Polymer based materials for solid electrolyte sensors Corinna Vonau a, b, ⁎, Jens Zosel b , Muthusamy Paramasivam c , Kristina Ahlborn b , Frank Gerlach b , Vladimir Vashook d , Ulrich Guth b, d a Universität Leipzig, Institut für Analytische Chemie, Johannisallee 29, D-04103 Leipzig, Germany b Kurt-Schwabe-Institut für Mess-und Sensortechnik e.V. Meinsberg, Kurt-Schwabe-Straße 4, D-04720 Ziegra-Knobelsdorf, Germany c Central Electrochemical Research Institute, Karaikudi 630 006, Tamil Nadu, India d Technische Universität Dresden, Institut für Physikalische Chemie und Elektrochemie, Bergstraße 66b, D-01062 Dresden, Germany abstract article info Article history: Received 9 September 2011 Received in revised form 29 February 2012 Accepted 17 April 2012 Available online 12 May 2012 Keywords: Conductive polymer composite Solid electrolyte Potentiometric gas sensor Mixed potential Electrochemical solid electrolyte sensors based on Yttria Stabilised Zirconia (YSZ) with mixed potential electrodes are suited for in-situ measurements of low concentrations of combustibles like hydrogen, carbon monoxide or hy- drocarbons and also nitrogen oxides. The parameters sensitivity, selectivity and long-term stability of these sensors are correlated mainly with the performance of the electrode material. This work is directed on the investigation of newly developed conductive polymer composite materials (CPC) based on polyaniline (PANI). These materials have been characterised with respect to their morphology, thermal stability, catalytic activity and electrochemical behaviour on solid electrolytes in gases containing hydrogen, ethene and propene. For the first time it could be demonstrated, that CPC, consisting of PANI and different metal oxides or metal salts can be used at high temper- ature measurement up to temperatures of 450 °C because of improved thermal properties. © 2012 Elsevier B.V. All rights reserved. 1. Introduction Electrochemical solid electrolyte sensors are suited for the reliable, highly sensitive and rapid measurement of different gases in hot envi- ronments and also applications at lower temperatures [1]. Important sensor parameters like sensitivity, selectivity and long-term stability are correlated mainly with the performance of the electrode material [2]. During the last two decades extensive efforts were directed espe- cially on the development of new electrode materials for mixed poten- tial sensors [3–5], which are based on the kinetically controlled electrochemical conversion of oxidizable gases with oxide ions from the solid electrolyte [3,4]. Despite this intensive work there is still a con- siderable variety of potential applications for these sensors, which can- not be addressed due to insufficient sensor performance. One of the most important issues concerns the long-term stability [6,7], which is still critical for measuring electrodes based on gold and other noble metals if measuring times of several months without calibration are strived for. Therefore, new conductive fillers for composite mixed po- tential electrodes are needed, which provide sufficient electrochemical activity, thermal stability and low catalytic activity. This work is focused on the preparation of new composite materials for mixed potential sensors made of conductive polyaniline (PANI) filled with different metal oxides or salts such as Nb 2 O 5 or FeCl 3 and Co(NO 3 ) 2 during the polymerisation process. Intrinsically conducting polymers such as PANI have been the subject of extensive theoretical and experimental studies in recent years [8]. By filling the polymer with i.e. metal oxides, the thermal stability of the resulting conductive polymer composite (CPC) could be improved significantly. Because of its relatively high thermal stability, low costs, ease of synthesis and good environmental behaviour, among the conductive polymers PANI is most suited for this purpose [9–15]. The synthesised new materials have been characterised with respect to their thermal stability, their structure and morphology, their catalytic activity and their sensing behaviour in different non equilibrated gas mixtures in correlation to their impedances. 2. Experimental Pure PANI has been prepared by two different methods. One method is described elsewhere [16], the other one serves as point of departure for synthesising the polymer composites. It includes the in- troduction of 0.1 mol aniline into 1 M HCl and the following polymer- isation by adding 0.05 mol ammonium peroxidisulfate solution. The polymerisation of aniline in an acidic medium results in the formation of a protonated, partially oxidised form of PANI, the conductive emer- aldine salt 4 (Fig. 1). Two composites have been prepared by adding Nb 2 O 5 -powder to the solution described above before and after starting the polymerisa- tion respectively. The molar ratio aniline/Nb 2 O 5 has been adjusted at Solid State Ionics 225 (2012) 337–341 ⁎ Corresponding author at: Universität Leipzig, Institut für Analytische Chemie, Johannisallee 29, D-04103 Leipzig, Germany. E-mail address: cvonau@ksi-meinsberg.de (C. Vonau). 0167-2738/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.ssi.2012.04.015 Contents lists available at SciVerse ScienceDirect Solid State Ionics journal homepage: www.elsevier.com/locate/ssi