Index

AAccelerated testing and statistical lifetime

modelinglifetime tests

end-use, 391load profile effect, 393MEA/system, 392system variables, 391–392

mechanistic test, 390–391membrane electrode assemblies (MEAs),

385–386screening tests

catalyst, 388–389gas-diffusion layer, 389–390membrane, 386–388

SPLIDA data, 394–395standard deviation, 393–394statistical analysis, 393Weibull distribution, 395

AC impedance analysis. See Tafel slopeAciplex®, 134Air impurities

automotive applications, 290–291cathode compartment, 291contaminant propagation routes

accelerated tests, 296airstream components, 293bipolar plate, 292–293cathode compartment case, 297Donnan exclusion, 296elements, 291–292exposure scale, 296sources, 294–295system process flow diagram, 292testing protocols, 296unit cell design, 292–293

mathematical modelscatalyst layer level, 297flow-field channel, 297, 303

fluid ingress causes, 304, 306gas-diffusion layer, 303hydrophilic electrode, 304–305ionomer degradation effects, 304, 306ionomer dehydration, 305Langmuirian-based model, 307metallic bipolar plate, 304nafion hydrophilic channels, 304–305oxygen reduction pathway, 304performance losses types and

mechanisms, 298–302platinum dissolution rate, 304thermodynamic properties, 303

mitigation strategiescathode compartment, 308, 314kinetic and ohmic effects, 314material approaches, 308types, approaches, effects, and

mechanisms, 308–313Aoki, M., 62Azaroual, M., 10

BBakelite®, 162Base polymers, 135–136Baurmeister, J., 350Bett, J.A.S., 407Binder, H., 403Bindra, P., 10, 14Bipolar plate design

channel-based flow fieldsgas-diffusion layer (GDL), 421–423humidification system, 423–424

integrated air injection, 427–428interdigitated flow field, 424–425plate requirements, 420–421porous cathode/cooling plate, 426–427porous gas distribution structures, 425–426

497

498 Index

Borup, R., 10, 18Bradean, R., 436Butler–Volmer expression, 218

CCapillary flow porometry (CFP) data,

184–185CARBEL® CL substrate, 169, 170Carbon bipolar plates, 253–254Carbon black

applications, 29properties, 30

Carbon corrosion. See Start–stop degradationdurability

local anode hydrogen starvation, 50start/stop conditions, 49–50

general theory of, 15–16heterogeneous sessile-drop contact angles

modelingCassie equation, 178fluropolymers, surface coverage,

178, 179hydrophobicity, 179surface porosity, 179–180

kineticscarbon weight loss, 32, 34cell voltage loss, 35–36electrochemical oxidation, 30–31vs. corrosion rates, 33

in PEMFCs, 16–18RH sensitivity changes

constant-voltage current density, 183ex-situ aging effects, 183, 184GDLs vs. identical cells, 182hydrophobic interface, 183scanning, 182

surface chemistry and wettability changesLANL in-house goniometer, contact

angle measurement, 176surface energy measurement, 178Toray TGP-H GDL, Owens–Wendt

technique, 177X-ray photoelectron spectroscopy (XPS)

analysisdrive-cycling experiment, ELAT®

version 2.0, 180–181oxygen to carbon signal intensity ratio,

181–182Carbon oxidation reaction (COR) current, 38Carbon potential effect

electrochemical oxidation, 403energy-storage system, 405reverse-current mechanism, 404

Carbon-supported membrane electrode assemblies

in automotive operative conditionsglobal anode hydrogen starvation,

40–41local anode hydrogen starvation,

42–43start/stop conditions, 38–40steady-state conditions, 36–37transient conditions, 37–38

carbon blackapplications, 29properties, 30

carbon corrosion kineticscarbon weight loss, 32, 34cell voltage loss, 35–36electrochemical oxidation, 30–31vs. corrosion rates, 33

corrosion-resistant carbonBET surface normalized, 46electrochemical corrosion, 44–45gas-phase oxidation, 44graphitized and nongraphitized carbon

blacks, 45Cassie equation, 178Cathode degradation, 478–481Cathode electrocatalysts

platinum monolayerlong-term stability test, 19–20oxygen reduction reaction (ORR), 18

