126
particularly the shift of the weighted d-band center that depends upon the cumulative contributions of lattice strain and ligand effect, is likely to account for the
observed activities.
The onset of the formation of PtOH on a Pt/PdPb catalyst occurs at considerably
more negative potential than that observed for Pt nanoparticles. This fact implies
that the surface will not be a very active ORR catalyst, as is depicted in Fig. 8.17.
Thus, although the surface layer contains Pd atoms, they apparently are expanded
because of the larger lattice and atomic size of Pb, thereby increasing the reactivity
of that surface and favoring the easier formation of the oxide, as indicated by the
negative potential shift in PtOH formation [14].
Therefore, a new class of core-shell electrocatalysts for the ORR composed of a
Pt monolayer shell and ordered intermetallic compounds cores that are highly stable
have been synthesized. Inexpensive intermetallics are coupled with a Pt monolayer
for high activity and low metal content make electrocatalysts that exhibit high activity and very high stability. Data indicate strategies suitable for selecting the types of
intermetallic compounds as the support for a Pt monolayer. This fabrication method
holds excellent potential for creating efficient fuel cell electrocatalysts.
8.1.4 Modifications of Pt Monolayer Surfaces
Large and specific effect of the supporting nanoparticles on the activity of a Pt
monolayer for the ORR limits the number of suitable materials. If the costs or stability of the nanoparticle material are suitable, but the effect on the Pt monolayer activity is adverse, a modification of Pt-support interaction can be effectuate using an
“interlayer,” such as a Pd monolayer. Two systems that are improved by a Pd inter0
–1
–2
–3
–4
–5
–6
j / mA cm
2
0
0.2
0.4
0.6
0.8
1
E / V vs. RHE
Pt/PdPb
Pt/PdFe(550)
Pt/PtPb
Fig. 8.17 Polarization
curves for the ORR on Pt/
PtPb, Pt/PdPb, and Pt/
PdFe(550) in 0.1 M HClO 4
solution at 1600 rpm;
sweep rate 10 mV/s.
Reproduced from [14] with
permission by American
Chemical Society.
8 Catalytic Properties of Pt Monolayer Electrocatalysts
particularly the shift of the weighted d-band center that depends upon the cumulative contributions of lattice strain and ligand effect, is likely to account for the
observed activities.
The onset of the formation of PtOH on a Pt/PdPb catalyst occurs at considerably
more negative potential than that observed for Pt nanoparticles. This fact implies
that the surface will not be a very active ORR catalyst, as is depicted in Fig. 8.17.
Thus, although the surface layer contains Pd atoms, they apparently are expanded
because of the larger lattice and atomic size of Pb, thereby increasing the reactivity
of that surface and favoring the easier formation of the oxide, as indicated by the
negative potential shift in PtOH formation [14].
Therefore, a new class of core-shell electrocatalysts for the ORR composed of a
Pt monolayer shell and ordered intermetallic compounds cores that are highly stable
have been synthesized. Inexpensive intermetallics are coupled with a Pt monolayer
for high activity and low metal content make electrocatalysts that exhibit high activity and very high stability. Data indicate strategies suitable for selecting the types of
intermetallic compounds as the support for a Pt monolayer. This fabrication method
holds excellent potential for creating efficient fuel cell electrocatalysts.
8.1.4 Modifications of Pt Monolayer Surfaces
Large and specific effect of the supporting nanoparticles on the activity of a Pt
monolayer for the ORR limits the number of suitable materials. If the costs or stability of the nanoparticle material are suitable, but the effect on the Pt monolayer activity is adverse, a modification of Pt-support interaction can be effectuate using an
“interlayer,” such as a Pd monolayer. Two systems that are improved by a Pd inter0
–1
–2
–3
–4
–5
–6
j / mA cm
2
0
0.2
0.4
0.6
0.8
1
E / V vs. RHE
Pt/PdPb
Pt/PdFe(550)
Pt/PtPb
Fig. 8.17 Polarization
curves for the ORR on Pt/
PtPb, Pt/PdPb, and Pt/
PdFe(550) in 0.1 M HClO 4
solution at 1600 rpm;
sweep rate 10 mV/s.
Reproduced from [14] with
permission by American
Chemical Society.
8 Catalytic Properties of Pt Monolayer Electrocatalysts