Solid-state Hydrogen Storage Research Articles

Nanoconfinement of lithium alanate for hydrogen storage

LiAlH4 is considered as a promising material for solid state hydrogen storage. However, the lack of reversibility along with sluggish kinetics hinders its practical application. In this paper, hollow carbon nanospheres (HCNs) were used as a porous scaffold to confine LiAlH4 via solvent impregnation method. Nanoconfined LiAlH4 (LiAlH4@HCNs) exhibited significant improvements in hydrogen sorption compared to its bulk counterpart. LiAlH4@HCNs releases hydrogen sharply at 146 °C with full conversion to LiH within 1.5 h. The desorbed material can also be regenerated back to some extent into LiAlH4 under 8 MPa H2 at 150 °C. Measurement of the pressure-composition isotherm suggests an alteration in the equilibrium state upon confinement of LiAlH4 in voids of a few nanometres and thus altered hydrogen thermodynamic paths.

Recent advance of metal borohydrides for hydrogen storage.

Hydrogen energy is an excellent carrier for connecting various renewable energy sources and has many advantages. However, hydrogen is flammable and explosive, and its density is low and easy to escape, which brings inconvenience to the storage and transportation of hydrogen. Therefore, hydrogen storage technology has become one of the key steps in the application of hydrogen energy. Solid-state hydrogen storage method has a very high volumetric hydrogen density compared to the traditional compressed hydrogen method. The main issue of solid-state hydrogen storage method is the development of advanced hydrogen storage materials. Metal borohydrides have very high hydrogen density and have received much attention over the past two decades. However, high hydrogen sorption temperature, slow kinetics, and poor reversibility still severely restrict its practical applications. This paper mainly discusses the research progress and problems to be solved of metal borohydride hydrogen storage materials for solid-state hydrogen storage.

High capacity hydrogen storage on zirconium decorated γ-graphyne: A systematic first-principles study

In this work, we investigate the hydrogen-storage properties of Zr-decorated γ-graphyne monolayer employing Density Functional Theory (DFT) for green energy storage. We predict that each Zr atom decorated on graphyne sheet (2D) can adsorb up to seven H2 molecules with an average adsorption energy of −0.44 eV/H2, leading to a hydrogen gravimetric density of 7.95 wt%, and desorption temperature of 574 K, particularly suited to fuel-cell applications. Decorated Zr atom strongly attached to graphyne due to charge transfer from Zr to graphyne sheet. Hydrogen molecules adsorb on Zr decorated graphyne due to Kubas type of interactions. The 4.05 eV diffusion energy barrier for the movement of Zr atoms may avoid the metal-metal (Zr–Zr) clustering. The stability of Zr+γ-graphyne is confirmed by performing ab-initio molecular dynamics simulations at room temperature and at estimated average desorption temperature. Hence, our calculations show that Zr functionalized on γ-graphyne could be a promising solid-state hydrogen storage material.

Performance of solid state hydrogen storage assisted standalone polygeneration microgrids for various climatic zones of India

In stand-alone microgrids, by employing hydrogen storage coupled with fuel cell, multiple outputs such as electricity, heat, water, and fuel, can be achieved. This study presents an approach to optimize the size of different components of a solar photovoltaic field based microgrid configured with electrolyzer, fuel cell, hydrogen storage and battery bank. The optimum configuration is based on maximizing the utilization of electricity produced by the solar photovoltaic field. Two performance parameters, namely, Unmet Electric Load (fUL) and Excess Electricity (fEX) are defined. The monthly and annual performance of the microgrid is studied for diverse climatic conditions with five climatic zones across six Indian locations as example. As is obvious, the polygeneration microgrid gives the best performance at mountainous zone due to abundant solar radiation. The thermal effects due to sorption and desorption reactions of metal hydride hydrogen storage and fuel cell exhaust provide more than 50% of thermal load in each zone. Even though the optimized configuration can serve the electrical load demand of the different zones, the benefits of polygeneration are more pronounced for mountainous, humid subtropical and arid climatic zones, in that order.