stabilizationaccelerated stability testing, 21catalytic activities, 21–22electronic effects, 22–23scanning tunneling microscope, 21X-ray absorption near-edge structure

measurement, 21–22CCD. See Charge-coupled-device cameraCell and stack operation

accelerated testing and statistical lifetime modeling

lifetime tests, 391–393mechanistic test, 390–391membrane electrode assemblies

(MEAs), 385–386screening tests, 386–390SPLIDA data, 394–395standard deviation, 393–394statistical analysis, 393Weibull distribution, 395

contaminants impactair impurities, 289–314electrode reactions, 323–337performance and durability, 341–361

Index 499499

freezingdynamics, 379–380ice formation and frost heave, 378–379material properties and morphology,

373–374mitigation strategies, 380–381performance degradation, 372–373requirements, 371–372water state, 374–377

technical level, 285Celtec® membranes, 200CFP. See Capillary flow porometry dataChang, P.A.C., 433Channel-based flow fields

gas-diffusion layer (GDL), 421–423humidification system, 423–424

Charge-coupled-device (CCD) camera, 191Chemical degradation, PFSA membranes

accelerated testing methodology, 62–63decomposition mechanism

hydrogen-containing end groups, 66hydroxy/hydroperoxy radicals, 65–66

durability, 66–67mechanism

diagnostic life testing, 59–60electron spin resonance (ESR) signals,

61–62H

2O

2 formation, 60–61

H2 permeability in current density, 59

Nafion®, 58open-circuit conditions, 63–64platinum-band formations, 64–65vs. physical degradation, 57

Chen, J., 141, 148Chen, Y.L., 141, 148Condensation, 411Contaminants impact

air impuritiesautomotive applications, 290–291cathode compartment, 291contaminant propagation routes,

291–297mathematical model, 297–306mitigation strategies, 308–314

electrode reactionsmembrane electrode assembly

(MEA), 323oxygen reduction reaction (ORR),

326–337rotating disk electrode (RDE), 324–326

performance and durabilityAB optimization process, 351–353anode overpotential measurement,

342–344

CO mitigation methods, 344–351crossover O

2 effect, 353–354

N2 dilution and inertial effect, 358–359

potential electrode-poisoning species, 359–361

reformate, 341–342transient CO effect, 354

Conway, B.E., 8CO tolerance decrease

Cole–Cole plot and Bode plot, 458–460limiting current density model, 457–458simulated reformed gas (SRG), 456–457

Crosslinked graft copolymer, 137Curtin, D.E., 66

DDarcy air permeability, 185, 186Degradation

cathode activity loss, surface oxide formation

methanol-oxidation electrocatalysis, 226oxide-layer growth process, 226–227six-cell DMFC stack, 226, 227

cathode degradation, 478–481cathode (oxygen reduction) kinetics

cyclic voltammetry measurements, 213oxygen reduction overpotentials,

212, 213cathode mass-transport overpotentials, 214dual-cell setup

cathode potential measurement, 206, 207

current flow measurement, 208H

2/air and air/H

2 fronts passage,

208–209reverse current cell, 207startup and shutdown situation, 209

electrochemical surface area loss (ECSA)sintering mechanisms, 231transmission electron microscope

images, DMFC catalysts, 231, 232electrode degradation modes, 204–205idling

disadvantages, 478operational phenomena, 476–477

load-cycling, 475–476low- vs. high-temperature PEFCs

cell voltage, 215, 216linear regression lines, 216

membrane degradation modes, 203–204membrane–electrode interface

electrode flooding, 235electrophoretic deposition process, 236

500 Index

Degradation (cont.)high-frequency resistance (HFR),

234, 235long-term performance, 233, 234Nafion®-bonded electrodes, 233polymer electrolyte membrane

(PEM), 236postmortem analysis, 234

Ohmic cell impedance, 211operating conditions, 469–470platinum nanoparticles

crystallite migration and coalescence, 13–14

dissolution and redeposition, 14precipitation, 15

ruthenium crossovercarbon monoxide stripping scan,

DMFC cathode, 228, 229cathode contamination, 230electrochemical treatment, 230, 231MEA fabrication process, 229–230nanocrystalline Pt–Ru alloy,

electrochemical oxidation, 228start/stop operation, 205–206start–stop operation

carbon oxidation, 471–472mitigation effect, 473–474operation, 470–471

underlying process, 214–215Del Popolo, M.G., 22Density–potential curve, 246Direct methanol fuel cell durability (DMFC)

