Electrochimica Acta 101 (2013) 158–168 Contents lists available at SciVerse ScienceDirect Electrochimica Acta j our nal homep age : www.elsevier.com/locate/electacta Oxygen reduction voltammetry on platinum macrodisk and screen-printed electrodes in ionic liquids: Reaction of the electrogenerated superoxide species with compounds used in the paste of Pt screen-printed electrodes? Junqiao Lee 1 , Krishnan Murugappan 1 , Damien W.M. Arrigan 1 , Debbie S. Silvester ∗,1 Nanochemistry Research Institute, Department of Chemistry, Curtin University, GPOBox U1987, Perth, Western Australia 6845, Australia a r t i c l e i n f o Article history: Received 28 June 2012 Received in revised form 26 September 2012 Accepted 26 September 2012 Available online 4 October 2012 Keywords: Screen-printed electrodes Oxygen reduction Gas sensing Room temperature ionic liquids Cyclic voltammetry a b s t r a c t Screen-printed electrodes (SPEs) are widely investigated as simple, three-electrode planar surfaces for electrochemical sensing applications, and may be ideal for gas sensing purposes when combined with non-volatile room temperature ionic liquids (RTILs). In this report the suitability of SPEs with RTIL solvents has been investigated for oxygen detection. Oxygen reduction has been studied on commercially available platinum SPEs in eight RTILs. Cyclic voltammetric wave shapes were found to be significantly different on Pt SPE surfaces compared to conventional solid Pt macroelectrodes, suggesting a possible reaction of the electrogenerated superoxide with the compounds that make up the ink/paste of the SPE surface. The only RTIL that did not show such drastically different voltammetry was one that contained a pyrrolidinium cation, suggesting a more chemically stable solvent environment compared to the other imidazolium and phosphonium cations studied. The analytical utility was then studied on four SPE surfaces (carbon, gold, platinum and silver) in two RTILs (one with a pyrrolidinium and one with an imidazolium cation) and linear responses were observed between current and % concentration in the range 10–100% O 2 . This suggests that SPEs may indeed be suitable for oxygen sensing in some RTILs, but significantly more pre- treatment of the surface is required to obtain reliable results. However, the reaction of superoxide with the SPE ink, together with a noticeable deterioration of the signal over time, suggests that this type of sensing platform may only be suitable for “single-use” oxygen sensing applications. © 2012 Elsevier Ltd. All rights reserved. 1. Introduction Screen-printed electrodes (SPEs) are low-cost, disposable sensing surfaces that have been widely used in applications such as glucose biosensing and heavy metal detection since the 1990s [1–3]. However, despite their wide use, there is still relatively little fundamental understanding of analyte redox behaviour at these surfaces. Recently, SPEs have become commercialized by a num- ber of companies and are readily available for academic study. As a result, several groups have characterized various commer- cially available SPEs from companies such as Alderon, Florence, DropSens, Kanichi and Zensor [4–6]. In general, it has been reported that SPEs manufactured by DropSens appear to give the best cyclic voltammetric responses (lowest background current, sharpest peak shapes and fastest kinetics) [4,5]. Most SPEs currently reported in the literature are large sur- face area (e.g. 4 mm diameter) carbon materials, probably due ∗ Corresponding author. Tel.: +61 0 892667148; fax: +61 0 892662300. E-mail address: d.silvester-dean@curtin.edu.au (D.S. Silvester). 1 ISE member. to the low cost of carbon (compared to inert gold and platinum metals). Although manufacturers often do not disclose informa- tion on the formulation of the printing inks, they are generally thought to be comprised of synthetic grade graphite or metal par- ticles (the electrochemically active material), vinyl or epoxy-based polymeric binders (to enhance the adhesion properties of the ink to the substrate) and solvents (to improve the viscosity of the ink for the printing process) [4]. Carbon-based SPEs usually perform well in aqueous solvents and show similar electrode kinetics to those observed on conventional disk-electrodes [4–6]. Gold [7,8] and platinum [9,10] SPEs have also been used, but much more rarely. Moving away from experiments in aqueous-based solvents, we recently found that the background currents of DropSens car- bon SPEs are very large compared to Pt and Au SPEs when room temperature ionic liquid (RTIL) solvents are employed [11]. This could be due to the high viscosity and lower “wettability” capa- bilities of RTILs at carbon surfaces, compared to aqueous solvents. Alternatively, there could be an interaction of the carbon mate- rials with ionic liquids that is causing the screen-printed film to swell or dissolve. This observation should be considered when employing RTILs as solvents in sensing applications using carbon SPEs. 0013-4686/$ – see front matter © 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.electacta.2012.09.104