Measuring the strain induced by graphene in rGO/Metal nanoparticles for hydrogen storage application

Abstract

High-pressure compression gas currently used in hydrogen vehicles have low volume storage density, which leads to inefficiency and stability problems. Mg is a promising material for hydrogen storage due to their high gravimetric capacity and outstanding reversibility, but the limitation is in high reactivity that results in easy oxidation of Mg. This problem can be solved by rGO/Metal nanolaminate which is a solid-state hydrogen storage materials, and have hydrogen permeability allowing it to have stable hydrogen storage properties in the air. Since the charge and discharge rates of hydrogen are influenced by pressure in solid hydrogen storage materials, in this paper, using synthesized samples from a collaborative group to measure the strain induced by graphene and lay the groundwork for a study of its impact on hydrogen storage performance. It was confirmed that the nanoparticles were covered with the graphene, and there were small MgO particles of few nm and relatively large Mg particles of several tens of nm. In the hydrogenated rGO/$MgH_2$ sample, not only MgO particles, but also several tens of nm sized Mg particles were found. As a result of strain analysis using TEM, most particles showed compressive strain which contrast to tensile deformation of the XRD data. The measured data was within the margin of error, so it was hard to determine the exact direction of the strain, but the size of the particle was so large that the strain effect of the graphene was insufficient. A new material system of rGO/Pd was also explored, where Pd is also a promising hydrogen storage material due to its sponge like properties which can absorb up to 900times of hydrogen than its own volume. It is also, less prone to oxidize that results in chemical stability, and synthesis method allowed for fabrication of nanoscale particle that will further enhance the hydrogen storage performance. The effect of strain of rGO/Pd was therefore explored in its as-fabricated condition.