Cyc
les
appl
icat
ion
Cycles réels Cycles réelssimplifiés
An
alys
est
atis
tique Cycles réels
modifiés
4 TESTSréf.
Modificationdes motifs
Modification de la séquencedes motifs
4 tests par cycle modifié ⇒⇒⇒⇒ 16 TESTS
OUI
Nouveauxessais
Suggestion de stratégies de
fonctionnement
Validationexpérimentale
Cyc
les
sim
ples
Modification des conditions opératoires :- Tpile (Tmin, Tmax),- P (PH2max/Pair, PH2/Pairmax),- st (stH2max, stair max)
6 tests par cycle modifié ⇒⇒⇒⇒ 24 TESTS
20 TESTS
Conditions opératoiresmodifiées
MODELISATION
Impact des Impact des conditionsconditionsde cyclagede cyclage
Impact des Impact des conditionsconditionsopératoiresopératoires
MODELISATION Validé ?
NON
Lien avec les autres projets : DECODE, DVD-AME, SPACT-80…
Cycles “simples”, conditions opératoires de l’applic ation
Cyc
les
appl
icat
ion
Cycles réels Cycles réelssimplifiés
An
alys
est
atis
tique Cycles réels
modifiés
4 TESTSréf.
Modificationdes motifs
Modification de la séquencedes motifs
4 tests par cycle modifié ⇒⇒⇒⇒ 16 TESTS
OUI
Nouveauxessais
Suggestion de stratégies de
fonctionnement
Validationexpérimentale
Cyc
les
sim
ples
Modification des conditions opératoires :- Tpile (Tmin, Tmax),- P (PH2max/Pair, PH2/Pairmax),- st (stH2max, stair max)
6 tests par cycle modifié ⇒⇒⇒⇒ 24 TESTS
20 TESTS
Conditions opératoiresmodifiées
MODELISATION
Impact des Impact des conditionsconditionsde cyclagede cyclage
Impact des Impact des conditionsconditionsopératoiresopératoires
MODELISATION Validé ?
NON
Lien avec les autres projets : DECODE, DVD-AME, SPACT-80…
Cycles “simples”, conditions opératoires de l’applic ation
Fix -
+
Fix -
Fix -
Fix -
Fix -
Fix -
++++
HH++CoCo2+2+
Compact layerCompact layer
)),,(( txrφ
),( trψ
0=x
Diffuse layerDiffuse layer
Lx =
ir
Oxide (Oxide ( ----O)O)
Intermediate reaction Intermediate reaction speciesspecies
Adsorbed water Adsorbed water dipolesdipoles
Surface catalyst layerSurface catalyst layerInner layer Inner layer
)),(( trηFix -
OO22
++
++
OH 2
++++
++++
++++
++++
++++
++++
PtPt2+2+
++++
ee--
PtPtzz++, , CoCoyy++
PtPtzz++, , CoCoyy++
CC--supportsupport
IonomerIonomer
WaterWater
GDL Channels
Catalyst nano-particle
Membrane
−e+
H
22 OOH +
22 OOH +
Carbon support
OH 2
−e
−e
−e
+2Co
Cathode electrode
−e
2O
2O
2O
−e
−e
Impregnated ionomer
+2Pt
CutCut viewview
ElectrodeElectrode
Dr. Alejandro A. FrancoDr. Alejandro A. Franco11**, Dr. Olivier Lemaire, Dr. Olivier Lemaire11, Dr. Laure Guetaz, Dr. Laure Guetaz11, , RomainRomain CoulonCoulon11, Rodrigo Ferreira de Morais, Rodrigo Ferreira de Morais1,41,4, , Dr. Serge Dr. Serge GambarelliGambarelli22, Dr. Vincent Maurel, Dr. Vincent Maurel22, , Dr. Nicolas FouquetDr. Nicolas Fouquet33, Dr. Franck Masset, Dr. Franck Masset33, Dr. David Loffreda, Dr. David Loffreda44, Prof. Philippe Sautet, Prof. Philippe Sautet44
11CEACEA--Grenoble/LITEN, Grenoble/LITEN, 22CEACEA--Grenoble/INAC, Grenoble/INAC, 33PSA Peugeot CitroPSA Peugeot Citroëën, n, 44ENS de LyonENS de Lyon--CNRS/CNRS/LaboratoireLaboratoire de de ChimieChimie*Contact: *Contact: [email protected]@cea.fr
A.A. Franco et al., A.A. Franco et al., ““A Dynamic Mechanistic Model of an A Dynamic Mechanistic Model of an Electrochemical InterfaceElectrochemical Interface””, , J. Electrochem.Soc.J. Electrochem.Soc., , 153153, A1053 (2006)., A1053 (2006).
