Hydrogen Storage Using Metal-Organic Frameworks (MOFs): A Computational Fluid Dynamic Study

Limited conventional energy resources and serious environmental calamities have motivated researchers to find new and efficient sources of energy. The considerable efforts devoted to this end include the development of bio-diesel, solar cells, coal liq-uefaction/gasification technologies, and fuel cells. Hydrogen is considered by many an ideal energy source owing to its renewable and clean energy characteristics. In addition, it mostly produces water, which is eco-friendly compared to the byproducts of many other energy sources [1-6]. To use hydrogen as an energy source, various hydrogen stor -age methods such as the use of metal hydrides, liquefied hydrogen, and adsorption of hydrogen in porous materials have been studied [7-14]. The adsorption of hydrogen in porous materials is particularly suitable for hydrogen storage, which is critical for suit -ably utilizing hydrogen energy, owing to the reversibility and stability of this method. To date, the wide ranging attempts to develop hydrogen storage mechanisms include studies on carbon materials [15-17], metal-organic frameworks, and zeolites [18-21]. Carbon materials offer many advantages for hydrogen storage, such as easy preparation, suitable surface functional groups, low mass density, thermal stability, and hydropho -bicity [22-24]. Carbon aerogels (CAs) in particular have been recognized as potential hydrogen storage materials because of their suitable structural properties, controllable mass densities, high specific surface areas, and mesopore volumes. However, it is neces -sary to modify the surfaces of carbon materials in order to reach the hydrogen storage capacities determined by the US Department of Energy (DOE).Carbon materials containing transition metals such as platinum, copper, vanadium, and nickel exhibit attractive hydrogen storage properties [10,22,25]. Nickel is particularly prom -ising since it is easily obtained on Earth, and it is inexpensive compared to other metals and enhances hydrogen storage properties. Improved hydrogen storage capacities have been obtained with nickel-plated porous carbon nanofibers owing to the spillover of hydrogen molecules onto the metal-carbon interfaces. In general, the presence of nickel particles on carbon materials has been shown to enhance the hydrogen storage capacity [3,9,19].In this work, CAs were chemically activated by KOH to produce well-developed pore structures and ultimately increase the hydrogen storage capacities. Nickel-loaded activated carbon aerogels (ACAs/Ni hybrid materials) with various nickel content were prepared. Ni particles were loaded onto ACAs to introduce hydrogen-favorable active sites onto the ACA surfaces and improve the hydrogen storage capacities.The CAs were prepared using resorcinol as the carbon precursor and formaldehyde as the initiator. Resorcinol (7.5 g) was dissolved in a solution of distilled water (75 mL) and formaldehyde (25 g). Sodium carbonate was then added to this solution, and the mixture was stirred for 3 h in an open container and dried for 3 h at room temperature. Subsequently, the wet gel was dried at 80°C for 48 h and then immersed in an acetone solution for 24 h without stirring. The aerogels were obtained after drying at 80°C for 24 h. Prior to use, the aerogels were carbonized in a furnace with a heating rate of 2°Cmin

Both from the point of view of global warming and from that of the inevitable exhaustion of Earth’s oil reserve, worldwide interest is focused on using a clean burning substitute such as hydrogen in place of fossil fuels. However the storage of hydrogen is one of the most important challenges impeding its practical application. Metal–organic frameworks (MOFs) are a new emerging class of crystalline porous materials, displaying very low density, significant thermal stability and very high surface area. They offer significant opportunities for hydrogen storage. Therefore, the main objectives of present study were to develop and investigate the synthesis methods, fine structural characterization, and capacity of hydrogen-storage mechanism of MOFs using XRD, FE-SEM/EDS, TEM, BET, TGA, ESCA, high pressure TGA, and XANES/EXAFS techniques. Experimentally, MOFs were synthesized with different metal nitrates in the presence of different solvents combined with organic linkers. The solvothermal method was used to synthesize the MOFs with the reaction temperatures range from 200 to 220oC. These MOFs was named as MIL-53(Cr) having the particle size about 0.5~0.7 μm, respectively identified by FE-SEM microphotos. Since as-synthesized MOFs contain many impurities, it may cause low porosity. Therefore the cleaning methods, such as optimum calcination temperatures or washing several times with different solvents at different warm temperatures were effective and approved to improve higher specific surface area and porosity. The specific surface area of MIL-53(Cr) was 1015 m2/g. N2 adsorption isotherms of MOFs were type I and the distribution of pore diameter curves revealed that MOFs were microporous and mesopores materials. The XRD patterns represented that MOFs had well crystallinity after chemical treatment. The EDS data indicated that MOFs consist of C or O elements and different kinds of metals. The FTIR spectra exhibited vibrational bands in the usual region of 1400~1700 cm-1 for the carboxylic function and 3000~3500 cm-1 for OH- group of these MOFs. TGA curves showed that these MOFs were stable around 200~400oC. XANES/EXAFS spectroscopy was performed to identify the fine structures of MIL-53(Cr). The XANES spectra indicated that the valence of MIL-53(Cr) was Cr(III). The EXAFS data also revealed that MIL-53(Cr) had a first shell of Cr-O bonding with bond distance of 1.96 A and the coordination number was 5.4. The hydrogen storage capacity of MIL-53(Cr) was 0.462 wt%, respectively at 450 psig (30 atm) and room temperature measured using high-pressure thermogravimetric analyzer. In order to improve the hydrogen storage capacity of MOFs, metal/activated carbons were mixed with MOFs. FE-SEM microphotos of Pt/AC and Pd/AC indicated that the particle sizes were 2~5 and 5~10 nm, respectively. By using XPS and XANES spectra, it had found that both Pt and Pd species had zero valency. The EXAFS data revealed that Pt/AC and Pd/AC have a first shell of Pt-Pt and Pd-Pd bonding with bond distances of 2.78 and 2.75 A, respectively. Coordination numbers of both nanoparticles were close to 8 with a FCC structure. The catalytic properties of Pt/AC and Pd/AC were studied for hydrogen spillover in MIL-53(Cr) modified by 5 wt % of catalyst. The hydrogen adsorption capacity of modified MIL-53(Cr) was significantly enhanced up to 0.612 wt% by using the secondary spillover by carbon bridges measured at 450 psig and room temperature. In addition, the adsorption thermodynamic of the data was also confirmed using thermodynamic equations for thermodynamic consistency. Under lower pressures, the adsorption heat is affected by adsorption behaviors. The adsorption heats decrease of increasing adsorption capacities. The adsorption heat of hydrogen onto modified MIL-53(Cr) is < 51 kJ/mol using the secondary spillover of carbon bridges under lower pressures.

