The synthesis and hydrogen storage properties of a MgH₂incorporated carbon aerogel scaffold

Abstract

A new approach to the incorporation of MgH2 in the nanometer-sized pores of a carbon aerogel scaffold was developed, by infiltrating the aerogel with a solution of dibutylmagnesium (MgBu2) precursor, and then hydrogenating the incorporated MgBu2 to MgH2. The resulting impregnated material showed broad x-ray diffraction peaks of MgH2. The incorporated MgH2 was not visible using a transmission electron microscope, which indicated that the incorporated hydride was nanosized and confined in the nanoporous structure of the aerogel. The loading of MgH2 was determined as 15-17 wt%, of which 75% is reversible over ten cycles. Incorporated MgH2 had >5 times faster dehydrogenation kinetics than ball-milled activated MgH2, which may be attributed to the particle size of the former being smaller than that of the latter. Cycling tests of the incorporated MgH(2) showed that the dehydrogenation kinetics are unchanged over four cycles. Our results demonstrate that confinement of metal hydride materials in a nanoporous scaffold is an efficient way to avoid aggregation and improve cycling kinetics for hydrogen storage materials.

High capacity hydrogenstorage materials: attributes for automotive applications and techniques for materials discovery

“…Scaffolding, a technique relatively new to the field of hydrogen storage, involves the deposition of a storage material within the (nano-sized) pores of a host scaffold material. 76,77 High-throughput materials screening, a promising technique commonly used in the pharmaceutical industry, couples the steps of synthesis, processing, and characterization to accelerate the discovery of hydrogen storage materials. 78,79 V. Materials attributes and methods for their evaluation…”

Accelerating the Understanding and Development of Hydrogen Storage Materials: A Review of the Five-Year Efforts of the Three DOE Hydrogen Storage Materials Centers of Excellence

“…Work by Vajo and co-workers [24,25] in the MHCoE shows that nanoconfinement can lead to dramatic (~509) increases in hydrogen release rates. However, a synthetic difficulty is finding a way to introduce the complex metal hydride into the nanoscaffold.…”

“…However, a synthetic difficulty is finding a way to introduce the complex metal hydride into the nanoscaffold. A significant breakthrough [25] in nanoconfinement came from the organometallic synthesis methods developed by Jensen and co-workers at the University of Hawaii (UH). The original syntheses [21] of nanoconfined LiBH 4 required infusing the carbon aerogel with liquid (i.e., melted) LiBH 4 .…”

“…Studies of this approach [25] have shown that high (9 to 16 wt pct) MgH 2 loadings can be achieved in the carbon aerogel without host degradation. Figure 4 shows that the rate of dehydrogenation from MgH 2 incorporated in 13 nm pores in C-aerogel at 525 K (252°C) is~17 times faster than the initial rate found for bulk ball-milled MgH 2 .…”

Thermal stability of gas phase magnesium nanoparticles

“…14 Indeed, it has been reported that the desorption temperature T d can be decreased to 85 and 115°C compared to T d Ͼ 350°C for bulk Mg. 11,12 Nanoconfinement of MgH 2 nanoparticles incorporated in carbon aerogel scaffold prohibits nanoparticles to coarsen and leads to increased number of hydrogenation/dehydrogenation cycles and with faster dehydrogenation kinetics compared to the ball milled nanostructured materials. 15,16 However, so far, insufficient attention has been paid to the thermal stability of Mg nanoparticles. Moreover, knowledge and understanding of the structural evolution of Mg nanoparticles during hydrogenation is lacking.…”