Improved hydrogen storage properties of combined Ca(BH4)2 and LiBH4 system motivated by addition of LaMg3 assisted with ball milling in H2

Abstract

A combined Ca(BH4)2+LiBH4 system with improved hydrogen storage properties is obtained by the addition of a particulate LaMg3 alloy assisted with ball milling in a H2 atmosphere. It is found that LaMg3 is mostly hydrogenated to symbiotic low crystalline MgH2 and amorphous La-containing hydride of fine particles after the milling, which are homogenously embedded in the Ca(BH4)2+LiBH4 matrix. The multi-hydride system shows significant improvements in both hydrogen storage thermodynamics and kinetics. Particularly, the system with LaMg3 addition in a molar ratio of 0.3 shows an overall superior hydrogen storage property. The main dehydrogenation starts from ca. 200 °C, which is 100 °C lower than the main dehydrogenation temperature of the pristine Ca(BH4)2+LiBH4 system. Re-hydrogenation initiates at a low temperature of ca. 150 °C, and the system maintains 70% of its first hydrogen desorption capacity after 5 cycles. The mechanism of the improved hydrogen storage properties of the combined system is discussed.