Khalifa University Introduction to Hydrogen Technologies and Applications Lecture Notes PDF 2024

Introduction to Hydrogen Technologies and Applications (CHEG 360) – FALL 2024 Chapter 6: Hydrogen Storage Lecture 15: Chemical and Physical Storage of Hydrogen (Ch6-2) Dr. Lourdes F. Vega Professor, Chemical and Petroleum Engineering Departm...

Introduction to Hydrogen Technologies and Applications (CHEG 360) – FALL 2024 Chapter 6: Hydrogen Storage Lecture 15: Chemical and Physical Storage of Hydrogen (Ch6-2) Dr. Lourdes F. Vega Professor, Chemical and Petroleum Engineering Department Director, Research and Innovation Center on CO2 and Hydrogen (RICH Center) 17th October 2024  ku.ac.ae 2 Hydrogen news to share today CHEG360 – Fall 2024 Lecture 15: Chemical and Physical Hydrogen Storage (Ch 6-2) Prof. Lourdes F. Vega  ku.ac.ae 3 Content of this lecture: Chemical and physical hydrogen storage Chapter 6: Hydrogen generation, storage and utilization, Zhang et al. – 6.1 – 6.3 The hydrogen supply chain Physical and material-based storage of hydrogen Underground hydrogen storage Metal hydrides for chemical hydrogen storage - Types of metal hydrides - Challenges with metal hydrides practical application Physical storage using nanostructured and porous materials ─ Basics on adsorption ─ Physical storage using metal-organic frameworks ─ Physical storage using carbon nanostructures ─ Other nanostructures (Clathrate Hydrates) ─ Current status for hydrogen storage technology CHEG360 – Fall 2024 Lecture 15: Chemical and Physical Hydrogen Storage (Ch 6-2) Prof. Lourdes F. Vega  ku.ac.ae 4 Hydrogen storage solutions From Lecture 14 Material-based Lecture 14 Physical-based Physi-sorbents Liquid carriers Hydrides Underground H2 Cryo Storage Metal organic Compressed H2 Liquid H2 compressed H2 Frameworks Metal Hydrides (MOFs) Chemi- sorbents Carbon-based Liquid organic Complex Materials hydrogen hydrides (CBM) carriers (LOHCs) UHS: https://www.hsu-hh.de/hmech/wp- Zeolites content/uploads/sites/845/2022/09/uhs-1024x506.png MOFs: Rivard, Etienne, et al. "Hydrogen Storage for Mobility: A Covalent Review." Materials, vol. 12, no. 12, 2018, p. 1973, organic Ammonia Methanol https://doi.org/10.3390/ma12121973. framework CNTs: Froudakis, George E. "Hydrogen Storage in Nanotubes & (COFs)) Nanostructures." Materials Today, vol. 14, no. 7-8, 2011, pp. 324-328, https://doi.org/10.1016/S1369-7021(11)70162-6. CHEG360 – Fall 2024 Lecture 15: Chemical and Physical Hydrogen Storage (Ch 6-2) Prof. Lourdes F. Vega  ku.ac.ae 5 Physical Storage of Hydrogen Remember concepts from lecture 13 Hydrogen can be stored in cylinders/tanks by changing its physical state into compressed or liquid hydrogen. Issues: (1) low volumetric energy content, (2) stringent operating conditions to change physical state of hydrogen, (3) high cost for storage cylinders Storage of 1 kg of H2 CHEG360 – Fall 2024 Lecture 15: Chemical and Physical Hydrogen Storage (Ch 6-2) Prof. Lourdes F. Vega  ku.ac.ae 6 Material-based storage of hydrogen Alternative option is to store hydrogen in materials, either physically or chemically bonded. Examples: Ammonia and LOHC are liquids that chemically store hydrogen. Solid materials have lower volumes than liquids for same mass. Chemical storage in liquids Physical storage Chemical storage in solids in solids CHEG360 – Fall 2024 Lecture 15: Chemical and Physical Hydrogen Storage (Ch 6-2) Prof. Lourdes F. Vega  ku.ac.ae 7 Metal hydrides for hydrogen storage Metal hydrides are solid materials formed from chemically reacting hydrogen with transition metals, intermetallic compounds, or alloys. Metal hydrides have higher volumetric hydrogen storage capacity than liquid hydrogen, making them ideal for on-board hydrogen storage applications. Metal hydrides are stable at low pressure, hence, safer and easier for hydrogen storage. Metal hydride powder H2 gas Metal CHEG360 – Fall 2024 Lecture 15: Chemical and Physical Hydrogen Storage (Ch 6-2) Prof. Lourdes F. Vega  ku.ac.ae 8 Storing hydrogen in metal hydrides Source: Helmholtz-Zentrum Hereon (Youtube Channel) https://www.youtube.com/watch?v=9j2UMT06MTI CHEG360 – Fall 2024 Lecture 15: Chemical and Physical Hydrogen Storage (Ch 6-2) Prof. Lourdes F. Vega  ku.ac.ae 9 Calculating storage capacity of metal hydrides Either using gravimetric or volumetric storage capacities. The ideal storage capacity is determined by the stoichiometry of the hydride. 𝑥𝑀𝐻 𝑀𝐻 : Atomic mass of hydrogen Gravimetric: 𝜌′ = × 100 𝑀 𝑥𝑀𝐻 + 𝑀𝑀 𝑀𝑀 : Atomic mass of metal 𝑚𝐻 𝑥𝑀𝐻 𝑚𝐻 : Mass of stored hydrogen ′ Volumetric: 𝜌𝑉 = = 𝑉𝑀 𝑀𝑀 /𝜌𝑀 𝜌𝑀 : Mass density of metal Real capacity differs from ideal due to presence of impurities or defects in material, or hydrogen physical adsorption. CHEG360 – Fall 2024 Lecture 15: Chemical and Physical Hydrogen Storage (Ch 6-2) Prof. Lourdes F. Vega  ku.ac.ae 10 Measuring storage capacity of metal hydrides Compared to liquid hydrogen, metal hydrides have higher volumetric density, but low gravimetric density. But, safer and easier to store. CHEG360 – Fall 2024 Lecture 15: Chemical and Physical Hydrogen Storage (Ch 6-2) Prof. Lourdes F. Vega  ku.ac.ae 11 Metal hydrides for hydrogen storage: Process Storage in metal hydrides is a reversible chemical process, involving: (1) hydrogenation: the formation of metal-hydrogen bonds, and (2) dehydrogenation: releasing hydrogen by breaking chemical bonds. 𝑥 𝑀 + 𝐻2 2 𝑀𝐻𝑥 + 𝑄 𝑄: Heat of hydride formation Hydrogenation Process Dehydrogenation Process Occurs at high pressure and is an Occurs at low pressure and is an exothermic process. endothermic process (393 – 573 K) CHEG360 – Fall 2024 Lecture 15: Chemical and Physical Hydrogen Storage (Ch 6-2) Prof. Lourdes F. Vega  ku.ac.ae 12 Hydrogenation of metal hydrides: Thermodynamics Increasing hydrogen pressure (PA), the metal starts to Pressure-composition-temperature adsorb hydrogen to form metal-hydrogen solution (α- (P-C-T) curve for hydrogenation and phase). dehydrogenation cycles. When pressure reached “A”, hydrides start to form (β- 𝛼+𝛽 phase). The hydrogen pressure (PA) remains nearly constant while hydrogen content increases. The hydrogenation process is completed at location “B”. 𝛼+𝛽 CHEG360 – Fall 2024 Lecture 15: Chemical and Physical Hydrogen Storage (Ch 6-2) Prof. Lourdes F. Vega  ku.ac.ae 13 Dehydrogenation of metal hydrides: Thermodynamics Pressure-composition-temperature A desorption plateau with lower near-constant hydrogen (P-C-T) curve for hydrogenation and pressure (PD). dehydrogenation cycles. A hysteresis loop is formed between adsorption and desorption plateaus that represents loss in efficiency due to 𝛼+𝛽 reversable degradation of materials. The plateau width Δ(H/M)r is the reversible capacity that is smaller than the maximum ideal storage capacity. 