1
Cycles application Cycles réels Cycles réels simplifiés Analyse statistique Cycles réels modifiés 4 TESTS réf. Modification des motifs Modification de la séquence des motifs 4 tests par cycle modifié ⇒⇒ 16 TESTS OUI Nouveaux essais Suggestion de stratégies de fonctionnement Validation expérimentale Cycles simples 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 opératoires modifiées MODELISATION Impact des Impact des conditions conditions de cyclage de cyclage Impact des Impact des conditions conditions opératoires opératoires MODELISATION Validé ? NON Lien avec les autres projets : DECODE, DVD-AME, SPACT-80… Cycles “simples”, conditions opératoires de l’application Cycles application Cycles réels Cycles réels simplifiés Analyse statistique Cycles réels modifiés 4 TESTS réf. Modification des motifs Modification de la séquence des motifs 4 tests par cycle modifié ⇒⇒ 16 TESTS OUI Nouveaux essais Suggestion de stratégies de fonctionnement Validation expérimentale Cycles simples 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 opératoires modifiées MODELISATION Impact des Impact des conditions conditions de cyclage de cyclage Impact des Impact des conditions conditions opératoires opératoires MODELISATION Validé ? NON Lien avec les autres projets : DECODE, DVD-AME, SPACT-80… Cycles “simples”, conditions opératoires de l’application Fix- + Fix- Fix- Fix- Fix- Fix- ++ ++ H+ Co Co2+ 2+ Compact layer Compact layer )) , , ( ( t x r φ ) , ( t r ψ 0 = x Diffuse layer Diffuse layer L x = i r Oxide ( Oxide (-- --O) O) Intermediate reaction Intermediate reaction species species Adsorbed water Adsorbed water dipoles dipoles Surface catalyst layer Surface catalyst layer Inner layer Inner layer )) , ( ( t r η Fix- O2 + + + + O H2 ++ ++ ++ ++ ++ ++ ++ ++ ++ ++ ++ ++ Pt Pt2+ 2+ ++ ++ e- Pt Ptz+, , Co Coy+ Pt Ptz+, , Co Coy+ C-support support Ionomer Ionomer Water Water GDL Channels Catalyst nano-particle Membrane - e + H 2 2 O O H 2 2 O O H + Carbon support O H 2 - e - e - e + 2 Co Cathode electrode - e 2 O 2 O 2 O - e - e Impregnated ionomer + 2 Pt Cut Cut view view Electrode Electrode Dr. Alejandro A. Franco Dr. Alejandro A. Franco 1 * , Dr. Olivier Lemaire , Dr. Olivier Lemaire 1 , Dr. Laure Guetaz , Dr. Laure Guetaz 1 , , Romain Romain Coulon Coulon 1 , Rodrigo Ferreira de Morais , Rodrigo Ferreira de Morais 1,4 1,4 , , Dr. Serge Dr. Serge Gambarelli Gambarelli 2 , Dr. Vincent Maurel , Dr. Vincent Maurel 2 , , Dr. Nicolas Fouquet Dr. Nicolas Fouquet 3 , Dr. Franck Masset , Dr. Franck Masset 3 , Dr. David Loffreda , Dr. David Loffreda 4 , Prof. Philippe Sautet , Prof. Philippe Sautet 4 1 CEA CEA-Grenoble/LITEN, Grenoble/LITEN, 2 CEA CEA-Grenoble/INAC, Grenoble/INAC, 3 PSA Peugeot Citro PSA Peugeot Citroën, n, 4 ENS de Lyon ENS de Lyon-CNRS/ CNRS/Laboratoire Laboratoire de de Chimie Chimie *Contact: *Contact: [email protected] [email protected] A.A. Franco et al., A.A. Franco et al., “A Dynamic Mechanistic Model of an A Dynamic Mechanistic Model of an Electrochemical Interface Electrochemical Interface”, , J. Electrochem.Soc. J. Electrochem.Soc., , 153 153, A1053 (2006). , A1053 (2006). A.A. Franco et A.A. Franco et al., al.,“A multi multi-scale dynamic mechanistic model for scale dynamic mechanistic model for transient analysis of PEFC transient analysis of PEFC” Fuel Cells Fuel Cells, , 7, 99 (2007). , 99 (2007). MAFALDA Project MAFALDA Project (Feb09 (Feb09-Jan12) Jan12) Experimental and Experimental and M odeling odeling A nalyses nalyses f or the or the PEFC PEFC A ctive ctive L ayers ayers D egradation egradation A ssessment ssessment MEMEPhys MEMEPhys: Invited lectures and oral presentations in about : Invited lectures and oral presentations in about 64 64 international conferences international conferences (e.g. (e.g. american