Thermodynamics and kinetics of nano-engineered Mg-MgH2 system for reversible hydrogen storage application
TL;DR: In this paper, the authors studied the thermodynamics and kinetics of hydrogenation-dehydrogenation of nanometric iron (nFe) doped Mg-MgH 2 system.
About: This article is published in Thermochimica Acta.The article was published on 2017-06-10. It has received 38 citations till now. The article focuses on the topics: Dehydrogenation & Hydrogen storage.
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TL;DR: In this article, the authors provide a comprehensive insight into the current state of the art of research on several typical TCES systems at high operation temperatures (673 − 1273 K), including hydride, metal oxide and organic systems.
139 citations
TL;DR: In this article, the authors review the recent progress in improving the thermodynamics and kinetics of Mg-based materials with an emphasis on the models and the influence of various parameters in the calculated models.
129 citations
TL;DR: In this paper, a two-dimensional layered Fe is prepared via a facile wet-chemical ball milling method and has been confirmed to greatly enhance the hydrogen storage performance of MgH2.
90 citations
TL;DR: In this paper, the authors showed that carbon is uniformly distributed between the MgH2 grains covering segregated TiH2, preventing the grain growth and thus keeping the reversible storage capacity and the rates of hydrogen charge and discharge unchanged.
Abstract: TiH2-modified MgH2 was prepared by high energy reactive ball milling (HRBM) of Mg and Ti in hydrogen and showed high weight H storage capacity and fast hydrogenation/dehydrogenation kinetics. However, a decrease in the reversible H storage capacity on cycling at high temperatures takes place and is a major obstacle for its use in hydrogen and heat storage applications. Reversible hydrogen absorption/desorption cycling of the materials requires use of the working temperature ≥330 °C and results in a partial step-by-step loss of the recoverable hydrogen storage capacity, with less significant changes in the rates of hydrogenation/dehydrogenation. After hydrogen desorption at 330–350 °C, hydrogen absorption can proceed at much lower temperatures, down to 24 °C. However, a significant decay in the reversible hydrogen capacity takes place with increasing number of cycles. The observed deterioration is caused by cycling-induced drastic morphological changes in the studied composite material leading to a segregation of TiH2 particles in the cycled samples instead of their initial homogeneous distribution. However, the introduction of 5 wt% of graphite into the MgH2–TiH2 composite system prepared by HRBM leads to an outstanding improvement of the hydrogen storage performance. Indeed, hydrogen absorption and desorption characteristics remain stable through 100 hydrogen absorption/desorption cycles and are related to an effect of the added graphite. The TEM study showed that carbon is uniformly distributed between the MgH2 grains covering segregated TiH2, preventing the grain growth and thus keeping the reversible storage capacity and the rates of hydrogen charge and discharge unchanged. Modelling of the kinetics of hydrogen absorption and desorption in the Mg–Ti and Mg–Ti–C composites showed that the reaction mechanisms significantly change depending on the presence or absence of graphite, the number of absorption–desorption cycles and the operating temperature.
89 citations
TL;DR: In this paper, the authors summarized the research process of nanosized metal hydrides and nanoadditives for metal hyddrides in the recent five years and discussed the effect of nanomodification strategy on the improvement of hydrogen storage and sensing properties.
69 citations
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10,842 citations
TL;DR: In this paper, the authors present a review of hydrogen storage on materials with high specific surface area, hydrogen intercalation in metals and complex hydrides, and storage of hydrogen based on metals and water.
1,486 citations
TL;DR: In this paper, the authors present a set of recommendations for obtaining kinetic data that are adequate to the actual kinetics of various processes, including thermal decomposition of inorganic solids; thermal and thermo-oxidative degradation of polymers and organics; reactions of solids with gases; polymerization and crosslinking; crystallization of polymer and inorganics; hazardous processes.
890 citations
TL;DR: This paper reviews the various storage methods for hydrogen and highlights their potential for improvement and their physical limitations.
Abstract: 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. The most common storage systems are high-pressure gas cylinders with a maximum pressure of 20 MPa (200 bar). New lightweight composite cylinders have been developed which are able to withstand pressures up to 80 MPa (800 bar) and therefore the hydrogen gas can reach a volumetric density of 36 kg·m−3, approximately half as much as in its liquid state. Liquid hydrogen is stored in cryogenic tanks at 21.2 K and ambient pressure. Due to the low critical temperature of hydrogen (33 K), liquid hydrogen can only be stored in open systems. The volumetric density of liquid hydrogen is 70.8 kg·m−3, and large volumes, where the thermal losses are small, can cause hydrogen to reach a system mass ratio close to one. The highest volumetric densities of hydrogen are found in metal hydrides. Many metals and alloys are capable of reversibly absorbing large amounts of hydrogen. Charging can be done using molecular hydrogen gas or hydrogen atoms from an electrolyte. The group one, two and three light metals (e.g. Li, Mg, B, Al) can combine with hydrogen to form a large variety of metal–hydrogen complexes. These are especially interesting because of their light weight and because of the number of hydrogen atoms per metal atom, which is two in many cases. Hydrogen can also be stored indirectly in reactive metals such as Li, Na, Al or Zn. These metals easily react with water to the corresponding hydroxide and liberate the hydrogen from the water. Since water is the product of the combustion of hydrogen with either oxygen or air, it can be recycled in a closed loop and react with the metal. Finally, the metal hydroxides can be thermally reduced to metals in a solar furnace. This paper reviews the various storage methods for hydrogen and highlights their potential for improvement and their physical limitations.
747 citations