Hydrogen (H2) is predicted to play a significant role in various sectors, including transportation, energy storage, and rechargeable batteries. Several research initiatives are underway to identify appropriate alloys for storing and using hydrogen in portable devices. The purpose of this article is to explore the significance, properties, functions, and effects of heat treatment on hydrogen storage in alloys.
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Hydrogen Storage Alloys: Overview and Significance
Storage of hydrogen is a critical enabler for the growth of hydrogen and fuel cell systems in sectors such as stationary power generation, power transmission, and mobility.
Hydrogen has the greatest energy density per weight of any fuel resource; yet, because of its low ambient temperature efficiency, it has a low energy density per unit volume, necessitating the development of new storage technologies with the potential for greater energy density.
The safe and effective storage of hydrogen is critical to attaining a carbon-free energy cycle. Metal-hydride forming alloy systems have piqued interest for volume-efficient hydrogen storage due to the high-volume density of hydrogen atoms in metal-hydrides, which often surpasses the atomic density of liquid hydrogen.
The major benefits of storing hydrogen in metal hydride alloys are their high volumetric and gravimetric capabilities, safety, and cheap overall cost.
Characteristics and Functions of Hydrogen Storage Alloys
Hydrogen is easily integrated into hydrogen storage alloys, and metal hydrides occur when the amount of hydrogen in the alloy reaches a particular limit. As a consequence, hydrogen inhabits certain locations inside the metal crystallites.
The parameters of hydrogen storage in an alloy are governed by the contact of hydrogen with metallic atoms in the interfacial region, and hence the hydrogen storage qualities are heavily influenced by the alloy's crystal structure. Several hydrogen-storing alloys have been produced and widely utilized in industry.
Metals from periodic table groups IIA through VA easily mix with hydrogen to generate metal hydrides. Except for Vanadium, all of these metals create highly stable hydrides that are challenging to absorb and desorb hydrogen selectively at normal temperature and pressure.
Conversion of energy, hydrogen isotope isolation, catalysis, hydrogen storage, dissociation, purification, restoration, and transport are the primary functions of hydrogen storage alloys.
Heat Treatment: An Important Manufacturing Technique
Heat treatment is the technique of heating metals without allowing them to reach a liquid or melted state, and then freezing them in a controlled manner to choose desirable mechanical qualities. Heat treatment is used to make metals harder or more pliable, more scratch tolerant, or more malleable.
Annealing, case tempering, deposition strengthening, searing, carburizing, normalizing, and quenching are all heat treatment procedures. Although the phrase "heat treatment" refers to techniques in which heating and cooling are done specifically to modify characteristics, heating and cooling sometimes occur accidentally during other production processes such as forming processes or soldering.
Impacts of Heat Treatment on H2 Storage Alloys: Research Examples
In a recent article published in the Journal of Alloys and Compounds, a titanium-based hydrogen storage alloy was created to boost hydrogen storage capacity using low-temperature heat treatment. The microstructure, hydrogen storage characteristics, and mechanism of hydrogen absorption/desorption were all examined.
The heat-treated hydrogen storage alloy had a 12% greater hydrogen storage capability than the as-cast alloy, according to the results. Furthermore, the activation energy of the as-cast alloy was around 83.30 kJ/mol, but heat-treated alloy activation energies fell to 66.26 kJ/mol. The reduced stability of hydride following heat treatment caused this drop in activation energy.
The influence of heat treatment on the crystalline structure, morphology, hydrogen storage characteristics, and heat resistance of an arc-melted vanadium alloy was investigated in another study published in the journal Progress in Natural Sciences.
Both the as-cast and tempered vanadium-based hydrogen storage alloys were discovered to be composed of a single body-centered cubic (bcc) phase. Because of the uniform composition and excellent structure, the as-cast alloy's hydrogen absorption/desorption kinetic properties were considerably enhanced after heat treatment.
Future Outlook on Hydrogen Storage Alloys
Worldwide, the rising use of renewable energy sources, allowed by higher efficiency and lower prices and motivated by the need to minimize the consequences of global warming, has greatly expanded research in the fields of renewable energy generation, storage, transmission, and end-use.
The utilization of hydrogen as a clean, effective energy channel for energy storage is crucial for this debate. Hydrogen energy is the potential mainstream replacement for fossil-based fuels since it is environmentally friendly, renewable, efficient, and cost-effective.
Following several years of in-depth study and evaluation of hydrogen storage alloys for energy storage technologies, the next move toward industrialization is the scaling up of these energy storage solutions. The production of compact hydrogen storage alloys with reduced desorption temperatures at atmospheric hydrogen pressure and higher cycle stability would be aided by progress in these research areas.
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References and Further Reading
Chen, X. et al. (2022). Effect of heat treatment on microstructure and thermal stability of Ti19Hf4V40Mn35Cr2 hydrogen storage alloy. Journal of Alloys and Compounds. Available at: https://www.sciencedirect.com/science/article/pii/S0925838822017467?via%3Dihub
Hirscher, M. et al. (2020). Materials for hydrogen-based energy storage – past; recent progress and future outlook. Journal of Alloys and Compounds. Available at: https://www.sciencedirect.com/science/article/pii/S0925838819347942?via%3Dihub
Rong, M. et al. (2017). Effect of heat treatment on hydrogen storage properties and thermal stability of V 68 Ti 20 Cr 12 alloy. Progress in Natural Science. Available at: https://www.sciencedirect.com/science/article/pii/S1002007117301442?via%3Dihub
Zheng, J. et al. (2021). Current Research Trends and Perspectives on Solid-State Nanomaterials in Hydrogen Storage. Research. Available at: https://spj.sciencemag.org/journals/research/2021/375068