Effects of Ti interlayers on microstructures and hydrogen storage capacity in Mg/Pd multilayer thin films

• Hydrogen storage capacities of 60 multilayer Mg/Pd and Ti/Mg/Ti/Pd films fabricated by an UHV sputter.
• The hydrogen absorption capacity of the Ti/Mg/Ti/Pd film is 1.7, 3.5, and 4.7 wt% at 50, 100, and 150 °C.
• The hydrogen absorption capacity of the Mg/Pd film is significantly lower values, 0.18, 0.65, and 1.35 wt%.
• The hydrogen absorption capacity is greatly dependent upon the formation of Mg–Pd intermetallic phases.
• Ti interlayers play a crucial role in preventing the formation of Mg–Pd intermetallic phases.

In this work, we examine the microstructural and hydrogen storage properties of 60 multilayer Mg/Pd and Ti/Mg/Ti/Pd films using an ultra-high-vacuum (UHV) DC magnetron sputtering system. The hydrogen absorption capacity of the Ti/Mg/Ti/Pd film was found to be 1.7, 3.5, and 4.7 wt% at 50, 100, and 150 °C, respectively, while that of the Mg/Pd film was measured at significantly lower values, 0.18, 0.65, and 1.35 wt%. The hydrogen absorption capacity for the Mg/Pd and Ti/Mg/Ti/Pd films is greatly dependent upon the formation of Mg–Pd intermetallic phases, formed during the hydrogenation process. Our results demonstrate that Ti interlayers in the Ti/Mg/Ti/Pd film play a crucial role in preventing the formation of Mg–Pd intermetallic phases, which originate from the inter-diffusion of Mg and Pd atoms during hydrogenation, and thus result in an improved hydrogen storage capacity.