A.A. Franco et A.A. Franco et al.,al.,““AA multimulti--scale dynamic mechanistic model for scale dynamic mechanistic model for transient analysis of PEFCtransient analysis of PEFC”” Fuel CellsFuel Cells, , 77, 99 (2007). , 99 (2007).
MAFALDA ProjectMAFALDA Project (Feb09(Feb09--Jan12)Jan12)
Experimental and Experimental and MModelingodeling AAnalyses nalyses ffor the or the PEFC PEFC AActive ctive LLayers ayers DDegradation egradation AAssessmentssessment
•• MEMEPhysMEMEPhys: Invited lectures and oral presentations in about : Invited lectures and oral presentations in about 6464 international conferences international conferences (e.g. (e.g. americanamerican ElectrochemElectrochem. Soc.. Soc., , Int. Soc. ElectrochemistryInt. Soc. Electrochemistry……)) all around the world all around the world (e.g. Qu(e.g. Quéébec 2005, Vienna 2006, Chicago 2007, Miami 2007, Phoenix 2008, Vbec 2005, Vienna 2006, Chicago 2007, Miami 2007, Phoenix 2008, Vancouver 2008, Seville 2008, San Francisco 2009ancouver 2008, Seville 2008, San Francisco 2009……). ). •• Invited seminars on Invited seminars on MEMEPhysMEMEPhys in high level institutes, e.g. Heidelberg University (2006), Stin high level institutes, e.g. Heidelberg University (2006), Stanford University (2007), British Columbia University (2008), Saanford University (2007), British Columbia University (2008), Santa Barbara (2009). nta Barbara (2009). •• 5656 publications on publications on MEMEPhysMEMEPhys in peerin peer--reviewed journals (reviewed journals (J. J. ElectrochemElectrochem. Soc.. Soc., , ElectrochemElectrochem. Soc. Trans.. Soc. Trans., , ElectrochimElectrochim. . ActaActa, , Fuel CellsFuel Cells……) and proceedings + ) and proceedings + 153153 citationscitations•• 11 invited book in preparation by Dr. Franco (publisher: Pan Stanfinvited book in preparation by Dr. Franco (publisher: Pan Stanford) +ord) + 11 patent filled from the patent filled from the modelingmodeling results within MAFALDAresults within MAFALDA
Publications, communications, patents
OurOurapproachapproach
advantagesadvantages
More realistic description More realistic description of of electrocatalysiselectrocatalysis : :
account for the nonaccount for the non --equilibriumequilibriumphysicochemical environment physicochemical environment
Feedback instantaneous Feedback instantaneous performance performance ���������������� degradationdegradation((prediction of durability as function prediction of durability as function of the materials and compositionsof the materials and compositions ))
Bridging spatiotemporal scales with Bridging spatiotemporal scales with reasonable reasonable
computational efforts computational efforts
Fast integration of new Fast integration of new physicochemical phenomena physicochemical phenomena
((study of study of synergies/synergies/ interplayingsinterplayings ……))
HydrogenHydrogen atomatom
Equilibrated PtEquilibrated Pt --RhRh nanonano --structures in vacuum and structures in vacuum and in a Hin a H --rich environment:rich environment:
reconstruction phenomenareconstruction phenomena
IT
PA, PC
RHA, RHC
