Due to its high hydrogen storage efficiency and safety, Mg/MgH2 stands out from many solid hydrogen storage materials and is considered as one of the most promising solid hydrogen storage materials. ...However, thermodynamic/kinetic deficiencies of the performance of Mg/MgH2 limit its practical applications for which a series of improvements have been carried out by scholars. This paper summarizes, analyzes and organizes the current research status of the hydrogen storage performance of Mg/MgH2 and its improvement measures, discusses in detail the hot studies on improving the hydrogen storage performance of Mg/MgH2 (improvement measures, such as alloying treatment, nano-treatment and catalyst doping), and focuses on the discussion and in-depth analysis of the catalytic effects and mechanisms of various metal-based catalysts on the kinetic and cyclic performance of Mg/MgH2. Finally, the challenges and opportunities faced by Mg/MgH2 are discussed, and strategies to improve its hydrogen storage performance are proposed to provide ideas and help for the next research in Mg/MgH2 and the whole field of hydrogen storage.
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Schematic diagram of the de/rehydrogenation processes of the MgH2+NiO@NiMoO4 composite.
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The design of catalysts with excellent catalytic activity plays an important role in the field ...of solid-state hydrogen storage of new energy sources. Herein, a novel hydrangea-like NiO@NiMoO4 composite catalyst was prepared through a facile hydrothermal reaction. Subsequently, NiO@NiMoO4 was doped into MgH2 by ball milling to solve the problems of high dehydrogenation temperature and slow desorption kinetics of MgH2. It can be seen from the experimental results that the MgH2 + 10 wt% NiO@NiMoO4 composite starts to dehydrogenate at about 190 °C, which is about 170 °C lower than that of pure MgH2. Meanwhile, after complete dehydrogenation, the composites can start to absorb hydrogen below 40 °C. Compared with pure MgH2, the activation energy of hydrogen absorption and dehydrogenation of the composite decreased by 47.6 kJ/mol and 46.5 kJ/mol, respectively. In 10th cycle tests, the MgH2 + 10 wt% NiO@NiMoO4 composite still has good cycle stability. After adding a small amount of biomass charcoal, the hydrogen storage capacity can even be maintained above 97%. Furthermore, the characterization results show that the in situ generated new species Mo and Mg2Ni/Mg2NiH4 synergistically promote the adsorption and dissociation of hydrogen. This new synergistic mechanism provides new comprehensive insights for improving reversible hydrogen storage in MgH2.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
CeO2 is an important rare earth (RE) oxide and has served as a typical oxygen storage material in practical applications. In the present study, the oxygen storage capacity (OSC) of CeO2 was enhanced ...by doping with other rare earth ions (RE, RE = Yb, Y, Sm and La). A series of Undoped and RE–doped CeO2 with different doping levels were synthesized using a solvothermal method following a subsequent calcination process, in which just Ce(NO3)3∙6H2O, RE(NO3)3∙nH2O, ethylene glycol and water were used as raw materials. Surprisingly, the Undoped CeO2 was proved to be a porous material with a multilayered special morphology without any additional templates in this work. The lattice parameters of CeO2 were refined by the least–squares method with highly pure NaCl as the internal standard for peak position calibrations, and the solubility limits of RE ions into CeO2 were determined; the amounts of reducible–reoxidizable Cen+ ions were estimated by fitting the Ce 3d core–levels XPS spectra; the non–stoichiometric oxygen vacancy (VO) defects of CeO2 were analyzed qualitatively and quantitatively by O 1s XPS fitting and Raman scattering; and the OSC was quantified by the amount of H2 consumption per gram of CeO2 based on hydrogen temperature programmed reduction (H2–TPR) measurements. The maximum OSC of CeO2 appeared at 5 mol.% Yb–, 4 mol.% Y–, 4 mol.% Sm– and 7 mol.% La–doping with the values of 0.444, 0.387, 0.352 and 0.380 mmol H2/g by an increase of 93.04, 68.26, 53.04 and 65.22%. Moreover, the dominant factor for promoting the OSC of RE–doped CeO2 was analyzed.
