Supercritical fluid chemical deposition of Pd nanoparticles on magnesium–scandium alloy for hydrogen storage

• Nanoparticles of Pd were deposed on the binary compound Mg0.65Sc0.35 using the Supercritical Fluid Chemical Deposition (SFCD) method.
• Numerous parameters were tested and optimized in order to obtain a homogeneous deposition.
• At the first step, Pd@Mg0.65Sc0.35 decomposes into ScH2 and MgH2 under hydrogen pressure (1 MPa) at 330 °C.
• The mixture, after decomposition absorbs hydrogen reversibly on Mg/MgH2 couple with good kinetics.

The deposition of Pd nanoparticles on the binary compound Mg0.65Sc0.35 using the Supercritical Fluid Chemical Deposition (SFCD) method was performed. There, the SFCD operating parameters (co-solvent, temperature, CO2 and hydrogen pressure, reaction time) have been optimized to obtain homogeneous deposition of Pd nanoparticles (around 10 nm). The hydrogenation properties of the optimized Pd@Mg0.65Sc0.35 material were determined and compared to those of Mg0.65Sc0.35Pd0.024. The latter compound forms at 300 °C and 1 MPa of H2 a hydride that crystallizes in the fluorite structure, absorbs reversibly 1.5 wt.% hydrogen and exhibits fast kinetics. In contrast, Pd@Mg0.65Sc0.35 compound decomposes into ScH2 and MgH2 during hydrogen absorption under the same conditions. However, reversible sorption reaches 3.3 wt.% of hydrogen while keeping good kinetics. The possible roles of Pd on the hydrogen-induced alloy decomposition are discussed.