CO-sensing properties of a NASICON-based gas sensor attached with Pt mixed with Bi2O3 as a sensing electrode

Abstract

NASICON (Na 3 Zr 2 Si 2 PO 12 )-based gas sensors capable of detecting various gases (CO 2 , NO 2 , Cl 2 , VOC and so on) have so far been developed by many researchers. In this study, planar-type gas sensors using a NASICON disc attached with Pt mixed with Bi 2 O 3 as a sensing electrode (Pt(nBi 2 O 3 ), n (0.01~30): the amount of Bi 2 O 3 addition (wt%)) and Pt as a reference electrode were fabricated, and their sensing properties to CO and H 2 were examined in the operating temperature range of 25~300ºC in dry and wet air. The sensors obtained were denoted as Pt(nBi 2 O 3 )/Pt. All Pt(nBi 2 O 3 )/Pt sensors fabricated responded to CO at all operating temperatures tested, and the magnitude of CO response increased with a decrease in the operating temperature. In addition, the magnitude of CO response largely depended on the additive amounts of Bi 2 O 3 to the Pt sensing electrode. The increase in the additive amount of Bi 2 O 3 to the Pt sensing electrode (0.01 ≤ n ≤ 1) enhanced markedly the magnitude of CO response, 90% response time and CO selectivity against H 2 . The Pt(1Bi 2 O 3 )/Pt sensor showed a linear relationship between the CO response and the logarithm of CO concentration (1~3000 ppm) in dry air at 25C and the CO selectivity against H 2 was enhanced in wet air, in comparison with those observed in dry air. The interfacial layer, which was formed between the NASICON and the Pt(1Bi 2 O 3 ) electrode, was suggested to play an important role in improving of the CO-sensing properties.

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

“…17 mV). 9 This result demonstrated that even the addition of 1 wt% Bi 2 O 3 into the Pt SE was quite effective in improving the CO-sensing properties. However, the E values in air of these Pt(nBi 2 O 3 )/Pt sensors shifted to the negative direction after the 1st CO exposure, even though the E value of the Pt(nBi 2 O 3 )/Pt sensors at the the 1st CO exposure was comparable to that at the 2nd CO exposure.…”

“…Bi 2 O 3 powder was synthesized as follows. 9 After Bi(NO 3 ) 3 ·5H 2 O was fully dissolved in HNO 3 aqueous solution, an appropriate amount of polyvinyl pyrrolidone was added to the solution as a stabilizing agent and then they were stirred for 15 min. The resultant solution was slowly and continuously dropped into NaOH solution while stirring, until the pH reached 11.…”

“…[9][10][11][12] Stoichiometric amounts of these raw materials were dissolved in pure water, together with an appropriate amount of citric acid. The mixture was subjected to heat treatment at 80°C to prepare an organic metal complex, followed by an overnight drying at 120°C.…”

“…On the other hand, we have recently reported that the sensor using NASICON (sodium super ionic conductor, Na 3 Zr 2 Si 2 PO 12 ) as an electrolyte and a Bi 2 O 3 -added Pt sensing electrode (SE) showed large response to CO at room temperature (RT) and the magnitude of CO response increased with an increase in the additive amount of Bi 2 O 3 in the SE. 9 In this study, our efforts have been directed to the enhancement of the CO response of the NASICON-based solid electrolyte-type sensor by adding one of various kinds of metal oxides In addition, we have attempted to enhance the CO-sensing properties of the sensor by the addition of an appropriate MO into the Pt counter electrode (CE). We have also proposed the possible CO-sensing mechanism of representative sensors.…”

CO-sensing Properties of Potentiometric Gas Sensors Using an Anion-conducting Polymer Electrolyte and Au-loaded Metal Oxide Electrodes

“…Takeda et al also reported that an addition of Bi 2 O 3 into a Pt-sensing electrode of a NASICON-based sensor was dramatically improved the CO selectivity against H 2 at RT [22,23]. SnO 2 mixed with CeO 2 and PdO x [24], partially-reduced TiO 2 [25], In-doped ZnO [26], CuO-coated Zn 2 SnO 4 [27] and Pd/SnO 2 nanocomposite mixed with carbon nanotube [28] were utilized as a promising CO-sensing material for semiconductor gas sensors with high CO selectivity against inflammable gases.…”