Hydrogen uptake performance of nanocomposites derived from Metal-Organic Framework (Cu-BTC) and metal decorated multi-walled carbon nanotubes (Ni@f-MWCNTs or Pd@f-MWCNTs)

Energy is regarded as a key resource that may encourage numerous companies to expand and flourish given the rapid advancement of technology. However, due to the contamination of the usage of traditional fossil fuels, deploying new and clean energy resources is the concentrated solution. New energy sources such as wind energy and solar energy are constantly being developed. In addition, three methods exist for storing hydrogen that is a typical clean energy source, including compressed gas storage, cryogenic liquid gas storage, and hydrogen storage materials via adsorption and desorption. As a result, hydrogen storage is receiving more and more attention, and different hydrogen storage materials have been developed. This research will introduce the application of four different types of porous materials in the field of hydrogen storage, including zeolites, activated carbons (AC), carbon nanotubes (CNTs), and metal-organic frameworks (MOFs). Hydrogen can be successfully adsorbed on these materials to varying degrees through chemisorption and physisorption. For improving the hydrogen storage capability (HSC), synthetic strategies such as doping metal elements and synthesizing composite porous materials were designed and used to enhance the hydrogen storage properties of the materials. In the future, satisfying the U.S. Department of Energy (DOE) target would stimulate more and more great-performing porous materials to be synthesized, which can provide a new idea for new hydrogen storage technologies.

Sorption properties of nanostructured ball-milled porous silicon for solid-state hydrogen storage up to 80 bar

This study investigates the activation, characterization, and hydrogen adsorption properties of pristine and hydrochloric acid-activated Cu-BDC metal-organic frameworks (MOFs). The activation process aimed to enhance the surface area and pore volume, thereby improving hydrogen storage capabilities. Structural and morphological analyses were conducted using various techniques. X-ray diffraction (XRD) revealed a highly crystalline, well-organized framework, with additional peaks in the activated sample indicating phase transitions induced by activation. Fourier-transform infrared (FT-IR) spectroscopy confirmed the presence of functional groups, including -COO and C-H vibrations of aromatic rings, signifying the retention of essential framework components. Scanning electron microscopy (SEM) showcased regular, cubic microcrystals with homogeneously distributed particles. Thermal stability was assessed via thermogravimetric analysis (TGA), demonstrating that the material is thermally robust. Hydrogen adsorption measurements were performed at 300 K, 126 K, and pressures of 8 and 10 bar. The pristine Cu-BDC MOF exhibited a hydrogen uptake of 0.88 wt% at 126 K and 10 bar, which improved to 1.12 wt% upon activation. The enhanced uptake in the activated sample is attributed to the increased surface area and pore volume, providing more adsorption sites for hydrogen molecules. Notably, low-temperature and high-pressure conditions were found to significantly enhance hydrogen storage performance. These findings highlight the potential of functionalized Cu-BDC MOFs as promising candidates for hydrogen storage applications, contributing to advancements in sustainable energy storage technologies. The study aligns with global efforts to meet the DOE targets for efficient hydrogen storage systems.

