Ammonia Borane Based Nanocomposites as Solid‐State Hydrogen Stores for Portable Power Applications

Abstract

Ammonia borane (AB) based nanocomposites are studied with the aim of developing a promising solid‐state hydrogen store that complies with the requirements of a modular polymer electrolyte membrane fuel cell (PEM FC) in a portable power pack system. AB‐carbon nanocomposites (prepared via ball milling or solution‐impregnation) demonstrate improved hydrogen release performance compared to AB itself in terms of onset temperature and hydrogen purity, while maintaining a gravimetric density of more than 5 wt. % H2. The most promising of these materials is an AB‐AC (activated carbon) composite, synthesized via solution impregnation with an optimal dehydrogenation temperature of 96 °C. When combined with an external nickel chloride filter downstream, no evolved gaseous by‐products can be detected above 100 ppb. The feasibility of an AB‐AC storage tank is further investigated using simulations in which the reaction rate and the hydrogen flux is found to be nearly constant as the temperature front propagated from the bottom to the top of the tank after initiation.

Nano-inclusion in one step: spontaneous ice-templating of porous hierarchical nanocomposites for selective hydrogen release

“…3a), matching literature data. 10,27 This gas release during the AB polymerisation step leads to a documented foam formation and volume expansion. The gaseous by-products are not only toxic, but also poison fuel cell catalysts.…”

“…16 Otherwise, the only alternative is to employ lters such as metal halides as part of a storage system which abstracts ammonia from hydrogen downstream. 27,29 Given that thermal analyses indicate that not only the kinetics but also the thermodynamics of AB decomposition are altered in AB-(r)GO nanocomposites, then the decomposition reaction pathways must differ signicantly from AB itself. This would suggest that gaseous by-product species are not simply physically trapped by the matrix and previous evidence suggests that AB follows alternative reaction paths when conned in certain porous structures.…”

“…This would suggest that gaseous by-product species are not simply physically trapped by the matrix and previous evidence suggests that AB follows alternative reaction paths when conned in certain porous structures. 10,18 From experimental and theoretical studies it has been proposed that AB inltrated into porous silica, 21,30,31 or activated carbons, 10,20,27 can undergo acid-base reactions with surface hydroxyl groups evolving H 2 and tethering the remainder of the AB molecule to the surface for subsequent reactions with other AB molecules or other surface groups. The formation of strong B-O bonds at the matrix surface prevents the evolution of borazine and diborane observed in free AB.…”

Efficient Hydrolysis of Ammonia Borane for Hydrogen Evolution Catalyzed by Plasmonic Ag@Pd Core–Shell Nanocubes

“…Among various hydrogen storage materials, ammonia borane (AB, NH 3 BH 3 ) has stood out as one of the most promising choices, thanks to its top gravimetric hydrogen storage capacity (19.6 wt %), satisfactory physicochemical stability, and environmentally friendly nature. , Since choosing AB as ideal hydrogen storage material, the research emphasis has turned to how to release hydrogen gas from it in a controllable and efficient manner. To date, there are three main routes, including pyrolysis, methanolysis, and hydrolysis, to dehydrogenate AB for H 2 production. , Competitively, metal-catalyzed hydrolysis of AB is a more promising way with its advantages of mild reaction conditions and relatively low cost by using water as a solvent as well as a dehydrogenation agent . In the past decade, various sorts of catalysts, such as Pd, Ru, Cu, PdPt, CoPt, NiCoP, and Ni/ZIF-8 have been tested, and much progress has indeed been witnessed.…”

“…To date, there are three main routes, including pyrolysis, methanolysis, and hydrolysis, to dehydrogenate AB for H 2 production. 6,7 Competitively, metal-catalyzed hydrolysis of AB is a more promising way with its advantages of mild reaction conditions and relatively low cost by using water as a solvent as well as a dehydrogenation agent. 8 In the past decade, various sorts of catalysts, such as Pd, 9 Ru, 10 Cu, 11 PdPt, 12 CoPt, 13 NiCoP, 14 and Ni/ZIF-8 15 have been tested, and much progress has indeed been witnessed.…”