Polymers for carrying and storing hydrogen

Exploring Nanomaterials for Hydrogen Storage: Advances, Challenges, and Perspectives

Hydrogen energy heralded for its environmentally friendly, renewable, efficient, and cost-effective attributes, stands poised as the primary alternative to fossil fuels in the future. Despite its great potential, the low volumetric density presents a formidable challenge in hydrogen storage. Addressing this challenge necessitates exploring effective storage techniques for a sustainable hydrogen economy. Solid-state hydrogen storage in nanomaterials (physically or chemically) holds promise for achieving large-scale hydrogen storage applications. Such approaches offer benefits, including safety, compactness, lightness, reversibility, and efficient generation of pure hydrogen fuel under mild conditions. This article presents solid-state nanomaterials, specifically nanoporous carbons (activated carbon, carbon fibers), metal-organic frameworks, covalently connected frameworks, nanoporous organic polymers, and nanoscale metal hydrides. Furthermore, new developments in hydrogen fuel cell technology for stationary and mobile applications have been demonstrated. The review outlines significant advancements thus far, identifies key barriers to practical implementation, and presents a perspective for future sustainable energy research. It concludes with recommendations to enhance hydrogen storage performance for cost-effective and long-lasting utilization.

Challenges of Green Transition in Polymer Production: Applications in Zero Energy Innovations and Hydrogen Storage

The green transition in the sustainable production and processing of polymers poses multifaceted challenges that demand integral comprehensive solutions. Specific problems of presences of toxic trace elements are often missed and this prevents shifting towards eco-friendly alternatives. Therefore, substantial research and the development of novel approaches is needed to discover and implement innovative, sustainable production materials and methods. This paper is focused on the most vital problems of the green transition from the aspect of establishing universally accepted criteria for the characterization and classification of eco-friendly polymers, which is essential to ensuring transparency and trust among consumers. Additionally, the recycling infrastructure needs substantial improvement to manage the end-of-life stage of polymer products effectively. Moreover, the lack of standardized regulations and certifications for sustainable polymers adds to the complexity of this problem. In this paper we propose solutions from the aspect of standardization protocols for the characterization of polymers foreseen as materials that should be used in Zero Energy Innovations in Hydrogen Storage. The role model standards originate from eco-labeling procedures for materials that come into direct or prolonged contact with human skin, and that are monitored by different methods and testing procedures. In conclusion, the challenges of transitioning to green practices in polymer production and processing demands a concerted effort from experts in the field which need to emphasize the problems of the analysis of toxic ultra trace and trace impurities in samples that will be used in hydrogen storage, as trace impurities may cause terrific obstacles due to their decreasing the safety of materials. Overcoming these obstacles requires the development and application of current state-of-the-art methodologies for monitoring the quality of polymers during their recycling, processing, and using, as well as the development of other technological innovations, financial initiatives, and a collective commitment to fostering a sustainable and environmentally responsible future for the polymer industry and innovations in the field of zero energy applications.

Molecular Dynamics Simulation of Helium Barrier Performance of Modified Polyamide 6 Lining of IV Hydrogen Storage Tank with Montmorillonite

In order to investigate the type IV hydrogen storage bottle with better hydrogen storage capacity, the polymer lining of the hydrogen storage bottle was further developed. In this paper, the molecular dynamics method was used to simulate the helium adsorption and diffusion processes within a modified montmorillonite (OMMT)-filled polyamide 6 (PA6) system. The effects of the barrier properties of the composites were investigated at different filler contents (3%, 4%, 5%, 6% and 7%), different temperatures (288 K and 328 K) and different pressures (0.1 MPa, 41.6 MPa, 52 MPa and 60 MPa) for certain contents. It was found that when the filler content was 5%, the permeability coefficient of the material was lower than 2 × 10^-13 cm³∙cm/(cm²∙s∙Pa) and the barrier performance was the best. The modified filler with 5% OMMT/PA6 at 328 K still had the strongest barrier performance. When the pressure increased, the permeability coefficient of the modified material first decreased and then increased. In addition to this, the effect of the fractional free volume on the barrier properties of the materials was also investigated. This study provides a basis and reference for the selection and preparation of polymer linings for high-barrier hydrogen storage cylinders.