instantaneous U cell (t)
Instantaneous cumulative materials losses
instantaneous local operatingconditions
instantaneousnano-micro-structure
Con
rolp
aram
eter
s
Coupled no-aging phenomena
Coupled aging phenomena
Coupled agingCoupled agingphenomenaphenomena
Coupled no agingCoupled no agingphenomenaphenomena
Transient elementary Transient elementary kineticskinetics
and electrochemical and electrochemical double layer effectsdouble layer effects
(MF elementary kinetics + Monte Carlo)(MF elementary kinetics + Monte Carlo)
Transient transfer phenomena Transient transfer phenomena --charges, Ocharges, O 22, water, water --
MEMEPhysMEMEPhys: : multiscalemultiscale mechanisticmechanistic model of the PEMFC electrochemical processes, scaling up model of the PEMFC electrochemical processes, scaling up abab initio initio concepts into anconcepts into an irreversible thermodynamics framework, accounting for:irreversible thermodynamics framework, accounting for:
•• the MEA the MEA physicochemistryphysicochemistry at spatial NANO and MICRO scales (elementary kinetic approach at spatial NANO and MICRO scales (elementary kinetic approach �� nono ButlerButler--VolmerVolmer equations are used hereequations are used here).).•• the intrinsic MEA the intrinsic MEA nanomaterialsnanomaterials degradation and couplings between aging mechanismsdegradation and couplings between aging mechanisms
Coupled agingCoupled agingphenomenaphenomena
E.g. E.g. elementaryelementary kinetickinetic description of description of Pt Pt electrochemicalelectrochemical agingaging processesprocesses
E.g. E.g. elementaryelementary kinetickineticdescription of HOR/ORRdescription of HOR/ORR……
PEMFC MEA durability prediction in automotive conditions: engineering challenges
�� PEMFC are nonPEMFC are non--equilibrium electrochemical equilibrium electrochemical systems!systems!�� In PEMFC electrochemistry is dominated by In PEMFC electrochemistry is dominated by nanoscalenanoscale (quantum and interfacial) effects(quantum and interfacial) effects�� The The nanomaterialsnanomaterials reconstruct even without reconstruct even without polarization!polarization!
�� Engineering requirement: Engineering requirement: improvement of PEMFC improvement of PEMFC nanomaterialsnanomaterials in terms of cost, in terms of cost, performance and durability.performance and durability.�� Physical modeling of the Physical modeling of the nanomaterialsnanomaterials properties and properties and behavior is crucial to suggest behavior is crucial to suggest new operating conditions filling new operating conditions filling these requirements. these requirements.
““ OnOn--thethe --flyfly ”” coupling of scales coupling of scales within within MEMEPhysMEMEPhys
MEMEPhysMEMEPhys algorithm architecture: dual corealgorithm architecture: dual core
(DFT)(DFT)
TEM images for 38 wt.% Pt/C (Tanaka) taken after (A ) 2 min. (B) TEM images for 38 wt.% Pt/C (Tanaka) taken after (A ) 2 min. (B) 22 min. 22 min. (C) 45 min. (D) 65 min. under the electron beam (U= 300keV).(C) 45 min. (D) 65 min. under the electron beam (U= 300keV).