Nanoscale microstructures and novel hydrogen storage performance of as cast V47Fe11Ti30Cr10RE2 (RE = La, Ce, Y, Sc) medium entropy alloys

As classical BCC structure solid state hydrogen storage materials, vanadium-based solid solution alloys occupied a prominent position in the field of hydrogen storage materials due to their significant advantages such as the ability to absorb and desorb hydrogen with high capacity under moderate conditions. In this paper, RE-containing medium entropy BCC solid solution alloys were designed. The microstructure, phase composition and hydrogen storage properties of the medium entropy alloys were systematically studied. Microstructural analysis showed that nanoscale crystals were found in as-cast medium entropy alloys obtained by arc melting followed by natural cooling inside the furnace. This is different from the vanadium-based alloys that are often regarded as traditional coarse-grained alloys in the past decades. The V 47 Fe 11 Ti 30 Cr 10 RE 2 alloys can be fully activated by one cycle of hydrogen ab/de-sorption after pretreatment. The kinetic test shows that the time required for the as-cast RE-containing medium entropy alloys hydrogen uptake to 90% saturation is less than 100 s at room temperature. The alloys exhibit very excellent hydrogen absorption kinetic properties than reported alloys takes at least about 300 s. This is due to the fact that the present alloys are composed of nanocrystals with numerous interfaces and grain boundaries, and these defects can act as good channels for the diffusion of hydrogen atoms. The V 47 Fe 11 Ti 30 Cr 10 Y 2 alloy exhibits a maximum capacity of 3.41 wt% at 295 K. The thermodynamics of hydrogen ab/de-sorption and the hydrogen desorption under non-isothermal conditions were also studied in detail. • Nanoscale crystals were found in as cast RE-containing medium entropy BCC solid solution alloys prepared by arc melting. • The alloys have numerous interfaces and grain boundaries. • The time required for the alloys hydrogen uptake to 90% saturation is less than 100 s.

Achieve high-efficiency hydrogen storage of MgH2 catalyzed by nanosheets CoMoO4 and rGO

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 CoMoO 4 sheet-like nanocatalysts uniformly supported on the surface of reduced graphene oxide (CoMoO 4 /rGO) were successfully prepared by a simple hydrothermal reaction . The novel CoMoO 4 /rGO catalyst was subsequently doped into MgH 2 to improve its hydrogen storage performance. MgH 2 –10 wt% CoMoO 4 /rGO starts to release hydrogen at around 204 °C, which is about 36 °C and 156 °C lower than that of MgH 2 −10 wt%CoMoO 4 and pure MgH 2 , respectively. In addition, 6.25 wt% H 2 can be released within 10 min at 300 °C. After complete dehydrogenation , H 2 can be absorbed below 80 °C. Meanwhile, it can absorb 4.2 wt% H 2 in 20 min under the condition of 150 °C and 3 MPa. Moreover, the activation energy of hydrogen absorption and dehydrogenation of MgH 2 –10 wt%CoMoO 4 /rGO composites are reduced by 31.44 kJ mol −1 and 33.78 kJ mol −1 , respectively, compared with pure MgH 2 . Cycling experiment shows that the MgH 2 –10 wt%CoMoO 4 /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, Co 7 Mo 6 and Mo may help to promote the diffusion of H 2 , thereby improving the MgH 2 Hydrogen storage properties. • MgH 2 –10 wt%CoMoO 4 /rGO composite system was reported for the first time. • MgH 2 –10 wt%CoMoO 4 /rGO composite material starts dehydrogenation at about 204 °C. • MgH 2 –CoMoO 4 /rGO composites showed promising kinetic properties. • MgH 2 –CoMoO 4 /rGO composites showed good cyclic stability. • MgO, Mo and Co 7 Mo 6 were formed in situ during the reaction.

