Improvment of PEM fuel cells for car application ...

EMP/CEP - ACHARD - July 09

Improvment of PEM fuel cells for car application:from stack characterisation to tailored electrodes &

membranes nanostructured materials

Prof Patrick Achard

Center for Energy and Processes

Sophia Antipolis

[email protected]


CEP PARIS (51 persons)

• Systems thermal behaviour

• Systems thermodynamics

• Environnemental performance of buildings

• Energy demand size managment

• Cooling systems

• Energy production environnemental Impacts

• Energetic systems and processes sizing and

control optimization

CEP SOPHIA (44 persons)

• Renewable energies

• Energetics, Materials & Processes - EM&P team

• Plasma

• Observation, Modeling & Decision

CEP/SCPI (7 persons)

• Synthesis of oxyde particules and

metallic hydroxydes

About our lab: Center for Energy and Processes CEP

CEP/TEP (19 persons)

• Design of specific apparatus

• Measure of thermophysical properties in

difficult conditions

• Software and modeling

• Gaz-liquid Transfer


Fifteen years ago, the european

project FEVER (Fuel cell Electrical

Vehicle for Extended Range)

coordinated by Renault was

launched.

This project has permitted the

creation of the laboratory of CEP/

Mines-ParisTech devoted to

Hydrogen and Fuel cells @ Sophia-

Antipolis (south of France).

The EM&P team which developped

it has parallelly a strong background

on functional materials for energy

and particularly on aerogels.

Yet a long road untill todayto realize zero emission vehicle with a large range


First of all let us speak of "PEM fuel cells"(PEM stands for Proton Exchange Membrane)

What is a PEM fuel cell?

A clean and efficient energy converter generating electricity from chemical energy


Ele

ctr

ical eff

icie

ncy

[%]

60

40

2

0

Power


11/05/2009 6

Stack ZSW Ulm, Allemagne

Low working temperature

Quick start

BUT

Cost has to be reduced

Power density and durability have to be increased

Proton Exchange Membrane Fuel Cell (PEMFC)

heat

e- e-

H2 O2 or air

O2 or air

+H2OH2+H2O

Solid electrolyte

(membrane)

load

H+

+-

Gas diffusion

layercatalytic area

H2 2H+ + 2 e- ½ O2 + 2H+ + 2 e- H2O

anode cathode

bipolar plate


PEM fuel cell stack assembly


PEM fuel cell stack characterization: U/I curve


S.J. Lee et al. J. Power Source (2005)

PEM fuel cell monocell assembly


Secondly let us speak of particular

materials called "aerogels"

What is an aerogel?

A nanostructured material which issynthesized thanks to green chemistry,and of which architecture can be taylored


C.J. Brinker, G.W. Scherer,Sol-Gel science : the physics and chemistry of sol-gel processing (1990)


principal drawbacks

• Rather low mechanical properties

( ~ 0,1 Mpa pour ~ 0.15 g/cm3)

• A careful drying step:

generaly, in supercritical conditions (CO2)


0

0,04

0,08

0,12

0,16

0,2

0 20 40 60 80

Lp (nm)

DT

P (

cm

3/g

.nm

)

70vol% 30vol%50vol%

0

0,04

0,08

0,12

0,16

0,2

0 20 40 60 80

Lp (nm)

DT

P (

cm

3/g

.nm

)

70vol% 30vol%50vol%

Influence of the sol concentration on the microstructure

Volumic fraction of ethanolic solutions of PEDS-Px from PCAS society

(solutions TEOS, hydrolysis under stoechiometry)

Yasmine MASMOUDI, PhD Thesis EMP (2006)


0

0,05

0,1

0,15

0,2

0,25

0 20 40 60 80 100

L (nm)

PS

D (

cm

3/g

.nm

)

Aérogel (0.120 g/cm3)

Cryogel (0.140 g/cm3)

Xérogel (0.320 g/cm3)

0

0,05

0,1

0,15

0,2

0,25

0 20 40 60 80 100

L (nm)

PS

D (

cm

3/g

.nm

)







Polyurethane


Cellulose Acetate

MEB FEG (CTMC-INPG)


16/06/2009 16

water

Resorcinol (R)

+

Formaldehyde (F)

Catalyst (C)

Sol-gel

reaction

85°C

Organic gels

Carbon aerogels (monolithic)

Pyrolysis

under N2

(1050°C)

R/F fixed

R+F+C=solid

CO2

supercritical

drying

Organic aerogels

(35°C, 80 bar)

Carbon aerogels elaboration


11/05/2009 17

Carbon aerogels: Pore size distribution


Why do we work on carbon aerogels

as PEM electrode materials?

