H2 Sorption Research Articles

Innovative microkinetic modelling-supported structure–activity analysis of Ni/ZSM-5 during vapor-phase hydrogenation of levulinic acid

The study examines Ni/ZSM-5 catalysts in vapor phase hydrogenation of levulinic acid (LA) under continuous flow conditions (ambient pressure, 210–250 °C). Advanced characterization revealed the interplay between Al and Ni. This was further reinforced by new approach of microkinetic modeling, which demonstrates a pioneering work on mathematical description of pulse H2 sorption, TPD kinetics, DRIFT-supported determination of sorption energy barriers and (de)sorption kinetics. The Ni/ZSM-5 (3.7 wt.% Ni, Si/Al = 28) emerged as the optimal choice for obtaining γ-valerolactone (GVL) as the desired product. Al-rich catalysts with high acid site amounts and low metallic Ni active site concentrations favored esterification, reducing hydrogenation activity, and impeding further hydrogenation of GVL to pentanoic/valeric acid (PA). To enhance PA formation, Ni/ZSM-5 (4 wt.% Ni, Si/Al = 750) with a high Si/Al ratio, was identified as crucial. The combination of described experiments and modelling is demonstrated beneficial for insightful investigation of the structure–activity relationship of Ni/ZSM-5 or any other mono/bi-functional catalysts.

Catalysis/sorption enhanced pyrolysis-gasification of biomass for H2-rich gas production: Effects of various nickel-based catalysts addition and the combination with calcined dolomite

The effects of addition of various Ni-based catalysts and their combination with calcined dolomite on H2-rich gas production were investigated during catalysis/sorption enhanced pyrolysis-gasification of sawdust. It was found that catalyst support greatly affected the catalytic performance of Ni-based catalysts, the highest H2 concentration and yield was obtained by NiO/SiO2, followed by NiO/γ-Al2O3 and NiO/ZSM-5. Additional active sites on Ni-based catalyst would be formed by introduction of secondary metals onto NiO/γ-Al2O3. Positive synergistic effect between secondary metals and Ni was observed, especially for Mg and Co, resulting in further improved H2 production. Calcined dolomite was further introduced into the process to enhance H2 production, simultaneous catalysis and sorption was found to be better for H2 production than sequential catalysis and sorption. The addition of calcined dolomite could offset the catalytic performance difference for varied Ni-based catalysts due to its catalysis/sorption enhancing effect. Comparatively, bimetallic catalysts were more effective than monometallic catalysts when combined use with calcined dolomite, the H2 concentration was significantly improved despite of the slight changes in H2 yield. Ni-Cu/γ-Al2O3 and Ni-Zn/γ-Al2O3 with good performance on WGS reaction showed better synergistic effect with calcined dolomite, a highest H2 concentration of 87.06 vol.% was achieved by Ni-Cu/γ-Al2O3 catalyst.

Investigation of the Dynamic Behaviour of H2 and D2 in a Kinetic Quantum Sieving System.

Porous organic cages (POCs) are nanoporous materials composed of discrete molecular units that have uniformly distributed functional pores. The intrinsic porosity of these structures can be tuned accurately at the nanoscale by altering the size of the porous molecules, particularly to an optimal size of 3.6 Å, to harness the kinetic quantum sieving effect. Previous research on POCs for isotope separation has predominantly centered on differences in the quantities of adsorbed isotopes. However, nuclear quantum effects also contribute significantly to the dynamics of the sorption process, offering additional opportunities for separating H2 and D2 at practical operational temperatures. In this study, our investigations into H2 and D2 sorption on POC samples revealed a higher uptake of D2 compared to that of H2 under identical conditions. We employed quasi-elastic neutron scattering to study the diffusion processes of D2 and H2 in the POCs across various temperature and pressure ranges. Additionally, neutron Compton scattering was utilized to measure the values of the nuclear zero-point energy of individual isotopic species in D2 and H2. The results indicate that the diffusion coefficient of D2 is approximately one-sixth that of H2 in the POC due to the nuclear quantum effect. Furthermore, the results reveal that at 77 K, D2 has longer residence times compared to H2 when moving from pore to pore. Consequently, using the kinetic difference of H2 and D2 in a porous POC system enables hydrogen isotope separation using a temperature or pressure swing system at around liquid nitrogen temperatures.