Performance and energy efficiency of a solid-state hydrogen storage system: An experimental study on La0.7Ce0.1Ca0.3Ni5

This study presents an experimental investigation conducted on an annular porous metal hydride reactor equipped with radial fins. The reactor was filled with 9 kg of La0.7Ce0.1Ca0.3Ni5, and water was considered as heat transfer fluid. The absorption characteristics were studied under different supply pressures (5–20 bar) and desorption characteristics under different inlet temperatures of heat transfer fluid (30–50 °C). An energy efficiency based on the higher heating value of hydrogen was evaluated for the developed solid-state hydrogen storage device. Further, the effect of pre-sensible heating on desorption performance and energy efficiency was analyzed. Finally, the experimental results were compared with the extensively studied LaNi5 alloy. The results showed that the alloy exhibited a constant desorption rate despite slower desorption kinetics. The energy efficiency of the developed system was found to be 76.76%. The comparison results showed that La0.7Ce0.1Ca0.3Ni5 exhibited higher storage capacity than LaNi5 after 20 cycles and approximately similar absorption and desorption rates. The desorption process without pre-sensible heating was more efficient and reduced overall desorption time by 46.5% than the desorption with pre-sensible heating. However, the desorption process without pre-sensible heating has not significantly affected the energy efficiency.

An Ab-initio study of the Y decorated 2D holey graphyne for hydrogen storage application

Expanding pollution and rapid consumption of natural reservoirs (gas, oil, and coal) led humankind to explore alternative energy fuels like hydrogen fuel. Solid-state hydrogen storage is most desirable because of its usefulness in the onboard vehicle. In this work, we explored the yttrium decorated ultra porous, two-dimensional holey-graphyne for hydrogen storage. Using the first principles density functional theory simulations, we predict that yttrium doped holey graphyne can adsorb up to seven hydrogen molecules per yttrium atom resulting in a gravimetric hydrogen weight percentage of 9.34, higher than the target of 6.5 wt% set by the US Department of Energy. The average binding energy per H2 and desorption temperature come out to be −0.34 eV and ∼438 K, respectively. Yttrium atom is bonded strongly on HGY sheet due to charge transfer from Y 4d orbital to C 2p orbital whereas the adsorption of H2 molecule on Y is due to Kubas-type of interactions involving charge donation from H 1s orbital to Y 3d orbital and back donation with net charge gain by H 1s orbital. Furthermore, sufficient energy barriers for the metal atom diffusion have been found to prevent the clustering of transition metal (yttrium) on HGY sheet. The stability of the system at higher temperatures is analyzed using Ab-initio molecular dynamics (AIMD) method, and the system is found to be stable at room and the highest desorption temperature. Stability of the system at higher temperatures, presence of adequate diffusion energy barrier to prevent metal–metal clustering, high gravimetric wt% of H2 uptake with suitable binding energy, and desorption temperature signifies that Y doped HGY is a promising material to fabricate high capacity hydrogen storage devices.

