Search Results (131)

Hydrogen is widely recognized as a key enabler of the clean energy transition, but the lack of safe, efficient, and scalable storage technologies continues to hinder its broad deployment. Conventional hydrogen storage approaches, such as compressed hydrogen storage, cryo-compressed hydrogen storage, and liquid hydrogen storage, face limitations, including high energy consumption, elevated cost, weight, and safety concerns. In contrast, solid-state hydrogen storage using carbon-based adsorbents has gained growing attention due to their chemical tunability, low cost, and potential for modular integration into energy systems. This review provides a comprehensive evaluation of hydrogen storage using carbon-based materials, covering fundamental adsorption mechanisms, classical materials, emerging architectures, and recent advances in computationally AI-guided material design. We first discuss the physicochemical principles driving hydrogen physisorption, chemisorption, Kubas interaction, and spillover effects on carbon surfaces. Classical adsorbents, such as activated carbon, carbon nanotubes, graphene, carbon dots, and biochar, are evaluated in terms of pore structure, dopant effects, and uptake capacity. The review then highlights recent progress in advanced carbon architectures, such as MXenes, three-dimensional architectures, and 3D-printed carbon platforms, with emphasis on their gravimetric and volumetric performance under practical conditions. Importantly, this review introduces a forward-looking perspective on the application of artificial intelligence and machine learning tools for data-driven sorbent design. These methods enable high-throughput screening of materials, prediction of performance metrics, and identification of structure–property relationships. By combining experimental insights with computational advances, carbon-based hydrogen storage platforms are expected to play a pivotal role in the next generation of energy storage systems. The paper concludes with a discussion on remaining challenges, utilization scenarios, and the need for interdisciplinary efforts to realize practical applications. Full article

The increasing consumption of edible oils has resulted in a parallel rise in waste cooking oil (WCO), a harmful waste stream but one that also represents a promising raw material. In this study, oil-based binders were synthesised from WCO using various reagents: Sulfuric(VI) acid, hydrobromic acid, acetic acid, salicylic acid, glycolic acid, zinc acetate, ethanol, hydrogen peroxide, and their selected mixtures. The manufacturing process was optimised, and the composites were evaluated for physicochemical and mechanical properties, including compressive strength, bending strength, and water absorption. The best performance was observed for composites catalysed with a mixture of sulfuric(VI) acid and 20% hydrogen peroxide, cured at 240 °C, yielding compressive and bending strengths of 5.20 MPa and 1.34 MPa, respectively. Under modified curing conditions, a compressive strength of 5.70 MPa and a bending strength of 0.75 MPa were obtained. The composite modified with glycolic acid showed the lowest water absorption (3%). These findings demonstrate how catalyst type and curing parameters influence composite structure, porosity, and mechanical behaviour. The study provides new insights into the process–structure–property relationships in oil-based materials and supports the development of environmentally friendly composites from waste feedstocks. Full article

Approximately 20% of emissions from air travel are attributed to the auxiliary power units (APUs) carried in commercial aircraft. This paper proposes to reduce greenhouse gas emissions in international air transport by adopting proton-exchange membrane (PEM) fuel cells to replace APUs in commercial aircraft: we consider the design of three compressed hydrogen storage vessels made of 304 stainless steel, 6061-T6 aluminium, and Grade 5 (Ti-6Al-4V) titanium and capable of delivering 440 kW—enough for a PEM fuel cell for a Boeing 777. Complete structural analyses for pressures from 35 MPa to 70 MPa and wall thicknesses of 25, 50, 100, and 150 mm are used to determine the optimal material for aviation applications. Key factors such as deformation, safety factors, and Von Mises equivalent stress are evaluated to ensure structural integrity under a range of operating conditions. In addition, CO₂ emissions from a conventional 440 kW gas turbine APU and an equivalent PEM fuel cell are compared. This study provides insights into optimal material selection for compressed hydrogen storage vessels, emphasising safety, reliability, cost, and weight reduction. Ultimately, this research aims to facilitate the adoption of fuel cell technology in aviation, contributing to greenhouse emissions reduction and hence sustainable air transport. Full article

