Water activation on selected group 8-12 catalysts

In the present time environmental and energy problems are one of the biggest concerns. On the one hand the energy consumption rises from year to year but the fossil energy resources are limited and on the other hand the use of fossils produces billions of tons of CO2 which is part of the global warming problem. So it`s important to search and develop new and clean sources of energy. A promising and environmentally friendly technology is the production of electrical power with the use of fuel cells. The fuel cells require hydrogen as a fuel, which is extremely difficult to store and transport in a direct way but one alternative is the steam reforming of alcohols and hydrocarbons which allows a hydrogen production in situ and thus avoids the problems of direct hydrogen usage. Even though the purpose of steam reforming reactions is the production of hydrogen, there are also other products formed such as carbon dioxide and carbon monoxide. If the hydrogen production is used for PEM fuel cell applications, it is clear that the formation of carbon monoxide must be minimized. The limit is 10 ppm, otherwise it poisons the anodic catalyst of the low temperature fuel cells. This clearly shows the importance of the catalyst performance in the steam reforming reactions. The ideal catalyst is highly active to achieve large amounts of hydrogen, and highly selective so that the carbon monoxide production is extremely low or negligible, and the catalyst should be stable for a long time. My current work is focused on methanol steam reforming over various catalysts (PdZn, PdGa, CuZn, ...). During my research one key finding was that the particular water activation ability of the catalysts strongly affects the selectivity and activity. Only if water is splitted/activated by the catalyst or support during the methanol steam reforming, oxygen is available for oxidation of carbon to CO2. Otherwise the methanol is mainly dehydrogenated and CO is produced. This clearly shows how important water activation/splitting abilities of the catalyst/support are. So far, beside some theory calculations in the literature, an intense study of the water activation/splitting abilities under humid conditions of group 8-12 catalysts is scarce (except for Cu). This is the reason why it is important to focus future research on the topic of water activation/splitting under realistic conditions (>298 K and mbar pressure range). Synchrotron-based XPS with its high resolution allows to distinguish site-specifically between H2O(ads), OH(ads) and O(ads) species. The Advanced Light Source (Synchrotron) of the Lawrence Berkeley National Laboratory and scientific experience of Dr. Hendrik Bluhm provides the proper support for this research. The goal of this project is to provide new knowledge about water activation/splitting for a better understanding of the selectivity and activity of steam reforming catalysts and to obtain directional information`s for future optimisation of these by optimized water activation and -binding. This will become a part of the scientific base for future optimisation of steam reforming catalysts.