Room Temperature Hydrogen Storage Research Articles

Machine learning to explore high-entropy alloys with desired enthalpy for room-temperature hydrogen storage: Prediction of density functional theory and experimental data

Safe and high-density storage of hydrogen, for a clean-fuel economy, can be realized by hydride-forming materials, but these materials should be able to store hydrogen at room temperature. Some high-entropy alloys (HEAs) have recently been shown to reversibly store hydrogen at room temperature, but the design of HEAs with appropriate thermodynamics is still challenging. To explore HEAs with appropriate hydride formation enthalpy, this study employs machine learning (ML), in particular, Gaussian process regression (GPR) using four different kernels by training with 420 datum points collected from literature and curated here. The developed ML models are used to predict the formation enthalpy of hydrides for the TixZr2-xCrMnFeNi (x = 0.5, 1.0 and 1.5) system, which is not in the training set. The predicted values by ML are consistent with data from experiments and density functional theory (DFT). The present study thus introduces ML as a rapid and reliable approach for the design of HEAs with hydride formation enthalpies of −25 to −39 kJ/mol for hydrogen storage at room temperature.

Investigation of Anionic Metal–Organic Frameworks with Extra-Framework Cations for Room Temperature Hydrogen Storage

Investigation of Anionic Metal–Organic Frameworks with Extra-Framework Cations for Room Temperature Hydrogen Storage

Experimental and theoretical insights into vanadium-based alloys for room temperature hydrogen storage on the example of Ti16Cr22Zr5V55-xFe2Mnx (x=0–3) alloys

In this work, the microstructures and hydrogen storage properties of the Ti16Zr5Cr22V55-xFe2Mnx (x =0, 1, 2, 3) hydrogen storage alloys were comprehensively investigated toward application under ambient conditions. The X-ray diffraction (XRD) patterns and scanning electron microscopy (SEM) images of the alloys indicated that all of the alloys consist of a BCC main phase and a small amount of C14 Laves secondary phase. All of the studied alloys have a good activation performance and fast absorption/desorption kinetics at 298 K. The flatness of desorption plateau of alloy is improved by the tiny Mn introduction. With the increase of Mn content, the lattice parameter of BCC main phase, electron density and hydrogen absorption/desorption capacity decrease, and the desorption plateau pressure at 298 K increases in the range of 0.1–1 MPa. In addition, the essence of the dependence of high hydrogen capacity on electron density was revealed based on Fermi level. The Tilt, hysteresis, and width of plateau of PCT curve of vanadium-based alloys were clarified on the basis of Sievert's law. And a good quadratic fitting between desorption plateau pressure and Mn content was manifested.

Machine learning assisted design of BCC high entropy alloys for room temperature hydrogen storage

Body-centered cubic (BCC) alloy systems can theoretically store double amounts of hydrogen compared with commercial metal hydrides at room temperature, and BCC high entropy alloys (HEAs) have shown the potential to reach this theoretic limit. However, the high thermodynamic stability of the dihydrides formed during hydrogen storage results in high operating temperatures. Here, by employing multi-objective Bayesian optimization-aided density functional theory calculations, we discovered 8 new HEA candidates for hydrogen storage, including the VNbCrMoMn HEA that can store 2.83 wt% hydrogen at room temperature and atmospheric pressure, vastly exceeding the hydrogen capacities of 1.38 wt% and 1.91 wt% for commercial LaNi5H6 and TiFeH2. Such a high performance of VNbCrMoMn is ascribed to the optimized hydrogen absorption thermodynamics, which is achieved under the guidance of interpretable machine learning which revealed that the thermodynamics of the first and second stages of absorption are largely determined by the bulk modulus and the number of states in the d-band, respectively.

Mg-MOF-74 Derived Defective Framework for Hydrogen Storage at Above-Ambient Temperature Assisted by Pt Catalyst.

