Characterization and catalytic investigation of NO + CO reaction on perovskites of the general formula La x M 1  x FeO 3 (M = Sr and/or Ce) prepared via a reverse micelles microemulsion route A.E. Giannakas a, * , A.A. Leontiou a , A.K. Ladavos b , P.J. Pomonis a a Department of Chemistry, University of Ioannina, Ioannina 45110, Greece b Department of Farm Organization and Management, University of Ioannina, Agrinio 30100, Greece Received 7 December 2005; received in revised form 9 May 2006; accepted 10 May 2006 Abstract Four different perovskite type solids with nominal composition LaFeO 3 (LFOr), La 0.85 Sr 0.15 FeO 3 (LSFOr), La 0.8 Sr 0.1 Ce 0.1 FeO 3 (LSCFOr) and La 0.8 Ce 0.2 FeO 3 (LCFOr) were prepared via a reverse micelles microemulsion route. The aim of this work was to investigate the effect of doping with Sr and Ce in the structural properties, surface area and catalytic properties of final solids in comparison with the undoped reference solid LaFeO 3 . The microemulsion system which was used is composed of cetyl-trimethyl-ammonium-bromide (CTAB), 1-butanol, n-octane and nitrate salts of the metals. XRD measurements combined with Rietveld analysis helped us to identify the % quantity of structural phases which were formed. Scanning electron microscopy (SEM) images showed that the obtained solids consist of nanoparticles in the range of 20–80 nm. BET experiments showed that the final solids achieve much higher specific surface area (ssa) (30–61 m 2 /g) than similar solids which have been prepared by other methods. Catalytic tests in NO + CO reaction were made with the use of gases He/NO/CO in the ratio 96/2/2 with a total flow rate of 100 cm 3 /min. The full sequence of catalytic activity of tested solids is LCFOr > LSCFOr > LSFOr  LFOr and this sequence is in full agreement with the sequence of increment of ssa of the solids. # 2006 Elsevier B.V. All rights reserved. Keywords: Perovskites; Ce; Sr; NO + CO; Reverse microemulsion 1. Introduction In the mid 1970s, introduction of catalysis for the exhaust- gas treatment of an automobile opened a new area for catalytic applications. The development of catalysts for controlling both mobile and stationary sources of emissions has been accelerated due to the development of three-way catalysts (TWC) for converting HC, CO and NO x simultaneously [1]. The need for NO x reduction, which is one of the main topics for the catalytic control of air pollution, led to the development of new catalyst compositions containing noble metals (Pt, Rh and Pd) and cerium oxide as oxygen storage agent. Perovskite-type oxides of the general type ABO 3 are an important class of compounds and have been widely studied as far as their physical and chemical properties are concerned. Their catalytic properties have been extensively studied for oxidation and reduction reactions. The catalytic reduction of NO by CO is an important chemical process because of the need to control both NO and CO emissions from motor vehicles. This reaction has been studied extensively for perovskites. These studies have shown that to control NO and CO emissions perovskites must be placed on inert substrates. The properties of ABO 3 perovskites can be easily modified by substitution of the A site cation, usually La 3+ , by another cation of different oxidation state such as Sr 2+ or Ce 4+ [2–6]. The high catalytic activity of such substituted structures is considered to be related with their defective structure and the effect of the valence alternation on the catalytic activity [7,8]. Perovskites are normally formed by physically mixing metal oxide precursors, or by coprecipitation of mixed salts, followed by calcination at high temperatures (H.T.s), typically exceeding 1000 8C. The specific surface area (ssa) of perovskite materials prepared using these techniques are low, typically lower than 5m 2 /g, which is disadvantageous for catalytic applications [2]. www.elsevier.com/locate/apcata Applied Catalysis A: General 309 (2006) 254–262 * Corresponding author. Tel.: +32 6510 98351; fax: + 32 6510 98795. E-mail address: agiannak@cc.uoi.gr (A.E. Giannakas). 0926-860X/$ – see front matter # 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.apcata.2006.05.016