Dr. Paramaconi Rodriguez
Cutting edge method for the preparation of catalyst for PEFC, AFC and DAFC
H2FC Supergen Dec 2013
Group of
Advanced
Materials and
Electrochemistry
Surfactant
+ +
+ =
NaX Graphite (CE) Pt (WE)
Battery
A very simple experiment (water electrolysis)
Cathodic treatment of a Pt wire: 1 minute at -10V in 10M NaOH
99.99% Pt
0.1mm
Pt -10V / 5min
NaOH
Cyclic voltammogram of Pt in 0.5M H2SO4
Surface area
increase x17
0
-5
AC generator
A
Characterization of cathodic nanoparticles
TEM
EDX
XRD
0
20
40
60
80
100
120
140
160
180
200
0-2 2-4 4-6 6-8 8-10 10-12 12-14 14-16 16-18 18-20 20-22 22-24 More
nm
Size distribution
The mechanism….!
0 5 10 15 20 25 301.0
1.2
1.4
1.6
1.8
2.0
2.2
2.4
2.6
2.8
3.0
3.2
3.4
3.6 1M LiOH
1M NaOH
1M CsOH
1M t-Bu4NOH
10M NaOH
1M Na2SO4
1M NaCl
1M NaClO4
1M NaCl + 1M NaOH
1M NaClO4 + 1M NaOH
1M NaClO4 + 1M HClO4
1M NH4ClO4 + 1M HClO4
molten NaOH
log
(e
tch
ing
tim
e / s
eco
nd
s)
AC Amplitude / V
A.I. Yanson et al. Angew. Chem. Int. Ed, 50, 2011, 6346-6350.
Some cases the nanoparticles appear as oxides
Chemical oxidation in the solution
A.I. Yanson et al. Angew. Chem. Int. Ed, 50, 2011, 6346-6350.
Catalytic activity of cathodic platinum nanoparticles
Black – commercial (TKK) 5 nm Red – cathodic platinum 8-10 nm
Hydrogen adsorption
CO monolayer oxidation
Methanol oxidation
110mV
DOE 2017 target
Cathode loading: 0.125mg/cm2
Cost of Pt in a 50 cm2 cathode by reduction of PtCl4 salt: £50
Cost of Pt in a 50 cm2 cathode by cathodic corrosion: £15,08
Size control of “cathodic” nanoparticles
0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35
6
7
8
9
10
11
12
13
N
P s
ize b
y 1
st X
RD
peak (
nm
)
"rms" ac current (A)
Pt NP prepared in 5M NaOH
0.0
5.0x10-3
1.0x10-2
1.5x10-2
Effic
iency (
s-1)
Alloys?
… what if the starting wire is an alloy?
EDX analysis of nanoparticles
… then we get alloyed nanoparticles!
Electro-oxidation performance of PtRh NPs
Pt
Pt90Rh10
Pt70Rh30
Pt20Rh80
Rh
Blank CV
Methanol oxidation
P. Rodriguez, et al.J. Am. Chem. Soc., 2011, 133 (44), 17626–17629.
CO
Methanol
Pt Pt95Ru5
P. Rodriguez, et al.J. Am. Chem. Soc., 2011, 133 (44), 17626–17629.
Catalytic activity towards FC reactions
Metal
Size
Alloy
Shape (surface orientation)
Parameters that influence catalysis
Preferential oriented nanoparticles
Cu
M.Duca et al. Topics in Catalysis 2013 DOI: 10.1007/s11244-013-0180-5
Problems with the degradation of the carbon support in the Fuel cell?
Schulenburg, H. et al. Journal of Physical Chemistry C 2011, 115, 14236.