Metal-organic frameworks (MOFs) are promising candidates for room-temperature hydrogen storage materials after modification, thanks to their ability to chemisorb hydrogen. However, the hydrogen adsorption strength of these modified MOFs remains insufficient to meet the capacity and safety requirements of hydrogen storage systems. To address this challenge, a highly defective framework material known as de-MgMOF is prepared by gently annealing Mg-MOF-74. This material retains some of the crystal properties of the original Mg-MOF-74 and exhibits exceptional hydrogen storage capacity at above-ambient temperatures. The MgO5 knots around linker vacancies in de-MgMOF can adsorb a significant amount of dissociated and nondissociated hydrogen, with adsorption enthalpies ranging from -22.7 to -43.6kJmol-1, indicating a strong chemisorption interaction. By leveraging a spillover catalyst of Pt, the material achieves a reversible hydrogen storage capacity of 2.55wt.% at 160°C and 81bar. Additionally, this material offers rapid hydrogen uptake/release, stable cycling, and convenient storage capabilities. A comprehensive techno-economic analysis demonstrates that this material outperforms many other hydrogen storage materials at the system level for on-board applications.

Enhanced room-temperature hydrogen storage by CuNi nanoparticles decorated in metal-organic framework UiO-66(Zr)

This study demonstrates the significant effect of incorporating inexpensive transition metal nanoparticles into metal-organic frameworks (MOFs) to improve their room-temperature hydrogen storage properties. Low-cost nanoparticles (Cu, Ni, and CuNi) were incorporated into UiO-66(Zr) via the double-solvent approach (DSA) plus chemical reduction processes. All composites exhibited higher hydrogen storage capacity compared to pure UiO-66 at both room temperature and 60 bar. Notably, the hydrogen spillover efficiency of CuNi nanoparticles loaded in UiO-66 was comparable to that of MOF adsorbents embedded with noble metals such as Pd and Pt. The hydrogen storage capacity of CuNi@UiO-66 was significantly increased from 0.20 wt% to 0.74 wt%. DFT calculations showed that the CuNi alloys facilitated the adsorption and dissociation of hydrogen molecules in comparison to the single metal nanoparticles, thus favoring the hydrogen spillover effect and improving the hydrogen storage performance. This work demonstrates the potential of designing MOF loaded with inexpensive metal nanoparticles for optimized room-temperature hydrogen storage.

Development of AB2-type TiZrCrMnFeCoV intermetallic high-entropy alloy for reversible room-temperature hydrogen storage

Intermetallic high-entropy alloys (HEAs) with C14 Laves phase structure have shown promise as hydrogen storage materials due to their ability to maintain the advantages of the AB2-type hydrogen storage alloys while offering the potential for the improvement of hydrogen storage properties through the use of multi-principal elements. However, some intermetallic HEAs are limited in their ability to scale-up production using the low-cost induction melting method and reversible hydrogen storage at room temperature due to their extremely low equilibrium desorption pressure. In this work, intermetallic HEAs with reversible room-temperature hydrogen storage are designed using an empirical model based on calculation of the electronic and geometrical factors. An orthogonal experiment was conducted to optimize the composition and the optimal (Ti1.3Zr0.7)1.1Cr1.1Mn1.8Fe0.3Co0.4V0.4 HEA with a single C14 Laves phase was found to exhibit the best overall hydrogen performance. It can reversibly store 1.84 wt% hydrogen with a relatively low plateau hysteresis factor (0.71) and slope factor (0.89) at a temperature of 15 °C. The dehydrogenation enthalpy and entropy of the optimal HEA were determined to be 35.0 kJ mol−1 and 115.3 J mol−1 K−1, respectively. To reduce the cost of HEAs, FeV80 was employed to replace the V. It was found that the optimal HEA could be successfully scaled-up for production, and our findings demonstrate the potential of intermetallic HEAs for efficient hydrogen storage.