A Comparative Density Functional Theory Study of Hydrogen Storage in Cellulose and Chitosan Functionalized by Transition Metals (Ti, Mg, and Nb)

The focus of this work is hydrogen storage in pristine cellulose, chitosan, and cellulose. Chitosan doped with magnesium, titanium, and niobium is analyzed using spin unrestricted plane-wave density functional theory implemented in the Dmol³ module. The results of this study demonstrate that hydrogen interaction with pure cellulose and chitosan occurred in the gas phase, with an adsorption energy of Eb = 0.095 eV and 0.090 eV for cellulose and chitosan, respectively. Additionally, their chemical stability was determined as Eb= 4.63 eV and Eb = 4.720 eV for pure cellulose and chitosan, respectively, by evaluating their band gap. Furthermore, the presence of magnesium, titanium, and niobium on cellulose and chitosan implied the transfer of an electron from metal to cellulose and chitosan. Moreover, our calculations predict that cellulose doped with niobium is the most favorable medium where 6H₂ molecules are stored compared with molecules stored in niobium-doped chitosan with T_max = 818 K to release all H₂ molecules. Furthermore, our findings showed that titanium-doped cellulose has a storage capacity of five H₂ molecules, compared to a storage capacity of four H₂ molecules in titanium-doped chitosan. However, magnesium-doped cellulose and chitosan have insufficient hydrogen storage capacity, with only two H₂ molecules physisorbed in the gas phase. These results suggest that niobium-doped cellulose and chitosan may play a crucial role in the search for efficient and inexpensive hydrogen storage media.

Materials Research Directions Toward a Green Hydrogen Economy: A Review

A constellation of technologies has been researched with an eye toward enabling a hydrogen economy. Within the research fields of hydrogen production, storage, and utilization in fuel cells, various classes of materials have been developed that target higher efficiencies and utility. This Review examines recent progress in these research fields from the years 2011-2021, exploring the most commonly occurring concepts and the materials directions important to each field. Particular attention has been given to catalyst materials that enable the green production of hydrogen from water, chemical and physical storage systems, and materials used in technical capacities within fuel cells. The quantification of publication and materials trends provides a picture of the current state of development within each node of the hydrogen economy.

Cu0.33@Co0.22Ni0.45 core–shell nanoparticles as hydrogen generation catalysts via hydrolysis of ammonia borane

A Cu0.33@Co0.22Ni0.45 core–shell nanocatalyst was produced for hydrolysis of ammonia borane and hydrogen generation. The catalyst has high hydrogen release rate, low activation energies, high cycle performance and excellent structural stability.

Graphene and Carbon Nanotubes Fibrous Composite Decorated with PdMg Alloy Nanoparticles with Enhanced Absorption-Desorption Kinetics for Hydrogen Storage Application

We describe a graphene and fibrous multiwall carbon nanotubes (f-MWCNT) composite film prepared by plasma-enhanced chemical vapor deposition for use as a suitable and possible candidate of hydrogen storage materials. A high storage capacity of 5.53 wt% has been obtained with improved kinetics. The addition of binary PdMg alloy nanoparticles to the surface of graphene-fibrous nanotubes composite films raised the storage capacity by 53% compared to the film without PdMg decorated nanoparticles. Additionally, the graphene/f-MWCNT composite film decorated with PdMg nanoparticles exhibited an enhanced hydrogen absorption-desorption kinetics. The fibrous structure of the MWCNTs, alongside graphene sheets within the film, creates an enormous active region site for hydrogen reaction. The addition of PdMg nanoparticles enhanced the reaction kinetics due to the catalytic nature of Pd, and increased the hydrogen content due to the high absorption capacity of Mg nanoparticles. The combination of Pd and Mg in a binary alloy nanoparticle enhanced the hydrogen capacity and absorption-desorption kinetics.

Design and Characterization of Metal Nanoparticle Infiltrated Mesoporous Metal-Organic Frameworks

The infiltration of palladium and platinum nanoparticles (NPs) into the mesoporous metal-organic framework (MOF) CYCU-3 through chemical vapor infiltration (CVI) and incipient wetness infiltration (IWI) processes was systematically explored as a means to design novel NP@MOF composite materials for potential hydrogen storage applications. We employed a traditional CVI process and a new ″green″ IWI process using methanol for precursor infiltration and reduction under mild conditions. Transmission electron microscopy-based direct imaging techniques combined with synchrotron-based powder diffraction (SPD), energy-dispersive X-ray spectroscopy, and physisorption analysis reveal that the resulting NP@MOF composites combine key NP and MOF properties. Room temperature hydrogen adsorption capacities of 0.95 and 0.20 mmol/g at 1 bar and 2.9 and 1.8 mmol/g at 100 bar are found for CVI and IWI samples, respectively. Hydrogen spillover and/or physisorption are proposed as the dominating adsorption mechanisms depending on the NP infiltration method. Mechanistic insights were obtained through the crystallographic means using SPD-based difference envelope density analysis, providing previously underexplored details on NP@MOF preparations. Consequently, important host-guest correlations influencing the global hydrogen adsorption properties are discussed, and they demonstrate that employing MOFs as platforms for NPs is an alternative approach to the development of versatile materials for improving current hydrogen storage technologies.

