HYDROGEN STORAGE

(Materials) Arturo Fernandez Madrigal

Instituto de Energias Renovables-UNAM

afm@ier.unam.mx

¿what is the state of the art on hydrogen as energy

storage?

¿Which are the main challenges of involved

technologies?

Questions

Hydrogen Economic

Hydrogen and other fuels [Sørensen, 2005].

Propiedad Hidrógeno Metanol Metano Propano Gasolina Unidad Mínima energía de

ignición

0.02 ---- 0.29 0.25 0.24 mJ

Temperatura de

flama

2045 ---- 1875 ---- 2200 °C

Temperatura de

autoignición

585 385 540 510 230-500 °C

Máxima velocidad

de flama

3.46 ---- 0.43 0.47 ---- m/s

Rango de

flamabildad

4-75 7-36 5-15 2.5-9.3 1.0-7.6 Vol. %

Rango de

explosividad

13-65 ---- 6.3-13.5 ---- 1.1-3.3 Vol. %

Coeficiente de

difusión

0.61 0.16 0.20 0.10 0.05 10-3

m2/s

Energy Content of Comparative Fuels

Physical storage of H2

Chemical storage of hydrogen

New emerging methods

•Metal Hydride (“sponge”)

•Carbon nanofibers•Compressed

•Cryogenically liquified

•Methanol

•Alkali metal hydrides

•Sodium borohydride

•Ammonia

•Amminex tablets

•DADB (predicted)

•Solar Zinc production

•Alkali metal hydride slurry

Compressed

•Volumetrically and Gravimetrically inefficient, but

the technology is simple, so by far the most common in

small to medium sized applications.

•3500, 5000, 10,000 psi variants.

Liquid (Cryogenic)

•Compressed, chilled, filtered, condensed

•Boils at 22K (-251 C).

•Slow “waste” evaporation

•Kept at 1 atm or just slightly over.

•Gravimetrically and volumetrically efficient

but very costly to compress

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Metal Hydrides (sponge)

•Sold by “Interpower” in Germany

•Filled with “HYDRALLOY” E60/0

(TiFeH2)

•Technically a chemical reaction,

but acts like a physical storage

method

•Hydrogen is absorbed like in a

sponge.

•Operates at 3-30 atm, much

lower than 200-700 for

compressed gas tanks

•Comparatively very heavy, but

with good volumetric efficiency,

good for small storage, or where

weight doesn’t matter

Carbon Nanofibers

Complex structure

presents a large surface

area for hydrogen to

“dissolve” into

Early claim set the

standard of 65 kgH2/m2

and 6.5 % by weight as a

“goal to beat”

The claim turned out not

to be repeatable

Research continues…

Methanol

Broken down by reformer, yields CO, CO2,

and H2 gas.

Very common hydrogen transport method

Distribution infrastructure exists – same as

gasoline

Ammonia

Slightly higher volumetric efficiency than methanol

Must be catalyzed at 800-900 deg. C for hydrogen

release

Toxic

Usually transported as a liquid, at 8 atm.

Some Ammonia remains in the catalyzed hydrogen

stream, forming salts in PEM cells that destroy the

cells

Many drawbacks, thus Methanol considered to be a

better solution

Alkali Metal Hydrides

“Powerball” company, makes

small (3 mm) coated NaH

spheres.

“Spheres cut and exposed to

water as needed”

H2 gas released

Produces hydroxide solution

waste

Sodium Borohydrate

Sodium Borohydrate is the most popular of many

hydrate solutions

Solution passed through a catalyst to release H2

Commonly a one-way process (sodium metaborate

must be returned if recycling is desired.)

Some alternative hydrates are too expensive or toxic

The “Millennium Cell” company uses Sodium

Borohydrate technology

Amminex

•Essentially an Ammonia storage method

•Ammonia stored in a salt matrix, very stable

•Ammonia separated & catalyzed for use

•Likely to have non-catalyzed ammonia in hydrogen stream

•Ammonia poisoning contraindicates use with PEM fuel cells,

but compatible with alkaline fuel cells.

Amminex

•High density, but relies on ammonia production for fuel.

•Represents an improvement on ammonia storage,

which still must be catalyzed.