Novel fluorinated MOFs with hydrophobic properties

Novel fluorinated lanthanide-based metal–organic frameworks (Ln-F-MOFs) constructed from the 3,3′-difluorobiphenyl-4,4′-dicarboxylic acid as a ligand (H2L) and M(III) metal ions (M(III) = Dy for UPJS-18(Dy), Tb for UPJS-18(Tb), Ho for UPJS-18(Ho), Er for UPJS-18(Er), Eu for UPJS-19(Eu), UPJS = materials prepared at the University of Pavol Jozef Safárik in Košice) have been successfully synthesized under solvothermal conditions leading to a series of MOFs with the same basic formula and the composition {[M2(L)3(DMF)2]∙xDMF·yH2O}n. Structural analyses revealed that complexes UPJS-18(Dy), UPJS-18(Tb), UPJS-18(Ho), UPJS-18(Er) are isostructural while complex UPJS-19(Eu) has different but a very similar structural motif. These complexes show high surface hydrophobicity with “rose petal effect”, thermal stability up to 300 °C and photoluminescence properties determined the characteristic f-f transitions for the individual metal ions. The porosity of some activated coordination polymers was studied by N2, CO2 and H2 adsorption, with the highest N2 and CO2 adsorption capacities observed for the UPJS-18(Dy) complex. Moreover, the H2 sorption capacity was determined for UPJS-19(Eu). The high water-repelling properties and thermal stability predetermines these materials for industrial as well as everyday-life use, while channels lined with fluorine atoms with their high affinity to fluorinated compounds predetermine the possibility of further investigations in the field of sorption fluorinated waste or fluorinated drugs.

A Porous Crystalline Nitrone-Linked Covalent Organic Framework.

Herein, we report the synthesis of a nitrone-linked covalent organic framework, COF-115, by combining N, N', N', N'''-(ethene-1, 1, 2, 2-tetrayltetrakis(benzene-4, 1-diyl))tetrakis(hydroxylamine) and terephthaladehyde via a polycondensation reaction. The formation of the nitrone functionality was confirmed by solid-state 13 C multi cross-polarization magic angle spinning NMR spectroscopy of the 13 C-isotope-labeled COF-115 and Fourier-transform infrared spectroscopy. The permanent porosity of COF-115 was evaluated through low-pressure N2 , CO2 , and H2 sorption experiments. Water vapor and carbon dioxide sorption analysis of COF-115 and the isoreticular imine-linked COF indicated a superior potential of N-oxide-based porous materials for atmospheric water harvesting and CO2 capture applications. Density functional theory calculations provided valuable insights into the difference between the adsorption properties of these COFs. Lastly, photoinduced rearrangement of COF-115 to the associated amide-linked material was successfully demonstrated.

A Porous Crystalline Nitrone‐Linked Covalent Organic Framework**

AbstractHerein, we report the synthesis of a nitrone‐linked covalent organic framework, COF‐115, by combining N, N′, N′, N′′′‐(ethene‐1, 1, 2, 2‐tetrayltetrakis(benzene‐4, 1‐diyl))tetrakis(hydroxylamine) and terephthaladehyde via a polycondensation reaction. The formation of the nitrone functionality was confirmed by solid‐state 13C multi cross‐polarization magic angle spinning NMR spectroscopy of the 13C‐isotope‐labeled COF‐115 and Fourier‐transform infrared spectroscopy. The permanent porosity of COF‐115 was evaluated through low‐pressure N2, CO2, and H2 sorption experiments. Water vapor and carbon dioxide sorption analysis of COF‐115 and the isoreticular imine‐linked COF indicated a superior potential of N‐oxide‐based porous materials for atmospheric water harvesting and CO2 capture applications. Density functional theory calculations provided valuable insights into the difference between the adsorption properties of these COFs. Lastly, photoinduced rearrangement of COF‐115 to the associated amide‐linked material was successfully demonstrated.

