ABSTRACT
Proton.exchange.membrane.(PEM).fuel.cell.technology.is.a.promising.alternative. for.a.secure.and.clean.energy.source.in.portable,.stationary,.and.automotive.applications..However,.it.has.to.compete.in.cost,.reliability,.and.energy.efficiency.with. established.energy.sources.such.as.batteries.and.internal.combustion.engines..Many. of. the.major.challenges.in.PEM.fuel.cell.commercialization.are.closely.related.to. three.critical.materials.considerations:.cost,.durability,.and.performance..The.challenge.is.to.find.a.combination.of.materials.that.will.give.an.acceptable.result.for.the. three.criteria.combined..For.example,.Hamilton.Standard. (a. subsidiary.of.United. Technologies.Corporation).demonstrated.individual.cell.lifetimes.of.over.87,600.run. hours. on. at. least. three. individual. test. cells. operated. continuously. at. 0.54. A/cm2. using.a.thick.membrane.(Nafion®.120,.250.μm.thick).and.Pt.black.electrodes.(>10. mg.Pt/cm2).1,2.They.also.achieved.stable.voltage.(decay.rate.~.1.μV/h).for.40,000.h. on.a.four-cell.stack.operated.continuously.at.low.current.density.(CD).(~0.13.A/cm2).. These. lifetime. performances. met. or. exceeded. the. Department. of. Energy. (DOE). target.(40,000.h).for.stationary.applications.3.However,.the.cost.of.these.systems.is. prohibitively.high.for.commercial.applications.(DOE.targets:.$30/kW.for.transportation.applications.using.neat.H2.and.$750/kW.for.stationary.power.applications.using. natural. gas. reformate).. On. the. other. hand,. state-of-the-art. PEM. fuel. cells,. using. thinner.membranes.(<40.μm).and.Pt/C.electrodes.(<1.mg.Pt/cm2).for.cost.reduction,. are.less.expensive.(but.still.higher.than.DOE.cost.targets).but.only.have.a.demonstrated.lifetime.of.less.than.15,000.h.operating.on.reformate.3-5.There.are.numerous. reviews.on.general.PEM.fuel.cell.technology,5-11.fuel.cell.components,12-15.electrode. catalysts,16-24. membrane. electrolytes,25-32. bipolar. plates,33,34. and. system. reliability. and. compatibility.4,35,36. This. chapter. summarizes. the. current. status. of. materialsrelated.aspects.of.PEM.fuel.cell. research.and.development,. including.basic. functional. requirements,. state-of-the-art. materials,. and. technical. challenges. for. each. individual.component..Hydrogen.production,.distribution,.and.storage.are.covered. in.sections.12.1.to.12.3.
