Solid-state chemistry route for supported tungsten and tungsten carbide nanoparticles N. Hugot a , A. Desforges a , S. Fontana a,n , J.F. Marˆ eche ´ a , C. He ´ rold a , A. Albiniak b , G. Furdin a a Institut Jean Lamour, UMR 7198 CNRS—Universite´ de Lorraine, De ´partement CP2S, Faculte´ des Sciences et Technologies, Campus Victor Grignard, BP 70239, 54506 Vandœuvre-l  es-Nancy Cedex, France b Wroclaw University of Technology, Faculty of Chemistry, ul. Gdanska 7/9, 50 344 Wroclaw, Poland article info Article history: Received 24 April 2012 Received in revised form 10 July 2012 Accepted 13 July 2012 Available online 26 July 2012 Keywords: Tungsten carbide Gas solid reactions Vapor deposition X-ray diffraction Transmission Electron microscopy abstract Nanoparticles of tungsten and tungsten carbide have been prepared using solid-state chemistry methods. After the vapor phase impregnation of a tungsten hexachloride precursor on a carbon support, a temperature-programmed reduction/carburization was performed. Several parameters were investigated and the evolution of obtained samples was followed by XRD and TEM. The optimization of the reaction parameters led to the preparation of W, W 2 C and WC particles well dispersed on the support. WC phase however could not be obtained alone with less than 10 nm mean size. This could be explained by the carburization mechanism and the carbon diffusion on the support. & 2012 Elsevier Inc. All rights reserved. 1. Introduction With the exhaustion of fossil resources, several ways of replacing them by clean power sources, such as Proton Exchange Membrane Fuel Cells (PEMFC), which convert chemical reaction energy directly into electrical energy without the combustion process have drawn extensive attention. However, the cost of PEMFC is a major blocking point to their commercialization. Actually, electrode materials for PEMFCs are made of compacted carbon black, such as Vulcan XC72 s , supporting electroactive catalytic platinum nanoparticles. The amount of platinum necessary to catalyze the reactions at the electrodes in particular needs to be tuned. Indeed, this noble metal is rare, expansive and easily contaminated by carbon monoxide. Current works deal with the substitution of metallic platinum by Pt-alloys or alloys [1,2]. The alloying of Pt with another metal (new Pt-based ternary catalysts [3,4]) has been proposed, with limited success, as the second metal is leached during the use and the performance gain is not so important. The replacement of platinum would be a better solution, but the finding of a substitute cheaper but as active has not been achieved yet. The most promising was the preparation of the active layer using cobalt or iron phthalocyanine derivatives, but this solution still suffers from serious drawbacks [5]. As a hard and refractory material, tungsten carbide is mostly used for applications such as reinforcing alloys. Another application had been proposed in the 70’s, when Levy and Boudart discovered that the electronic structure of WC was close to that of platinum, giving the opportunity to use it as a catalyst for organic reactions [6]. Since then, tungsten carbide nanoparticles were proved to be good catalysts for hydrodenitrogenation (HDN) [7], hydrogenation reac- tions [8], the Fischer–Tropsch reaction [9], and hydrocarbon iso- merization [9–11]. Leclercq et al. [12] showed that tungsten carbide supported on carbon black could be considered as an acceptable substitution solution to nanoplatinum on the anodic part of the PEMFCs. Tungsten carbide presents many advantages as it is a thousand times less expensive than Pt, shows good tolerance to CO contamination and is resistant to the corrosion by acid media. The binary W–C phase diagram presents two defined compounds W 2 C and WC stable at room temperature. Leclercq et al. [12] showed that WC was more active than W 2 C. However, as a highly refractory material, tungsten carbide requires high temperature to be synthesized. This is a problem for the obtention of tungsten carbide with the high specific surface area necessary for a good catalytic activity. Various methods have been employed to overcome the sintering of particles at high temperature and obtain fine nanoparticles. Unsupported carbides have been obtained through a wide range of methods, including temperature-programmed reduction (TPR) [13–15], mechanical alloying [16], pyrolysis of metal complexes [17], or chemical vapor condensation with relative success [18–20], leading to Contents lists available at SciVerse ScienceDirect journal homepage: www.elsevier.com/locate/jssc Journal of Solid State Chemistry 0022-4596/$ - see front matter & 2012 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.jssc.2012.07.027 n Corresponding author. E-mail address: sebastien.fontana@ijl.nancy-universite.fr (S. Fontana). Journal of Solid State Chemistry 194 (2012) 23–31