american Electrochem Electrochem. Soc. . Soc. , , Int. Soc. Electrochemistry Int. Soc. Electrochemistry…) all around the world all around the world (e.g. Qu (e.g. Québec 2005, Vienna 2006, Chicago 2007, Miami 2007, Phoenix 2008, V bec 2005, Vienna 2006, Chicago 2007, Miami 2007, Phoenix 2008, Vancouver 2008, Seville 2008, San Francisco 2009 ancouver 2008, Seville 2008, San Francisco 2009…). ). Invited seminars on Invited seminars on MEMEPhys MEMEPhys in high level institutes, e.g. Heidelberg University (2006), St in high level institutes, e.g. Heidelberg University (2006), Stanford University (2007), British Columbia University (2008), Sa anford University (2007), British Columbia University (2008), Santa Barbara (2009). nta Barbara (2009). 56 56 publications on publications on MEMEPhys MEMEPhys in peer in peer-reviewed journals ( reviewed journals (J. J. Electrochem Electrochem. Soc. . Soc., , Electrochem Electrochem. Soc. Trans. . Soc. Trans., , Electrochim Electrochim. . Acta Acta, , Fuel Cells Fuel Cells) and proceedings + ) and proceedings + 153 153 citations citations 1 invited book in preparation by Dr. Franco (publisher: Pan Stanf invited book in preparation by Dr. Franco (publisher: Pan Stanf ord) + ord) + 1 patent filled from the patent filled from the modeling modeling results within MAFALDA results within MAFALDA Publications, communications, patents Our Our approach approach advantages advantages More realistic description More realistic description of of electrocatalysis electrocatalysis: : account for the non account for the non-equilibrium equilibrium physicochemical environment physicochemical environment Feedback instantaneous Feedback instantaneous performance performance degradation degradation (prediction of durability as function prediction of durability as function of the materials and compositions of 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/ interplayings interplayings…) Hydrogen Hydrogenatom atom Equilibrated Pt Equilibrated Pt-Rh Rh nano nano- structures in vacuum and structures in vacuum and in a H in a H-rich environment: rich environment: reconstruction phenomena reconstruction phenomena I T P A , P C RH A , RH C instantaneous U cell (t) Instantaneous cumulative materials losses instantaneous local operating conditions instantaneous nano-micro-structure Conrol parameters Coupled no-aging phenomena Coupled aging phenomena Coupled aging Coupled aging phenomena phenomena Coupled no aging Coupled no aging phenomena phenomena Transient elementary Transient elementary kinetics kinetics and electrochemical and electrochemical double layer effects double layer effects (MF elementary kinetics + Monte Carlo) (MF elementary kinetics + Monte Carlo) Transient transfer phenomena Transient transfer phenomena -charges, O charges, O 2 , water , water- MEMEPhys MEMEPhys: : multiscale multiscale mechanistic mechanistic model of the PEMFC electrochemical processes, scaling up model of the PEMFC electrochemical processes, scaling up ab ab initio initio concepts into an concepts into an irreversible thermodynamics framework, accounting for: irreversible thermodynamics framework, accounting for: the MEA the MEA physicochemistry physicochemistry at spatial NANO and MICRO scales (elementary kinetic approach at spatial NANO and MICRO scales (elementary kinetic approach no no Butler Butler-Volmer Volmer equations are used here equations are used here). ). the intrinsic MEA the intrinsic MEA nanomaterials nanomaterials degradation and couplings between aging mechanisms degradation and couplings between aging mechanisms Coupled aging Coupled aging phenomena phenomena E.g. E.g. elementary elementary kinetic kinetic description of description of Pt Pt electrochemical electrochemical aging aging processes processes