•Ammonia process still problematic.

Diammoniate of Diborane (DADB)

So far, just a computer simulation.

Compound discovered via exploration of Nitrogen/Boron/Hydrogen compounds (i.e. similar to Ammonia Borane)

Thermodynamic properties point towards spontaneous hydrogen re-uptake – would make DADB reusable (vs. other borohydrates)

Solar Zinc production

Zinc powder can be easily transported

Zinc can be combined with water to produce H2

Alternatively could be made into Zinc-Air batteries (at higher energy efficiency)

CeMIESol-Proyecto 10. “Combustibles

Solares y Procesos Industriales” (COSOLπ).

•Objetivo: Investigación y desarrollo en la utilización de energía solar para el

desarrollo sustentable de procesos termoquímicos, producción de combustibles

límipos y valorización de materiales empleados en la industria nacional.

Alkaline metal hydride slurry

SafeHydrogen, LLC

Concept proven with Lithium Hydride, now working on magnesium hydride slurry

Like a “PowerBall” slurry

Hydroxide slurry to be re-collected to be “recycled”

Competitive efficiency to Liquid H2

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On Board Hydrogen Storage Targets were set by the FreedomCAR Partnership in January 2002 between the

United States Council for Automotive Research (USCAR) and U.S. DOE

(Targets assume a 5-kg H2 storage system).

The 2005 targets were not reached in 2005. The targets were revised in 2009 to

reflect new data on system efficiencies obtained from fleets of test cars. The

ultimate goal for volumetric storage is still above the theoretical density of liquid

hydrogen.

It is important to note that these targets are for the hydrogen storage system,

not the hydrogen storage material. System densities are often around half those

of the working material, thus while a material may store 6 wt % H2, a working

system using that material may only achieve 3 wt % when the weight of tanks,

temperature and pressure control equipment, etc., is considered.

In 2010, only two storage technologies were identified as being susceptible to

meet DOE targets: MOF-177 exceeds 2010 target for volumetric capacity, while

cryo-compressed H2 exceeds more restrictive 2015 targets for both gravimetric

and volumetric capacity).

Storage Method Comparison

Method Gravimetric storage

efficiency (% mass H2)

Volumetric mass (in kg)

of H2 per litre

Comments

High pressure in cylinders 0.7-3.0 0.015 Widely used

Metal Hydride 0.65 0.028 Suitable for small systems

Cryogenic liquid 14.2 0.040 Widely used for bulk

storage

Methanol 6.9 0.020 Low cost chemical

Sodium Hydride 2.2 0.036 Problem of disposing of

spent solutions

NaBH4 solution in water 3.35 1.0 Very expense to run

Sodium hydride slurry 0.9 1 Must reclaim used slurry

DABD 0.1-0.2 0.09-0.1 (numbers for plain

“diborane”and sodium

borohydride, should be

similar)

Amminex 9.1 0.081

US-DOE goal 9.0 0.81

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What Are the Challenges?

Hydrogen has a very high energy content by weight (about 3 times more than

gasoline), but it has a very low energy content by volume (liquid hydrogen is about 4

times less than gasoline). This makes hydrogen a challenge to store, particularly within

the size and weight constraints of a vehicle.

A light-duty fuel cell vehicle will carry approximately 4-10 kg of hydrogen on board

(depending on the size and type of the vehicle) to allow a driving range of more than

300 mi, which is generally regarded as the minimum for widespread public acceptance.

Drivers must also be able to refuel at a rate comparable to the rate of refueling today’s

gasoline vehicles.

Using currently available high-pressure tank storage technology, placing a sufficient

quantity of hydrogen onboard a vehicle to provide a 300-mile driving range would

require a very large tank — larger than the trunk of a typical automobile. Aside from

the loss of cargo space, there would also be the added weight of the tank(s), which

could reduce fuel economy. Low-cost materials and components for hydrogen storage

systems are needed, along with low-cost, high-volume manufacturing methods for

those materials and components.

Hydrogen can be stored on the surfaces of solids by adsorption. In adsorption,

hydrogen associates with the surface of a material either as hydrogen molecules (H2)

or hydrogen atoms (H). This figure depicts hydrogen adsorption within MOF-74.