“accelerated testing,” 225catalyst degradation

cathode activity loss, surface oxide formation, 226–228

electrochemical surface area loss, 230–232

ruthenium crossover, 228–230cathode catalyst oxidation, 237H

2–air fuel cells, 225

membrane–electrode interface degradationelectrode flooding, 235electrophoretic deposition process, 236high-frequency resistance (HFR), 234, 235long-term performance, 233, 234Nafion®-bonded electrodes, 233polymer electrolyte membrane

(PEM), 236postmortem analysis, 234

“required-power line,” 224stack performance degradation, 236–237steady-state performance, 225voltage loss, cell operation, 224

Durabilitycarbon-support corrosion

local anode hydrogen starvation, 50start/stop conditions, 49–50

for commercialization of PEFCs, 3perfluorinated polymer-based MEA

constant current durability, 127–129current–voltage curves of, 127degradation reactions, 131open circuit voltage (OCV) conditions,

126–127scanning electron microscope, 129–130

PFSA membranes, 66–67radiation-grafted membranes

base polymers, 135–136grafting monomers, 136–138membrane aging, 134membrane material properties,

141–144proton transport, 133

EECSA. See Electrochemical surface area lossElectrochemical carbon corrosion, 205Electrochemical Ostwald ripening, 14Electrochemical reactions

nonoptimal conditionsglobal anode hydrogen starvation,

40–41local anode hydrogen starvation, 42–43

optimal conditionsstart/stop conditions, 38–40steady-state conditions, 36–37transient conditions, 37–38

Electrochemical surface area (ECSA), 230–232, 453–454

Electrode potentialcarbon potential effect

electrochemical oxidation, 403energy-storage system, 405reverse-current mechanism, 404

oxygen-reduction reaction (ORR), 400–401

platinum electrode potential cycling, 402–403

Electrode reactions, fuel cellsmembrane electrode assembly (MEA), 323oxygen reduction reaction (ORR)

alkylammonium ion impurities, 328–330

impurity cations, 332–334metal cation impurities, 326–328methanol concentrations, 334–335

Index 501501

organic impurities, 330–332platinum surface, 336–337

rotating disk electrode (RDE)Nafion® polymer, 324–325organic impurities, 325Pt/Nafion® film analysis, 325pyridyl compounds, 325–326

Electrolyte membrane degradation. See Idling degradation

Electron spin resonance (ESR) spectramembrane chemical degradation, 100–101perfluorinated polymer-based MEA,

121–124relative humidity effects, 78–79

FFilter-press-type stacks, 431–432Flemion® membrane, 66, 150Freezing

dynamics, 379–380ice formation and frost heave, 378–379material properties and morphology,

373–374mitigation strategies, 380–381performance degradation, 372–373requirements, 371–372water state

cell models, 377gas-diffusion medium, 376–377liquid–solid phase, 374–375mass-transport characteristics, 375Nafion, 375porous-electrode theory, 377saturation levels vs. temperature, 376thermodynamic equilibrium, 374

Fuel cell stack, vehicle applicationdegradation phenomena

cathode degradation, 478–481idling, 476–478load-cycling, 475–476operating conditions, 469–470start–stop, 470–474

membrane electrode assembly (MEA) degradation, 467–469

Fuel cell testingessential improvements, 144–146grafting parameters, 146innovative monomer and crosslinker

combinations, 146–148postmortem degradation analysis,

151–152sample and testing, 148–151

Fuel processors, 200

GGalvanic cells, 432–433Gas-diffusion layer (GDL), 421–423

carbon corrosionCassie equation, 178fluropolymers, surface coverage,

178, 179hydrophobicity, 179RH sensitivity changes, 182–184surface chemistry and wettability

changes, 176–178surface porosity, 179–180X-ray photoelectron spectroscopy

(XPS) analysis, 180–182compression nonuniformity effects

electrical and thermal maldistribution effects, 190–191

mass-transport effects, 191–192substrate fiber puncturing,

membrane, 190conventional materials

Bakelite® usage, 162durability, 162heat treatment, 162–163pore size distribution (PSD)

properties, 163substrate raw-material fibers,

oxidation, 162hydrophobicity loss

durability testing, 171, 172fluoropolymer treatment, 172GDL and MEA chemical interaction,

