Highly improved electrooxidation of formaldehyde on nickel/poly (o-toluidine)/Triton X-100 film modified carbon nanotube paste electrode Jahan-Bakhsh Raoof*, Reza Ojani, Samaneh Abdi, Sayed Reza Hosseini Department of Analytical Chemistry, Faculty of Chemistry, University of Mazandaran, 3rd Kilometer of Air Force Road, Postal Code: 47416-95447, Babolsar, Iran article info Article history: Received 14 August 2011 Received in revised form 10 October 2011 Accepted 11 October 2011 Available online 25 November 2011 Keywords: Formaldehyde Nickel hydroxide Carbon nanotube paste electrode Poly (o-toluidine) Triton X-100 abstract In present work, o-toluidine (OT) monomer is electropolymerized in the presence of an aqueous acidic solution containing Triton X-100 (TX-100) non-ionic surfactant onto multi- walled carbon nanotube paste electrode (CNTPE). The as-prepared substrate is used as a porous matrix for dispersion of Ni (II) ions by immersing the modified electrode in a nickel (II) sulfate solution. The modified electrodes are characterized by field emission scanning electron microscopy (FE-SEM) and electrochemical methods. The electrochemical characterization of the nickel/poly (o-toluidine)/Triton X-100 film modified carbon nano- tube paste electrode (Ni/POT (TX-100)/MCNTPE) exhibits redox behavior of Ni(III)/Ni(II) couple in alkaline medium. It has been shown that POT/TX-100 film at surface of the CNTPE improves efficiency of the catalyst toward formaldehyde electrooxidation. Moreover, the effects of various parameters such as TX-100 concentration, formaldehyde concentration, OT concentration, film thickness and accumulation time on the electrooxidation of formaldehyde as well as long-term stability of the Ni/POT (TX-100)/MCNTPE have also been investigated. Copyright ª 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved. 1. Introduction Knowledge of the reactivity of formaldehyde (HCHO) in an electrochemical environment is important for various appli- cations including fuel cells and electrochemical detection. Therefore, electrochemical oxidation of HCHO at various electrodes has been receiving much attention. Pt and Pt alloys [1e8], copper and copper alloys [9e11], polycrystalline palla- dium [12], gold [13], palladium nanoparticles electrodeposited on carbon ionic liquid composite electrode [14] and palladium nanoparticles on functional multi-walled carbon nanotubes [15,16] have been studied as anode catalysts for the HCHO oxidation. However, one of the limiting factors is that precious metals (Pt, Pd, Au, etc.) are readily poisoned by adsorbed intermediates, which blocks the metal active sites. Besides, the high cost and short supply of these metals are not economical for practical and industrial application [17]. Thus, a great deal of interest has, recently, been focused on an alternative metal (non-noble metal) while maintaining the high catalytic activity and less expensive materials as anodes for HCHO oxidation. On the other hand, nickel is a low cost, relatively abundant material that is used extensively in numerous industrial applications. It is well established that Ni can be used as a catalyst due to its surface oxidation * Corresponding author. Tel.: þ98 112 5342392; fax: þ98 112 5342350. E-mail address: j.raoof@umz.ac.ir (J.-B. Raoof). Available online at www.sciencedirect.com journal homepage: www.elsevier.com/locate/he international journal of hydrogen energy 37 (2012) 2137 e2146 0360-3199/$ e see front matter Copyright ª 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.ijhydene.2011.10.052