Proton exchange membranes are widely used in environmentally friendly applications such as fuel cells and electrochemical hydrogen compression. In these applications, an ideal proton exchange membrane should have both excellent proton conductivity and mechanical strength. Polymer proton exchange membranes, such as sulfonated poly(ether ether ketone) (SPEEK) membranes with high ion exchange capacity, can lead to higher proton conductivity. However, the ionic groups may reduce the interaction between polymer segments, lower the membrane’s mechanical strength, and even cause it to dissolve in water as the temperature exceeds 55 °C. The porous graphitic C₃N₄ (Pg–C₃N₄) nanosheet is an important two–dimensional polymeric carbon–based material and has a high content of –NH₂ and –NH– groups, which can interact with the sulfonic acid groups in the sulfonated SPEEK polymer, form a more continuous proton transfer channel, and inhibit the movement of the polymer segment, leading to higher proton conductivity and mechanical strength. In this study, we found that a SPEEK membrane containing 3% Pg–C₃N₄ nanosheets achieves the optimized proton conductivity of 138 mS/cm (80 °C and 100% RH) and a mechanical strength of 74.1 MPa, improving both proton conductivity and mechanical strength by over 50% compared to the SPEEK membrane. Full article

In this study, platinum (Pt) nanocatalysts were synthesized via a sol-gel method over the non-stoichiometric, Magnéli phase titanium oxides (TinO_2n−1) at varying Pt loadings (10–40 wt.%). Their structural and morphological properties were characterized, and after preliminary electrochemical screening, the catalysts were integrated into commercially available gas diffusion electrodes (GDEs) with a three-layer structure to enhance mass transport and catalyst utilization. Membrane electrode assemblies (MEAs) were fabricated using a Nafion^® 117 polymer membrane and tested in a laboratory PEM cell under controlled conditions. The electrochemical activity toward the hydrogen reduction reaction (HRR) was evaluated at room temperature and at elevated temperatures to determine the catalytic efficiency and stability. The optimal Pt loading was determined to be 30 wt.%, achieving a current density of approximately 0.12 A cm⁻² at 0.25 V, demonstrating a balance between catalyst efficiency and material utilization. The chronoamperometry tests showed minimal degradation over prolonged operation, suggesting that the catalysts were durable. These findings highlight the potential of Pt-based catalysts supported on Magnéli phase titanium oxides (TinO_2n−1) for efficient HRRs in electrochemical hydrogen pumps/compressors, offering a promising approach for improving hydrogen compression efficiency and advancing sustainable energy technologies. Full article

Hydrogen is a key energy carrier, playing a vital role in sustainable energy systems. This review provides a comparative analysis of physical, chemical, and innovative hydrogen storage methods from technical, environmental, and economic perspectives. It has been identified that compressed and liquefied hydrogen are predominantly utilized in transportation applications, while chemical transport is mainly supported by liquid organic hydrogen carriers (LOHC) and ammonia-based systems. Although metal hydrides and nanomaterials offer high hydrogen storage capacities, they face limitations related to cost and thermal management. Furthermore, artificial intelligence (AI)- and machine learning (ML)-based optimization techniques are highlighted for their potential to enhance energy efficiency and improve system performance. In conclusion, for hydrogen storage systems to achieve broader applicability, it is recommended that integrated approaches be adopted—focusing on innovative material development, economic feasibility, and environmental sustainability. Full article