165–166“GDL hydrophobicity gradient,” 172quick water-spraying experiment, 171resistivity trends vs. durability testing

time, 173, 174single cell polarization analysis,

172–173single-fiber contact angle, 166–169surface energy and dynamic contact

angle, 169–171“US06” drive-cycling testing, 173, 175

microporous layer coating (MPL), 160MPL degradation

carbon corrosion, 189material loss and air permeability,

184–186total and hydrophobic PSD changes,

186–189and MPL limitations, overview, 164MPL materials and GDL substrates

evaluation, 163–164scanning electron micrographs, 160, 161

502 Index

Gas diffusivity, 454–456Gaskets

material selectionadvantages, 277compression stress, 277, 279elastomers, 276–277R-class rubbers, 278silicone fragments (SiO

2), 279

mechanical requirementsflat design, 273, 275gas-diffusion layer, 276media resistance, 275membrane materials, 274sealing design concepts, 273–274stack components, 273

test methods, 280GDL. See Gas-diffusion layerg-PSSA membranes, 105–106Graft copolymerization, 138–141

advantages, 138ex situ properties, 140–141membrane-electrode interface, 140swollen membranes, 139

Grafting monomers, 136–138crosslinkers, 137α-methylstyrene (AMS), 138styrene monomers, 136

Groβ, A., 22Gruver, G.A., 406Guilminot, E., 15

HHe, S., 379Heterogeneous cell operation

galvanic cells, 432–433start/stop stochastic differences, 437start/stop systemic differences, 435–436stochastic differences, 436–437systemic differences, 433–435

High-frequency resistance (HFR), 234, 235High-temperature polymer electrolyte fuel

cellsfuel processors, 200high-temperature PBI membranes,

201–202individual overpotentials calculations

Butler–Volmer expression, 218fuel cell cathode, 217Tafel slope analysis, 217–218

membrane electrode assemblies (MEAs), 200

oxygen reduction reaction (ORR), 200proton conductivity mechanism, 200

start/stop cycling, 200typical degradation mechanisms

cathode (oxygen reduction) kinetics, 211–214

cathode mass-transport overpotentials, 214dual-cell setup, 206–209electrode degradation modes, 204–205low- vs. high-temperature PEFCs,

215–217membrane degradation modes,

203–204Ohmic cell impedance, 211start/stop operation, 205–206underlying process, 214–215

Hodgdon, R.B., 144Hommura, S., 63, 66Honji, A., 14Hubner, G., 130Humidification process, 413–414Humidity. See Humidification processHydrocarbon-based membranes, 58Hydrocarbon polymers, 104Hydrogen oxidation reaction (HOR), 42–43Hydrophobicity loss

cathode mass-transport overpotentialdurability testing, 171, 172fluoropolymer treatment, 172“GDL hydrophobicity gradient,” 172quick water-spraying experiment, 171resistivity trends vs. durability testing

time, 173, 174single cell polarization analysis,

172–173“US06” drive-cycling testing, 173, 175

composite surface energyCARBEL® CL substrate, 169, 170electrochemical impedance

spectroscopy measurements, 170sessile-drop contact-angle, 169, 170SIGRACET® GDL layer, 170, 171

GDL and MEA chemical interactioncathode degradation process, 166corrosion, 165

single-fiber contact angleaging environment, 168TGP-H paper, water droplet

penetration, 167–168Wilhelmy-plate technique, 166

IIdling degradation

disadvantages, 478operational phenomena, 476–477

Index 503503

Integrated air injection, 427–428Interdigitated flow field, 424–425

JJohnson, D.C., 12

KKangasniemi, K.H., 403Komanicky, V., 11Kulikovsky, A.A., 437

LLaConti, A.B., 60, 61, 63, 152LANL in-house goniometer, 176Load-cycling degradation, 475–476Localized membrane degradation

anode vs. cathode, 90–92inlets and edges, 94–95ionomer binder, 95–96platinum precipitation line, 92–94