𝛼+𝛽 CHEG360 – Fall 2024 Lecture 15: Chemical and Physical Hydrogen Storage (Ch 6-2) Prof. Lourdes F. Vega  ku.ac.ae 14 Hydrogenation process - Microscopic 1. Physisorption of molecular hydrogen (H2) on metal surface via weak interactions. 2. Chemisorption of atomic hydrogen (H) via dissociation of adsorbed molecule (H2) by electron transfer at high temperature and pressure. Thermal or catalytic activation is needed. 3. Diffusion of H atoms through material at subsurface sites to become H solution in metal (α-phase). 4. Phase transition to stable hydride (β-phase) with increasing hydrogen concentration. CHEG360 – Fall 2024 Lecture 15: Chemical and Physical Hydrogen Storage (Ch 6-2) Prof. Lourdes F. Vega  ku.ac.ae 15 Hydrogenation process - Macroscopic 1. Hydrogen adsorption on metal surface and diffusion through metal. 2. Reaction between hydrogen and metal to form metal hydride, with random hydrides formed on the surface. 3. Reaction propagation through metal core and coalescence of hydride patches forming hydride shell around metal. 4. Thickening of hydride shell with reaction propagation, however, the shell prevents diffusion of hydrogen from atmosphere into the metal core. CHEG360 – Fall 2024 Lecture 15: Chemical and Physical Hydrogen Storage (Ch 6-2) Prof. Lourdes F. Vega  ku.ac.ae 16 Binary metal hydrides Even if they are called “binary metal hydrides”, they only contain a single element of metal bonded with hydrogen, that are either very stable or unstable. Most famous is magnesium hydride (MgH2) and aluminum hydride (AlH3) with high gravimetric densities (7.5 – 10 wt.%), but high desorption temperatures (603 K). CHEG360 – Fall 2024 Lecture 15: Chemical and Physical Hydrogen Storage (Ch 6-2) Prof. Lourdes F. Vega  ku.ac.ae 17 Metal alloy hydrides They are ternary systems (ABxHy) formed when two or more metallic elements are combined and reacted with hydrogen. Element A is typically a rare earth or an alkaline metal that forms stable hydride, while element B is a transition metal that forms unstable hydride with x = 0.5, 1, 2, and 5, resulting in intermediate stable hydrides. Most famous is LaNi5H7 , but they have low gravimetric density (1.25 wt.%), and high sorption temperatures. Structure of LaNi5H7. The sizes of the atom are declined from La, to Ni, to H. Source: Sorensen Hydrogen and Fuel Cells, 3rd ed., Elsevier Academic Press, Amsterdam, 2004. CHEG360 – Fall 2024 Lecture 15: Chemical and Physical Hydrogen Storage (Ch 6-2) Prof. Lourdes F. Vega  ku.ac.ae 18 Complex metal hydrides They have the chemical formula of AxByHz, with A an element in the first or second group in periodic table, and B is either aluminum, nitrogen or boron forming alanates, nitrides, and borohydrides, with the hydrogen bounded either ionically or covalently, and have with the highest storage density. Most investigated is sodium alanate (NaAlH4): 3𝑁𝑎𝐴𝑙𝐻4 → 𝑁𝑎3 𝐴𝑙𝐻6 + 2𝐴𝑙 + 3𝐻2 @ 483 – 493 K NaAlH4 Dehydrogenation: @ 523K 𝑁𝑎3 𝐴𝑙𝐻6 → 3𝑁𝑎𝐻 + 𝐴𝑙 + 1.5 𝐻2 This process is irreversible with slow desorption kinetics, which becomes reversible with addition of TiCl3 catalyst. Ti-doped NaAlH4 has practical applications with good gravimetric density (7.5 wt%) and desorption at 393 K and hydrogenation at 443 K. CHEG360 – Fall 2024 Lecture 15: Chemical and Physical Hydrogen Storage (Ch 6-2) Prof. Lourdes F. Vega  ku.ac.ae 19 Challenges with practical application of metal hydrides The major challenges with metal hydrides include their high adsorption/desorption temperature, and slow kinetics. Strong chemical bonds (> 50 kJ.mol-1) between hydrogen and metals in hydride result in high storage capacity, stability at room temperature, and high energy release during hydrogenation process. However, high temperature is needed to break these bonds and release hydrogen. Target is to reduce binding energy (Eb) for hydrides through thermodynamic destabilization, while minimizing reduction in storage capacity. Proposed methods include nanometer size hydride crystals or adding nano-sized catalysts. Targeted range of bond strengths that allow hydrogen release around room temperature for chemisorption and physisorption storage materials. Source: V. Berube et al. International Journal of Energy Research 2007, 31(6–7), 637–663. CHEG360 – Fall 2024 Lecture 15: Chemical and Physical Hydrogen Storage (Ch 6-2) Prof. Lourdes F. Vega  ku.ac.ae 20 Summary - metal hydrides for hydrogen storage Storage in metal hydrides is a reversible chemical process, involving: (1) hydrogenation: the formation of metal-hydrogen bonds, and (2) dehydrogenation: releasing hydrogen by breaking chemical bonds. Hydrogenation Process Dehydrogenation Process high pressure low pressure and high temperature (393 – 573 K) Metal hydrides have higher volumetric hydrogen storage capacity than liquid hydrogen, making them ideal for on-board hydrogen storage applications. Main challenge with metal hydrides is the low gravimetric storage capacity and high desorption temperature. CHEG360 – Fall 2024 Lecture 15: Chemical and Physical Hydrogen Storage (Ch 6-2) Prof. Lourdes F. Vega  ku.ac.ae 21 Hydrogen Storage - adsorption Lecture 14 Underground H2 Storage Lecture 13 Chemical storage in liquids Chemical storage in solids Physical storage in solids Chemical storage in https://hydrogeneurope.eu/hydrogen-storage liquids CHEG360 – Fall 2024 Lecture 15: Chemical and Physical Hydrogen Storage (Ch 6-2) Prof. Lourdes F. Vega  ku.ac.ae 22 Absorption vs. Adsorption Bulk (Volume) Surface Phenomenon Phenomenon Adsorbing inside (borrowed from Dr. Daniel Bahamon) pores ADSORPTION: a fluid accumulates on the surface of a solid adsorbent (or a liquid), forming a film CHEG360 – Fall 2024 Lecture 15: Chemical and Physical Hydrogen Storage (Ch 6-2) Prof. Lourdes F. Vega  ku.ac.ae 23 Types of Adsorption Factors affecting adsorption Temperature: the amount adsorbed increases with decrease in temperature. Pressure: adsorption increases with pressure up to certain extent until saturation is achieved. PROPERTIES PHYSISORPTION CHEMISORPTION Bonding Van der Waals Chemical bonding Surface Area: the adsorption capacity interactions (e.g. involving orbital overlap increases with increase in surface area. London dispersion, and charge transfer. dipole-dipole). Activation of Adsorbent: Enthalpy 5-50 kJ mol-1 40-800 kJ mol-1 Saturation Multi-layer Mono-layer Nature Reversible Mostly Irreversible CHEG360 – Fall 2024 Lecture 15: Chemical and Physical Hydrogen Storage (Ch 6-2) Prof. Lourdes F. Vega  ku.ac.ae 24 Adsorption isotherm Source: Hand of Brothers Animations (Youtube