Concrete is popular in construction due to its strong performance and low maintenance. However, some structures become unsafe over time due to poor maintenance and design flaws. As demand for maintenance grows, restoring older structures is a cost-effective option. Advanced repair techniques aim to extend service life and improve concrete properties, with a focus on eco-friendly solutions. Recent trends have highlighted the potential of incorporating polymers into repair methods, but the use of glycoluril–formaldehyde, a polymeric material known for its hydrogen bonding capacity, remains unexplored in repairing existing structures. This research investigates the effects of glycoluril–formaldehyde in simple matrices like cement paste and mortar to understand its impact. By examining the chemical reactions between glycoluril–formaldehyde with cement paste, this study delves into the fresh, mechanical, and microstructural characteristics. To evaluate the influence of glycoluril–formaldehyde, cement paste specimens were subjected to various tests, including consistency, initial and final setting time, and miniature slump flow tests. Cement mortar specimens were then subjected to compression strength tests conducted at various ages. The results demonstrate that a 3% addition of glycoluril–formaldehyde in concrete offers optimum performance, ensuring improved mechanical strength and microstructure. The microstructural investigation using optical microscopy, an X-ray diffraction, and SEM analysis confirms the polymerization of glycoluril–formaldehyde and the formation of a denser microstructure. The thermogravimetric (TG) and differential thermogravimetric (DTG) analysis provides crucial insights into the thermal stability of the cementitious system, aiding its characterization for high-temperature applications. Full article

Liquid hydrogen is regarded as a key energy source and propellant for lunar bases due to its high energy density and abundance of polar water ice resources. However, its low boiling point and high latent heat of vaporization pose severe challenges for storage and management under the extreme lunar environment characterized by wide temperature variations, low pressure, and low gravity. This paper reviews the strategies for siting and deployment of liquid hydrogen storage systems on the Moon and the technical challenges posed by the lunar environment, with particular attention for thermal management technologies. Passive technologies include advanced insulation materials, thermal shielding, gas-cooled shielding layers, ortho-para hydrogen conversion, and passive venting, which optimize insulation performance and structural design to effectively reduce evaporation losses and maintain storage stability. Active technologies, such as cryogenic fluid mixing, thermodynamic venting, and refrigeration systems, dynamically regulate heat transfer and pressure variations within storage tanks, further enhancing storage efficiency and system reliability. In addition, this paper explores boil-off hydrogen recovery and reutilization strategies for liquid hydrogen, including hydrogen reliquefaction, mechanical, and non-mechanical compression. By recycling vaporized hydrogen, these strategies reduce resource waste and support the sustainable development of energy systems for lunar bases. In conclusion, this paper systematically evaluates passive and active thermal management technologies as well as vapor recovery strategies along with their technical adaptability, and then proposes feasible storage designs for the lunar environment. These efforts provide critical theoretical foundations and technical references for achieving safe and efficient storage of liquid hydrogen and energy self-sufficiency in lunar bases. Full article

This review article investigates the rising global energy demand, which is primarily driven by population growth and industrialization, raising significant environmental concerns due to the extensive reliance on fossil fuels. In response, hydrogen is being explored as a potential eco-friendly energy solution to meet the urgent need for sustainable energy. This review covers various hydrogen storage methods, including compressed gas, cryogenic liquids, solid materials, and electrochemical techniques. Among these, electrochemical technology is highly regarded as a leading experimental approach for hydrogen storage, and it is noted for its outstanding performance under normal conditions. The characteristics of a material’s surface play a crucial role in determining its electrochemical hydrogen storage capacity. Innovative materials, such as graphene oxide and 3D graphene oxide, are particularly significant in this regard, as they can significantly enhance hydrogen storage capacity; electrochemical hydrogen storage functions by incorporating atomic hydrogen into carbon materials following the reduction of water. This article underscores the significance of green energy and the need to ensure safety and precision at room temperature and ambient pressure using electrochemical hydrogen storage techniques and mechanisms. Furthermore, it offers a comprehensive review of developments in electrochemical hydrogen storage and its mechanisms, focusing on carbon, graphene oxide, and the contributions of 3D graphene foam. Full article