CORCOR--driven driven Pt coarseningPt coarsening
submodelsubmodel
2 min2 min 22 min22 min
45 min45 min 65 min65 min
Project goals and methodology
Interplaying between aging mechanisms in Interplaying between aging mechanisms in real PEFC operationreal PEFC operation
Durability-predictive modeling approach MEMEPhys: concepts and applications
Cell levelCell level
ATOMIC scaleATOMIC scale
MESO scaleMESO scale
NANO scaleNANO scale
MICRO scaleMICRO scale(CFD)(CFD)(pseudo(pseudo--µµstructural structural
resolved CFD)resolved CFD)
Electrochemical Electrochemical dissolution and dissolution and
ripeningripening
NANO scaleNANO scale
(Franco (Franco et alet al nonnon--equilibrium equilibrium
interfacial theory)interfacial theory)
Channels
GDL
Active Layer
Membrane
I(t)I(t)
(CFD)(CFD)
Physical Physical parametersparameters
+H
+H
2O
+H
−e
−e
22 OOH +
OH 2
2O
Cathode electrodeAnode electrode GDLGDL Membrane
CO
2H
COHOH ++ 22+2
Pt
+2Pt
2H
2O
+H
−e
−e
CO CO
Competition between local ORR and CO-catalyst poisoning
Cathode catalyst C-support corrosion
+2Pt
+2Pt
+2Pt
Carbon Support(C)
−e2
−e2
−e2
−e −
e
Lx =
Pt grainPt grain
Pt oxydation/dissolution/electrochemicalOstwald’s ripening
A.A. Franco et al., A.A. Franco et al., J. J. ElectrochemElectrochem. Soc.. Soc., , 155155 (4) B367 (2008).(4) B367 (2008).
A. A. Franco et al., A. A. Franco et al., J. J. ElectrochemElectrochem. Soc.. Soc., , 154154 (7) A712 (2007).(7) A712 (2007).
A.A. Franco et al., A.A. Franco et al., ECS ECS TransTrans.., , 1313 (15) 35 (2008).(15) 35 (2008).
Pt particlePt particle
MEMEPhysMEMEPhys model:model: Prediction of synergies between PEM and C Prediction of synergies between PEM and C degradation mechanisms.degradation mechanisms.
PredictionPrediction of of experimentalexperimental observables observables (e.g. (e.g. polarizationpolarization curvescurves, , potentialpotential vs. vs.
time, EIStime, EIS……))
Cathode Aged Cathode
Carbon corrosionCarbon corrosion
Oxidation/dissolution/ripening of Oxidation/dissolution/ripening of catalyst catalyst nanoparticlesnanoparticles
BeforeBefore 24h @OCC24h @OCC AfterAfter 24h @OCC24h @OCC
Cathode
Cathode
t (h)
0.10.1--15 A 15 A cyclescycles
steady state 0.1 Asteady state 0.1 A
Potential Potential ““collapsecollapse””
PEM degradation PEM degradation
5 µ mCathode
M embrane
ht 10000 +
Catalyst detachment/dissolved Catalyst detachment/dissolved metallic ions crystallization metallic ions crystallization
Main objectivesMain objectives ::
�� to propose a novel approach to propose a novel approach aiming on a deeper aiming on a deeper understanding of the interplaying understanding of the interplaying of the physicochemical of the physicochemical phenomena responsible of the phenomena responsible of the PEFC MEA degradation under PEFC MEA degradation under steadysteady--state and transient state and transient operating conditionsoperating conditions�� to provide a predictive model to provide a predictive model of PEFC durability under of PEFC durability under automotive operating conditionsautomotive operating conditions
Atomic Hydrogen on Pt3Ni(111) Bulk Truncate
Water Molecule on Pt(111)
Atomic Hydrogen on Pt(111)
Oxygen on Pt(111)
OH on Pt(111) OOH on Pt(111)
Atomic Oxygen on Pt(111)
Oxygen on Pt3Ni(111) Bulk Truncate
Atomic Oxygen on Pt3Ni(111) Bulk Truncate
Atomic Hydrogen on Pt3Ni(111) Skeleton
Oxygen on Pt3Ni(111) Skeleton
Atomic Oxygen on Pt3Ni(111) Skeleton