EDA/PANI derived FeNxC with Fe-Nx active sites as room temperature hydrogen storage material

FeNxC is explored as an efficient and cost-effective hydrogen storage material. Fe/Ethylenediamine (EDA) complex formed initially is protected by (Polyaniline) PANI polymer that gets converted to FeNxC through two-step pyrolysis process. In the first pyrolysis, (Iron sulfide) FeS particles are formed, which get converted to Fe3O4 nanoparticles in second pyrolysis. Fe-Nx active sites get exposed in micro/mesoporous carbon matrix after oxide removal through acid wash. Hydrogen adsorption studies are conducted at 25–100 °C temperature, 5–30 bar pressure. The maximum hydrogen storage capacity is observed as 2.83 wt% at 26 bar, 25 °C for the two-step calcined, acid-washed FeNxC-900–800 A, which possesses large surface area of 995 m2/g, pore volume of 0.711 cm3/g when compared to FeNxC-900–800 and FeNxC-900. The adsorption mechanism, spillover occurring at covalently bonded Fe-Nx active sites and subsequent migration, diffusion to get physisorbed within porous carbon surface, leads to the enhancement in the hydrogen adsorption.

(TiVZrNb)83Cr17 high-entropy alloy as catalyst for hydrogen storage in MgH2

High-entropy alloys (HEAs) hold the promise as excellent catalysts to improve the hydrogen storage properties of MgH2 due to their distinctive compositional and structural characteristics and superior room-temperature hydrogen storage performance. In this work, the (TiVZrNb)83Cr17 HEA was successfully designed and synthesized. Moreover, different amounts of the (TiVZrNb)83Cr17 HEA were introduced into MgH2 as catalysts by ball milling to prepare MgH2-x wt% (TiVZrNb)83Cr17 (x = 3, 6, 10) composites. MgH2-6 wt% (TiVZrNb)83Cr17 composite showed excellent hydrogen absorption and desorption properties. At 573 K, the composite can rapidly absorb 5.3 wt% H2 within 5 min, and even at 523 K, it can still absorb 4.0 wt% H2 within 60 min. Also, it can rapidly desorb 6.0 wt% and 4.1 wt% H2 within 60 min at 623 K and 573 K, respectively. In addition, the MgH2-6 wt% (TiVZrNb)83Cr17 composite possessed relatively low activation energy for hydrogen absorption (70.6 kJ/mol H2) and desorption (90.5 kJ/mol H2). Moreover, the capacity retention was as high as 98.5 % after 10 hydrogen de/absorption cycles at 573 K. Interestingly, (TiVZrNb)83Cr17 HEA transformed from the as-prepared biphasic structure (FCC + BCC) to the hydrogenated single-phase structure (FCC) in the hydrogenation process and returned to the initially biphasic structure (FCC + BCC) in the desorption process, which provided more diffusion pathways for H and more nucleation sites for Mg/MgH2. The multi-element (TiVZrNb)83Cr17 HEA catalyst realized the synergistic catalysis of the hydrogen ab/de-sorption of Mg/MgH2. Our findings provide useful insights into the design and development of HEAs catalysts for improving the hydrogen storage properties of MgH2.

Unveiling room temperature hydrogen storage in tubular graphitic carbon nitride with diverse morphologies

The 21st century stands as the hydrogen century, embodying profound possibilities for an economy driven by hydrogen. However, a main obstacle in realizing the hydrogen economy revolves around establishing a secure and efficient method for storing hydrogen. In this work, tubular graphitic carbon nitride (g-C3N4) was synthesized for the potential in hydrogen storage. The strategic fabrication of tubular g-C3N4 takes shape via three distinctive routes: hydrothermal, thermal condensation, and double calcination. Each pathway yields g-C3N4 with varying attributes such as surface area and size, thereby laying the groundwork for an intricate exploration and discussion of their hydrogen storage capabilities. Among the synthesized materials, those obtained through the hydrothermal route (H-g-C3N4) exhibited the most substantial dimensions, boasting an impressive length exceeding 10 µm. Conversely, both the thermal condensation-derived nanotubes (T-g-C3N4) and their double calcination counterparts (D-g-C3N4) displayed similar dimensions, with lengths hovering around 1 µm. It became evident that D-g-C3N4 exceeded the results of the other two samples in this aspect, showcasing an elevated BET surface area of 114.2 m2/g. In contrast, H-g-C3N4 and T- g-C3N4 demonstrated lower surface areas, registering at 59.3 and 70.2 m2/g. Regarding hydrogen storage, all samples were found to be able to adsorb and desorb hydrogen within 5 min. The hydrogen storage of the three distinct materials (H-g-C3N4, T-g-C3N4, and D-g-C3N4), as measured using a Sivert’s system under room temperature and 3.7 MPa, manifested as 0.68 wt%, 0.72 wt%, and 0.8 wt%, respectively. This observed variation in storage capacity potentially found a correlation with the distinctive morphologies of the three materials. Despite the current hydrogen storage capacities of these materials being below 1 wt%, their inherent potential remains considerable. Achieving further advancements in fabrication techniques to enhance nanotube purity and reduce their size holds the promise of substantially augmenting their capacity for hydrogen storage.