To get nano-carbonaceous materials elaborated through a clean process & permitting to understand better the behaviour of porous electrodes and toimprove the fuel cell efficiency


16/06/2009 19

Controlled porous structure: pores diameter, particles size

High BET surface area Pt dispersion

Opened porous network

Monolithic materialsCarbon Aerogel

SBET ≈ 650 m²/g

100 nmCarbon black

SBET ≈ 250 m²/g

Interest of carbon aerogels


Vulcan XC72, SBET= 250 m2 /g

Carbon Aerogel, SBET= 970 m2 /g40 nm

40 nm

•Spherical particles agregates

•Microporous and macroporous

•Carbon partially graphitized

•Monolithic structure

•Principaly mesoporous

•Carbon non graphitized


Carbon aerogel ground

with nano sized

particulates of Platinum

deposited inside the

nanostructure


11/05/2009 22

Catalytic layer


water

Pt/CNafion®

Ultrasonic bath:Nafion®/carbon stabilisation

Kapton®

support

“Ink” =carbon +Nafion®

50 cm2 spray

Ultrasonic

Paxitech anode and GDL

Cathodic catalytic layer

cathode

anode

MEA

Same GDL than in anode

Nafion®

Membrane NE112

Hot Pressing

200 bars, 120ºC

MEA : Membrane Electrode Assembly


MEA: Membrane Electrode Assembly

(Carbon aerogel electrodes)


Experimental

Monocell

EMA Cell


PEM

Monocell

test bench


0 1 2 3 4

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1,0CA#1-I-0.5

CA#1-I-0.21

CA#2-I-0.5

CA#2-I-0.21

CA#2-I-0.13

Ref. -0.6

Ce

ll V

oltag

e /

V

Specific Intensity / kA gPt

-1

mgPt/cm²


0 10000 20000 30000 40000 50000

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1,0

E /

V

I / mA

Aérogel S3

Carbone TKK

Nanofibres de carbone


16/06/2009 29

U = Erev(pH2, pO2, Tcell) - ORR – ohm - diff

Analysis of polarization curves

ORR

Gasteiger et al., Applied Catalysis B: Environmental, 56.1-2 (2005): 9-35

ηORR : activation losses

ηohm: ohmic losses

ηdiff: diffusive losses


Sepiolite fibers

Realisation of composite

Membranes based on Nafion

commercial polymer adding

mineral nanofibers

MET picture of Nafion membrane with sepiolite fibers

CF2

x

CF2

CF2 CF

O CF2

CF O

CF3

CF2

CF2

CF2 SO

3H

m

n

Nafion formula


Composite membranes based on Nafion with sepiolite fibers


Analyse mécanique dynamique

0.0E+00

1.0E+08

2.0E+08

3.0E+08

4.0E+08

5.0E+08

6.0E+08

7.0E+08

20 40 60 80 100 120 140 160

température (°C)

Module

(P

a) n112

h112

H112S05

H112S10

h112S20

Evolution of Young modulus versus temperature

For different membranes based on Nafion


Courbes E=f(j) pour N112 - 100°C et (25, 50, 75)% HR

0

0.2

0.4

0.6

0.8

1

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6

j (A/cm2)

E(V)

25%

50%

75%

UI curves for a PEM monocell with a Nafion membrane

@ 100°C for different relative humidities


Nanostructured materials appear to be promissing

materials as catalyst supports or membranes fillers

for PEM fuel cells permitting respectively to decrease

catalyst loading (and so to reduce the cost),

or to increase operating temperature,

and finally to improve cell efficiency.

clean energy conversion to power cars or to

generate electricity on board (APU-Auxiliary Power Unit).

An hope to get zero emission vehicle for a cleaner future

CONCLUSION & PERSPECTIVES


THANK YOU

for your attention

Improvment of PEM fuel cells for car application ...

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