Significantly improved hydrogen storage properties of Mg90Al10 catalyzed by TiF3

Magnesium hydride (MgH 2 ) is one of the most promising materials for solid state hydrogen storage, but overly stable thermodynamics and sluggish kinetics of hydrogenation and dehydrogenation hinders its application. In this study, Mg 90 Al 10 was prepared by hydriding combustion synthesis (HCS), and then various Ti-based compounds (Ti, TiH 2 , TiO 2 and TiF 3 ) were introduced into Mg 90 Al 10 by ball milling. Mg 90 Al 10 + 10 wt% TiF 3 displays the most excellent dehydrogenation property compared with those doped with other Ti-based compounds. For instance, due to the addition of 10 wt% TiF 3 , the peak dehydrogenation temperature and the apparent dehydrogenation activation energy of the composite are 86 °C and 77.1 kJ/mol lower than those of Mg 90 Al 10 (364 °C and 155.95 kJ/mol). In addition, the catalytic effect of TiF 3 on the hydrogen storage properties of Mg 90 Al 10 has been investigated in detail. Except for the unreacted TiF 3 , Al 3 Ti and MgF 2 can be found during the first dehydrogenation process and remain stable in the subsequent de/hydrogenation cycles, which can act as the active sites to accelerate the hydrogen dissociation and recombination. Therefore, the excellent hydrogen storage properties of Mg 90 Al 10 + 10 wt% TiF 3 can be attributed to the catalytic effect of TiF 3 , in-situ formed Al 3 Ti and MgF 2 . Our result is very significant to emphasize the practical application of the Mg-Al hydrogen storage alloys. • The hydrogen storage property of Mg 90 Al 10 doped with TiF 3 is remarkably improved. • The onset dehydrogenation temperature is reduced to 175 °C after TiF 3 addition. • The Mg 90 Al 10 -TiF 3 shows superior hydrogenation/dehydrogenation cycling stability. • TiF 3 , the in-situ formed Al 3 Ti and MgF 2 exhibit excellent catalytic effect.

Microwave Plasma Enhancing Mg-Based Hydrogen Storage: Thermodynamics Evaluation and Economic Analysis of Coupling SOFC for Heat and Power Generation

Hydrogen, as a kind of green and efficient energy, plays an increasingly important role in current social development. Hydrogen storage technology is considered to be one of the main bottlenecks in limiting the large-scale application of hydrogen energy. The solid-state hydrogen storage technology based on Mg-based materials has received extensive attention due to its advantages of high hydrogen capacity, good reversibility, and low cost, but there are still shortcomings such as high reaction temperature, large energy consumption, and slow reaction kinetics. In order to solve these problems, this article proposes a new method of using microwave plasma to ionize hydrogen into H− ion. The possible activation mechanism of microwave plasma to improve the hydrogen storage properties is put forward. Based on the activation mechanism, the thermodynamic performance of Mg-based hydrogen storage is evaluated using density functional theory. It is concluded that the reaction temperature is significantly reduced from 339°C to 109°C with the help of microwave plasma. In addition, the comparison between the conventional heating hydrogen storage process based on MgH2 and microwave enhanced advanced hydrogen storage process based on MgH2 systems coupled with solid oxide fuel cells for heat and power generation is conducted to evaluate the economic feasibility. The results show that the energy consumption cost of the proposed microwave plasma enhancing hydrogen storage system is approximately 1.71 $/kgH2, which is about 50% of the energy consumption cost of the conventional system.

Simultaneous preparation of sodium borohydride and ammonia gas by ball milling

Hydrogen and ammonia are both potential energy carriers being considered for large scale energy transport. Sodium borohydride (NaBH4) has been widely applied as a potential solid-state hydrogen storage material. It can produce hydrogen gas and sodium metaborate (NaBO2) after hydrolysis with water at room temperature. The regeneration of NaBH4 from NaBO2 could significantly reduce the cost of NaBH4 and enable its wide-spread industrial use. In this work, we demonstrate a simple method for regenerating NaBH4 from NaBO2·4H2O using Mg2N3, which combines NaBH4 production with NH3 gas production in a single step at room temperature. NaBH4 is successfully synthesized from NaBO2·4H2O using the Mg3N2 reducing agent via ball milling under a hydrogen atmosphere. NaBH4 is formed at a 76.6% yield by planetary ball milling at 600 rpm under 40 bar hydrogen for 12 h. NH3 gas is also formed, which can be easily separated from the solid products. Therefore, this one-step process could produce two different types of carbon-free hydrogen carriers suitable for energy export from renewable sources.

