Investigation of the Oxidation of Stoichiometric and Carbon-Rich Tungsten Carbide Surfaces

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NON-TECHNICAL DESCRIPTION: Fuel cells are a cornerstone of future energy systems, and their functionality relies on the presence of a powerful and durable catalyst material. The majority of catalysts used in current fuel cell technology are based on costly noble metal materials. An alternative is the use of tungsten carbide, which is also compatible with novel microbial fuel cells. Unfortunately, carbide performance is hindered by surface oxidation. The current project aims to design carbon-rich, nano-structured carbide surfaces to remedy this critical issue. The investigation combines the synthesis and characterization of a set of novel carbon-rich carbide surfaces, and the observation with surface science analytical methods of the critical chemical reactions with oxygen and water. It is positioned at the intersection between fundamental and applied research, and has the potential to decisively broaden the range of effective catalyst materials. TECHNICAL DETAILS: Transition metal carbide surfaces such as tungsten carbide, are promising substitutes for noble metal catalysts in fuel cells, steam reforming and as a catalyst support. A critical limitation to their use is their susceptibility to oxidation, which modifies and depresses performance. The present study is based on the hypothesis that a carbon-rich, nanostructured carbide surface can be designed, where degradation through oxidation is minimized. A non-stoichiometric tungsten carbide is grown using a method that is closely related to molecular beam epitaxy, and the transformation of the surface during the reaction with water and oxygen is observed with a suite of complementary surface science techniques. This investigation connects surface characteristics to reactivity from the atomic to the mesoscale, and opens the pathway to the design of advanced tungsten carbide catalysts. The research is coupled with an educational component that engages the public and students at all levels. A particular focus is informal science education, which includes the design of a new exhibit, the "Energy Corner", and a strong collaboration with NISE (Nanoscale Informal Science Education, http://www.nisenet.org/).