In this study, fumed silica (FS) was used as a support material and infused with the hydrated salt sodium hydrogen phosphate dodecahydrate (DHPD) to create shape-stabilized constant phase change materials (CPCMs). These CPCMs were integrated into a polyurethane matrix as a functional filler, resulting in low-exothermic polyurethane composite foams (CPCM-RPUFs) that demonstrate thermoregulation and flame-retardant properties. Recent findings show that CPCM-RPUF excels in thermal stability compared to pure polyurethane, with a melt phase transition enthalpy of 115.8 J/g. The use of fumed silica allows for the encapsulation of hydrated salts up to 87%, ensuring the structural integrity of the vesicles. As FS content in CPCMs increased, the internal temperature of the composite foam significantly decreased, showing excellent thermal regulation. Thermogravimetric analysis showed that the synergistic effect of DHPD and FS improved the thermal stability and flame retardancy of the composites. By monitoring the internal and surface temperature changes in the foam, it was verified that CPCMs can effectively alleviate heat accumulation during the curing process and reduce the core temperature (56.9 °C) and surface warming rate, thus realizing the thermal buffering effect. With the increase in FS content in CPCMs, the compressive strength of CPCM-RPUF can be maintained or even enhanced. This study provides a theoretical basis and technical support for the development of polyurethane composite foams with integrated thermal regulation and flame-retardant properties, which can have broad application prospects in the fields of building energy conservation, energy storage equipment, and thermal mine insulation. Full article

In the context of the “carbon peaking and carbon neutrality” era, China’s steel industry, as one of the pillars of the national economy, must accelerate the exploration and adoption of innovative production processes to effectively reduce its carbon footprint. The numerical simulation of hydrogen-based shaft furnaces is an important method for studying the internal characteristics of steelmaking processes. Its objective is to set reasonable furnace parameters to significantly enhance production efficiency and environmental friendliness, ensuring that sustainability and economic benefits coexist in the steel manufacturing process. In order to develop a new shaft furnace, which simplifies the cooling parts, the mathematical model was used to conduct a numerical simulation analysis of hydrogen-based shaft furnaces. The Discrete Element Method (DEM) was employed to focus on the stress and wear behavior of internal components within the hydrogen-based shaft furnace. The results indicated that during the charging of iron ore pellets, the outlet area experienced friction and compression from Direct Reduced Iron (DRI), resulting in a maximum stress of 47,422.1 Pa at the output section. The stresses on the loosening roller were locally concentrated due to its clockwise rotational motion, with a maximum shear stress of 219,896.1 Pa. By applying the Archard wear theory and the moving bed model, the theoretical wear degrees of the refractory materials in the reduction section and the steel shell in the cooling section were obtained; the monthly wear rate of the loosening roller was approximately 0.601 mm. Reasonably setting the parameters and feeding speed of the hydrogen-based shaft furnace can optimize the force and wear conditions of internal components, achieving optimal operating conditions. This provides a reference for factories to effectively extend the service life of hydrogen-based shaft furnaces and offers reasonable suggestions for the future industrial application of hydrogen metallurgy. Full article

In order to address the issue of wind leakage leading to spontaneous coal combustion in goafs during gob-side entry mining, a KH570 silane coupling agent (SCA)-modified vinyl acetate–ethylene (VAE)/cement-based flexible spraying sealing material was developed. The mechanical properties and wind leakage sealing performance of the material were evaluated using specialized testing equipment. Furthermore, molecular dynamics simulations and microstructural characterization techniques were utilized to assess and model the interface compatibility of the material. The experimental results demonstrate that KH570 significantly enhanced the material’s mechanical properties. Following modification, the material exhibited increases in the maximum tensile strength, compressive strength, and flexural strength by 53%, 38%, and 29%, respectively. KH570 not only promotes the formation of additional calcium silicate hydrate (C-S-H) gel through cement hydration, but also establishes Si-O-Si chemical bonds with cement hydration products and hydrogen bonds with the VAE emulsion. This functions as a “molecular bridge”, significantly enhancing the interface performance of the composite. The interaction between the organic and inorganic phases contributes to the formation of an interpenetrating network structure, imparting excellent compressive, flexural, and tensile deformation resistance to the material. The wind leakage of the spray-modified material was reduced by 2.7 times compared to the unmodified material, significantly improving its sealing performance under mining-induced pressure conditions. This enhancement effectively minimizes spontaneous combustion in mined-out coal areas caused by wind leakage, thereby ensuring safer mining operations. Full article