Storage Hydrogen (Metal Hydride)

Some metals and metal alloys have the property of forming reversible covalent bonds when they react with hydrogen.

Metal Hydride can store hydrogen by adsorb-desorb cycles.

Metal hydrides carry a proportion of 1-7% by weight of hydrogen.

More than 200 different alloys have been studied being. The metal transition group are more suitable.

Metal hydrides requires high temperatures (300-350ºC) to release hydrogen.

Metal Hydride stored at pressures between 3 and 6 MPa

Contin………

M + nH2 → M-H2n + heat (absorption)

M-H2n + heat → M + nH2 (desorption)

M represents the metal, element or alloy.

The one of the major problem of the metal-hydride tanks is necessary the addition energy to recover the hydrogen

Hydride storage systems are becoming a very safe way to store hydrogen in domestic applications .

Fuels and

storage

Storage energy

density

Storage of 3 kg

H2 (360 MJ)

Storage of 10

kg de H2

(1200MJ)

MJ/kg MJ/l kg l kg l

Gasoline 43 32 8.3 11.3 28 37.5

H2 liq. 120 8.5 3 42.3 10 141

FeTiH 1.80 3 200 84 665 280

MgH2 8.73 7.85 41.3 46 138 153

http://hcc.hanwha.co.kr/english/pro/ren_hsto_idx.jsp

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Targets for On-Board Hydrogen Storage

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Metal-organic frameworks (MOFs)

Metal-organic frameworks represent another class of synthetic porous materials that store hydrogen and energy at the molecular level.

MOFs are highly crystalline inorganic-organic hybrid structures that contain metal clusters or ions (secondary building units) as nodes and organic ligands as linkers.

When guest molecules (solvent) occupying the pores are removed during solvent exchange and heating under vacuum, porous structure of MOFs can be achieved without destabilizing the frame and hydrogen molecules will be adsorbed onto the surface of the pores by physisorption.

Compared to traditional zeolites and porous carbon materials, MOFs have very high number of pores and surface area which allow higher hydrogen uptake in a given volume.

The, research interests on hydrogen storage in MOFs have been growing since 2003 when the first MOF-based hydrogen storage was introduced. Since there are infinite geometric and chemical variations of MOFs based on different combinations of SBUs and linkers, many researches explore what combination will provide the maximum hydrogen uptake by varying materials of metal ions and linkers.

In 2006, chemists at UCLA and the University of Michigan have achieved hydrogen storage concentrations of up to 7.5 wt% in MOF-74 at a low temperature of 77 K.

In 2009, researchers at University of Nottingham reached 10 wt% at 77 bar (1,117 psi) and 77 K with MOF NOTT-112.

Most articles about hydrogen storage in MOFs report hydrogen uptake capacity at a temperature of 77K and a pressure of 1 bar because such condition is commonly available and the binding energy between hydrogen and MOF is large compare to the thermal vibration energy which will allow high hydrogen uptake capacity.

Varying several factors such as surface area, pore size, catenation, ligand structure, spillover, and sample purity can result different amount of hydrogen uptake in MOFs.

Common ligands in MOFs

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MOF-177 On-Board Hydrogen Storage System

(Argonne National Laboratory, USA)

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Clathrate hydrates H2 caged in a clathrate hydrate was first reported in 2002, but

requires very high pressures to be stable. In 2004, researchers from Delft University of Technology and Colorado School of Mines showed solid H2-containing hydrates could be formed at ambient temperature and 10s of bar by adding small amounts of promoting substances such as THF. These clathrates have a theoretical maximum hydrogen densities of around 5 wt% and 40 kg/m3.

Glass capillary arrays A team of Russian, Israeli and German scientists have

collaboratively developed an innovative technology based on glass capillary arrays for the safe infusion, storage and controlled release of hydrogen in mobile applications. The C.En technology has achieved the United States Department of Energy (DOE) 2010 targets for on-board hydrogen storage systems.

Glass microspheres Hollow glass microspheres (HGM) can be utilized for controlled

storage and release of hydrogen.

