A catalytic effect on hydrogen absorption kinetics in Pd/Ti/Mg/Ti multilayer thin films

In this work, we have investigated the microstructural and hydrogen storage properties of a 60 layer film of Pd(40 nm)/Ti(x nm)/Mg(360 nm)/Ti(x nm) (x = 10, 20, 30, 40, and 50) using an ultra-high vacuum DC magnetron sputtering system. The highest hydrogen absorption capacity of the Pd/Ti/Mg/Ti film was 4.46 wt% for x = 50. The hydrogen absorption rate accelerated remarkably with increased thickness of the Ti layer, from 209 min for x = 10 to 39 min for x = 40 - overall, an increase by a factor of ∼5. These results demonstrate that the Ti layer in the Pd/Ti/Mg/Ti films serves as a blocking layer preventing the formation of Mg Pd intermetallic phases and provides additional diffusion paths for hydrogen atoms, which leads to enhanced hydrogen storage properties.