Achievement in modifying dehydrogenation kinetics for Sc-containing Mg matrix in Mg–Y–Zn alloy

To eliminate the adverse effects of coarse α-Mg phase on the hydrogen storage kinetics of Mg-rich alloys, element Sc with high solid solubility in α-Mg is introduced into Mg–Y–Zn alloy initiatively, which shows positive effects to enhance the hydrogen storage performance. The Sc-doping effectively enhances the dehydrogenation kinetics by motivating the formation of abundant stacking faults. The stacking faults provide the hydrogen atoms with diffusion channels to accelerate the mutual phase transformation of metal/hydride. With 1 at.% Sc substituting for Y, the apparent activation energy for dehydrogenation obtains a 11% reduction compared with Sc-free alloy. Besides, Sc-doping facilities the decomposition of YH3, which provides “electron transfer” effect to accelerate the decomposition of MgH2. Sc-doping affects the hydrogenation behavior by weakening the H2 sorption but ensuring the H atoms diffusion in Mg matrix. With the gradually substitution of Sc for Y, the developed dendrite arms make it difficult for hydrogen to diffuse deeper into the samples, resulting in large ratio of unhydrided Mg. It can be concluded that the quantity of defects within Mg and catalytic sites outside the Mg matrix are important for achieving rapid hydrogen absorption and desorption simultaneously.

Bulk-Processed Plasmonic Plastic Nanocomposite Materials for Optical Hydrogen Detection.

ConspectusSensors are ubiquitous, and their importance is only going to increase across many areas of modern technology. In this respect, hydrogen gas (H2) sensors are no exception since they allow mitigation of the inherent safety risks associated with mixtures of H2 and air. The deployment of H2 technologies is rapidly accelerating in emerging energy, transport, and green steel-making sectors, where not only safety but also process monitoring sensors are in high demand. To meet this demand, cost-effective and scalable routes for mass production of sensing materials are required. Here, the state-of-the-art often resorts to processes derived from the microelectronics industry where surface-based micro- and nanofabrication are the methods of choice and where (H2) sensor manufacturing is no exception.In this Account, we discuss how our recent efforts to develop sensors based on plasmonic plastics may complement the current state-of-the-art. We explore a new H2 sensor paradigm, established through a series of recent publications, that combines (i) the plasmonic optical H2 detection principle and (ii) bulk-processed nanocomposite materials. In particular, plasmonic plastic nanocomposite sensing materials are described that comprise plasmonic H2-sensitive colloidally synthesized nanoparticles dispersed in a polymer matrix and enable the additive manufacturing of H2 sensors in a cost-effective and scalable way. We first discuss the concept of plasmonic plastic nanocomposite materials for the additive manufacturing of an active plasmonic sensing material on the basis of the three key components that require individual and concerted optimization: (i) the plasmonic sensing metal nanoparticles, (ii) the surfactant/stabilizer molecules on the nanoparticle surface from colloidal synthesis, and (iii) the polymer matrix. We then introduce the working principle of plasmonic H2 detection, which relies on the selective absorption of H species into hydride-forming metal nanoparticles that, in turn, induces distinct changes in their optical plasmonic signature in proportion to the H2 concentration in the local atmosphere. Subsequently, we assess the roles of the key components of a plasmonic plastic for H2 sensing, where we have established that (i) alloying Pd with Au and Cu eliminates hysteresis and introduces intrinsic deactivation resistance at ambient conditions, (ii) surfactant/stabilizer molecules can significantly accelerate and decelerate H2 sorption and thus sensor response, and (iii) polymer coatings accelerate sensor response, reduce the limit of detection (LoD), and enable molecular filtering for sensor operation in chemically challenging environments. Based on these insights, we discuss the rational development and detailed characterization of bulk-processed plasmonic plastics based on glassy and fluorinated matrix polymers and on tailored flow-chemistry-based synthesis of Pd and PdAu alloy colloidal nanoparticles with optimized stabilizer molecules. In their champion implementation, they enable highly stable H2 sensors with response times in the 2 s range and an LoD of few 10 ppm of H2. To put plasmonic plastics in a wider perspective, we also report their implementation using different polymer matrix materials that can be used for 3D printing and (an)isotropic Au nanoparticles that enable the manufacturing of macroscopic plasmonic objects with, if required, dichroic optical properties and in amounts that can be readily upscaled. We advertise that melt processing of plasmonic plastic nanocomposites is a viable route toward the realization of plasmonic objects and sensors, produced by scalable colloidal synthesis and additive manufacturing techniques.

