Hydrogen storage
Nanomaterials, particularly those produced by ball mill and severe plastic deformation, offer an alternative that overcomes the two major barriers of bulk materials, rate of sorption and activation.
[10][11] Enhancement of sorption kinetics and storage capacity can be improved through nanomaterial-based catalyst doping, as shown in the work of the Clean Energy Research Center in the University of South Florida.
The optimum amount of Ni particles was found to be 3 mol%, for which the temperature was within the limits established (around 100 °C) and the weight loss was notably greater than the undoped species.
Where pH2 is the partial pressure of hydrogen, ΔH is the enthalpy of the sorption process (exothermic), ΔS is the change in entropy, R is the ideal gas constant, T is the temperature in Kelvin, Vm is the molar volume of the metal, r is the radius of the nanoparticle and γ is the surface free energy of the particle.
A French company McPhy Energy is developing the first industrial product, based on magnesium hydride, already sold to some major clients such as Iwatani and ENEL.
Mg element exists abundantly and accounts for ≈2.35% of the earth's crust with the rank of the eighth; 2) low density of merely 1.74 g cm-3; 3) superior hydrogen storage capacity.
[58] The imidazolium ionic liquids such alkyl(aryl)-3-methylimidazolium N-bis(trifluoromethanesulfonyl)imidate salts can reversibly add 6–12 hydrogen atoms in the presence of classical Pd/C or Ir0 nanoparticle catalysts and can be used as alternative materials for on-board hydrogen-storage devices.
Pure ammonia burns poorly at the atmospheric pressures found in natural gas fired water heaters and stoves.
[78] In September 2005 chemists from the Technical University of Denmark announced a method of storing hydrogen in the form of ammonia saturated into a salt tablet.
Amongst the compounds that contain only B, N, and H (both positive and negative ions), representative examples include: amine boranes, boron hydride ammoniates, hydrazine-borane complexes, and ammonium octahydrotriborates or tetrahydroborates.
Theoretical limitations and experimental results are considered[83] concerning the volumetric and gravimetric capacity of glass microvessels, microporous, and nanoporous media, as well as safety and refilling-time demands.
While it does not directly contribute to radiative forcing, hydrogen is estimated to have an effective 100-year global warming potential of 11.6 ± 2.8 due to its impact on processes such as atmospheric methane oxidation and tropospheric ozone production.
MOFs are highly crystalline inorganic-organic hybrid structures that contain metal clusters or ions (secondary building units) as nodes and organic ligands as linkers.
Compared to traditional zeolites and porous carbon materials, MOFs have very high number of pores and surface area which allow higher hydrogen uptake in a given volume.
There might be formation of interconnected pores and low corrosion resistance in MOFs with metal centers, while they might have good binding energy and enhanced stability.
Varying several factors such as surface area, pore size, catenation, ligand structure, and sample purity can result in different amounts of hydrogen uptake in MOFs.
[107] As of 2010, the BMW Group has started a thorough component and system level validation of cryo-compressed vehicle storage on its way to a commercial product.
In 2004, researchers showed solid H2-containing hydrates could be formed at ambient temperature and tens of bars by adding small amounts of promoting substances such as THF.
A team of Russian, Israeli and German scientists have collaboratively developed an innovative technology based on glass capillary arrays for the safe infusion, storage and controlled release of hydrogen in mobile applications.
[115] A study done by Rapp and Shelby sought to increase the hydrogen release rate through photo-induced outgassing in doped HGMs in comparison to conventional heating methods.
The round-trip efficiency is approximately 40% (vs. 75-80% for pumped-hydro (PHES)), and the cost is slightly higher than pumped hydro, if only a limited number of hours of storage is required.
[120]: 15 The European project Hyunder[124] indicated in 2013 that for the storage of wind and solar energy an additional 85 caverns are required as it cannot be covered by PHES and CAES systems.
Auditors KPMG found that converting the UK to hydrogen gas could be £150bn to £200bn cheaper than rewiring British homes to use electric heating powered by lower-carbon sources.
The use of the existing natural gas pipelines for hydrogen was studied by NaturalHy[157] Portability is one of the biggest challenges in the automotive industry, where high density storage systems are problematic due to safety concerns.
They are currently being considered for onboard storage systems due to their versatility, multi-functionality, mechanical properties and low cost with respect to other alternatives.
Another application of nanomaterials in water splitting has been introduced by a research group at Manchester Metropolitan University in the UK using screen-printed electrodes consisting of a graphene-like material.
Tanks made of carbon and glass fibres reinforcing plastic as fitted in Toyota Marai and Kenworth trucks are required to meet safety standards.
[166] The European project Hyunder[167] indicated in 2013 that for the storage of wind and solar energy an additional 85 caverns are required as it cannot be covered by PHES and CAES systems.
[171] According to Papers in the 2000 to 2015 period collected from Web of Science and processed in VantagePoint® bibliometric software, a scientometric review of research in hydrogen storage materials was constituted.
China kept the leading position throughout the entire period, and had a higher share of hydrogen storage materials publications in its total research output.