Long-term durability tests, 460–463

MMader, J., 201Mathias, M.F., 16, 409Media manifolding, 428Membrane aging, 134Membrane chemical degradation

catalystcobalt, 89membrane durability tests, 88–89platinum, 88

characterization techniqueselectron spin resonance spectroscopy,

100–101energy dispersive X-ray (EDX)

spectroscopy, 102Fourier transfer IR (FTIR)

spectroscopy, 96–99nuclear magnetic resonance, 103–104Raman spectroscopy, 99–100X-ray photoelectron spectroscopy

(XPS), 102–103contamination effects

catalyst contamination, 87–88membrane contamination, 84–87

end-group stabilization, 110–111external load effects

electrochemical consumption, 76reactant gas depletion, 75

fluoride release rate (FRR), 72g-PSSA membranes, 105–106hydrocarbon membranes

chemical stability, 112long-term durability, 104–105

key elements for, 72–73localized degradation

anode vs. cathode, 90–92inlets and edges, 94–95ionomer binder, 95–96platinum precipitation line, 92–94

membrane thickness effects, 83–84mitigation strategies, 112–113operating temperature effects, 81–82PFSA membranes

chain scission mechanism, 107–108chain unzipping mechanism, 106–107side-group attack, 108

radical sources, 109–110reactant gas partial pressure effects, 79–81relative humidity effects

degradation rate vs. H2O

2 concentration,

77–78humidification, 76–77hydroxyl radicals, 79permeability, 77in situ electron spin resonance (ESR),

78–79two-electron reduction mechanism, 74

Membrane electrode assemblies (MEAs), 160, 200

accelerated testing and statistical lifetime modeling, 385–386

in automotive operative conditionsglobal anode hydrogen starvation,

40–41local anode hydrogen starvation, 42–43start/stop conditions, 38–40steady-state conditions, 36–37transient conditions, 37–38

carbon blackapplications, 29properties, 30

carbon corrosion kineticscarbon weight loss, 32, 34cell voltage loss, 35–36electrochemical oxidation, 30–31vs. corrosion rates, 33

corrosion-resistant carbonBET surface normalized, 46electrochemical corrosion, 44–45gas-phase oxidation, 44graphitized and nongraphitized carbon

blacks, 45

504 Index

Membrane electrode assemblies (MEAs) (cont.)

current–voltage curves, 450–451electrode reactions, 323perfluorinated polymer

degradation mechanism, 121–126durability, 126–131experimental descriptions, 120–121

platinum-containing electrode, 244stack durability degradation, 468–469

Mench, M., 379Metallic bipolar plates

base materialsdensity–potential curve, 246formability, 247high bulk conductivity, 245–246

degradation procedure, 247–248surface treatment and coating

ceramic coatings and prototypes, 251–252

corrosion-resistant stainless steels, 250–251

cost issues, 252–253vs. carbon bipolar plates, 253–254

α-Methylstyrene, 138Microporous layer coating (MPL)

degradationcarbon corrosion, 189material loss and air permeability

capillary flow porometry (CFP) measurements, 184–185

Darcy air permeability, 185, 186total and hydrophobic PSD changes

aging/durability testing, 187mercury and water (intrusion)

porosimetry, 187, 188Mitsushima, S., 10, 12

NNafion®, 59Nagy, Z., 10New Energy and Industrial Technology

Development Organization (NEDO)CO poisoning, 491–492road development

Fuel Cell Hydrogen Technology Development Road Map, 492–493

polymer electrolyte fuel cell system, 494–496

Newman, J., 377New polymer composites (NPLs), 67Nonfluorinated hydrocarbon polymer

membranes, 104

OOhma, A., 65Ohmic cell impedance, 211Operating temperatures, PEFC

carbon corrosion effect, 408–410perfluorosulfonic acid (PFSA) membrane

system, 405–406platinum sintering, 406–408

Organic impuritiesalcohol oxidation, 331characteristics, 330–331polarization curves, 330, 332