Overcoming the Trade-Off between C2 H2 Sorption and Separation Performance by Regulating Metal-Alkyne Chemical Interaction in Metal-Organic Frameworks.

Designing porous materials for C2 H2 purification and safe storage is essential research for industrial utilization. We emphatically regulate the metal-alkyne interaction of PdII and PtII on C2 H2 sorption and C2 H2 /CO2 separation in two isostructural NbO metal-organic frameworks (MOFs), Pd/Cu-PDA and Pt/Cu-PDA. The experimental investigations and systematic theoretical calculations reveal that PdII in Pd/Cu-PDA undergoes spontaneous chemical reaction with C2 H2 , leading to irreversible structural collapse and loss of C2 H2 /CO2 sorption and separation. Contrarily, PtII in Pt/Cu-PDA shows strong di-σ bond interaction with C2 H2 to form specific π-complexation, contributing to high C2 H2 capture (28.7 cm3 g-1 at 0.01 bar and 153 cm3 g-1 at 1 bar). The reusable Pt/Cu-PDA efficiently separates C2 H2 from C2 H2 /CO2 mixtures with satisfying selectivity and C2 H2 capacity (37 min g-1 ). This research provides valuable insight into designing high-performance MOFs for gas sorption and separation.

Experimental investigation on sorption performance of new high–efficiency, inexpensive H2 getters in high–vacuum, variable density–multilayer insulated hydrogen storage equipment

Hydrogen (H2) is released by the manufactured materials, which results in the deterioration of the insulation performance of liquid hydrogen (LH2) storage tanks. The getter is found in the vacuum annular space of equipment and helps maintain the high vacuum of LH2 tanks. Palladium oxide (PdO), an effective H2 getter, is expensive, resource–constrained and unsuitable for the LH2 equipment. Therefore, suitable and inexpensive alternatives were examined using LH2 storage tanks, to maintain the insulation property of the high–vacuum variable–density multilayer insulation (VDMLI) equipment better. Eight types of H2 getters were designed using in the LH2 tanks, and classified into three categories, namely, chemical, physical and physico–chemical getters (PCNHG). The sorption performance of new H2 getters was compared with that of PdO. PdO could be replaced by in the 7:1, 5:1 and 4:1 ratio by PCNHG1, PCNHG2 and CNHG in the LH2 tanks, respectively. The results demonstrated that the sorption capacity of PCNHG1 and PCNHG2 were 1.70 and 2.14 times that of the same type of getters in the market (16.35% and 20.62% higher than that of PdO, respectively). Their average H2 sorption efficiency was 1.17 times and 1.05 times of that of PdO, respectively. The minimum thermal conductivity exhibited by CNHG was only 6.34% of that of PdO, and the sorption capacity of CNHG was 1.82 and 1.44 times that of PCNHG1 and PCNHG2, respectively. However, the sorption capacities of PCNHG1, PCNHG2 and CNHG were belows that of PdO. These results help facilitate reduction in the expense of H2 getters and provide an important reference to enhance the sorption performance of getters.

