Nanoconfined NaAlH4: Determination of Distinct Prolific Effects from Pore Size, Crystallite Size, and Surface Interactions

Abstract

Nanoconfinement is a new method to improve the hydrogen storage properties for metal hydrides. A systematic study of melt-infiltrated NaAlH4 in resorcinol formaldehyde carbon aerogels with pore sizes of Dmax = 4, 7, 10, 13, 19, 22, 26, 39 and >100 nm is presented. A linear correlation between pore size and crystalline domain size is observed using PXD. The distinct effects from pore size, crystallite size, and interfacial contact between NaAlH4 and carbon aerogel on hydrogen release and uptake properties are investigated. In situ synchrotron powder X-ray diffraction shows that formation of crystalline NaAlH4 nanoparticles only occurs in the nanoporous scaffolds (4 100 nm) as compared to bulk NaAlH4, i.e., reduction of the temperature for maximum hydrogen release rate of ΔTmax = −90 °C. Additional improvement is induced by reducing the pore sizes in the range 7 ≤ Dmax ≤ 39 nm and...