The role of interface in the mechanism of hydrogen absorption by metal-polymer composites

Abstract

We have studied the hydrogen storage capacity and sorption kinetics of composite materials made of LaNi5 particles dispersed into hydrogen permeable polymers. Samples consisted of metal particles well separated and completely embedded in the polymeric matrix. Experimental results by Sievert analysis show that the composite material made with polysiloxane presents negligible H2 storage capacity while in that made with polyethylene the LaNi5 particles result completely hydrogenated. The hydrogenation of the metallic phase depends on the type of chemical interaction at metal-polymer interface. Strong interfacial interactions occur in the composite made with polysiloxane due to the formation of dative bonds between polymer side-groups and the metal surface atoms. Weak Van der Waals interfacial interactions occur on the contrary in the composite material made with polyethylene. We suggest that strong metal-polymer interfacial interactions impede the H2 molecular dissociation at the metal surface and the H transfer to the metal lattice.