ORR. See Oxygen reduction reactionOwens–Wendt technique, 177Oxygen evolution reaction (OER), 38Oxygen reduction reaction (ORR), 40, 200,

400–401alkylammonium ion impurities

Nafion® film, 330noncontaminant condition, 328–329oxygen transport, 329–330platinum oxide formation, 328

impurity cationsoxygen transport, 334platinum–ionomer interface, 332polarization curves, 333polymer mass, 332–333Pt–ionomer interface, 333–334

metal cation impuritiesion-exchange processes, 327–328kinetic current, 326–327metal–polymer electrolyte, 328Pt–Nafion® electrodes, 326

methanol concentrations, 334–335organic impurities

alcohol oxidation, 331characteristics, 330–331polarization curves, 330, 332

platinum surface, 336–337

PPEM. See Polymer electrolyte membranePerfluorinated polymer-based MEA

degradation mechanismaccelerated degradation method,

124–125electron spin resonance (ESR) spectra,

121–124molecular weight distributions, 126radical species identification, 121

durabilityconstant current durability, 127–129current–voltage curves of, 127

Index 505505

degradation reactions, 131open circuit voltage (OCV) conditions,

126–127scanning electron microscope, 129–130

experimental descriptioncell performances, 120hydrogen peroxide formation, 120radical species, 120–121

Perfluorinated sulfonic acid (PFSA) membranes

accelerated testing methodology, 62–63decomposition

hydrogen-containing end groups, 66hydroxy/hydroperoxy radicals, 65–66

durability, 66–67mechanisms

diagnostic life testing, 59–60electron spin resonance (ESR) signals,

61–62H

2O

2 formation, 60–61

H2 permeability in current density, 59

Nafion®, 58membrane chemical degradation

chain scission mechanism, 107–108chain unzipping mechanism, 106–107side-group attack, 108

open-circuit conditions, 63–64platinum-band formations, 64–65vs. physical degradation, 57

Performance and durabilityAB optimization process

AB-FRR chart, 351, 353CO–air bleed endurance tests, 351–352CO reformate test, 353steps, 351

anode overpotential measurementair bleed (AB), 343current density (CD) region, 344polarization data, 342–343

CO2 and reverse WGS (RWGS) reaction

anode overpotential anode, 357electrode poison, 355PtRu and platinum electrode, 356RWGS reaction, 357–358

CO mitigation methodsAB methods, 346–347CO-tolerant electrode, 345–346current pulsing method, 348–349high temperature PEFC, 350–351poisoning effects, 344–345pulsed AB (PAB) technology, 347–348reconfigured anode, 349–350

crossover O2 effect, 353–354

N2 dilution and inertial effect, 358–359

potential electrode-poisoning speciesH

2S and small organic molecules, 361

NH3 effect, 359–361

reformate, 341–342transient CO effect, 354

Perry, M.L., 408Phosphoric acid evaporation rates, 203, 204Physical degradation, 57Pianca, M., 98, 104Platinum

electrode potential cycling, 402–403sintering, 406–408

Platinum dissolution. See Load-cycling degradation

bulk materialpotential–pH diagram, 8–9PtO growth mechanism, 9–10thermodynamic behavior, 8

equilibrium solubility, 10–11potential cycling conditions, 11–12

Platinum nanoparticles, degradationcrystallite migration and coalescence,

13–14dissolution and redeposition, 14precipitation, 15

Polybenzimidazole (PBI), 200Polymer-electrolyte fuel cells (PEFCs)

auto manufacturers and stack makers, 489–491

corrosion initiators influence, 248–250durability, 443–444electrode potential

carbon potential effect, 403–405oxygen-reduction reaction (ORR),

400–401platinum electrode potential cycling,

402–403filter-press-type stacks, 431–432heterogeneous cell operation

galvanic cells, 432–433start/stop stochastic differences, 437start/stop systemic differences,

435–436stochastic differences under operation,

436–437systemic differences under operation,

433–435humidity, 410–414long-term durability tests, 460–463membrane electrode assembly (MEA),

