New Electrocatalysts For Fuel Cells
Principal Investigator: Philip N. Ross, Jr.
Staff Scientist: Nenad M. Markovic
Post Doctoral Fellow: Thomas J. Schmidt
Vojislav Stamenkovic
Visiting Scientist: Ursula Paulus
Matthias Arenz
Berislav Blizanac
A research program conducted at the Lawrence Berkeley National Laboratory for the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Advanced Transportation Technologies of the U.S. Department of Energy under contract No. DE-AC03-76SF00098
Materials-by-Design Approach
synthesis of nanoparticles
Nafionfilm
Glassy-Carbon(RDE)
Catalysts
Characterization techniques
LEIS, XPS, AES, LEED HRTEM, XRD
Kinetics
HOR, ORR, CO Tolerance
HOR, ORR, CO Tolerance
Fuel cell catalyst
Taylor made surfaces
Modification oAl acac
CH3
Al CH3acac
Al
acac
CH3
Alacac
CH3
AlCH3
acac
AlCH3
acac
Collaborations
Industry
GM, Rochester, NY, USA Honda, Japan E-Tek, New Jersey, NJ, USA 3M, Minneapolis, MN, USA
Universities and Institutes
Max-Planck-Institut fuer Kohlenforschung, Muelheim/Ruhr, Germany
University of Ulm, Germany Paul-Scherrer-Insitut, Villigen, Switzerland Universidad d’Alicante, Spain Texas Tech University, Lubbock, TX, USA University of Eindhoven, Holland University of Wales, UK University of Bonn, Germany University of Liverpool, UK
Future Research 2000
Anode Side
Optimization of PdAu catalysts
Stoichiometry and particle size
Electrocatalysis on Pd thin metal films
Electronic effects
Select the most promising substrate for the Pd thin filmelectrode concept
Simulation of ‘Air-bleed’
on FC catalysts under FC conditions
Cathode Side
Optimization of PtNi and PtCo catalysts
Stoichiometry
Minimization of Pt amount
Pt-skin effects (electronic modification of Pt)
Anion effects
New class of ORR catalysts
Publications (Since 10/2000)
Refereed Journals and Refereed Conference Proceedings:
Markovic, N. M. and P. N. Ross, “Electrocatalysts by Design: From the TailoredSurface to a Commercial Catalyst”, Electrochim. Acta, 45, 4101, 2000.
Markovic, N. M. and P. N. Ross, “New Electrocatalysts for Fuel Cells: From ModelSurfaces to Commercial Catalysts”, CATTECH 4 (2000) 110.
V. Stamenkovic, N. M Markovic, P. N. Ross, “Structure-relationships inelectrocatalysis: Oxygen Reduction and Hydrogen Oxidation Reactions on Pt(111) and Pt(100) in Solution Containing Chloride Ions”, J. Electroanal. Chem. 500 (2001) 43.
T.J. Schmidt, B. N. Grgur, N.M. Markovic, and P.N. Ross, “Oscillatory Behavior inthe Electrochemical Oxidation of Formic Acid on Pt(100): Rotation and Temperature Effects”, J. Electroanal. Chem. 500 (2001) 43.
C. Saravanan, N.M. Markovic, M. Head-Gordon, P.N. Ross, “Stripping and BulkCOElectro-oxidation at the Pt-Electrode Interface: Dynamic Monte Carlo Simulations”, J. Chem. Phys. 114 (2001) 6404.
N. M Markovic, T.J. Schmidt, V. Stamenkovic, P.N. Ross, “Oxygen ReductionReaction on Pt and Pt Bimetallic Surfaces: A Selective Review”, Fuel Cells-FromFundamentals to Systems 1(2001)105-116.
T.J. Schmidt, V. Stamenkovic, C.A. Lucas, N.M. Markovic, and P.N. Ross, “SurfaceProcesses and Electrocatalysis of the Pt(hkl)/Bi –Solution Interface”, PhysicalChemistry Chemical Physics 3 (2001)3879.
T.J. Schmidt, N.M. Markovic, and P.N. Ross, “Temperature-Dependent SurfaceElectrochemistry of Pt Single Crystal Surfaces in Alkaline Solution Part I. COOxidation”, J.Phys. Chem, B 105 (2001)12082.