Experimental and simulation study on structural characterization and hydrogen storage of metal organic structured compounds

Performances comparison of adsorption hydrogen storage tanks at a wide temperature and pressure zone

The rise of MOFs and their derivatives for flame retardant polymeric materials: A critical review

Chapter 9 - Metal organic framework-based nanomaterials as suitable electrocatalysts for evolution of hydrogen

Conventional storage of large amounts of hydrogen in its molecular form is difficult and expensive because it requires employing either extremely high pressure gas or very low temperature liquid. Because of the importance of hydrogen as a fuel, the DOE has set system targets for hydrogen storage of gravimetric (5.5 wt%) and volumetric (40 g L-1) densities to be achieved by 2015. Given that these are system goals, a practical material will need to have higher capacity when the weight of the tank and associated cooling or regeneration system is considered. The size and weight of these components will vary substantially depending on whether the material operates by a chemisorption or physisorption mechanism. In the latter case, metal-organic frameworks (MOFs) have recently been identified as promising adsorbents for hydrogen storage, although little data is available for their sorption behavior. This grant was focused on the study of MOFs with these specific objectives. (1) To examine the effects of functionalization, catenation, and variation of the metal oxide and organic linkers on the low-pressure hydrogen adsorption properties of MOFs. (2) To develop a strategy for producing MOFs with high surface area and porosity to reduce the dead space and increase the hydrogen storage capacity per unit volume. (3) To functionalize MOFs by post synthetic functionalization with metals to improve the adsorption enthalpy of hydrogen for the room temperature hydrogen storage. This effort demonstrated the importance of open metal sites to improve the adsorption enthalpy by the systematic study, and this is also the origin of the new strategy, which termed isoreticular functionalization and metalation. However, a large pore volume is still a prerequisite feature. Based on our principle to design highly porous MOFs, guest-free MOFs with ultrahigh porosity have been experimentally synthesized. MOF-210, whose BET surface area is 6240 m2 g-1 (the highest among porous solids), takes up 15 wt% of total H2 uptake at 80 bar and 77 K. More importantly, the total H2 uptake by MOF-210 was 2.7 wt% at 80 bar and 298 K, which is the highest number reported for physisorptive materials.

Against the backdrop of rising emissions of greenhouse gasses and the need for sustainable fuel, hydrogen storage has recently become a popular energy storage option due to its many benefits, such as high energy capacity, low concentrations of side products, and relative ease of access. However, hydrogen storage is not perfect and possesses some critical flaws that prevent it from reaching its full potential, which include volatility and flammability. There are many candidates for hydrogen storage and also extant technologies to target hydrogen storage. Among all the ways proposed to store hydrogen, metal-organic frameworks (MOFs) have become increasingly popular because of their exemplary high surface area and adaptable pore structure. This research explores the various developments of MOFs in the field of hydrogen storage and how they may be improved and compared to one another. It will discuss the issues with current MOFs and design procedures and elements, such as making use of void spaces in MOFs. Then it will proceed to explore how MOFs have been enhanced through impregnation, catenation, and open metal sites. Lastly, this review will feature some breakthrough MOFs that have been promising for hydrogen storage.

Tuning the hydrogen adsorption properties of Zn–based metal–organic frameworks: Combined DFT and GCMC simulations

Carbon fiber-reinforced epoxy (CF/EP) composites are attractive materials for hydrogen storage tanks due to their high strength-to-weight ratio and outstanding chemical resistance. However, cryogenic temperatures (CTs) have a substantial impact on the tensile strength and interfacial bonding of CF/EP materials, producing problems for their long-term performance and safety in hydrogen storage tank applications. This review paper investigates how low temperatures affect the tensile strength, modulus, and fracture toughness of CF/EP materials, as well as the essential interfacial interactions between carbon fibers (CFs) and the epoxy matrix (EP) in cryogenic environments. Material toughening techniques have evolved significantly, including the incorporation of nano-fillers, hybrid fibers, and enhanced resin formulations, to improve the durability and performance of CF/EP materials in cryogenic conditions. This review also assesses the hydrogen barrier properties of various composites, emphasizing the importance of reducing hydrogen permeability in order to retain material integrity. This review concludes by highlighting the importance of optimizing CF/EP composite design and fabrication for long-term performance and safety in hydrogen storage systems. It examines the prospects for using CF/EP composites in hydrogen storage tanks, as well as future research directions.

This study developed a heating mechanism applicable to hydrogen storage tank, in order to enhance the stability and durability of proton exchange membrane fuel cell (PEMFC). This study discussed two heating modes. The first mode was using heating wire to wind the hydrogen storage tank body. Heating wires were used to wind the upper, middle and lower parts of the hydrogen storage tank and the whole tank respectively for discussion. The second heating mode was to use the PEMFC cathode waste heat to heat the hydrogen storage tank body. This study discussed the variations of hydrogen release rate and tank body temperature with the hydrogen release time in different heating mechanisms. The research results can serve as reference for system design in various applications.