Nanostructured Palladium-Rhodium for Hydrogen Absorption: Processing, Structure, and Properties

Impetus to identify and implement alternatives to fossil fuels has driven research on several different energy sources. Use of hydrogen as a fuel has been of particular interest, due to its relative abundance and cleanliness as a fuel, amongst other desirable characteristics. However, one of the current challenges to using hydrogen is finding an effective and safe method to store it for later use. Metal hydrides have been proposed as possibilities for safe solid state storage of hydrogen.;In the present thesis, cryomilled Pd-10%Rh was investigated as potential solid state storage material of hydrogen. Pd-10%Rh was first atomized, and then subsequently cryomilled. The cryomilled Pd-10%Rh was then examined using microstructural characterization techniques including optical microscopy, electron microscopy, and X-ray diffraction. Pd-10%Rh particles were significantly flattened, increasing the apparent surface area. Microstructural refinement was observed in the cryomilled Pd-10%Rh, generating grains at the nanometric scale through dislocation based activity. Hydrogen sorption properties were also characterized, generating both capacity as well as kinetics measurements. It was found that the microstructural refinement due to cryomilling did not play a significant role on hydrogen sorption properties until the smallest grain size (on the order of ~25 nm) was achieved. Additionally, the increased surface area and other changes in particle morphology were associated with cryomilling changed the kinetics of hydrogen absorption.