TiO2
Au@TiO2
Pt@TiO2
Cathodic Corrosion as a potential method to
prepare clean High Surface Area Electrode Catalyst
and nanoparticles
Control over the composition, size, orientation
Prof. Marc T.M Koper
Dr. Alex Yanson
Dr. Nuria Garcia
Dr. Matteo Duca
Rik Mom
Rico Wanders
Pavel Antonov
Dr. Paramaconi Rodriguez
Cutting edge method for the preparation of catalyst for PEFC, AFC and DAFC
1PhD position available
Advances in Materials Science, Processing, and Engineering for
Fuel Cells and Electrolyzers
Dario Marrocchelli (Massachusetts Institute of Technology), Giuliano Gregori (Max-
Planck-Institut für Festkörperforschung), Enrico Traversa (KAUST), Daniele Pergolesi
(Paul Scherrer Institut), Monica Burriel (Imperial College), Kazunari Sasaki (Kyushu
University) Lin Zhuang (Wuhan University), Olaf Conrad (University of Cape Town),
Yang Shao-Horn (Massachusetts Institute of Technology), Hong Yang (University of
Illinois), Hubert Girault (EPFL), Jan Rossmeisl (Technical University of Denmark),
Venkat Viswanathan (Massachusetts Institute of Technology),.
November 30 - December 5, 2014
Boston, Massachusetts
Supporting info
• In 1907 experiments in liquid ammonia by Kraus produced species of Na+ and
Pb2-
• In the 1930’s Zintl deduced the existence of Na4Pb9,
or a “Zintl ion” Pb94-. Also detected anion Au-
• By the end of 1940’s anions of Hg-, Au- and Li-
were identified in gas phase by mass-spec
• In the 1950’s the first solid ionic compounds of the
type Cs+Au- were synthesized in vacuum
• In 1980’s unambiguous evidence appeared for the existence
of monatomic metal anions in solution and the solid state
• In 2003 a Cs2Pt solid containing Pt2- anion was obtained
Onset potential for Pt is less negative than -2V !
Ge94- Cs4Ge9
Experimental setup
Alloying of a cathode metal with an alkali, and subsequent
leaching of the alloy is inconsistent with the following observation:
• Crystallographic etch pits are indicative of chemical dissolution
short (above) and long (below) cathodic treatments
Haber’s mechanism: alloying with alkali and subsequent leaching
History of metal anions
• In 1907 experiments in liquid ammonia by Kraus produced species
of Na+ and Pb2-
In the 1930’s Zintl concluded that that was Na4Pb9, or a “Zintl ion”
Pb94-. Also detected anion Au-
By the end of 1940’s anions of Hg-, Au- and Li- were identified in gas
phase by mass-spectroscopy
In the 1950’s the first solid ionic compounds of the type Cs+Au- were
synthesized in vacuum
Not before the 1980’s did the world have unambiguous evidence for
the existence of monatomic metal anions in solution and the solid state
In 2003 a Cs2Pt solid containing Pt2- dianion was obtained
… they exist, but are hard to find and handle
(intolerant to air, water, anything reducible) History of metal anions
Low-temperature STM of Au on NaCl: switching Au J. Repp, G. Meyer, F.E. Olsson, and M. Persson, Science 305, 493 (2004)
Annealed gold wire cathodically treated at -10 Vdc in an
electrolyte containing 1M Na+ ions. Left image shows a clear
crystal grain boundary and different corrosion rates on different
crystal orientations. Right image is a zoom-in, showing how
within 1 micron of the grain boundary the surface concentration
of nanoparticles clearly changes. The latter is an indication of the
very limited diffusion of nanoparticle-forming species (metal
anions), corroborating our hypothesis of an extremely thin aprotic
layer and very short lifetimes of metal anions.
Supporting info
0 2 4 6 8 10 12 14200
300
400
500
600
Tim
e / s
pH
Time required to atomize 0.12 mm dia. Pt wire submerged
by 1mm in 0.5M NaOH + x HClO4 solution. 20 V p-p
square wave, 100 Hz. Weak (if any) dependence is
indicative of the fact that under extreme cathodic (anodic)
potentials the pH in the vicinity of the electrode is
strongly shifted towards high (low) pH values due to the
consumption of protons (hydroxyl ions).
Supporting info