Evaluation of a new lithium complex hydride: a derivative of BH4- and NH2- for fast Li-ion conduction and H2 sorption.

A new ternary complex hydride is synthesized by the interaction between Li2NH and LiBH4. The crystal structure of this new hydride is tentatively indexed using an orthorhombic cell with a space group of Pna21 and lattice parameters of a = 9.643 Å, b = 6.228 Å, and c = 5.563 Å. The Li2NH-2LiBH4 sample shows excellent hydrogenation properties with hydrogen absorption starting at near-ambient temperature (50 °C), which is more than 100 °C lower than that of pristine Li2NH. Furthermore, it attains 100% hydrogenation under isothermal conditions at 60 °C and 50 bar hydrogen pressure. Such superior low-temperature hydrogen absorption may be due to the formation of this new complex hydride. Interestingly, above 97 °C, the lithium-ion conductivity of this new hydride is higher than those of Li2NH and LiBH4 and reaches 10-2 S cm-1 at 114 °C. Meanwhile, the ionic conductivity of this new hydride is ∼30 times higher than that of LiBH4 reaching 10-5 S cm-1 at room temperature. The interaction between imides and borohydrides described in this work expands the options for strategic design of novel hydrogen storage materials and solid ionic conductors.

Graphene as a promising additive to hierarchically porous carbon monoliths for enhanced H2 and CO2 sorption

This study aimed to examine a synthesis of hierarchically porous carbon monoliths (HPCM) doped with graphene oxide (GO) for H2 and CO2 sorption applications. The synthesis procedure combining the sol-gel process with soft-templating was tuned by adding different quantities of GO (0.5; 2 and 10 wt% of the total amount of polycondensation mixture), as well as different carbonization temperatures (500 °C, 900 °C) of the composite materials during which the reduction of GO to graphene occurs. The degree of GO reduction to graphene and its incorporation into the HPCM matrix of prepared materials were characterized by Raman, FTIR, SEM, TEM, and elemental analysis. Although incorporation was successful, the higher pyrolysis temperature of 900 °C promotes the reduction of GO to graphene, which enhances the (ultra)microporosity (proven by gas physisorption experiments) of the samples, especially of the one with 10% GO addition. The effectivity of materials towards H2 and CO2 sorption was examined by sorption of H2 (77 K, up 1 bar) and CO2 (273 K, up 1 bar), respectively. Addition of any amount of GO together with the used lower pyrolysis temperature of 500 °C reduced the adsorption capacity of the samples for CO2 (from 2.4 to 1.8 mmol g−1) and H2 (from 5.8 to 3.6 mmol g−1) compared to the original HPCM. On the bright side, a 10% addition of GO in combination with a pyrolysis temperature of 900 °C results in industrially perspective material with an H2 and CO2 adsorption capacity of 9.6 mmol g−1 and 4.6 mmol g−1, respectively.

Ultramicroporous Carbon Nanofibrous Mats for Hydrogen Storage

Porous carbons with pore sizes in the ultramicropore range (0.6–0.7 nm) are of great interest for hydrogen storage, transportation, and application as a clean energy source. In particular, when they are nanomaterials, their high surface-to-volume ratio maximizes H2 adsorption capacity. Existing ultramicroporous carbon materials are often in powder form and obtained by environmentally hazardous processes. Here, two highly ultramicroporous, self-supporting, and nanostructured 2D carbonaceous materials with high H2 sorption capacity were developed from poly(vinyl alcohol) electrospun mats. The mats were stabilized by a heat treatment up to 195 °C, and subsequently, two strategies were followed: direct pyrolysis of the sample at 800 °C or application of an acidic activation treatment followed by pyrolysis. Both obtained materials showed high H2 adsorption capacity (6.48 and 11.47 mmol/g at 10 bar), similarly to or better than other materials reported in the literature, with the great advantage of being self-supporting. Moreover, both materials achieve complete desorption. Furthermore, the addition of the acidic activation enhances H2 adsorption capacity due to the greater ultramicroporous volume. This work will allow the development of a new range of ultramicroporous carbon materials obtained from green polymeric nanofibers for H2 storage.

