Materials for the Hydrogen Economy (2007) Episode 3 pdf

in.Proceedings of the Unified International Technical Conference on Refractories, UNITECR ’05,.Orlando,.FL,.November.2005,.. Refractories Applications and News,.. reformer.vessels,.in.Pr

high temperature black liquor gasifiers, in.Proceedings of the Unified International

Technical Conference on Refractories, UNITECR ’05,.Orlando,.FL,.November.2005,.

4.pp.

28 Taber, W.A., Refractories for Gasification, Refractories Applications and News, 8,.

18–22,.2003.

29 U.S Department.of.Energy,.Gasification Markets and Technologies — Present and

Future: An Industry Perspective,.Report.0447,.July.2002,.pp 1–53.

30 Johnson, R.C and Crowley, M.S., State of the art refractory linings for hydrogen.

reformer.vessels,.in.Proceedings of the Unified International Technical Conference on

Refractories, UNITECR ’05,.Orlando,.FL,.November.2005,.4.pp.

Electrolysis Cells

Paul A Lessing

ConTenTs

2.1 Background.of.Hydrogen.Generation.via.Electrolysis 37

2.2 Low-Temperature.Electrolysis.of.Water.Solutions 38

2.3 Low-Temperature.PEM-Type.Electrolyzers 41

2.4 Low-Temperature.Inorganic.Membrane.Electrolyzers 42

2.5 Moderate-Temperature.Inorganic.Membrane.Electrolyzers 44

2.5.1 Moderate-Temperature.Oxygen.Ion.Conductors 46

2.5.2 Moderate-Temperature.Proton.Conductors 48

2.5.3 Moderate-Temperature.Bipolar.Plates.(Interconnects) 50

2.6 High-Temperature.Inorganic.Membrane.Electrolyzers 52

2.6.1 High-Temperature.Oxygen.Ion.Conductors 52

Acknowledgments 53

References 54

. baCkground of hydrogen

generaTIon vIa eleCTrolysIs

Hydrogen.generation.can.be.accomplished.via.traditional.DC.electrolysis.of.aque-ous.solutions.at.temperatures.less.than.about.100°C However,.electrolysis.of.steam

can.also.be.accomplished.at.higher.temperatures.at.the.cathode.of.electrolytic.cells

utilizing.solid.membranes The.solid.membranes.typically.are.electronic.insulators

and.need.to.be.gas-tight.(hermetic),.but.have.the.special.property.of.being.able.to

conduct.ions.via.fast.diffusion.through.the.solid Generally.the.cells.(cathode/elec-trolyte/anode) are known by the chemical name of their solid electrolytes It has

been.found.for.some.operating.hydrogen.fuel.cell.anode/electrolyte/cathode.systems

that.the.fuel.cell.reactions.at.the.electrodes.are.reversible.and.can.be.operated.in.an

electrolysis.mode However,.reversibility.has.not.been.demonstrated.for.all.cathode/

electrolyte/anode.combinations

Hydrogen production via conventional electrolysis largely depends upon the

availability.of.cheap.electricity.(e.g.,.from.hydroelectric.generators) Consequently,

only.about.5%.of.the.world.hydrogen.production.is.via.electrolysis The.only.com-plete.hydrogen.production.process.that.is.free.of.CO2.emissions.is.water.electrolysis

(if.the.electricity.is.derived.from.nuclear.or.renewable.fuels) However,.97%.of.the

hydrogen.currently.produced.is.ultimately.derived.from.fossil.energy Currently,.the

most.widely.used.and.economical.process.is.steam.reforming.of.natural.gas,.a.pro-cess.that.results.in.CO2.emissions

. loW-TemPeraTure eleCTrolysIs of WaTer soluTIons

1.229.V In.addition,.heat.is.needed.for.the.operation.of.an.electrolysis.cell If.the

heat.energy.is.supplied.in.the.form.of.electrical.energy,.then.the.thermal.potential

is.0.252.V.(at.standard.conditions),.and.this.voltage.must.be.added.to.Erev.(i.e.,.add

entropic term T∆S to ∆G) The (theoretical) decomposition potential for water at

standard conditions (for ∆H.≅.∆H°).is.then 1.480 V This.is.shown in.figure.2.1

Anode.and.cathode.reactions.for.electrolysis.(see.figure.2.1).are:

energy consumption), many different catalytic materials have been examined for

use as anodes or cathodes (or coatings on underlying electrodes) Research was

conducted.in.Germany.in.the.1980s.and.1990s.on.advanced.materials.and.designs

to replace the conventional asbestos diaphragm (that dissolves in caustic KOH at

temperatures above 90°C) with polymer-bonded (PTFE-type) composites These

fIgure . (a).Schematic.of.water.(alkaline).electrolysis (b).Two.large.(200.Nm3

/h).atmo-spheric,.alkaline,.multicell.electrolysis.stacks.generating.hydrogen.at.the.Norsk.Hydro.Company.

