Plasma Processing for Fuel Cell TechnologyPlasma Processing for Fuel Cell Technology
GDL coated by platinum nanoparticles (100µg Pt /cm²)
A.Caillarda, D. Ramduttb , P. Braulta, C. Charlesb, R. Boswellb,a Groupe de Recherche sur l’Energétique des Milieux Ionisés, UMR 6606 Université d’Orléans – CNRS Polytech’Orléans BP6744, F-45067 Orleans Cedex 2, France
B Space Plasma, Power and Propulsion, Research School of Physical Science and Engineering Australian National University, Canberra ACT 0200, Australia
Plasma processing for fuel cell electrode deposition
Proton Exchange Membrane Fuel Cell
A PEMFC is an electrochemical cell that is fed hydrogen, whichis oxidized at the anode, and oxygen, which is reduced at thecathode. The protons released during the oxidation areconducted through the PEM to the cathode while the electronstravel along an external circuit and are available to do work.
There are three critical transport processes, (a) protons fromthe membrane to the catalyst, (b) electrons from the currentcollector to the catalyst through the GDL and (c) reactant toand catalyst layer from the gas channel. Part of theoptimisation of the electrode design is to correctly distribute thecatalyst layer throughout the transport media for each of thethree phases (electrons, protons and gases) to reducetransports losses.
Bipolar plate
Proton Exchange
Membrane
Anode Cathode
H2 O2
O2 + H2OH2
5x1011 1x1012c m-3 Ne and Ni
15 23 VPlasma potential
2 3.5 eVElectron temperature
1016 ions/s/cm2Ar+ flux on Pt
5 50 µbarDeposition pressure
-300 -100 VTarget bias
0 1000 WRF Generator Power
TEM image showing carbon particles surroundedby Pt nano-particles
50 nm
T. C
acci
ague
rra (C
RM
D, O
rléan
s,Fr
ance
)
Nafion MembraneCarbon ParticleCarbon Cloth
Nafion FilamentsActive CatalystInactive Catalyst
Half fuel cell
H+
H+
H+
e-
H2
The Membrane Electrode Assembly (MEA) of PEM fuel cells (two electrodes and an ion membrane) is usually produced by wet chemicalprocesses and assembled by hot pressing. During the last few years, some laboratories have developed low power micro-PEM fuel cell byplasma deposition processes. These PEM fuel cell, powered in general by methanol, are not yet optimised for industrial manufacture. Throughour expertise in plasma physics, our aim is to build an optimised nano-structured PEMFC by plasma depositing ultra thin films of platinum andplasma polymerisation of new membranes which allow proton diffusion while reducing poisoning and degradation of the PEM from methylgroups.
Toward a plasma PEM fuel cell
Styrene HC-CH2 +H2
Triflic acid (CF3-SO3H)+ H2
Argon
40 kHz ~50 W
+
Output
Precursor
Film growth
+
++
+
++
++
(b)
Plasma membrane deposition on catalysed GDL
Plasma membraneis deposited 6 µm
into the GDL
plasma membrane deposited on an E-Tek GDL
1 - High electrochemical activity due to the high electrodeactive volume.
Porous substrate(GDL)
Target (Catalyst)
Vb < 0
++
+
+
++
++
+
+
+
++
++
++
++
+
Helicon antennaArgon in
Argon out
13.56 MHz(0-100 Gauss)
(0-100 Gauss)
PIGLET (SP3, Canberra,Australia)
Institut Européen des Mem
branes (FR)
~ 250 nm/minDeposition rate
~ 50 WGenerator power
0,5 mbarTotal pressure (Ar + H2 + styrene + acid)
* 50 times less than the Nafion 117 whose the wet depth is 185 µm** 6 times less than the Nafion 117
3.10- 4 mol.cm²/s**Methanol permeability
10-4 σ/cm*Conductivity
2 - Plasma membrane is dense (high permeability) andthin (high conductivity).
Carbon paper05MEA8
Carbon cloth05MEA4
Carbon cloth-405MEA3
Carbon cloth020MEA2
Cathodic BackingGDL bias (V)Pressure (µbar)Parameters
Fuel cell I-V characteristics (70°C, 4 bar, chemical anode – 0.35 mgPt/cm^2)
Results on H2 fuel cell tests:
1 - Better proton conductivity at high deposition pressuredue to the porous catalyst layer (SEM and TEM)
2 - Better active surface area at low deposition pressuredue to smaller catalyst nano-particles (SEM and TEM)
3 - Voltage drop at high current density due to catalystabsence in the GDL : catalyst diffusion length is around200 nm (FC electrode model)
Platinum and carbon nano-structures must bemixed / deposited together in around a 1 µm
thickness.
Proton polymerCatalyst +Carbon
Catalyst + carbon 200 nm
Carbon
Carbon
Proton polymer
Catalyst +Carbon
Catalyst +carbon
20 µm
Standard chemical PEM fuel cell New “plasma” PEM fuel cell
Bipolar plateElectrodeMembraneAssembly
O2 + H2O
O2 +H2O
H2 +H2O
H2 + H2O
Gasket
FC testing station
FC stacks
1 - Platinum catalyst deposition on GDL by plasma sputtering 2 - Carbon nano-fibres (CNF) deposition by PECVD
SEM of GDL coated by Pt nano-particles
CNF deposition on a carbonpaper
Pt nano-particles deposition onCNFs (2)
Nano-sheets(PECVD)
Nano-horns (laserablation)
Nano-particles(Dusty plasma)
Ro
tar
y pu mp
Con
vec
tor
gaug e
DC Su bst
rat e bia s
Ni
tar
get
bia
sPt tar
get
bia
s
Ni
tar
get
Pt tar
get
Cu
rre nt ge ner
ato
r (he
ate
r)
Inp
ut ga s (Ar
– CH
4 )
ICP
ante
nna po
we
red
by a
RF
gene
rato
r& m
atc
hing
box
Car
bon clot
h
1) GDL (CNT/CNF) growing : Ni catalyst clusters deposition by sputtering then CH4 / N2 PECVD2) Pt nano-particles deposition by plasma sputtering
Ion and neutral beam modification of Nafion
π Matching Network
Nafion® membrane in mount Membrane mounted in diffusionchamber of plasma reactor
Water droplet on treated membrane surface
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 300 600 900 1200 1500 1800
Current Density (mA/cm^2)
Pote
ntial (V
)
E-Tek (0.35 mgPt/cm^2)
MEA2 (0.1 mgPt/cm^2 - Cathode)
MEA3 (0.1 mgPt/cm^2 - Cathode)
MEA4 (0.1 mgPt/cm^2 - Cathode)
MEA8 (0.1 mgPt/cm^2 - Cathode)