TiFe0.85Mn0.05 alloy produced at industrial level for a hydrogen storage plant

Moving from basic research to the implementation of hydrogen storage system based on metal hydride, the industrial production of the active material is fundamental. The alloy TiFe0.85Mn0.05 was selected as H2-carrier for a storage plant of about 50 kg of H2. In this work, a batch of 5 kg of TiFe0.85Mn0.05 alloy was synthesized at industrial level and characterized to determine the structure and phase abundance. The H2 sorption properties were investigated, performing studies on long-term cycling study and resistance to poisoning. The alloy absorbs and desorbs hydrogen between 25 bar and 1 bar at 55 °C, storing 1.0H2 wt.%, displaying fast kinetic, good resistance to gas impurities, and storage stability over 250 cycles. The industrial production promotes the formation of a passive layer and a high amount of secondary phases, observing differences in the H2 sorption behaviour compared to samples prepared at laboratory scale. This work highlights how hydrogen sorption properties of metal hydrides are strictly related to the synthesis method.

Catalytic role of binary oxides (CuO and Al2O3) on hydrogen storage in MgH2

AbstractHydrogen sorption characteristics of magnesium hydride (MgH2) were enhanced by ball milling for 12 h under an inert atmosphere with the addition of 20 wt% Al2O3 and as prepared CuO. X‐ray diffraction (XRD) characterization and thermal gravimetric analyzer coupled with a mass spectrometer (TGA‐MS) of the ball milled samples were carried out to determine the H2 sorption reactions. Additionally, XRD data were analyzed using Rietveld method to identify the crystallographic properties. Ball milled MgH2 with β and γ allotrope mixtures were found with broad peaks in XRD indicating the as prepared samples are amorphous and strain, alongside bare additives. H2 sorption in MgH2 is greatly enhanced by the presence of CuO and Al2O3 binary oxides. TGA experiment demonstrated fast desorption kinetics for ball milled samples with the oxide additives. Particularly, MgH2 milled with CuO showed a more remarkable effect on desorption kinetics rather than Al2O3. It takes less than 10 min to desorb more than 5 wt% H2 at 623 K. The activation energy of H2 desorption was estimated for the mixtures by Kissinger method and the lowest value (65 kJ mol−1) was obtained for the MgH2/CuO mixture. A kinetic model has been proposed in the context to illustrate the complex mechanism of dehydrogenation of MgH2 with the additives. Finally, the addition of metal oxides influences H2 sorption characteristics of MgH2 through lowering the activation energy and reducing the waste of energy for diffusing the thin layer of Mg that creates a pathway to store H2 within the system.

Intercalation optimized hexagonal boron nitride nanosheets for high efficiency hydrogen storage

Atomic doping or polymer grafting can significantly improve the hydrogen sorption performance of hexagonal boron nitride (h-BN) based materials. Herein, this paper reported h-BN nanosheets grafting degradable L-polylactic acid (PLLA) and h-BN nanosheets doping nickel nanoparticles (Ni NPs) for high efficiency hydrogen storage. Firstly, h-BN material was treated by sodium hydroxide solution, which the electronegativity B atom connected with –OH covalently and h-BN nanosheets would disperse uniformly. Then, Ni-h-BN powder would be achieved by calcining the mixture of Ni precursor and h-BN at 600 °C. PLLA-h-BN film would be achieved by PLLA composite alkali modified h-BN, so that the long molecular chains of PLLA were grafted to h-BN nanosheets. The experiment found h-BN nanosheets dope trace Ni and h-BN nanosheets graft PLLA would improve H2 sorption ability of h-BN by adjusting electron structure and expanding interlayer space of h-BN, simultaneously. The test indicted Ni-h-BN has H2 storage capacity of 7.3 wt%, PLLA-h-BN has H2 storage capacity of 6.1 wt% at room temperature and 15 bar, these h-BN materials exhibited an optimistic hydrogen storage performance than h-BN materials previously reported in literature. This work has provided effective strategy for the development of efficient hydrogen storage materials.

