Realizing nano-confinement of magnesium for hydrogen storage using vapour transport deposition

A new approach was developed to successfully load Mg into the nanometre-sized pores of an anodic aluminium oxide (AAO) template for realizing the nano-confinement of Mg. Structural characterization shows that Mg nano-particles are nucleated along the AAO pipe wall together with the formation of MgO and Mg17Al12 as by-products. The flow rate of argon gas, the temperature of the AAO template and the transporting distance between the Mg vapour source and the AAO template were optimized to achieve the confinement of Mg nano-particles with larger loading rate. Under optimized deposition conditions, the particle size of the loaded Mg is less than 100 nm and the effective filling factor is about 35 wt%. The confined Mg/MgH2 even after 10 de-/hydrogenation cycles still shows favourable kinetics. Furthermore, the slight reduction in hydrogen desorption enthalpy and entropy of MgH2 from (74.42 +/- 0.12) to (73.21 +/- 0.04) kJ.mol(-1) and (130.98 +/- 0.05) to (130.11 +/- 0.24) J.mol(-1).K-1 is also found in the present nano-confinement.