Hydrogen sorption in metal-polymer composites: the role of interfaces

We studied the hydrogen storage capacity and sorption kinetics of composite materials made of hydride forming metal particles LaNi5 or Pd, particle size of 1 micron embedded into hydrogen permeable polymers. Experimental analysis shows that (i) the composite material consisting of LaNi5 particles dispersed into polysiloxane PS-LaNi5 shows negligible H2 storage capacity while the LaNi5 particles dispersed into polyethylene PE-LaNi5 are completely hydrogenated and (ii) the Pd particles dispersed both into polysiloxane (PS-Pd) and polyvinylpyrrolidone (PVP-Pd) are completely hydrogenated. The interfacial interactions in the PE-LaNi5 and in the PS-Pd composite materials have weak Van der Waals character while strong interfacial interactions occur in the PS-LaNi5 and in the PVP-Pd composites due to the formation of chemical bonds between polymer side groups and the metal surface atoms. Results indicate that in the metal-polymer composites the hydrogenation of the metallic phase cannot be obtained when the interfacial interactions between metal and polymer impede the surface activation of the metallic phase as in the PS-LaNi5 composite.