0 2 4 6 8 10 12
x 104
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
Time (s)
UC
ell (V
)
I= 0 AI= 0.1 AI = 0.5 AI = 1 AI = 1.5 AI = 2 A
2 4 6 8 10 12 14 16
x 104
0
0.2
0.4
0.6
0.8
1
Time (s)
UC
ell (V
)
I= 0 AI= 0.1 AI = 0.5 AI = 1 AI = 1.5 AI = 2 A
610×610×
0 0.5 1 1.5 2
x 105
-10
0
10
20
30
40
50
Time (s)
C lo
ss (%
)
25 µm (PEM + C degradation)50 µm (PEM + C degradation)25 µm (C degradation)50 µm (C degradation)
0 0.5 1 1.5 2
x 105
0
0.01
0.02
0.03
0.04
0.05
0.06
Time (s)
SP
t (m-2
)
25 µm (PEM + C degradation)50 µm (PEM + C degradation)25 µm (C degradation)50 µm (C degradation)
710× 710×
First results (Feb09-Jun09)DFT model:DFT model: Adsorption energies of all the HOR and ORR Adsorption energies of all the HOR and ORR intermediates on Pt(111) and Ptintermediates on Pt(111) and Pt33Ni(111)Ni(111)--skeleton surfaces.skeleton surfaces.
Experimental:Experimental: Definition of simplified real cycles and first Definition of simplified real cycles and first tests in singletests in single--cells and excells and ex--situ characterizations.situ characterizations.
Global Global mechanisticmechanisticmodelmodel
ComplementaryComplementarymodellingmodelling toolstools
Atomistic (kinetics)parameters
Micro-structural (transport)parameters
ExperimentalExperimental inin --situsitu /ex/ex--situ situ electrochemicalelectrochemical tests tests andand
micromicro --structuralstructuralcharacterizationscharacterizations
Durabilityprediction• Coupled ageing mechanisms understanding
• Operating strategies mitigating degradation
Global Global mechanisticmechanisticmodelmodel
ComplementaryComplementarymodellingmodelling toolstools
Atomistic (kinetics)parameters
Micro-structural (transport)parameters
ExperimentalExperimental inin --situsitu /ex/ex--situ situ electrochemicalelectrochemical tests tests andand
micromicro --structuralstructuralcharacterizationscharacterizations
Durabilityprediction• Coupled ageing mechanisms understanding
• Operating strategies mitigating degradation
Project structure: strong coupling between Project structure: strong coupling between targeted experiments and targeted experiments and multiscalemultiscale modelingmodeling
Project methodology for the MEA durability Project methodology for the MEA durability prediction under real automotive power cyclesprediction under real automotive power cycles
MEMEPhysMEMEPhys
HalfHalf cellscells, RRDE, RRDE
Single Single cellscells
EPR, HR TEMEPR, HR TEM……
DFTDFT µµ--structural structural resolvedresolved
PEM + C PEM + C degradationdegradation
Cathode potential degradation
OnlyOnly feedback feedback withwith C C
corrosioncorrosion
Cumulative C corroded Active surface area
Automotive power cycle single cell MEA degradation test
EPR spectra of aged Nafion ® PEM
ab ab initioinitio kineticskinetics of of catalyticcatalytic eventsevents atat the the atomisticatomistic scalescale in in periodicperiodic boundaryboundary conditionsconditions
A.A. Franco et al., A.A. Franco et al., ElectrochimElectrochim. Acta. Acta, , 5454 (22) 5267 (2009).(22) 5267 (2009).
P. P. SautetSautet et al., et al., PhysicalPhysical ReviewReview BB, , 5959, 15437 (1999)., 15437 (1999).D. Loffreda et al., D. Loffreda et al., J. Chem. Phys.J. Chem. Phys., , 130130, 124716 (2009)., 124716 (2009).
A.A. Franco et al., A.A. Franco et al., ECS TransECS Trans., ., 2525 (1) 65 (2009).(1) 65 (2009).
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