Impact of Polymers on Magnesium-Based Hydrogen Storage Systems.

In the present scenario, much importance has been provided to hydrogen energy systems (HES) in the energy sector because of their clean and green behavior during utilization. The developments of novel techniques and materials have focused on overcoming the practical difficulties in the HES (production, storage and utilization). Comparatively, considerable attention needs to be provided in the hydrogen storage systems (HSS) because of physical-based storage (compressed gas, cold/cryo compressed and liquid) issues such as low gravimetric/volumetric density, storage conditions/parameters and safety. In material-based HSS, a high amount of hydrogen can be effectively stored in materials via physical or chemical bonds. In different hydride materials, Mg-based hydrides (Mg–H) showed considerable benefits such as low density, hydrogen uptake and reversibility. However, the inferior sorption kinetics and severe oxidation/contamination at exposure to air limit its benefits. There are numerous kinds of efforts, like the inclusion of catalysts that have been made for Mg–H to alter the thermodynamic-related issues. Still, those efforts do not overcome the oxidation/contamination-related issues. The developments of Mg–H encapsulated by gas-selective polymers can effectively and positively influence hydrogen sorption kinetics and prevent the Mg–H from contaminating (air and moisture). In this review, the impact of different polymers (carboxymethyl cellulose, polystyrene, polyimide, polypyrrole, polyvinylpyrrolidone, polyvinylidene fluoride, polymethylpentene, and poly(methyl methacrylate)) with Mg–H systems has been systematically reviewed. In polymer-encapsulated Mg–H, the polymers act as a barrier for the reaction between Mg–H and O2/H2O, selectively allowing the H2 gas and preventing the aggregation of hydride nanoparticles. Thus, the H2 uptake amount and sorption kinetics improved considerably in Mg–H.

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.

Graphene as a Promising Additive to Hierarchically Porous Carbon Monoliths for Enhanced H2 and Co2 Sorption

Graphene as a Promising Additive to Hierarchically Porous Carbon Monoliths for Enhanced H2 and Co2 Sorption

Sorption properties of novel-fashioned low-cost hydrogen getters in a high-vacuum-multilayer insulation structure

In a high-vacuum-multilayer insulation structure (HVMLIS), H2 is released into the vacuum jacket by manufactured materials, resulting in the deterioration of the insulation vacuum. Palladium oxide (PdO), which is expensive, is typically used as an H2 getter in HVMLIS. However, PdO generates sparks by vigorously reacting with H2, which are a potential threat to HVMLIS. Therefore, in this work, silver-exchanged zeolite is optimised to obtain an inexpensive and safe Ag–Z getter and a silver molecular sieve (SMS) together with a low-temperature active material getter (AMG). Moreover, an experimental platform was designed to test the H2 sorption properties of the three getters and compare them with traditional PdO. The experiment revealed that the cumulative sorption capacities of PdO, Ag–Z, SMS and AMG were 184.8, 63.1, 124.9 and 5.28 mL/g, respectively. However, the costs of SMS, Ag–Z and AMG were only ~7.37%, 5.08% and 6.13% of the cost of PdO, respectively, indicating that SMS is a promising alternative to PdO, which is expensive. Simultaneously, the microstructure of the H2 getters was analysed via X-ray powder diffraction. Further, PdH0.706 and Pd2H1.5 were obtained in addition to Pd, after H2 was absorbed by PdO. Ag+ was reduced to Ag in SMS, and Cu8O was produced by the reaction of CuO in AMG. These findings provide a basis for the subsequent optimisation of the H2 getters.