Significance of interphase boundaries on activation of high-entropy alloys for room-temperature hydrogen storage

The ability of high-entropy alloys (HEAs) for hydrogen storage is a rather new topic in the hydrogen community. HEAs with the C14 Laves phase have shown a high potential to reversibly store hydrogen at room temperature, but most of these alloys require a high-temperature activation treatment. This study explores the role of interphase boundaries on the easy activation of HEAs at room temperature. Two chemically similar HEAs with single and dual phases, TiV1.5ZrCr0.5MnFeNi (C14 + 4 vol% BCC phases) and TiV1.5Zr1.5CrMnFeNi (single C14 phase), are designed and synthesized. While the dual-phase alloy readily absorbs hydrogen at room temperature without any activation treatment, the single-phase alloy requires a high-temperature activation. It is suggested that interphase boundaries not only provide pathways for easy hydrogen transport and activation of HEAs at room temperature but also act as active sites for heterogeneous nucleation of hydride. This study introduces interphase-boundary generation as an effective strategy to address the activation drawback of HEAs.

ZIF-67 derived Co nanoparticles on ZIF-Derived carbon for hydrogen spillover and storage

Hydrogen spillover involves the dissociation of H2 on transition metal nanoparticles and further atomic hydrogen surface migration on catalyst supports. Hence, the spillover phenomenon has been reported in applications of heterogeneous catalysis in hydrogenation and room-temperature hydrogen storage. However, a proper catalyst design is requisite to initiate hydrogen spillover, considering the transition metal particle dispersion, sorbent surface modification, porosity, etc. In this report, we pyrolyzed the zeolitic imidazolate framework ZIF-67 for residual Co metal nanoparticles and N-dopant on ZIF-derived carbon (ZDC) for hydrogen adsorption via spillover effect. Catalyst optimization by proper ZIF carbonization process regarding manipulated pyrolytic temperatures, atmospheres, and ramping rates, results in different properties in ZDCs. Well-distributed Co nanoparticles can be obtained on N-rich graphitic sorbent ZDCs with retained high specific surface area. The Co on ZDC exhibits improved room-temperature hydrogen capacity of 0.77 wt% than neat ZIF-67 of 0.09 wt% at 30 bar, 300 K. The adsorption sites were examined experimentally by nitrogen hydrogenation, and possible atomic hydrogen diffusion was evaluated theoretically showing energy barrier reduced by over 0.1 eV. It demonstrates that cobalt nanoparticles can successfully initiate hydrogen spillover on ZIF-derived carbon with nitrogen functionality, even without noble metals.

Ultra-lightweight compositionally complex alloys with large ambient-temperature hydrogen storage capacity

In the burgeoning field of hydrogen energy, compositionally complex alloys promise unprecedented solid-state hydrogen storage applications. However, compositionally complex alloys are facing one main challenge: reducing alloy density and increasing hydrogen storage capacity. Here, we report TiMgLi-based compositionally complex alloys with ultralow alloy density and significant room-temperature hydrogen storage capacity. The record-low alloy density (2.83 g cm−3) is made possible by multi-principal-lightweight element alloying. Introducing multiple phases instead of a single phase facilitates obtaining a large hydrogen storage capacity (2.62 wt% at 50 °C under 100 bar of H2). The kinetic modeling results indicate that three-dimensional diffusion governs the hydrogenation reaction of the current compositionally complex alloys at 50 °C. The here proposed approach broadens the horizon for designing lightweight compositionally complex alloys for hydrogen storage purposes.

