Dr. Kohta ASANO
Senior Researcher of Senior Researcher of Research Institute of Energy Frontier
National Institute of Advanced Industrial Science and Technology (AIST)
Metal hydrides have a number of properties that may be utilized to promote the use of hydrogen as an energy carrier. Those with a high hydrogen permeability can be applied as membranes for hydrogen separation, while the optical changes occurring in metal thin films upon hydrogenation can be used for hydrogen sensing. Even better known is the fact that the high volumetric density of hydrogen makes metal hydrides an attractive option to store energy. The applicability of metal hydrides for storage applications depends on its affinity to hydrogen which determines the equilibrium pressure for (de-)hydrogenation. One of the most attractive hydride forming metals is Mg because of its light weight and low material costs. However, the Mg-H system has thermodynamic and kinetic limitations associated with hydrogen absorption and desorption processes: the high stability of the MgH2 phase and the slow diffusion of hydrogen in Mg and MgH2 at moderate temperatures and pressures.
A possible way to destabilize MgH2 and enhance the reaction kinetics is to reduce the size of Mg. It has been calculated that MgH2 is destabilized by decreasing the size on a nanometer scale. We have successfully synthesized nanometer-sized MgH2 clusters, which form in a self-organized way by the hydrogenation of non-equilibrium Mg-TM (TM: Ti, Mn, Cr, Fe etc.) alloys. Here MgH2 is destabilized by the interface energy between the two metal hydrides. Our results suggest that we can tune the thermodynamics and kinetics of hydrogen absorption and desorption in Mg-H. This concept paves the way for the development of lightweight and cheap Mg-based functional materials in the metal-hydrogen system.
Dr. Kohta Asano, (Ph.D. Eng.), now is a Senior Researcher, Hydrogen Industrial Use and Storage Group, Research Institute of Energy Frontier, National Institute of Advanced Industrial Science and Technology (AIST) in Tsukuba. He got his B. Eng., M. Eng. and Ph.D. Eng. in Materials Science at Tohoku University in Sendai. He has studied metal hydrides for hydrogen storage applications at AIST from 2005. His main research topics are diffusion of hydrogen studied by solid state NMR and synthesis of novel Mg based alloys and hydrides. He has studied them also at Delft University of Technology in the Netherlands from 2013 to 2014.