Influence of aminosilane surface functionalization of rare earth hydride-forming alloys on palladium treatment by electroless deposition and hydrogen sorption kinetics of composite materials

A pre-treatment technique was developed to facilitate electroless deposition of palladium layers on the surface of metal hydride-forming alloys for increasing hydrogen absorption kinetics. The technique involved functionalization of the oxidized surface of the alloys by deposition of assembled layers derived from γ-aminopropyltriethoxysilane. This results in the formation of a surface assembly of adhesive functional groups for the immobilization of palladium as a unique catalyst for hydrogen sorption. The layers of γ-aminopropyltriethoxysilane aided immobilization of Pd nuclei, in the activation procedure of electroless deposition, by increasing the chemical adhesion. Pd electroless deposition on rare-earth metal hydride-forming alloys, without γ-aminopropyltriethoxysilane pre-treatment, facilitated the deposition of Pd agglomerates, whereas the use of γ-aminopropyltriethoxysilane pre-treatment facilitated the deposition of continuous Pd layers on the surface of the alloy resulting in dramatic improvements in hydrogen sorption performances, including faster kinetics of hydrogenation of the non-activated material under mild conditions, compared to that observed for non-activated unmodified starting materials and materials surface modified by Pd electroless deposition without the additional γ-aminopropyltriethoxysilane pre-treatment step. The attractiveness of aminosilane pre-treatment for improvement of hydrogen sorption properties of rare earth–nickel-based AB5 alloys, and the influence of the differences in surface structure between deposited Pd agglomerates and layers was demonstrated.