Size-selected clusters as catalysts for fuel cell reactions

The investigation of electrochemical processes on size-selected clusters is a novel approach and offers great potential for understanding processes at the solid-liquid interface, for developing theoretical tools in quantum chemistry as well as for the development of new electrocatalysts, e.g. for fuel cells. The research group of Prof. Heiz at the Technical University in Munich has developed a technique to prepare size-selected particles below 1nm in UHV utilizing a laser vaporization source and a quadrupole mass spectrometer and is the worldwide leader in this field of nanoscience. They already gained very interesting results for clusters in gas-phase catalysis, which provide a basis for the promising electrocatalytic investigations planned with this project. The aim of the research project is primarily to understand the size-dependent electrocatalytic properties of metal particles supported on planar substrates. Size-selected clusters allow for the first time in electrochemistry the investigation of particle size effects in the non-scalable size regime, i.e. the size regime where the electronic, and thus electrocatalytic properties of the particles change in a non monotonic manner and are not scalable from the bulk properties, with a precision in particle size that was unknown up to now. In continuation of my PhD thesis at the Lawrence Berkeley National Lab, electrocatalytic measurements will be performed on these size-selected particles focusing on processes occurring in polymer electrolyte membrane fuel cells (PEMFC). That is, the oxidation of hydrogen, the influence of CO in the hydrogen fuel, methanol oxidation as well as the oxygen reduction reaction. By varying the particle size especially below 1nm in diameter, important insights about the active centers on nanoparticles and clusters are expected. These are required for any "materials by design" approach in catalysis. Another important aspect in any development of tailormade nanomaterials are theoretical ab- initio calculations. In electrocatalysis, however, the development of suitable theoretical tools is hampered by the lacking comparison to experimental results due to ill-defined conditions. Therefore the planned experiments with the well-defined clusters will be an important step towards a theoretical description of processes at the solid-liquid interface.