Development of a high-pressure Ti-Mn based hydrogen storage alloy for hydrogen compression

This work focuses on the selection and development of high-pressure Ti-Mn based alloy for a domestic 2-stage Metal Hydride Hydrogen Compressor (MHHC) capable of compressing hydrogen from 15 bar to over 350 bar with a maximum operating temperature of 130 °C. Thermodynamic, kinetics and hydrogen storage characteristics of Ti-Mn based alloy were shown to be very sensitive to the alloy's composition. Stability of the hydride phase could be significantly reduced by increasing the Mn content of the alloy and contracting the C14 Laves phase unit cell volume, therefore meeting the required thermodynamic for the target MHHC. The structure and hydrogen capacity of the alloy remained almost constant even after 1000 hydrogen absorption and desorption cycles at room
temperature. A significant reduction in the hydrogen absorption plateau slope of the modified high-pressure alloy was achieved by increasing the C14 Laves phase proportion. As a result, effective improvement in the hydrogen sorption kinetics of the modified alloy was observed with most of the hydrogen ab/desorbed in less than 5 min. Although compositional modification showed to be beneficial for lowering the hydrogen absorption plateau slope in high-pressure alloys, the level of hysteresis seemed to be mainly dominated by the alloys thermodynamic.