Research is currently being conducted into PEM-type membranes that have

to decompose two water molecules to simultaneously generate one molecule of.

hydrogen and one of hydrogen peroxide (used in paper/pulp and chemical

.pulsed-laser.plasma.evap-oration,46 or chemical vapor deposition (CVD).47 Very thin electrolytes generally

dc plasma torch

cooling water out

gas inlet liquid reactant atomizer

Over the last decade there has been significant R&D to reduce the operating.

or occasionally Ba on the A site.50 Other studies have been conducted to measure

doped.LaGaO3’s.electronic.conductivity51–53.and.develop.suitable.electrodes.54–57

et.al.67.has.also.reported.that.doped.PrGaO3.is.a.fast.oxygen.ion.conductor,.but.it.does

crystallographic.and.chemical.stability.problems.that.have.prevented.implementa-tion.in.practical.long-lived.cells As.reviewed.by.Azad.et.al.,74.α-Bi2O3.(monoclinic)

is.stable.below.730°C,.while.the.very.high.conductivity.δ-Bi2O3.(cubic,.CaF2.type).is

by alkaline–earth oxide dopants (e.g., CaO-Bi2O3, SrO-Bi2O3, or BaO-Bi2O3)76 or

partial substitution of various metal ions for vanadium These compounds were

termed BIMEVOX Investigations of fabrication with possible application as an

electrolyte,.with.particular.interest.in.copper.substituted.material.(BICUVOX,.e.g.,

Be2V0.9Cu0.1O5.35),79.followed There.is.some.electrical.conductivity.data.measured

be.an.indication.of.increased.electronic.conductivity82.(electronic.shorting.of.cells)

manganites, other perovksite compositions have been proposed for air electrodes.

(La0.8Sr0.2Fe0.8Co0.2O3-δ.and.LaFe0.5Ni0.5O3-δ).83

species.is.a.proton.bound.to.an.oxygen.ion.in.the.lattice However,.the.pro-Twenty.years.ago,.Iwahara.et.al.87.introduced.doped.(Y,.Yb,.Sc).SrCeO3

crystallites.100.Kofstad.and.Bredesen101.point.out.that.a.Cr.problem.may.also.exist.at

Oxidation in H2–H2O mixtures could be a long-term problem for uncoated.

metallic.bipolar.electrolyzer.plates.with.low.H2.content.gas Horita.et.al.105

. hIgh-TemPeraTure InorganIC

membrane eleCTrolyzers

2.6.1 h iGh -t emperature O xyGen i On C OnduCtOrS

The most common high-temperature cells being investigated are solid-oxide fuel

Some interdiffusion and formation of nonconductive compounds (e.g., La2Zr2O7)

has.been.reported.118.These.interactions.are.more.severe.at.high.temperatures119.and

High-steam electrolysis

unit

Heat

He High-

temperature heat exchanger

Recuperator Primary heat rejection

He

HP compressor

LP compressor

Gas turbine

in.New Materials for Electrochemical Systems IV Extended Abstracts of the Fourth

International Symposium on New Materials for Electrochemical Systems,.Montreal,.

Quebec,.Canada,.July.9–13,.2001,.pp 278–280.

11 Linkous, C.A et al Development of new proton exchange membrane electrolytes.

for water electrolysis at higher temperatures,.Int J Hydrogen Energy,.23,.525–529.

with proton exchange membrane (PEM) using sea water and fundamental study of.

hybrid.system.with.PV-ED-FC,.Mem Fac Eng.,.31,.213–218.(2002).

21 Giner Electrochemical Systems, LLC, 89 Rumford Ave., Newton, MA 02466,.

44 Henne,.R.H et.al.,.Light-Weight.SOFCs.for.Automotive.Auxiliary.Power.Units,.paper.

presented.at.the.2nd.International.Conference.on.Fuel.Cell.Science,.Engineering.and.

Technology,.Rochester,.NY,.June.14–16,.2004.

45

Wang,.L.S et.al.,.Sputter.deposition.of.yttria-stabilized.zirconia.and.silver.cermet.elec-trodes.for.SOFC.applications,.Solid State Ionics,.52,.261–267.(1992).

