Latest News on Hydrogen Storage : July 21
 Hydrogen storage methods
Hydrogen exhibits the highest heating value per mass of all chemical fuels. Furthermore, hydrogen is regenerative and environmentally friendly. There are two reasons why hydrogen is not the major fuel of today’s energy consumption. First of all, hydrogen is just an energy carrier. And, although it is the most abundant element in the universe, it has to be produced, since on earth it only occurs in the form of water and hydrocarbons. This implies that we have to pay for the energy, which results in a difficult economic dilemma because ever since the industrial revolution we have become used to consuming energy for free. The second difficulty with hydrogen as an energy carrier is its low critical temperature of 33 K (i.e. hydrogen is a gas at ambient temperature). For mobile and in many cases also for stationary applications the volumetric and gravimetric density of hydrogen in a storage material is crucial. Hydrogen can be stored using six different methods and phenomena: (1) high-pressure gas cylinders (up to 800 bar), (2) liquid hydrogen in cryogenic tanks (at 21 K), (3) adsorbed hydrogen on materials with a large specific surface area (at T<100 K), (4) absorbed on interstitial sites in a host metal (at ambient pressure and temperature), (5) chemically bonded in covalent and ionic compounds (at ambient pressure), or (6) through oxidation of reactive metals, e.g. Li, Na, Mg, Al, Zn with water.
 Hydrogen-storage materials for mobile applications
Mobility — the transport of people and goods — is a socioeconomic reality that will surely increase in the coming years. It should be safe, economic and reasonably clean. Little energy needs to be expended to overcome potential energy changes, but a great deal is lost through friction (for cars about 10 kWh per 100 km) and low-efficiency energy conversion. Vehicles can be run either by connecting them to a continuous supply of energy or by storing energy on board. Hydrogen would be ideal as a synthetic fuel because it is lightweight, highly abundant and its oxidation product (water) is environmentally benign, but storage remains a problem. Here we present recent developments in the search for innovative materials with high hydrogen-storage capacity.
 New approaches to hydrogen storage
The emergence of a Hydrogen Economy will require the development of new media capable of safely storing hydrogen in a compact and light weight package. Metal hydrides and complex hydrides, where hydrogen is chemically bonded to the metal atoms in the bulk, offer some hope of overcoming the challenges associated with hydrogen storage. The objective is to find a material with a high volumetric and gravimetric hydrogen density that can also meet the unique demands of a low temperature automotive fuel cell. Currently, there is considerable effort to develop new materials with tunable thermodynamic and kinetic properties. This tutorial review provides an overview of the different types of metal hydrides and complex hydrides being investigated for on-board (reversible) and off-board (non-reversible) hydrogen storage along with a few new approaches to improving the hydrogenation–dehydrogenation properties.
 Ball-Milled and Acid-Treated Mineral Activated Carbon as Hydrogen Storage Material
For several decades, carbon allotropes, including graphitic nanofibres and other nanostructures, have been studied as hydrogen storage materials. In this paper, activated mineral carbon (bituminous) was used for the hydrogen storage process. For 3 h, the carbon particle size was continuously reduced by mechanical milling, and the carbon was subsequently refluxed with concentrated nitric acid. Microstructural characterisation and evaluation of the hydrogenation behaviour of the chemically treated and milled mineral were performed. Hydrogen adsorption/desorption experiments were carried out using two methods: the first one using a thermogravimetric analysis (TGA) system with a hydrogen atmosphere during the process of adsorption and nitrogen as carrier gas in the desorption and the second method of hydrogenation was performed in the microreactor (MR) varying pressure, temperature and contact time. On the other hand, ten cycles of adsorption/desorption of hydrogen were performed with each method. The qualitative analysis for hydrogen identification was carried out with a gas chromatograph and the same thermogravimetric analyser with nitrogen used as the carrier gas. The hydrogen absorption capacity in powder samples was 0.45±0.01 and 1.38±0.05 wt% hydrogen in the TGA system and in the MR respectively, according to these results the best method for hydrogen adsorption was using the MR because the pressure applied was higher.
 Oxygen and Hydrogen Reaction “In situ” with Magnesium and Tantalum in a Mechanical Milling System When a Solvent is Used
The purpose of this paper is study the preparation “in situ” of magnesium–tantalum phases when reacted with oxygen and hydrogen during a mechanical milling process. Different phases were formed as function of the milling time. High energy ball milling was utilized to prepare hydrogenated compounds by controling the milling between 5 and 20 hours with a ball powder weight ratio of 10 and using methanol as the control agent. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to characterize the compounds. The XRD results at 20 h of milling revealed that only hydrogenated species (Ta2H and TaH0.5) and Mg(OH)2 were present.
 Züttel, A., 2004. Hydrogen storage methods. Naturwissenschaften, 91(4), pp.157-172.
 Schlapbach, L. and Züttel, A., 2011. Hydrogen-storage materials for mobile applications. Materials for sustainable energy: a collection of peer-reviewed research and review articles from nature publishing group, pp.265-270.
 Graetz, J., 2009. New approaches to hydrogen storage. Chemical Society Reviews, 38(1), pp.73-82.
 Iturbe-Garcia, J.L. and López-Muñoz, B.E., 2018. Ball-Milled and Acid-Treated Mineral Activated Carbon as Hydrogen Storage Material. Current Journal of Applied Science and Technology, pp.1-13.
 Iturbe-García, J.L. and López-Muñoz, B.E., 2016. Oxygen and Hydrogen Reaction “In situ” with Magnesium and Tantalum in a Mechanical Milling System When a Solvent is Used. Current Journal of Applied Science and Technology, pp.1-9.