Nanoscale microstructures and novel hydrogen storage performance of as cast V47Fe11Ti30Cr10RE2 (RE = La, Ce, Y, Sc) medium entropy alloys

Abstract

As classical BCC structure solid state hydrogen storage materials, vanadium-based solid solution alloys occupied a prominent position in the field of hydrogen storage materials due to their significant advantages such as the ability to absorb and desorb hydrogen with high capacity under moderate conditions. In this paper, RE-containing medium entropy BCC solid solution alloys were designed. The microstructure, phase composition and hydrogen storage properties of the medium entropy alloys were systematically studied. Microstructural analysis showed that nanoscale crystals were found in as-cast medium entropy alloys obtained by arc melting followed by natural cooling inside the furnace. This is different from the vanadium-based alloys that are often regarded as traditional coarse-grained alloys in the past decades. The V 47 Fe 11 Ti 30 Cr 10 RE 2 alloys can be fully activated by one cycle of hydrogen ab/de-sorption after pretreatment. The kinetic test shows that the time required for the as-cast RE-containing medium entropy alloys hydrogen uptake to 90% saturation is less than 100 s at room temperature. The alloys exhibit very excellent hydrogen absorption kinetic properties than reported alloys takes at least about 300 s. This is due to the fact that the present alloys are composed of nanocrystals with numerous interfaces and grain boundaries, and these defects can act as good channels for the diffusion of hydrogen atoms. The V 47 Fe 11 Ti 30 Cr 10 Y 2 alloy exhibits a maximum capacity of 3.41 wt% at 295 K. The thermodynamics of hydrogen ab/de-sorption and the hydrogen desorption under non-isothermal conditions were also studied in detail. • Nanoscale crystals were found in as cast RE-containing medium entropy BCC solid solution alloys prepared by arc melting. • The alloys have numerous interfaces and grain boundaries. • The time required for the alloys hydrogen uptake to 90% saturation is less than 100 s.