Department of Mechanical Engineering,

Yuan Ze University 33

Proposals and research

- Chemical storage Metal hydrides

Metal hydrides, such as MgH2, NaAlH4, LiAlH4, LiH, LaNi5H6, TiFeH2 and palladium hydride, with

varying degrees of efficiency, can be used as a storage medium for hydrogen, often reversibly. Some

are easy-to-fuel liquids at ambient temperature and pressure, others are solids which could be turned

into pellets. These materials have good energy density by volume, although their energy density by

weight is often worse than the leading hydrocarbon fuels.

Most metal hydrides bind with hydrogen very strongly. As a result high temperatures around 120 °C

(248 °F) – 200 °C (392 °F) are required to release their hydrogen content. This energy cost can be

reduced by using alloys which consists of a strong hydride former and a weak one such as in LiNH2,

NaBH4 and LiBH4. These are able to form weaker bonds, thereby requiring less input to release

stored hydrogen. However if the interaction is too weak, the pressure needed for rehydriding is high,

thereby eliminating any energy savings. The target for onboard hydrogen fuel systems is roughly

<100 °C for release and <700 bar for recharge (20-60 kJ/mol H2).

Currently the only hydrides which are capable of achieving the 9 wt. % gravimetric goal for 2015 (see

chart above) are limited to lithium, boron and aluminium based compounds; at least one of the first-

row elements or Al must be added. Research is being done to determine new compounds which can

be used to meet these requirements.

Proposed hydrides for use in a hydrogen economy include simple hydrides of magnesium or

transition metals and complex metal hydrides, typically containing sodium, lithium, or calcium and

aluminum or boron. Hydrides chosen for storage applications provide low reactivity (high safety) and

high hydrogen storage densities. Leading candidates are lithium hydride, sodium borohydride, lithium

aluminium hydride and ammonia borane. A French company McPhy Energy is developing the first

industrial product, based on magnesium hydrate, already sold to some major clients such as Iwatani

and ENEL.

New Scientist stated that Arizona State University is investigating using a borohydride solution to

store hydrogen, which is released when the solution flows over a catalyst made of ruthenium.

Metal hydride hydrogen storage34

US-DOE https://energy.gov/eere

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Carbohydrates

Carbohydrates (polymeric C6H10O5) releases H2 in an bioreformer

mediated by the enzyme cocktail—cell-free synthetic pathway

biotransformation. Carbohydrate provides high hydrogen storage

densities as a liquid with mild pressurization and cryogenic constraints:

It can also be stored as a solid power. Carbohydrate is the most

abundant renewable bioresource in the world.

In 2009 was demonstrated by Oak Ridge National Laboratory

announced a method of producing high-yield pure hydrogen from

starch and water. 12 moles of hydrogen per glucose unit from cellulosic

materials and water. Thanks to complete conversion and modest

reaction conditions, they propose to use carbohydrate as a high energy

density hydrogen carrier with a density of 14.8 wt %.

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Synthesized hydrocarbons

An alternative to hydrides is to use regular hydrocarbon fuels as the hydrogen

carrier. Then a small hydrogen reformer would extract the hydrogen as needed

by the fuel cell. However, these reformers are slow to react to changes in

demand and add a large incremental cost to the vehicle powertrain.

Direct methanol fuel cells do not require a reformer, but provide a lower energy

density compared to conventional fuel cells, although this could be

counterbalanced with the much better energy densities of ethanol and methanol

over hydrogen. Alcohol fuel is a renewable resource.

Solid-oxide fuel cells can operate on light hydrocarbons such as propane and

methane without a reformer, or can run on higher hydrocarbons with only partial

reforming, but the high temperature and slow startup time of these fuel cells are

problematic for automotive applications.

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Amine borane complexes

Prior to 1980, several compounds were investigated for hydrogen storage

including complex borohydrides, or aluminohydrides, and ammonium salts.

These hydrides have an upper theoretical hydrogen yield limited to about

8.5% by weight.

Amongst the compounds that contain only B, N, and H (both positive and

negative ions), representative examples include: amine boranes, boron

hydride ammoniates, hydrazine-borane complexes, and ammonium

octahydrotriborates or tetrahydroborates.

Of these, amine boranes (and especially ammonia borane) have been

extensively investigated as hydrogen carriers.

