Deuterium absorption in Mg70Al30 thin films with bilayer catalysts: A comparative neutron reflectometry study

We present a neutron reflectometry study of deuterium absorption in thin films of Al-containing Mg alloys capped with a Ta/Pd, Ni/Pd and Ti/Pd-catalyst bilayer. The measurements were performed at room temperature over the 0–1 bar pressure range under quasi-equilibrium conditions. The modeling of the measurements provided a nanoscale representation of the deuterium profile in the layers at different stages of the absorption process. The absorption mechanism observed was found to involve spillover of atomic deuterium from the catalyst layer to the Mg alloy phase, followed by the deuteration of the Mg alloy. Complete deuteration of the Mg alloy occurs in a pressure range between 100 and 500 mbar, dependent on the type of bilayer catalyst. The use of a Ti/Pd bilayer catalyst yielded the best results in terms of both storage density and kinetic properties.

► Mg70Al30 thin films studied for hydrogen absorption using in situ neutron reflectometry.
► Films with Ta/Pd, Ti/Pd and Ni/Pd bilayer catalysts systematically compared.
► Measurements reveals deuterium spillover from the catalysts to the MgAl phase.
► The use of Ti–Pd bilayer offers best results in terms of amount absorbed and kinetics.
► Key results cross-checked with X-ray reflectometry.