Channel) https://www.youtube.com/watch?v=a32jJJiimXU&ab_channel=HandofBrothersAnimations CHEG360 – Fall 2024 Lecture 15: Chemical and Physical Hydrogen Storage (Ch 6-2) Prof. Lourdes F. Vega  ku.ac.ae 25 Adsorption equilibria If the adsorbent and adsorbate are in contact long enough, an equilibrium will be established between the amount adsorbed and the amount in solution. This equilibrium relationship is described by isotherms. Adsorption-Desorption cycle Not recovered CHEG360 – Fall 2024 Lecture 15: Chemical and Physical Hydrogen Storage (Ch 6-2) Prof. Lourdes F. Vega  ku.ac.ae 26 Compressed hydrogen vs adsorption in materials- hydrogen storage Short question: Which materials can provide a high surface area? J. Ren et al., Int. J. Hydrog. Energ. 2017, 42, 289-311. CHEG360 – Fall 2024 Lecture 15: Chemical and Physical Hydrogen Storage (Ch 6-2) Prof. Lourdes F. Vega  ku.ac.ae 27 Physical Storage using Metal-Organic Frameworks (MOFs) Source: Micromeritics (Youtube Channel) https://www.youtube.com/watch?v=m91P-R3kxOs&ab_channel=Micromeritics CHEG360 – Fall 2024 Lecture 15: Chemical and Physical Hydrogen Storage (Ch 6-2) Prof. Lourdes F. Vega  ku.ac.ae 28 Physical Storage using Metal-Organic Frameworks (MOFs) MOFs are crystalline inorganic-organic hybrid structures containing metal cluster or ions as nodes, and organic ligands as linkers. https://www.numat.tech/pos t/ion-x-engineering- solutions-for-next- generation-electronics Inorganic Organic (metal ion) (ligand or complex) MOFs have higher number of pores and larger surface area compared to zeolites and porous carbon material, allowing higher hydrogen uptake. M. Garcia, et al., Organic & Biomolecular Chemistry (2020), 18, 8058-8073. CHEG360 – Fall 2024 Lecture 15: Chemical and Physical Hydrogen Storage (Ch 6-2) Prof. Lourdes F. Vega  ku.ac.ae 29 Physical Storage using Metal-Organic Frameworks (MOFs) Variety of nodes and linkers materials allow infinite geometric and chemical variations of MOFs. D. Britt et al., PNAS. 2008, 105(33), 11623-11627. A.H. Mashhadzadeh et al., J. Composites Science. 2020, 4(2), 75-85 CHEG360 – Fall 2024 Lecture 15: Chemical and Physical Hydrogen Storage (Ch 6-2) Prof. Lourdes F. Vega  ku.ac.ae 30 MOFs performance for H 2 storage Short question: H2 uptake is typically reported at 77 K. Why at this temperature? The amount of H2 uptake depends on surface area, pore size, catenation, ligand structure, spillover, and sample purity. Structural modifications of MOFs can greatly affect pore size and surface area. 2 BET surface area goes up to 7000 m /g 77 K, 2 bar D.P. Broom, et al. International Journal of Hydrogen Energy S.J. Yang et al. Chemistry of Materials 2012, 24(3), 464–470. 2019, 44, 7768-7779. CHEG360 – Fall 2024 Lecture 15: Chemical and Physical Hydrogen Storage (Ch 6-2) Prof. Lourdes F. Vega  ku.ac.ae 31 Physical Storage using Carbon Nanostructures Carbon nanostructures are carbon-based materials with nanoscale microstructure including carbon nanotubes (CNTs), fullerenes, nanofibers, graphene. They can be used for hydrogen storage due to their good adsorption ability, high specific surface area, porous microstructure, and low mass density. The mechanism can involve physisorption and chemisorption. CNT Fullerene (C60) Nanofibers Graphene CHEG360 – Fall 2024 Lecture 15: Chemical and Physical Hydrogen Storage (Ch 