This paper aims to present an overview of the current state of hydrogen storage methods, and materials, assess the potential benefits and challenges of various storage techniques, and outline future research directions towards achieving effective, economical, safe, and scalable storage solutions. Hydrogen is recognized as a clean, secure, and cost-effective green energy carrier with zero emissions at the point of use, offering significant contributions to reaching carbon neutrality goals by 2050. Hydrogen, as an energy vector, bridges the gap between fossil fuels, which produce greenhouse gas emissions, global climate change and negatively impact health, and renewable energy sources, which are often intermittent and lack sustainability. However, widespread acceptance of hydrogen as a fuel source is hindered by storage challenges. Crucially, the development of compact, lightweight, safe, and cost-effective storage solutions is vital for realizing a hydrogen economy. Various storage methods, including compressed gas, liquefied hydrogen, cryo-compressed storage, underground storage, and solid-state storage (material-based), each present unique advantages and challenges. Literature suggests that compressed hydrogen storage holds promise for mobile applications. However, further optimization is desired to resolve concerns such as low volumetric density, safety worries, and cost. Cryo-compressed hydrogen storage also is seen as optimal for storing hydrogen onboard and offers notable benefits for storage due to its combination of benefits from compressed gas and liquefied hydrogen storage, by tackling issues related to slow refueling, boil-off, and high energy consumption. Material-based storage methods offer advantages in terms of energy densities, safety, and weight reduction, but challenges remain in achieving optimal stability and capacities. Both physical and material-based storage approaches are being researched in parallel to meet diverse hydrogen application needs. Currently, no single storage method is universally efficient, robust, and economical for every sector especially for transportation to use hydrogen as a fuel, with each method having its own advantages and limitations. Moreover, future research should focus on developing novel materials and engineering approaches in order to overcome existing limitations, provide higher energy density than compressed hydrogen and cryo-compressed hydrogen storage at 70 MPa, enhance cost-effectiveness, and accelerate the deployment of hydrogen as a clean energy vector. Full article

This bibliometric study examines the evolution of compressed-hydrogen storage technologies over the last 20 years, revealing exponential growth in research and highlighting key advancements in compressed-hydrogen storage, materials-based solutions and integration with renewable energy systems. The analysis highlights the pivotal role of composite material tanks and the filament-winding process in revolutionizing storage technology. These innovations have enhanced safety, reduced weight and facilitated adaptation for use in automotive and industrial applications. Global research efforts are characterized by substantial international collaboration, spearheaded by a small cohort of highly productive researchers and supported by a broader network of contributors. Notwithstanding the ongoing challenges pertaining to safety considerations and cost scalability, the potential of hydrogen as a clean energy carrier and its role in balancing renewable energy systems serve to reinforce its importance in the transition to sustainable energy. Full article

Although there are various boron production methods for modified activated carbons used in sulfur removal, catalyst synthesis, and hydrogen capture/storage processes, the modification of activated carbon with borax solutions has attracted attention as the easiest synthesis method. However, structural characterization analyses in previous studies contradict each other and, therefore, more detailed characterization is needed. In this study, 0.25 M and 0.5 M borax solutions are prepared in distilled water; then, 2 g of commercial activated carbon is added to each one, mixed at 60 °C, filtered, and dried. Thus, two different boron-modified activated carbon materials are obtained. Structural characterization tests of these materials are performed and analyzed by comparing with the literature. As a result, two different boron-modified activated carbon structural analyzes are compared and it is confirmed that commercially activated carbon material induced phase composition and chemical bond modification as a result of modification with borax. It is revealed that the induction of phase composition and chemical bond modification is more dominant with increasing borax concentration. The produced boron-modified activated carbon materials have great promise for the development of new technologies in the fields of the environment, energy, lightweight compressible materials, thermal insulation, and composite materials. Full article