Synergistic effect of hydrogen spillover and nano-confined AlH3 on room temperature hydrogen storage in MOFs: By GCMC, DFT and experiments

In order to enhance the hydrogen storage capacity of Metal-Organic Frameworks (MOFs) under moderate conditions, a high-throughput screen was used to evaluate 7622 MOFs with a Pore Limit Diameter (PLD) greater than 2.89 Å and less than 10 Å. The hydrogen adsorption capacity at 25 °C and 1 bar was calculated using grand canonical Monte Carlo (GCMC) to comprehensively evaluate the effect of pore structure characteristics on the hydrogen storage capacity of MOFs. The optimal composite mass ratio between carbon-based materials, transition metals, and MOFs was determined by Density Functional Theory (DFT). The mechanism of hydrogen spillover affecting the hydrogen storage capacity of MOFs was analyzed by preparation, characterization, and hydrogen adsorption capacity testing. To further enhance the hydrogen storage capacity of MOFs composites and improve the kinetic properties and reversibility of metal hydrides, aluminum hydride (AlH3) was nano-confined in MOF@carbon matrix material@transition metal to form new nano-confined composites with improved dehydrogenation temperature and reduced reversibility conditions. The results showed that MOFs with a PLD in the range of 7–10 Å, porosity in the range of 0.75–0.90, and pore volume in the range of 1.4–2.2 cm3/g possess high hydrogen storage capacity. Compared to pristine MOFs, the hydrogen storage capacity of the composites with induced hydrogen spillover is at least 5 times higher. The new composites with improved kinetic hydrogen release characteristics after nano-confined AlH3 achieve reversible hydrogen release at 150 °C and 70 bar.

A detailed experimental comparison on the hydrogen storage ability of different forms of graphitic carbon nitride (bulk, nanotubes and sheets) with multiwalled carbon nanotubes

The reversible hydrogen storage of graphitic carbon nitride (g-C3N4) nanotubes at room temperature was first studied through experimental methods in this work and was compared to multiwalled carbon nanotubes (MWCNT), bulk g-C3N4, and g-C3N4 nanosheets. Compared with MWCNT which had a similar specific surface area around 60 m2/g, g-C3N4 nanotubes had a higher room temperature hydrogen storage capacity up from 0.46 wt% for MWCNT to 0.78 wt%. This value for the g-C3N4 nanotubes was also higher than the hydrogen storage capacity of bulk g-C3N4 (0.51 wt%) and g-C3N4 nanosheets (0.73 wt%), even though g-C3N4 nanosheets had the highest specific surface area of 161 m2/g. Temperature programming desorption (TPD) was applied to study the desorption behaviours and it was found that chemisorption contributed to the relative high storage capacity of g-C3N4 nanotubes.

Superfunctional Materials by Ultra-Severe Plastic Deformation.

Superfunctional materials are defined as materials with specific properties being superior to the functions of engineering materials. Numerous studies introduced severe plastic deformation (SPD) as an effective process to improve the functional and mechanical properties of various metallic and non-metallic materials. Moreover, the concept of ultra-SPD-introducing shear strains over 1000 to reduce the thickness of sheared phases to levels comparable to atomic distances-was recently utilized to synthesize novel superfunctional materials. In this article, the application of ultra-SPD for controlling atomic diffusion and phase transformation and synthesizing new materials with superfunctional properties is discussed. The main properties achieved by ultra-SPD include: (i) high-temperature thermal stability in new immiscible age-hardenable aluminum alloys; (ii) room-temperature superplasticity for the first time in magnesium and aluminum alloys; (iii) high strength and high plasticity in nanograined intermetallics; (iv) low elastic modulus and high hardness in biocompatible binary and high-entropy alloys; (v) superconductivity and high strength in the Nb-Ti alloys; (vi) room-temperature hydrogen storage for the first time in magnesium alloys; and (vii) superior photocatalytic hydrogen production, oxygen production, and carbon dioxide conversion on high-entropy oxides and oxynitrides as a new family of photocatalysts.