6-2) Prof. Lourdes F. Vega  ku.ac.ae 32 H2 Storage in Carbon Nanotubes H2 Storage in Graphene Loading the carbon nanotubes (CNTs) with Pd or Pt nanoparticles can promote chemisorption via spillover mechanism which enhances the H2 storage capacity. Graphene can have high hydrogen storage capacity (surf. area = 2,629 m2/g). Stream of hydrogen atoms can convert graphene to graphane, which can release stored hydrogen by heating to 723 K. Metal doping or composite structure can enhance storage capacity under T. Das et al. RSC Advances 2015, 5, 41468–41474 moderate pressure and temperature. CHEG360 – Fall 2024 Lecture 15: Chemical and Physical Hydrogen Storage (Ch 6-2) Prof. Lourdes F. Vega  ku.ac.ae 33 Physical Storage using Clathrate Hydrates Clathrate hydrates are solids formed when guest molecules occupy cages formed from hydrogen- bonded water molecule networks. The empty cages are usually unstable and can be stabilized with inclusion of appropriately sized molecules. Clathrate hydrates of hydrogen form sII structures Marboeuf, U. et al. Astron. Astrophys. 2012, 542, A821–A8219. with 136 H2O molecules resulting in two different- sized cages (512 and 51264). Extremely high pressures (2000 bar) are needed to maintain the stability of the hydrates, which is impractical. Y.H. Hu and E. Ruckenstein, Angewandte Chemie, 2006 45(13), 2011-2013. CHEG360 – Fall 2024 Lecture 15: Chemical and Physical Hydrogen Storage (Ch 6-2) Prof. Lourdes F. Vega  ku.ac.ae 34 Current status and US DOE targets for hydrogen storage technology Volumetric and gravimetric hydrogen density of existing developed hydrogen storage systems with respect to US DOE targets E. Boateng, A. Chen. Materials Today Advances 2020, 6, 100022 S-Y Lee et al., Processes 2022, 10(2), 304. Short question: Where are MOFs? CHEG360 – Fall 2024 Lecture 15: Chemical and Physical Hydrogen Storage (Ch 6-2) Prof. Lourdes F. Vega  ku.ac.ae 36 Take home messages S-Y Lee et al., Recent Progress Using Solid-State Materials for Hydrogen Storage: A Short Review. Processes 2022, 10(2), 304. Hydrogen storage Question: capacity of What are the main commonly used challenges for materials with physical adsorbents respect to operating to be used at large- temperature scale? D.J. Durbin et al., Int. J. Hydrog. Energ. 2013, 38 (2013) 14595-14617. CHEG360 – Fall 2024 Lecture 15: Chemical and Physical Hydrogen Storage (Ch 6-2) Prof. Lourdes F. Vega  ku.ac.ae 37 Content of Chapter 6 (lectures 14 and 15) Chapter 6: Hydrogen generation, storage and utilization, Zhang et al. – 6.1 – 6.3 The hydrogen supply chain Physical and material-based storage of hydrogen Underground hydrogen storage Metal hydrides for chemical hydrogen storage - Types of metal hydrides - Challenges with metal hydrides practical application Physical storage using nanostructured and porous materials ─ Basics on adsorption ─ Physical storage using metal-organic frameworks ─ Physical storage using carbon nanostructures ─ Other nanostructures (Clathrate Hydrates) ─ Current status for hydrogen storage technology CHEG360 – Fall 2024 Lecture 15: Chemical and Physical Hydrogen Storage (Ch 6-2) Prof. Lourdes F. Vega  Thank you ‫شكرا‬ Prof. Lourdes Vega Dr. Daniel Bahamon Garcia [email protected] [email protected] https://www.ku.ac.ae/research-centers/research-and-innovation-center-on-co2-and-hydrogen-rich