Nanocrystalline tungsten carbide (WC) synthesis/characterization and its possible application as a PEM fuel cell catalyst support

Nanocrystalline tungsten carbide (WC) with a high surface area and containing minimal free carbon was synthesized via a polymer route. Its physical properties, including solubility in acid solution, electronic conductivity, and thermal stability, were thoroughly studied at two elevated temperatures: 95 degrees C and 200 degrees C. Compared to commercially available WC, this in-house synthesized WC showed lower solubility in acidic media at 200 degrees C, higher electronic conductivity (comparable to that of carbon black), as well as higher thermal stability. However, this material exhibited low electrochemical stability in acidic media when subjected to potential cycling at potentials larger than 0.7 V vs. RHE, due to the electrooxidation of WC. The major product of WC electrooxidation is WO3, which was confirmed by X-ray photon spectroscopy measurements. Pt was uniformly deposited on the high surface area WC to form a 20 wt% of Pt supported catalyst for the oxygen reduction reaction (ORR). The ORR mass activity was then obtained using the rotating disk electrode technique. Crown Copyright (C) 2011 Published by Elsevier Ltd. All rights reserved.