Room temperature hydrogen storage enhancement in copper-doped zeolitic imidazolate frameworks with trioctylamine

Cu-doping and trioctylamine modulation are effective modification approaches for hydrogen storage in zeolitic imidazolate frameworks under near-ambient conditions.

A comprehensive investigation of the (Ti0.5Zr0.5)1(Fe0.33Mn0.33Cr0.33)2 multicomponent alloy for room-temperature hydrogen storage designed by computational thermodynamic tools

(Ti0.5Zr0.5)1(Fe0.33Mn0.33Cr0.33)2 multicomponent alloy designed by computational thermodynamic tools shows excellent room-temperature hydrogen storage properties.

Room-temperature hydrogen storage performance of metal-organic framework/graphene oxide composites by molecular simulations

Metal-organic framework/graphene oxide (MOF/GO) composites have been regarded as potential room-temperature hydrogen storage materials recently. In this work, the influence of MOF structural properties, GO functional group contents and different amounts of doped lithium (Li+) on hydrogen storage performance of different MOF/GO composites were investigated by grand canonical Monte Carlo (GCMC) simulations. It is found that MOF/GO composites based on small-pore MOFs exhibit enhanced hydrogen storage capacity, whereas MOF/GO based on large-pore MOFs show decreased hydrogen storage capacity, which can be ascribed to the novel pores at MOF/GO interface that favors the enhanced hydrogen storage performance due to the increased pore volume/surface area. By integrating the small-pore MOF-1 with GO, the hydrogen storage capacity was enhanced from 9.88 mg/go up to 11.48 mg/g. However, the interfacial pores are smaller compared with those in large-pore MOFs, resulting in significantly reduced pore volume/surface area as well as hydrogen storage capacities of large-pore MOF/GO composite. Moreover, with the increased contents of hydroxyl, epoxy groups as well as carboxyl group modification, the pore volumes and specific surface areas of MOF/GO are decreased, resulting in reduced hydrogen storage performance. Furthermore, the room-temperature hydrogen storage capacities of Li+ doped MOF/GO was improved with increased Li+ at low loading and decrease with the increased Li+ amounts at high loading. This is due to that the introduced Li+ effectively increases the accessible hydrogen adsorption sites at low Li+ loading, which eventually favors the hydrogen adsorption capacity. However, high Li+ loading causes ion aggregation that reduces the accessible hydrogen adsorption sites, leading to decreased hydrogen storage capacities. MOF-5/GO composites with moderate Li+ doping achieved the optimum hydrogen storage capacities of approximately 29 mg/g.

High-entropy hydrides for fast and reversible hydrogen storage at room temperature: Binding-energy engineering via first-principles calculations and experiments

Despite high interest in compact and safe storage of hydrogen in the solid-state hydride form, the design of alloys that can reversibly and quickly store hydrogen at room temperature under pressures close to atmospheric pressure is a long-lasting challenge. In this study, first-principles calculations are combined with experiments to develop high-entropy alloys (HEAs) for room-temperature hydrogen storage. TixZr2-xCrMnFeNi (x = 0.4-1.6) alloys with the Laves phase structure and low hydrogen binding energies of -0.1 to -0.15 eV are designed and synthesized. The HEAs reversibly store hydrogen in the form of Laves phase hydrides at room temperature, while (de)hydrogenation pressure systematically reduces with increasing the zirconium fraction in good agreement with the binding energy calculations. The kinetics of hydrogenation are fast, the hydrogenation occurs without any activation or catalytic treatment, the hydrogen storage performance remains stable for at least 1000 cycles, and the storage capacity is higher than that for commercial LaNi5. The current findings demonstrate that a combination of theoretical calculations and experiments is a promising pathway to design new high-entropy hydrides with high performance for hydrogen storage.