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Mg-based solid hydrogen storage materials have advantages such as high hydrogen storage capacity, safety and reliability, low price, and abundant magnesium resources. They are considered a solid ...hydrogen storage material with great application potential, however, their slow hydrogen absorption/desorption rate, high hydrogen absorption/desorption temperature, and relatively high activation energy and enthalpy limit their application in the field of hydrogen energy. Aiming at the current research on Mg-based solid hydrogen storage materials at home and abroad, this paper summarizes the improvement methods of Mg-based hydrogen storage materials, focusing on the effects of the addition of transition metal catalysts and carbon composite catalysts, as well as the construction of alloying, nanocrystallization, and composite systems on the hydrogen storage and desorption mechanism, microstructure, and dynamic/thermodynamic properties of Mg-based materials. Finally, the research results in this field are summarized, and the development trend and main challenges of magnesium-based hydrogen storage materials have been prospected.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Mg-based materials have been widely studied as potential hydrogen storage media due to their high theoretical hydrogen capacity, low cost, and abundant reserves. However, the sluggish hydrogen ...absorption/desorption kinetics and high thermodynamic stability of Mg-based hydrides have hindered their practical application. Ball milling has emerged as a versatile and effective technique to synthesize and modify nanostructured Mg-based hydrides with enhanced hydrogen storage properties. This review provides a comprehensive summary of the state-of-the-art progress in the ball milling of Mg-based hydrogen storage materials. The synthesis mechanisms, microstructural evolution, and hydrogen storage properties of nanocrystalline and amorphous Mg-based hydrides prepared via ball milling are systematically reviewed. The effects of various catalytic additives, including transition metals, metal oxides, carbon materials, and metal halides, on the kinetics and thermodynamics of Mg-based hydrides are discussed in detail. Furthermore, the strategies for synthesizing nanocomposite Mg-based hydrides via ball milling with other hydrides, MOFs, and carbon scaffolds are highlighted, with an emphasis on the importance of nanoconfinement and interfacial effects. Finally, the challenges and future perspectives of ball-milled Mg-based hydrides for practical on-board hydrogen storage applications are outlined. This review aims to provide valuable insights and guidance for the development of advanced Mg-based hydrogen storage materials with superior performance.
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Carbon materials play an important role in the development of solid hydrogen storage materials. The main purpose of this work is to study the low-cost synthesis of biomass carbon (BC) and its ...positive effect on the hydrogen storage behavior of magnesium hydride (MgH2). Herein, it is proven that when biomass carbon (BC) is used together with magnesium hydride (MgH2), biomass carbon can be used as an adsorption and desorption channel for hydrogen. The initial dehydrogenation temperature of MgH2 + 10 wt% BC composite is 250 °C, which is 110 °C lower than that of pure MgH2. In addition, the MgH2 + 10 wt% BC composite system can complete all dehydrogenation processes within 10 min at 350 °C. Meanwhile, 5.1 wt% H2 can also be dehydrogenated within 1 h at 300 °C. Under the same conditions, MgH2 hardly starts to release hydrogen. After complete dehydrogenation, the composite can start to absorb hydrogen at 110 °C. Under the conditions of 225 °C and 3 MPa, 6.13 wt% H2 can be absorbed within 1 h, basically reaching the theoretical dehydrogenation limit. Cycling experiments show that the MgH2 + 10 wt% BC composite has a good stability. After 10 cycles, the hydrogen storage capacity shows almost no obvious decline. It is believed that this study can help in the research and development of efficient carbon-based multifunctional catalysts.
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Transition metal catalysts are particularly effective in improving the kinetics of the reversible hydrogen storage reaction for light metal hydrides. Herein, K2MoO4 microrods were prepared using a ...simple evaporative crystallization method, and it was confirmed that the kinetic properties of magnesium hydride could be adjusted by doping cubic K2MoO4 into MgH2. Its unique cubic structure forms new species in the process of hydrogen absorption and desorption, which shows excellent catalytic activity in the process of hydrogen storage in MgH2. The dissociation and adsorption time of hydrogen is related to the amount of K2MoO4. Generally speaking, the more K2MoO4, the faster the kinetic performance and the shorter the time used. According to the experimental results, the initial dehydrogenation temperature of MgH2 + 10 wt% K2MoO4 composite is 250 °C, which is about 110 °C lower than that of As-received MgH2. At 320 °C, almost all dehydrogenation was completed within 11 min. In the temperature rise hydrogen absorption test, the composite system can start to absorb hydrogen at about 70 °C. At 200 °C and 3 MPa hydrogen pressure, 5.5 wt% H2 can be absorbed within 20 min. In addition, the activation energy of hydrogen absorption and dehydrogenation of the composite system decreased by 14.8 kJ/mol and 26.54 kJ/mol, respectively, compared to pure MgH2. In the cycle-stability test of the composite system, the hydrogen storage capacity of MgH2 can still reach more than 92% after the end of the 10th cycle, and the hydrogen storage capacity only decreases by about 0.49 wt%. The synergistic effect among the new species MgO, MgMo2O7, and KH generated in situ during the reaction may help to enhance the absorption and dissociation of H2 on the Mg/MgH2 surface and improve the kinetics of MgH2 for absorption and dehydrogenation.
