(658a) Nano Tungsten Carbide Catalysts for Polymer Electrolyte Membrane Fuel Cells

Zheng, W. - Presenter, University of Delaware
Wang, L. - Presenter, University of Delaware
Prasad, A. K. - Presenter, University of Delaware
Advani, S. G. - Presenter, University of Delaware
Vlachos, D. G. - Presenter, University of Delaware

The interstitial compounds of metal-C and metal-N, especially the early transition metal carbides have been of interest for catalysis since the pioneering work of Levy and Boudart,[1] who showed that tungsten carbides display Pt like behavior in several catalytic reactions. The conventional synthesis of carbides is through high temperature carburization of metals, leading to a low surface area. One of the most facile routes to high-surface-area transition metal carbides can be attributed to Lee et al.,[2]who developed a temperature-programmed reduction-carburization method that allows the formation of carbides from precursor oxides under a wide range of conditions. Unfortunately, the unstable meso-porous structure restricts the application of this material.

Here we report a simple and efficient preparation method for production of nano carbides dispersed in carbon by the combination of hydrothermal carbonization and temperature-programmed reduction-carburization. TEM and SEM confirm the presence of highly dispersed, uniform tungsten carbide nanoparticles of size around 5-10 nm. We have invented a novel composite membrane based on the proton exchange polymer that incorporates WC/C nanoparticles to provide self-hydrating functionality and reduction of gas crossover through the membrane. The nano WC/C catalyst is highly cost-effective and catalyzes H2/O2 to generate water during fuel cell operation. Specifically, the catalyst improves the proton conductivity of the membrane, while simultaneously reducing H2 and O2crossover through the membrane. The power density of the WC/C-Nafion membrane is 20% higher than that of the pure Nafion membrane. We have conducted a series of fuel cell durability tests operating at 90 °C and 35% relative humidity under open circuit voltage conditions for 100 hours. The results show that the durability of the WC/C-Nafion membrane surpasses that of both the pure recast Nafion membrane and a Pt-Nafion membrane. Using a dual-beam SEM microscope, we directly observe the tomography of fresh and used composite membranes and reveal the degradation mechanisms of the membrane.


[1] R. B. Levy, M. Boudart, Science 1973, 181, 547−549.

[2] J. S. Lee, S. T. Oyama, M. Boudart, J. Catal. 1987, 106, 125−133.