Hydrogen storage properties of Mg - High entropy alloy composite at mild temperatures

A Mg – 40 wt% (TiVNb) 75 Cr 15 Mo 10 composite was developed by reactive ball milling under hydrogen, combining the high gravimetric capacity of Mg with the high reactivity of a bcc high-entropy alloy (HEA). Milling for 4 h under hydrogen led to the in situ formation of MgH 2 and a uniform nanometric dispersion of HEA particles within the matrix, as confirmed by TEM. The composite exhibited significant hydrogen uptake under mild conditions (3.0 wt% at 25 °C and 4.4 wt% at 150 °C), along with fast absorption kinetics. Temperature desorption spectroscopy revealed a marked decrease in the main H-desorption peak from 361 to 195 °C, accompanied by a reduction in activation energy from 170 to 52 kJ/mol H2, calculated using the Kissinger method. The material showed good cycling stability, maintaining 4.2 wt% over 15 cycles. These improvements are attributed to the high density of reactive Mg/MgH 2 –HEA interfaces.