244–245metallic bipolar plates

base materials, 245–247degradation procedure, 247–248

506 Index

Polymer-electrolyte fuel cells (PEFCs) (cont.)surface treatment and coating, 250–253vs. carbon bipolar plates, 253–254

operating temperaturescarbon corrosion effect, 408–410perfluorosulfonic acid (PFSA)

membrane system, 405–406platinum sintering, 406–408

residential cogeneration systemCO tolerance derease, 456–460fuel processing system, 448–450gas diffusivity decrease, 454–456membrane electrode assemblies

(MEAs), 450–451Osaka Gas, 447–448

Tafel slope and AC impedance analysis, 451–454

Polymer electrolyte membrane (PEM), 236Pore size distribution (PSD), 163Porous cathode/cooling plate, 426–427Porous gas distribution structures, 425–426Pozio, A., 61Promislow, K., 437

RRadiation-grafted fuel cell membranes

base polymers, 135–136fuel cell testing

essential improvements, 144–146grafting parameters, 146innovative monomer and crosslinker

combinations, 146–148postmortem degradation analysis,

151–152sample and testing, 148–151

graft copolymerizationadvantages, 138ex situ properties, 140–141membrane-electrode interface, 140swollen membranes, 139

grafting monomerscrosslinkers, 137α-Methylstyrene (AMS), 138styrene monomers, 136

membrane aging, 134membrane material properties

proton conductivity, 142reactant permeability, 143–144tensile properties, 141water transport properties, 142–143

proton transport, 133Rand, D.A.J., 12

Reiser, C.A., 200Residential cogeneration system

CO tolerance dereaseCole–Cole plot and Bode plot, 458–460limiting current density model,

457–458simulated reformed gas (SRG),

456–457fuel processing system, 448–450gas diffusivity, 454–456membrane electrode assemblies (MEAs),

450–451Osaka Gas, 447–448Tafel slope and AC impedance analysis

current–voltage curves, 451–452electrochemical surface area (ECSA),

453–454Reverse-current mechanism, 404Reversible hydrogen electrode (RHE), 30, 244Roduner, E., 130Rotating disk electrode (RDE)

Nafion® polymer, 324–325organic impurities, 325Pt/Nafion® film analysis, 325pyridyl compounds, 325–326

Roudgar, A., 22

SSchaeffler diagram, 246Schmidt, T.J., 350Sealing function, gaskets

material selectionadvantages, 277compression stress, 277, 279elastomers, 276–277R-class rubbers, 278silicone fragments (SiO

2), 279

mechanical requirementsdesign concepts, 273–274flat design, 273, 275gas-diffusion layer, 276media resistance, 275membrane materials, 274stack components, 273

test methods, 280Shao-Horn, Y., 10, 13SIGRACET® GDL layer, 170, 171Simpson, S.F., 372Solid electrolyte, 134. See also Perfluorinated

sulfonic acid (PFSA) membranesSoto, H.J., 360Springer, T.E., 377

Index 507507

Stack-compression hardware, 428–429Start–stop degradation

carbon oxidation, 471–472mitigation effect, 473–474operation, 470–471

Statistical lifetime modelingSPLIDA data, 394–395standard deviation, 393–394statistical analysis, 393Weibull distribution, 395

Stochastic differences, heterogeneous cell

under operation, 436–437start/stop operation, 437

Styrene monomers, 136Subfreezing phenomena. See FreezingSystemic differences, heterogeneous

cellunder operation, 433–435start/stop operation, 435–436

TTafel slope

analysis, 217–218current–voltage curves, 451–452electrochemical surface area (ECSA),

453–454Thermal cycling process, 412

UUribe, F.A., 360

VVirkar, A.V., 14

WWang, G., 437Wang, X., 11Water-recovery devices, 411–412Weber, A.Z., 377Weibull distribution, 395Wetton, B., 437Wilhelmy-plate technique, 166Wilson, M.S., 372Woods, R., 12

XX-ray photoelectron spectroscopy (XPS)

analysisdrive-cycling experiment, 180–181gas-diffusion layer (GDL), 180–182membrane chemical degradation, 102–103oxygen to carbon signal intensity ratio,

181–182

YYou, H., 10

ZZhang, J., 10, 18Zhou, Y.K., 14