Enhancing the dehydrogenation properties of LiAlH4 using K2NiF6 as additive

Lithium alanate (LiAlH4) is a material that can be potentially used for solid-state hydrogen storage due to its high hydrogen content (10.5 wt%). Nevertheless, a high desorption temperature, slow desorption kinetic, and irreversibility have restricted the application of LiAlH4 as a solid-state hydrogen storage material. Hence, to lower the decomposition temperature and to boost the dehydrogenation kinetic, in this study, we applied K2NiF6 as an additive to LiAlH4. The addition of K2NiF6 showed an excellent improvement of the LiAlH4 dehydrogenation properties. After adding 10 wt% K2NiF6, the initial decomposition temperature of LiAlH4 within the first two dehydrogenation steps was lowered to 90 °C and 156 °C, respectively, that is 50 °C and 27 °C lower than that of the аs-milled LiAlH4. In terms of dehydrogenation kinetics, the dehydrogenation rate of K2NiF6-doped LiAlH4 sample was significantly higher as compared to аs-milled LiAlH4. The K2NiF6-doped LiAlH4 sample can release 3.07 wt% hydrogen within 90 min, while the milled LiAlH4 merely release 0.19 wt% hydrogen during the same period. According to the Arrhenius plot, the apparent activation energies for the desorption process of K2NiF6-doped LiAlH4 are 75.0 kJ/mol for the first stage and 88.0 kJ/mol for the second stage. These activation energies are lower compared to the undoped LiAlH4. The morphology study showed that the LiAlH4 particles become smaller and less agglomerated when K2NiF6 is added. The in situ formation of new phases of AlNi and LiF during the dehydrogenation process, as well as a reduction in particle size, is believed to be essential contributors in improving the LiAlH4 dehydrogenation characteristics.

Remarkable catalysis of spinel ferrite XFe2O4 (X = Ni, Co, Mn, Cu, Zn) nanoparticles on the dehydrogenation properties of LiAlH4: An experimental and theoretical study

Safe, compact, lightweight and cost-effective hydrogen storage is one of the main challenges that need to be addressed to effectively deploy the hydrogen economy. LiAlH4, as a solid-state hydrogen storage material, presents several advantages such as high hydrogen storage capacity, low price and abundant sources. Unfortunately, neither thermodynamic nor kinetic properties of dehydrogenation for LiAlH4 can fulfill the requirements of practical application. Thus, a series of spinel ferrite nanoparticles such as XFe2O4 (X = Ni, Co, Mn, Cu, Zn, Fe) were prepared by using the modified thermal decomposition method, and then doped into LiAlH4 by using ball milling. Our results show that LiAlH4 doped with 7 wt% NiFe2O4 starts to release hydrogen at 69.1 °C, and the total amount of hydrogen released is 7.29 wt% before 300 °C. The activation energies of the two-step hydrogen release reactions of LiAlH4 doped with 7 wt% NiFe2O4 are 42.32 kJ mol−1 and 71.42 kJ mol−1, which are 59.0% and 63.6% lower than those of as-received LiAlH4, respectively. Combining the density functional theory (DFT) calculations, we reveal that both the presence of NiFe2O4 and in-situ formed Al4Ni3 in ball-milling decrease the desorption energy barrier of Al-H bonding in LiAlH4 and accelerate the breakdown of Al-H bonding through the interfacial charge transfer and the dehybridization of the Al-H cluster. Thus, the experimental and theoretical results open a new avenue toward designing high effective catalysts applied to LiAlH4 as a candidate for hydrogen storage.

Carbon-Based Sorbents for Hydrogen Storage: Challenges and Sustainability at Operating Conditions for Renewable Energy.

It is estimated that all fossil fuels will be depleted by 2060 if we continue to use them at the present rate. Therefore, there is an unmet need for an alternative source of energy with high calorific value. In this regard, hydrogen is considered the best alternative renewable fuel that could be used in practical conditions. Accordingly, researchers are looking for an ideal hydrogen storage system under ambient conditions for feasible applications. In many respects, carbon-based sorbents have emerged as the best possible hydrogen storage media. These carbon-based sorbents are cost-effective, eco-friendly, and readily available. In this Review, the present status of carbon-based materials in promoting solid-state hydrogen storage technologies at the operating temperature and pressure was reported. Experimental studies have shown that some carbon-based materials such as mesoporous graphene and doped carbon nanotubes may have hydrogen storage uptake of 3-7 wt %, while some theoretical studies have predicted up to 13.79 wt % of hydrogen uptake at ambient conditions. Also, it was found that different methods used for carbon materials synthesis played a vital role in hydrogen storage performance. Eventually, this Review will be helpful to the scientific community for finding the competent material and methodology to investigate the existing hydrogen uptake issues at operating conditions.

