Semiconductors and Solid Electrolytes

“…counter electrode, respectively, followed by annealing at 700°C in air [3]. The change in electromotive force generated between two electrodes induced by the exposure of both two electrodes to CO or H 2 sample gases from base air was measured under different conditions.…”

“…We have so far been trying several approaches to improve toxic gas sensing properties. The present paper reports our recent research results on semiconductor NO 2 sensors fabricated with porous In 2 O 3 powder [1] and solid electrolyte CO sensors fabricated with an anion-conducting polymer [2] or NASICON [3].…”