In this study, the Ni/NiO catalyst was demonstrated to enhance the hydrogen storage performance of MgH2. The dehydrogenation of MgH2+10 wt% Ni/NiO started at approximately 180 °C, achieving 5.83 wt% ...of dehydrogenation within 10 min at 300 °C. Completely dehydrogenated, MgH2 began to rehydrogenate at about 50 °C, absorbing about 4.56 wt% of hydrogen in 10 min at 150 °C. In addition, the activation energies of dehydrogenation and rehydrogenation of MgH2+10 wt% Ni/NiO were 87.21 and 34.84 kJ/mol. During the dehydrogenation/rehydrogenation cycle, Mg2Ni/Mg2NiH4 could promote hydrogen diffusion, thus enhancing the hydrogen storage performance of Mg/MgH2.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Magnesium hydride (MgH2) is considered to be one of the most promising hydrogen storage materials owing to its safety profile, low cost and high hydrogen storage capacity. However, its slow kinetic ...performance and thermal stability limit the possibility of practical applications. Herein, it is confirmed that the hydrogen storage performance of MgH2 can be effectively improved via doping with a flake Ni nano-catalyst. According to experimental results, a MgH2 + 5 wt% Ni composite begins to dehydrogenate at almost 180 °C and could dehydrogenate 6.7 wt% within 3 min at 300 °C. After complete dehydrogenation, hydrogen can be absorbed below 50 °C, and 4.6 wt% H2 can be absorbed at 125 °C within 20 min at a hydrogen pressure of 3 MPa. In addition, the activation energies of MgH2 hydrogen absorption and dehydrogenation decreased by 28.03 and 71 kJ mol−1, respectively. Cycling stability testing showed that the hydrogen storage capacity decreases significantly in the first few cycles and decreases slightly after 10 cycles. Furthermore, it was found that Mg2Ni/Mg2NiH4 was formed initially during the hydrogen absorption or desorption reaction on the surface of Mg/MgH2, which acted as a “hydrogen pump”, accelerating the rates of hydrogen absorption and desorption.
The development of high-efficiency carbon-based multifunctional catalysts is of great significance for improving solid-state hydrogen storage materials. Herein, it was confirmed that CoMoO4 ...sheet-like nanocatalysts uniformly supported on the surface of reduced graphene oxide (CoMoO4/rGO) were successfully prepared by a simple hydrothermal reaction. The novel CoMoO4/rGO catalyst was subsequently doped into MgH2 to improve its hydrogen storage performance. MgH2–10 wt% CoMoO4/rGO starts to release hydrogen at around 204 °C, which is about 36 °C and 156 °C lower than that of MgH2 −10 wt%CoMoO4 and pure MgH2, respectively. In addition, 6.25 wt% H2 can be released within 10 min at 300 °C. After complete dehydrogenation, H2 can be absorbed below 80 °C. Meanwhile, it can absorb 4.2 wt% H2 in 20 min under the condition of 150 °C and 3 MPa. Moreover, the activation energy of hydrogen absorption and dehydrogenation of MgH2–10 wt%CoMoO4/rGO composites are reduced by 31.44 kJ mol−1 and 33.78 kJ mol−1, respectively, compared with pure MgH2. Cycling experiment shows that the MgH2–10 wt%CoMoO4/rGO composite system can still maintain about 98% of the hydrogen storage capacity after 10 cycles. Furthermore, studies on the catalytic mechanism show that the synergistic effect between the in-situ generated MgO, Co7Mo6 and Mo may help to promote the diffusion of H2, thereby improving the MgH2 Hydrogen storage properties.
•MgH2–10 wt%CoMoO4/rGO composite system was reported for the first time.•MgH2–10 wt%CoMoO4/rGO composite material starts dehydrogenation at about 204 °C.•MgH2–CoMoO4/rGO composites showed promising kinetic properties.•MgH2–CoMoO4/rGO composites showed good cyclic stability.•MgO, Mo and Co7Mo6 were formed in situ during the reaction.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