During the 1970s and 1980s, the U.S. Army and Navy funded efforts aimed

at developing hydrogen/deuterium gas-generating compounds for use in the

HF/DF and HCl chemical lasers, and gas dynamic lasers.

Earlier hydrogen gas-generating formulations used amine boranes and their

derivatives. Ignition of the amine borane(s) forms boron nitride (BN) and

hydrogen gas.

In addition to ammonia borane (H3BNH3), other gas-generators include

diborane diammoniate, H2B(NH3)2BH4.

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Formic acid In 2006 researchers of EPFL, Switzerland, reported the use of formic acid as a

hydrogen storage material.

Carbon monoxide free hydrogen has been generated in a very wide pressure range (1–600 bar).

A homogeneous catalytic system based on water soluble ruthenium catalysts selectively decompose HCOOH into H2 and CO2 in aqueous solution. This catalytic system overcomes the limitations of other catalysts (e.g. poor stability, limited catalytic lifetimes, formation of CO) for the decomposition of formic acid making it a viable hydrogen storage material. And the co-product of this decomposition, carbon dioxide, can be used as hydrogen vector by hydrogenating it back to formic acid in a second step.

The catalytic hydrogenation of CO2 has long been studied and efficient procedures have been developed. Formic acid contains 53 g L−1 hydrogen at room temperature and atmospheric pressure. By weight, pure formic acid stores 4.3 wt% hydrogen. Pure formic acid is a liquid with a flash point 69 °C (cf. gasoline −40 °C, ethanol 13 °C). 85% formic acid is not flammable.

Imidazolium ionic liquids In 2007 Dupont and others reported hydrogen-storage materials based on

imidazolium ionic liquids.

Simple alkyl(aryl)-3-methylimidazolium N-bis(trifluoromethanesulfonyl)imidate salts that possess very low vapour pressure, high density, and thermal stability and are not inflammable can add reversibly 6–12 hydrogen atoms in the presence of classical Pd/C or Ir0 nanoparticle catalysts and can be used as alternative materials for on-board hydrogen-storage devices.

These salts can hold up to 30 g L−1 of hydrogen at atmospheric pressure.

https://efree.gl.ciw.edu/content/molecular-hydrogen-storage-light-element-compounds

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Hydrogen storage density cost graph (USDOE)

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US-DOE https://energy.gov/eere

http://peswiki.com/index.php/Image:Hydrogen_power_park_concept_red.jpg

Centros de Investigación con programas de investigación

y formación de recursos humanos en Hidrogeno

Universidad Nacional Autónoma de Mexico

IIM,IER, Fac Ingenieria, CNN,

Producción de hidrogeno mediante biomasa, celdas de combustible, celdas de óxidos solidos, Almacenamiento mediante hidruros

Centro de Investigacion y estudios Avanzados del IPN

Unidades en Merida, DF, Queretaro, Saltillo Celdas de combustible tipo PEM,

Alcohol, Producción de hidrogeno, fotocatálisis,

• Centro de Investigación en Materiales Avanzados , producción de hidrogeno,

materiales para la mejoramiento de producción de hidrogeno

• Universidad Autónoma de Quintana Roo, modelaje y celdas de combustible tipo PEM

• Universidad de Artes y Ciencias de Chiapas, materiales para celdas de combustible.

• Centro de Investigaciones Científicas de Yucatán. Materiales para almacenamiento

de hidrogeno, y celdas de combustibles.

Centro de Investigaciones Cientificas de Yucatan. Materiales para alamacenamiento de hidrogeno, y celdas de combustibles.

Instituto tecnológico de Cancún, materiales para celdas tipo PEM.

Instituto Nacional de Electricidad y Energías Limpias, desarrrollo de celdas de combustible y electrolizadores.

Instituto Tecnológico de Tijuana, materiales para la produccion de hidrogeno y materiales electro catalíticos.

Universidad Autónoma Metropolitana Desarrollo de producccion de hidrogeno mediante ciclos termoquimicos

Instituto Politécnico Nacional , producción de hidrogeno mediante electro catalizadores y desarrollo de motores de combustión de hidrogeno en motores.

Instituto nacional de Investigaciones Nucleares. Producción de hidrogeno y almacenamiento de hidrogeno