Reversible Hydrogen Releasing and Fixing with Poly(Vinylfluorenol) through a Mild Ir-Catalyzed Dehydrogenation and Electrochemical Hydrogenation

The radical polymerization of 2-vinylfluorenol, an alcohol derivative of vinylfluorene, gives poly(vinylfluorenol), which quantitatively releases hydrogen gas (≈110 mL per gram polymer at standard temperature and pressure) by simply warming at 100 °C with an iridium catalyst. A high population of fluorenol units in the polymer accomplishes a large formula-weight-based theoretical hydrogen density (1.0 wt%). The dehydrogenated ketone derivative, poly(vinylfluorenone), exhibits reversible negative-charge storage with a high density of 260 mAh g^-1 . The electrolytically reduced poly(vinylfluorenone) is momentarily hydrogenated in the presence of an electrolyte with water as the hydrogen source to be converted to the original poly(vinylfluorenol). The formed poly(vinylfluorenol) almost quantitatively evolves hydrogen gas similar to the starting poly(vinylfluorenol). Both hydrogen and charge storage with the organic fluorenol/fluorenone polymer suggest a new type of energy-storage configuration.

Forming layered conjugated porous BBL structures

Ladder-like poly(benzoimidazobenzophenanthrolines) (BBLs) have attracted great interest due to their outstanding features, including thermal and chemical stability, electrical conductivity, and optical and electronic properties.

Introduction: hydrogen storage as solution for a changing energy landscape

The expansion of sustainable technologies and infrastructures for the production and delivery of energy to the final consumer and the development of new technologies for energy production, storage and distribution, are challenging and inevitable tasks. Power plants based on the combustion of fossil fuel resources or nuclear power plants are not suitable to provide energy in the future due to significant disadvantages and dangers associated with these outdated technologies. The development of new sustainable technologies for the production of energy is desirable. Besides focusing on the production step, the change in global energy landscape requires also new and improved energy storage systems. Requirements for these storage solutions will strongly depend on the application. Storing energy by producing and consuming hydrogen is in this context a very attractive approach. It may be suitable for storage of energy for transportation and also for the bulk energy storage. Due to physical restrictions of high pressure hydrogen storage, alternative techniques are developed. This is, in turn, an ongoing task with multidisciplinary aspects, which combines chemistry, physics, material science and engineering. Herein, we review the production and consumption of energy, different energy storage applications, and we introduce the concept of hydrogen storage based on hydrogenation and dehydrogenation reactions of small molecules.

Synthesis of Nitrogen-Rich Polymers by Click Polymerization Reaction and Gas Sorption Property

Microporous organic polymers (MOPs) are promising materials for gas sorption because of their intrinsic and permanent porosity, designable framework, and low density. The introduction of nitrogen-rich building block in MOPs will greatly enhance the gas sorption capacity. Here, we report the synthesis of MOPs from the 2,4,6-tris(4-ethynylphenyl)-1,3,5-triazine unit and aromatic azides linkers by click polymerization reaction. Fourier transform infrared (FTIR) and solid-state 13C CP-MAS (Cross Polarization-Magic Angle Spinning) NMR confirm the formation of the polymers. CMOP-1 and CMOP-2 exhibit microporous networks with a BET (Brunauer⁻Emmett⁻Teller) surface area of 431 m²·g-1 and 406 m²·g-1 and a narrow pore size distribution under 1.2 nm. Gas sorption isotherms including CO₂ and H₂ were measured. CMOP-1 stores a superior CO₂ level of 1.85 mmol·g-1 at 273 K/1.0 bar, and an H₂ uptake of up to 2.94 mmol·g-1 at 77 K/1.0 bar, while CMOP-2, with its smaller surface area, shows a lower CO₂ adsorption capacity of 1.64 mmol·g-1 and an H₂ uptake of 2.48 mmol·g-1. In addition, I₂ vapor adsorption was tested at 353 K. CMOP-1 shows a higher gravimetric load of 160 wt%. Despite the moderate surface area, the CMOPs display excellent sorption ability for CO₂ and I₂ due to the nitrogen-rich content in the polymers.