Na-modified cast hypo-eutectic Mg–Mg2Si alloys for solid-state hydrogen storage

Mg2Si is a promising catalyst for Mg-based H2 storage materials due to its low cost, light weight, and non-toxic properties. This study investigates the effects of Na in hypo-eutectic Mg-1wt.%Si alloys for H2 storage applications. The addition of trace amounts of Na is vital in improving the H2 sorption kinetics, achieving a H2 storage capacity of 6.72 wt.% H at 350 °C under 2 MPa H2, compared to 0.31 wt.% H in the non-Na added alloy. The hydrogen sorption mechanisms were analysed with Johnson-Mehl-Avrami-Kolmogorov models. It was identified that Na affects the surface of the Mg alloys, forming porous Na2O and NaOH in addition to MgO, facilitating the diffusion of H2. Finally, in-situ synchrotron powder X-ray diffraction showed the Mg2Si catalyst is stable during the H2 sorption reactions. This result demonstrates the potential use of Mg–Mg2Si casting alloys for large scale hydrogen storage and transportation applications.

Catalytical enhancement on hydrogen production from LiAlH4 by Fe–Fe2O3 addition

Hydrogen storage technology plays an important role on the development of hydrogen fuel cell and lithium aluminum hydride is a powerful candidate for solid-state hydrogen storage materials. However, the high stability and slow dehydrogenation kinetics of LiAlH4 hinder its application. In this paper, the two-step thermal decomposition properties of LiAlH4 with and without Fe–Fe2O3 catalysts are investigated. According to the master plots, the model of mample power law (Pn) and nucleation and growth (An) are the optimal mechanism functions for the two-step decomposition of LiAlH4, respectively. After doping catalysts, the activation energies decrease significantly. The theoretical and optimized kinetic method are consistent with each other on activation energy. And the latter can also yield other kinetic parameters for a more comprehensive kinetic modelling of LiAlH4 decomposition. Furthermore, Fe–Al2O3 and Fe–Al intermetallics generated during dehydrogenation might significantly improve the hydrogen release properties of LiAlH4.

Absorption based solid state hydrogen storage system: A review

To run a sustainable society, hydrogen is considered as one of the most reliable option for clean and carbon free energy carrier. Hydrogen can be produced through several means using renewable energy sources, and can be stored either in solid, liquid or gaseous state. Though, compressed and liquefied hydrogen storages are well-established technologies in the commercial sector, however, due to the leakage risk, boil-off losses and explosive nature, world is exploring a safer way of hydrogen storage i.e. absorption/adsorption based solid-state hydrogen storage technology. The present review focuses mainly on the different material options available for the absorption based solid state hydrogen storage technology. The study reports insight view of different absorption material, broadly classified as metal hydrides and complex hydrides, with their hydrogen storage and reversible characteristics. The review also reports the tailoring properties of different hydrogen storage alloys and effect of element substitution on the absorption/desorption characteristics of a particular alloy. Key issues like effect of ball milling, annealing, doping, grain size, etc., on the alloy synthesis have been addressed. The review broadly summarizes the progress and recent worldwide advancement in the absorption based solid state hydrogen storage materials, synthesis and their hydrogenation/dehydrogenation mechanisms.

