between PtNi/C and PtCo/C, while each transition metal should
have different electronic effect on the surface Pt atoms.
Compared to the acidic conditions in which the optimum
content of the transition metals was ca. 20-30 atom%,16 that in
alkaline solution was much higher. The result may imply
different ORR-enhancement mechanism of the alloys in
alkaline media, where Ni and Co hydroxides would be
involved.
Pt100-xCox/C (●) at 0.85 V.
4. Conclusion
A series of PtNi alloy nanoparticles deposited on
acetylene black carbon support (PtNi/C) were synthesized via
our original nanocapsule method so that the alloy compositions,
particles sizes and their distribution were well-controlled.
PtNi/C exhibited high ORR activity with volcano-type
dependence on the composition, where the optimum content of
Ni was ca. 50 atom%. The enhancement of the catalytic activity
in alkaline solution appeared in a very narrow range of Ni
content, similar to that of PtCo/C. Since the nanocapsule
method is applicable to many other binary and even ternary
alloy nanoparticles, more active alloy or non-precious metal
catalysts may be found in the future.
0.06
Ring
Ring
0.04
0.02
0
1750 rpm
x=0 (Pt)
28
1750 rpm
43
Acknowledgement
51
-0.5
-1.0
This work was partly supported by CREST
(JPMJCR12C3), Japan Science and Technology Agency (JST)
and the Ministry of Education, Culture, Sports, Science and
62
Technology (MEXT) Japan through
a Grant-in-Aid for
Scientific Research (18H02030). K.M. acknowledges the
Ogasawara Foundation for the Promotion of Science and
Engineering for financial support.
Disk
Disk
0.2
0.4
0.6
0.8
1.0
Potential / V vs. RHE
Potential (V vs. RHE)
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Figure 3. Hydrodynamic voltammograms for ORR in
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and the rotation rates were set at 5 mV s−1 and 1750 rpm,
respectively. The ring potential was set at 1.1 V vs RHE to
detect hydrogen peroxide formed at the working electrode.
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