Koper, MTM; Schmidt, TJ; Markovic, NM; Ross, PN. “Potential Oscillations and S-shaped Polarization Curve in the Continuous Electro-oxidation of CO on Pt Single-crystal Electrodes”, J. Phys. Chem. B 105 (2001) 8381.
Future Directions
Unified concept for both anode and cathode catalysts utilizing PGM-based bimetallic nanoparticles with “grape” structure (PGM skin with base metal core)stability of high surface area Pt-bimetallic catalysts
Choice of skin and core metals different for anode and cathode
New synthetic chemistry for nanoparticles with “grape” structure
Investigation of Re as metal core in PGM “grape”structured nanoparticles
Pt and Pd monolayers on Re(0001) model system
Re colloidal chemistry
Optimization of AuPd anode catalyst for HT membranes
Computational screening of non-PGM catalyst concepts using newly developed (under BES funding)ab initio theory of the ORR
Segregation on Pt3Ni and Pt3Co alloys surfaces
ResultsGroupGrenoble
Y.Gauthier, Surface Review and Letters, 3(1996)1663
AES
Pt3Co annealed
Pt3Co sputtered
Auger electron energy [eV]200 400 600 800
dN(E
)/dE
[arb
.uni
ts]
Pt3Co annealed
E/E0
0.4 0.6 0.8co
unts
[kH
z]
LEIS Ne+
a)
b)
E/E0
0.4 0.6 0.8
coun
ts [k
Hz]
LEIS Ne+
Pt3Co sputtered
c)
Pt251Pt237Pt158
Pt390 Co656
Co716
Co775 Co
Pt
Pt
Co
PtPlatinum ‘Skin’ on the surface
Pt3Co: AES, LEIS
AES:
-Co depeleted on the annealed surfaces
-Pt enrichment?
LEIS:
-Complete Pt enrichment on the annealed surface
-Bulk composition achievedduring in situ sputtering
Skin structure is either more or less active than sputtered structure
factor:
% H
2O2 ; i
R/µ
A
0
10
20
E/V vs RHE0.0 0.2 0.4 0.6 0.8 1.0
i D/m
Acm
-2
-4
-2
0
Pt3Co skinPt-poly
1600rpm
Pt3Ni skin
0.1M HClO4
333K
i k[m
A/c
m2 ]
2
4
6
8
10
12
14 0.1M HClO4 @ 0.85V 333K
Pt Pt3Ni Pt3Co
Sputtered SurfaceAnnealed surfaceSputtered SurfaceSkin Structure
Kinetic Enhancement by Skin Effect
The most active surface at 60°C: Pt3Co skin
Pt3Co (s) > Pt3Co (b) > Pt3Ni (b) >Pt > Pt3Ni (s)4.2 2.8 1.9 1 0.15
Electronic effects
Characterization of Pt/Vulcan Catalyst
10 nm
Particle Size [nm]
0 1 2 3 4 5 6 7 8 9 10
Freq
uenc
y [%
]
0
5
10
15
20
25
30
d~3.5 nm
low magnification
Transmision electron microscopy
5 nm
(111)
(100)
Mainly cubo-octahedral particleswith (111) and (100) facets
high magnification
The particle size effects:Correlation between the ORR on Pt(hkl) andexposed facets on Pt/C catalysts at fuel cells relevant conditions
3 nm3 nm
6 nm6 nm
mean particle size [nm]2.53.03.54.04.55.0
i [m
Acm
-2re
al ]
d=3.1 ± 1 nm, 3.3 ± 0.7 nm, 3.8 ± 1.7 nm, 4.7 ± 2.7 nm
catalysts: 10, 20, 30, 40% Pt/C
KOH
H2SO4
SA increases with SAD(100, e+c)
Particle size effect
10 % Pt/Vulcan
40 % Pt/Vulcan
SA increases with SAD(111)
E [V/RHE]
0.0 0.2 0.4 0.6 0.8 1.0
I [m
A/c
m2 ]
-1.0
-0.8
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
0.8
20% Pt/Vulcan20% PtNi/VulcanPt3Ni/Vulcan
Hupd coverage decreases with increase of Ni or Co wt%
(a)
Complete alloying
0.1M HClO4333K
HR Transmision electron microscopy
Pt/VulcanPtNi/VulcanPt3Ni/Vulcan
Characterization of PtCo/Ni Vulcan Catalysts
Cubo-octahedral shapewith (111) and (100) facets
PtM
ORR Kinetics on Pt-bimetallic SurfacesFuel Cells Relevant Conditions
Some Pt-M alloys have better performance than Pt
Pt-Co has the highest activity
i k [m
A/m
g Pt]
0
50
100
150
200
250
300
350
@ 850 mV @ 900 mV
0.1 M HClO4, 333 K, Anodic Step (hold 10 min./potential)
40 % Pt 50 % Pt PtCr PtFe PtCo PtNi
Benefits:Higher activity (!?) Substitution of Pt
n ~ 2
n < 1e)
n > 2
n = 10.6 0.8 1.0
Inte
nsity
/ a.