46 Chu,.W.F.,.Thin-.and.thick-film.solid.ionic.devices,.Solid State Ionics,.52,.243–248.

49 Kurumada,.M.,.Ito,.A.,.and.Fujie,.Y.,.Preparation.of.La2-xSrxGa0.8Mg0.2O3-δ.electrolyte.

for.solid.oxide.fuel.cell.by.citrate.method.using.industrial.raw.materials,.J Ceram Soc

Jpn.,.111,.200–204.(2003).

50 Choi, S.M., et al., Oxygen ion conductivity and cell performance of La0.9Ba0.1Ga1–

x MgxO3-δ.electrolyte,.Solid State Ionics,.131,.221–228.(2000).

51 Kharton, V.V et al., Ionic and p-type electronic conduction in LaGa(Mg,Nb)O3-δ.

perovksites,.Solid State Ionics,.128,.79–90.(2000).

52 Maffei, N and de Silveira, G., Interfacial layers in tape cast anoe-supported doped.

lanthanum.gallate.SOFC.elements,.Solid.State Ionics,.159,.209–216.(2003).

53 Kim, J.H and Yoo, H.I., Partial electronic conductivity and electrolytic domain of.

La0.9Sr0.1Ga0.8Mg0.2O3-δ,.Solid State Ionics,.140,.105–113.(2001).

Kuroda,.K et.al.,.Characterization.of.solid.oxide.fuel.cell.using.doped.lanthanum.gal-late,.Solid State Ionics,.132,.199–208.(2000).

60 Ma,.X et.al.,.The.power.of.plasma,.Ceramic Industry,.June.2004,.pp 25–28.

61 Pengnian,.H et.al.,.Interfacial.reaction.between.nickel.oxide.and.lanthanum.gallate.

during sintering and its effect on conductivity,.J Am Ceram Soc.,.82,.2402–2406.

(1999).

62 Maffei,.N and.de.Silveira,.G.,.Interfacial.layers.in.tape.cast.anode-supported.doped.

lanthanum.gallate.SOFC.elements,.Solid State Ionics,.159,.209–216.(2003).

63 Huang, K.G et al., Increasing power density of LSGM-based solid oxide fuel cells.

using.new.anode.materials,.J Electrochem Soc.,.148,.A788–A794.(2001).

67 Ishihara, T et al., Oxide ion conductivity in doubly doped PrGaO3 perovskite-type.

oxide,.J Electrochem Soc.,.146,.1643–1649.(1999).

68 Maricle,.D.L et.al.,.Enhanced.ceria:.a.low-temperature.SOFC.electrolyte,.Solid State

Ionics,.52,.173–182.(1992).

69 Kharton,.V.V et.al.,.Ceria-based.materials.for.solid.oxide.fuel.cells,.J Mater Sci.,.36,.

1105–1117.(2001).

70 Hidenori, Y et al., High temperature fuel cell with ceria-yttria solid electrolyte, J

Electrochem Soc Solid-State Sci Technol.,.2077–2080.(1988).

Azad,.A.M.,.Larose,.S.,.and.Akbar,.S.A.,.Review.bismuth.oxide-based.solid.electro-lytes.for.fuel.cells,.J Mater Sci.,.29,.4135–4151.(1994).

75 Fung, K.Z et al., Massive transformation in the Y2Oe-Bi2O3 system, J Am Ceram

Soc.,.77,.1638–1648.(1994).

76 Fung,.K.Z et.al.,.Thermodynamic.and.kinetic.considerations.for.Bi2O3

-based.electro-lytes,.Solid State Ionics,.52,.199–211.(1992).

77 Joshi, A.V et al., Phase stability and oxygen transport characteristics of yttria- and.

niobia-stabilized.bismuth.oxide,.J Mater Sci.,.25,.1237–1245.(1990).

84 Setoguchi, T et al., Effects of anode materials and fuel on anodic reaction of solid.

oxide.fuel-cells,.J Electrochem Soc.,.139,.2875–2880.(1993).

91 Chen, F.L et al., Preparation of Nd-doped BaCeO3 proton-conducting ceramic and.

its.electrical.properties.in.different.atmospheres,.J Eur Ceram Soc.,.18,.1389–1395.

drain.electrochemical.applications,.Solid State Ionics,.145,.295–306.(2001).

95 Kreuer,.K.D.,.Proton-conducting.oxides,.Annu Rev Mater Res.,.33,.333–359.(2003).

96 Hassan, D et al., Proton-conducting ceramics as electrode/electrolyte materials for.

SOFC’s Part.I Preparation,.mechanical.and.thermal.properties.of.sintered.bodies,.J

Eur Ceram Soc.,.23,.221–228.(2003).