Solid-State Hydrogen Storage Properties of Ti–V–Nb–Cr High-Entropy Alloys and the Associated Effects of Transitional Metals (M = Mn, Fe, Ni)

Recently, high-entropy alloys (HEAs) designed by the concepts of unique entropy-stabilized mechanisms, started to attract widespread interests for their hydrogen storage properties. HEAs with body-centered cubic (BCC) structures present a high potential for hydrogen storage due to the high hydrogen-to-metal ratio (up to H/M = 2) and vastness of compositions. Although many studies reported rapid absorption kinetics, the investigation of hydrogen desorption is missing, especially in BCC HEAs. We have investigated the crystal structure, microstructure and hydrogen storage performance of a series of HEAs in the Ti–V–Nb–Cr system. Three types of TiVCrNb HEAs (Ti4V3NbCr2, Ti3V3Nb2Cr2, Ti2V3Nb3Cr2) with close atomic radii and different valence electron concentrations (VECs) were designed with single BCC phase by CALPHAD method. The three alloys with fast hydrogen absorption kinetics reach the H/M ratio up to 2. Particularly, Ti4V3NbCr2 alloy shows the hydrogen storage capacity of 3.7 wt%, higher than other HEAs ever reported. The dehydrogenation activation energy of HEAs’ hydride has been proved to decrease with decreasing VEC, which may be due to the weakening of alloy atom and H atom. Moreover, Ti4V3NbCr2M (M = Mn, Fe, Ni) alloys were also synthesized to destabilize hydrides. The addition of Mn, Fe and Ni lead to precipitation of Laves phase, however, the kinetics did not improve further because of their own excellent hydrogen absorption. With increasing the content of Laves phase, there appear more pathways for hydrogen desorption so that the hydrides are more easily dissociated, which may provide new insights into how to achieve hydrogen desorption in BCC HEAs at room temperature.

Static and dynamic characterization of metal hydride tanks for energy management applications

In this paper, the dynamic and static characterization of commercial metal hydride tanks is developed based on black box modelling. The objective is to determine the thermodynamic parameters of the hydride, such as enthalpy and entropy, and then to perform an energy management of this hydrogen storage system coupled to a fuel cell generator. Therefore, for this study, a specific test bench was developed around two hydride tanks. The hydrogen temperature and pressure were measured as a function of time and used to evaluate the thermal energy produced and consumed, as well as the amount of hydrogen, stored and released, during the absorption and desorption process respectively. The analysis of the results allowed the determination of a number of parameters such as the maximum reversible hydrogen storage capacity, which was 100 [g] for each tank with a relative capacity of 0.8 [%], the equilibrium pressure between 1 and 4 [bar] for both processes (absorption/desorption) as well as the evaluation of the hysteresis. The black-box approach makes this characterization method suitable for any solid-state hydrogen storage system, regardless of metal hydride type, geometrical shape, and tank size.

Ultrafast hydrogenation of magnesium enabled by tetragonal ZrO2 hierarchical nanoparticles

Transition metal catalysts are particularly effective in improving the reaction kinetics of light metal hydrides for reversible hydrogen storage. Herein, tetragonal ZrO2 hierarchical nanoparticles (nano-ZrO2) composed of primary particles of ∼4 nm in diameter are successfully synthesized by a facile one-pot solvothermal process. The unique hierarchical structure features homogeneous distributions of in situ formed multivalent Zr-based species, which allow superior catalytic activity for hydrogen storage in MgH2. The MgH2+10 wt% nano-ZrO2 starts releasing H2 at 163 °C after one activation, which is 107 °C lower than additive-free MgH2, and 50 °C lower than that of bulk ZrO2-doped MgH2. At 230 °C, 5.9 wt% of H is rapidly liberated within 20 min from the nano-ZrO2-containing MgH2. More importantly, the material shows superior hydrogenation kinetics compared with all reported catalyst-modified MgH2. The nano-ZrO2-containing Mg took up 4.0 wt% of H in only 12 s at 100 °C under 50 bar H2, 400 times faster than the bulk-ZrO2-modified sample. Even at 50 °C, approximately 1.8 wt% H was absorbed within 1 min. Our findings provide useful insights into the design and development of high-performance catalysts toward solid-state hydrogen storage materials.