u.
n < 1
Pd
Pt
E1/E0
0.6 0.8 1.0
Inte
nsity
/ a.
u.n = 1
PtPd
Pt(111)
b)
E/V [RHE]0.0 0.2 0.4 0.6
0.05M H2SO4 293K
Pt(111) - nML Pd
x5Pt(111) n = 1
n ~ 2
n > 2
n < 1
E1/E0
E1/E0
0.6 0.8 1.0
Inte
nsity
/ a.
u. Pd
n > 1
c)
a)
d) 0.15 mA/cm2
0.25 mA/cm2
Pd thin metal films on Pt(111)
Pt(111)-Pd
E [V/RHE]0.0 0.2 0.4 0.6
j [m
Acm
-2]
-3
-2
-1
0
1
2
Pt(111)-1ML PdPt(111)-0.65ML PdPt(111)-0.42ML Pd
Pt(111)
Pt(111)-1ML PdPt(111)-0.65ML Pd
Pt(111)-0.42ML Pd 0.05M H2SO4
E [V/RHE]-0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2
i [m
Acm
-2]
-1
0
1
2
3
Pt (111)-1ML PdPt (111)-0.65ML PdPt (111)
HOR 0.1 M KOH 1600 rpm 293 K
ΘPd / MS
0.0 0.5 1.0 1.5 2.0 2.5 3.0
i k / m
Acm
-2
0.4
0.6
0.8
1.0
1.2
1.4 Pt(111)-Pd0,05M H2SO4
HER/HOR on Pt(111)-Pd in H2SO4/KOH
Maximum catalytic activity for 1 MLof Pd film
Adsorption vs Absorption of H
Activation energy:
Reduced by 50% on 1ML Pd
E [V/RHE]0.0 0.2 0.4 0.6 0.8 1.0
i [m
Acm
-2]
-5
-4
-3
-2
-1
0
Pt(111)Pt(111)-1ML PdPt(111)-1.5 ML Pd
I [µA
]
0
20
400.1 M KOH50 mV/s, 1600 rpm, 293 K
Electronic Effect
amount Pd / ML0.0 0.5 1.0 1.5 2.0
-I /m
Acm
-2
0
1
2
3
4 @ 0.9V
2
ORR on Pt(111)-x Pd in KOH
“Vulcano Plot”
ORR on UHV Prepared Au(hkl)-Pd Alloy Surfaces
i k[m
A/c
m2 ]
0
2
4
6
8
10 0.1M KOH @ 0.85V
333K
Au(111)
+30
%Pd
+50
%Pd
Au(100)
+30
%Pd
+50
%Pd
+0 %
Pd
+0 %
Pd
ORR
Pd coverage [%]0 20 40 60 80
i k [m
A/c
m2 ]
0
2
4
6
8
10
Au(111) + Pd
Au(100) + Pd
Structural Effect
Electronic Effect
Vapor deposition of Pd
50 % Pd
Inte
nsity
(arb
. uni
ts)
30 % Pd
Au(hkl)-PdLEIS He+
75 % Pd
E/E0
0.6 0.8 1.0
Pd
Pd
Pd
Au
Au
Au