97 Fehringer, G et al., Proton-conducting ceramics as electrode/electrolyte: materials.

for SOFCs: preparation, mechanical and thermal-mechanical properties of thermal.

sprayed.coatings,.material.combination.and.stacks,.J Eur Ceram Soc.,.24,.705–715.

.103 Larring, Y and Norby, T., Spinel and perovskite functional layers between Plansee.

metallic.interconnect.(Cr-5.wt%.Fe-1.wt%.Y2O3).in.ceramic.(La0.85Sr0.15)0.91MnO3

.cath-ode.materials.for.solid.oxide.fuel.cells,.J Electrochem Soc.,.147,.3251–3256.(2000).

.104 Kung, S.C et al., Performance of Metallic Interconnect in Solid-Oxide Fuel Cells,.

113 Subbarao,.E and.Maiti,.H.S.,.Solid.electrolytes.with.oxygen.ion.conduction,.Solid State

Ionics, 11,.317–338.(1984).

114

Kilner,.J.A and.Brook,.R.J.,.A.study.of.oxygen.ion.conductivity.in.doped.non-stoichio-metric.oxides,.Solid State Ionics, 6,.237–252.(1982).

115 USGS,.Year.2000.data:.Sc2O3.(99.99%.pure).$3,000/kg,.Sc2O3.(99.9%.pure).$700/kg;.

119 Misuyasu, H et al., Microscopic analysis of lanthanum strontium manganite

yttria-stabilized.zirconia.interface,.Solid State Ionics, 100,.11–15.(1997).

.126. Very High Temperature Reactor (VHTR) Survey of Materials Research and

Develop-ment Needs to Support Early DeployDevelop-ment,.INL/EXT-03-004-141,.January.31,.2003.

127. Design Features and Technology Uncertainties for the Next Generation Nuclear Plant,.

INEEL/EXT-04-01816,.Independent.Technology.Review.Group,.June.30,.2004.

.128 Ion, S et al., Pebble Bed Modular Reactor: The First Generation IV Reactor to Be.

Constructed,.paper.presented.at.the.World.Nuclear.Association.Annual.Symposium,.

London,.September.3–5.

Electrolysis

S Elangovan and J Hartvigsen

ConTenTs

3.1 Background 61

3.2 Materials.and.Design 62

3.2.1 Series-Connected.Tubes 63

3.2.2 Tubular.Stack.Design 65

3.2.3 Planar.Stack.Design 65

3.3 Modes.of.Operation 66

3.4 Alternative.Materials.for.High-Temperature.Electrolysis 69

3.5 Advanced.Concepts.for.High-Temperature.Electrolysis 73

3.5.1 Natural.Gas-Assisted.Mode 73

3.5.2 Hybrid.SOFC–SEOC.Stacks 74

3.5.3 Integration.of.Primary.Energy.Sources.with.High-Temperature Electrolysis.Process 74

3.6 Materials.Challenges 75

3.7 Summary 76

Acknowledgments 78

References 78

. baCkground Emphasis.on.energy.security.issues.has.brought.much.needed.attention.to.economic production.of.hydrogen.as.the.secondary.energy.carrier.for.nonelectrical.markets

The.recent.focus.on.hydrogen.comes.from.its.environmentally.benign.aspect How-ever,.much.of.the.hydrogen.currently.produced.is.used.near.the.production.facility

for.chemical.synthesis,.such.as.ammonia.and.methanol.production,.and.for.upgrad-ing.as.well.as.desulfurization.of.crude.oil While.steam.reforming.of.methane.is.the

current.method.of.production.of.hydrogen,.the.fossil.fuel.feed.consumes.nonrenew-able fuel while emitting greenhouse gases Thus, in the long run, efficient,

envi-ronmentally.friendly,.and.economic.means.of.hydrogen.production.using.renewable

energy.need.to.be.developed Additionally,.when.excess.energy.production.capacity

exists,.for.example,.during.off-peak.hours,.efficient.generation.of.hydrogen.may.be

an.option.to.make.an.effective.use.of.the.investment.in.power.generation.infrastruc-ture Steam electrolysis, particularly using high-temperature ceramic membrane

processes,.provides.an.attractive.option.for.efficient.generation.of.ultra.high.purity

(UHP).hydrogen

fuel.(hydrogen).electrodes,.respectively

3.2.1 S erieS -C OnneCted t ubeS

The earliest large-scale high-temperature electrolysis work was done at Dornier

System Gmbh in Germany.1 The cell used traditional SOFC materials such as 9

mol% yttria-doped zirconia (YSZ) as the electrolyte, a cermet mixture of 50:50

H (total energy for electrolysis)

G (electrical energy for electrolysis)

Q (heat of electrolysis)

fIgure . Energy.input.required.for.steam.electrolysis.