E.g. E.g. elementary elementary kinetic kinetic description of HOR/ORR description of HOR/ORR… PEMFC MEA durability prediction in automotive conditions: engineering challenges PEMFC are non PEMFC are non-equilibrium electrochemical equilibrium electrochemical systems! systems! In PEMFC electrochemistry is dominated by In PEMFC electrochemistry is dominated by nanoscale nanoscale (quantum and interfacial) effects (quantum and interfacial) effects The The nanomaterials nanomaterials reconstruct even without reconstruct even without polarization! polarization! Engineering requirement: Engineering requirement: improvement of PEMFC improvement of PEMFC nanomaterials nanomaterials in terms of cost, in terms of cost, performance and durability. performance and durability. Physical modeling of the Physical modeling of the nanomaterials nanomaterials 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. On On-the the-fly fly” coupling of scales coupling of scales within within MEMEPhys MEMEPhys MEMEPhys MEMEPhys algorithm architecture: dual core algorithm 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). COR COR-driven driven Pt coarsening Pt coarsening submodel submodel 2 min 2 min 22 min 22 min 45 min 45 min 65 min 65 min Project goals and methodology Interplaying between aging mechanisms in Interplaying between aging mechanisms in real PEFC operation real PEFC operation Durability-predictive modeling approach MEMEPhys: concepts and applications Cell level Cell level ATOMIC scale ATOMIC scale MESO scale MESO scale NANO scale NANO scale MICRO scale MICRO scale (CFD) (CFD) (pseudo (pseudo-μstructural structural resolved CFD) resolved CFD) Electrochemical Electrochemical dissolution and dissolution and ripening ripening NANO scale NANO scale (Franco (Franco et al et al non non- equilibrium equilibrium interfacial theory) interfacial theory) Channels GDL Active Layer Membrane I(t) I(t) (CFD) (CFD) Physical Physical parameters parameters + H + H 2 O + H - e - e 2 2 O O H + O H2 2 O Cathode electrode Anode electrode GDL GDL Membrane CO 2 H CO H O H + + 2 2 + 2 Pt + 2 Pt 2 H 2 O + H - e - e CO CO Competition between local ORR and CO-catalyst poisoning Cathode catalyst C- support corrosion + 2 Pt + 2 Pt + 2 Pt Carbon Support(C) - e 2 - e 2 - e 2 - e - e L x = Pt grain Pt grain Pt oxydation/dissolution/electrochemical Ostwald’s ripening A.A. Franco et al., A.A. Franco et al., J. J. Electrochem Electrochem. Soc. . Soc., , 155 155 (4) B367 (2008). (4) B367 (2008). A. A. Franco et al., A. A. Franco et al., J. J. Electrochem Electrochem. Soc. . Soc., , 154 154 (7) A712 (2007). (7) A712 (2007). A.A. Franco et al., A.A. Franco et al., ECS ECS Trans Trans., , 13 13 (15) 35 (2008). (15) 35 (2008). Pt particle Pt particle MEMEPhys MEMEPhys model: model: Prediction of synergies between PEM and C Prediction of synergies between PEM and C degradation mechanisms. degradation mechanisms. Prediction Prediction of of experimental experimental observables observables (e.g. (e.g. polarization polarization curves curves, , potential potential vs. vs. time, EIS time, EIS…) Cathode Aged Cathode Carbon corrosion Carbon corrosion Oxidation/dissolution/ripening of Oxidation/dissolution/ripening of catalyst catalyst nanoparticles nanoparticles Before Before24h @OCC 24h @OCC After After 24h @OCC 24h @OCC Cathode Cathode 0.1 0.1-15 A 15 A cycles cycles steady state 0.1 A steady state 0.1 A Potential Potential “collapse collapse” PEM degradation PEM degradation Catalyst detachment/dissolved Catalyst detachment/dissolved metallic ions crystallization metallic ions crystallization Main objectives Main 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 steady steady-state and transient state and transient operating conditions operating conditions to provide a predictive model to provide a predictive model of PEFC durability under of PEFC durability under automotive operating conditions automotive 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 10 4 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 Time (s) U Cell (V ) I= 0 A I= 0.1 A I = 0.5 A I = 1 A I = 1.5 A I = 2 A 2 4 6 8 10 12 14 16 x 10 4 0 0.2 0.4 0.6 0.8 1 Time (s) U Cell (V) I= 0 A I= 0.1 A I = 0.5 A I = 1 A I = 1.5 A I = 2 A 6 10 × 6 10 × 0 0.5 1 1.5 2 x 10 5 -10 0 10 20 30 40 50 Time (s) C loss (%) 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 10 5 0 0.01 0.02 0.03 0.04 0.05 0.06 Time (s) S Pt (m -2 ) 25 μm (PEM + C degradation) 50 μm (PEM + C degradation) 25 μm (C degradation) 50 μm (C degradation) 7 10 × 7 10 × 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 Pt intermediates on Pt(111) and Pt 3 Ni(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 single tests in single-cells and ex cells and ex-situ characterizations. situ characterizations. Global Global mechanistic mechanistic model model Complementary Complementary modelling modelling tools tools Atomistic (kinetics) parameters Micro-structural (transport) parameters Experimental Experimental in in-situ situ/ex /ex-situ situ electrochemical electrochemical tests tests and and micro micro-structural structural characterizations characterizations Durability prediction Coupled ageing mechanisms understanding Operating strategies mitigating degradation Global Global mechanistic mechanistic model model Complementary Complementary modelling modelling tools tools Atomistic (kinetics) parameters Micro-structural (transport) parameters Experimental Experimental in in-situ situ/ex /ex-situ situ electrochemical electrochemical tests tests and and micro micro-structural structural characterizations characterizations Durability prediction Coupled ageing mechanisms understanding Operating strategies mitigating degradation Project structure: strong coupling between Project structure: strong coupling between targeted experiments and targeted experiments and multiscale multiscale modeling modeling Project methodology for the MEA durability Project methodology for the MEA durability prediction under real automotive power cycles prediction under real automotive power cycles MEMEPhys MEMEPhys Half Half cells cells, RRDE , RRDE Single Single cells cells EPR, HR TEM EPR, HR TEM… DFT DFT μ-structural structural resolved resolved PEM + C PEM + C degradation degradation Cathode potential degradation Only Only feedback feedback with with C C corrosion corrosion Cumulative C corroded Active surface area Automotive power cycle single cell MEA degradation test EPR spectra of aged Nafion® PEM ab ab initio initio kinetics kinetics of of catalytic catalytic events events at at the the atomistic atomistic scale scale in in periodic periodic boundary boundary conditions conditions A.A. Franco et al., A.A. Franco et al., Electrochim Electrochim. Acta . Acta, , 54 54 (22) 5267 (2009). (22) 5267 (2009). P. P. Sautet Sautet et al., et al., Physical Physical Review Review B, , 59 59, 15437 (1999). , 15437 (1999). D. Loffreda et al., D. Loffreda et al., J. Chem. Phys. J. Chem. Phys., , 130 130, 124716 (2009). , 124716 (2009). A.A. Franco et al., A.A. Franco et al., ECS Trans ECS Trans., ., 25 25 (1) 65 (2009). (1) 65 (2009).

2008 MAFALDA project ANR PAN H OK · Cycles application Cycles réels Cycles réels simplifiés Analyse statistique Cycles réels modifiés 4 TESTS réf. Modification des motifs Modification

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Page 1: 2008 MAFALDA project ANR PAN H OK · Cycles application Cycles réels Cycles réels simplifiés Analyse statistique Cycles réels modifiés 4 TESTS réf. Modification des motifs Modification

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).