Thermal decomposition synthesis of functionalized PdPt
alloy nanodendrites with high selectivity for oxygen
reduction reaction
Fu-Min Li1, Xue-Qing Gao1, Shu-Ni Li1, Yu Chen1 and Jong-Min Lee2
1
Key Laboratory of Macromolecular Science of Shaanxi Province, School of
Materials Science and Engineering, School of Chemistry and Chemical Engineering,
Shaanxi Normal University, Xi'an 710062, PR China
2
School of Chemical and Biomedical Engineering, Nanyang Technological
University, Singapore 637459, Singapore
Correspondence: Professor Y Chen, Key Laboratory of Macromolecular Science of
Shaanxi Province, School of Materials Science and Engineering, Shaanxi Normal
University, Xi'an 710062, PR China or Professor JM Lee, School of Chemical and
Biomedical Engineering, Nanyang Technological University, Singapore 637459,
Singapore
E-mail: ndchenyu@gmail.com or jmlee@ntu.edu.sg.
1
CH2
CH
n
NH2 HCl
CH2
Scheme S1. The molecular structure of the polyallylamine hydrochloride (PAH).
Intensity / a.u.
Pt
Pd
C
Pt
0
2
4
6
8
10
Energy / KeV
Figure S1. EDX spectrum of PdPt@PtPd CSNDs.
Pd
Pt
1000
800
600
400
200
0
Binding Energy / eV
Figure S2. XPS survey scan spectrum of PdPt@PtPd CSNDs.
2
Figure S3. Photograph of PAH/K2PtCl4 mixture solution after heating 10 h at 140 oC.
200 nm
Figure S4. TEM image of Pt-Pd nanoparticles synthesized at 220 oC.
A
B
50 nm
50 nm
Figure S5. TEM images of (A) Pd nanodendrites and (B) Pt nanodendrites prepared
by same thermal decomposition method.
3
100
Weight / %
II
90
b
80
a
PAH-Pt
II
PAH-Pd
70
100
200
300
400
500
o
Temperature / C
Figure S6. TGA curves of (a) PAH-PdII complex and (b) PAH-PtII complex. After
adding ethanol into the mixture of K2PdCl4 and PAH, PAH-PdII complex precipitation
was achieved. After adding ethanol into the mixture of K2PtCl4 and PAH, PAH-PtII
Current / mA
complex precipitation was achieved.
0.00
-0.03
-0.06
a
b
-0.09
-0.4
-0.2
0.0
0.2
0.4
Potential / V (vs. RHE)
Figure S7. Linear sweeping voltammograms of (a) the mixture solution of 0.01 M
K2PdCl4 + 0.01 M PAH and (b) the mixture solution of 0.01 M K2PtCl4 + 0.01 M
PAH in N2-saturated 0.1 M KCl electrolyte (pH 3.0) at the glassy carbon electrode at
50 mV s–1.
4
A0h
B
0.5 h 1 h
0h 1h 2h
Figure S8. Representative photographs of (A) PAH/K2PdCl4 mixture solution and (B)
PAH/K2PtCl4 at the different heat times.
Intensity / a.u.
N 1s
405
400
395
390
Binding Energy /eV
Figure S9. N 1s XPS spectrum of PdPt@PtPd CSNDs after CV experiment.
5
0
i / mA cm
-2
a b c
-2
-4
-6
0.2
0.4
0.6
0.8
1.0
Potential / V (vs. RHE)
Figure S10. ORR polarization curves of (a) single-component Pd nanodendrites, (b)
single-component Pt nanodendrites, and (c) PdPt@PtPd CSNDs in O2-saturated 0.5 M
H2SO4 electrolyte at 5 mV s–1 and rotation rate of 1600 rpm.
As observed, PdPt@PtPd CSNDs show the higher ORR half-wave potential
compared to single-component Pd and Pt nanodendrites, indicating the synergistic
0.5
Pt
PdPt@PtPd CSNDs
Pt black
0.4
0.3
0.9 V (vs. RHE)
30
B
-1
A
Pt mass activity / A g
Specific activity / A m
-2
effect between Pt and Pd elements improves the ORR kinetics of PdPt@PtPd CSNDs.
PdPt@PtPd CSNDs
Pt black
20
10
0
0.9 V (vs. RHE)
Figure S11. (A) ECSA-specific activity and (B) Pt mass activity of PdPt@PtPd
CSNDs and commercial Pt black at a fixed potential of 0.9 V for the ORR.
6
-2
PdPt@PtPd CSNDs
PtPd alloys
18
-2
A
i / mA cm
Specific activity / A m
2
1
0
B
12
PdPt@PtPd CSNDs
PtPd alloys
6
0
-6
-1
0.0
0.3
0.6
0.9
0.2
1.2
Potential / V (vs. RHE)
0.4
0.6
0.8
1.0
Potential / V (vs. RHE)
Figure S12. (A) ECSA-normalized cyclic voltammograms of PdPt@PtPd CSNDs and
un-functionalized Pt1Pd1 alloy nanoparticles in N2-saturated 0.5 M H2SO4 + 0.1 M
CH3CH2OH electrolyte at 50 mV s–1. (B) ORR polarization curves of PdPt@PtPd
CSNDs and un-functionalized Pt1Pd1 alloy nanoparticles in O2-saturated 0.5 M H2SO4
electrolyte in the presence of 0.1 M CH3CH2OH at 5 mV s–1 and rotation rate of 1600
rpm. In order to further confirm that high ORR selectivity of PdPt@PtPd CSNDs
originates from the PAH functionalization, we synthesized un-functionalized Pt1Pd1
alloy nanoparticles in absence of PAH by NaBH4 reduction, and investigate their
alcohol tolerance for the ORR. ECSA-normalized CV shows the specific peak current
density of ethanol oxidation on un-functionalized Pt1Pd1 alloy nanoparticles is much
bigger than that on PdPt@PtPd CSNDs (Figure S11A). Meanwhile, ORR polarization
curves show un-functionalized Pt1Pd1 alloy nanoparticles have not obvious alcohol
tolerance for the ORR compared to PdPt@PtPd CSNDs (Figure S11B). Thus, the
influence of alloying effect on alcohol tolerance is ruled out.
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PdPt@PtPd CSNDs
Pt black
Current / mA
0.9
0.6
0.3
0.0
-0.3
0.0
0.2
0.4
0.6
0.8
1.0
1.2
Potential / V (vs. RHE)
Figure S13. Cyclic voltammograms of pre-adsorbed CO at PdPt@PtPd CSNDs and
commercial Pt black in N2-saturated 0.5 M H2SO4 electrolyte at 50 mV s–1.
ipdpt@ptpd/iPt=0.12
7.0 Å
ipdpt@ptpd/iPt=0.08
5.1 Å
ipdpt@ptpd/iPt=0.16
4.3 Å
Methanol Ethanol Isopropanol
oxidation oxidation oxidation
Pt black
PdPt@PtPd CSNDs
Figure S14. The ratios of specific peak current densities of methanol, ethanol, and
1-propanol at PdPt@PtPd CSNDs (ipdpt@ptpd) to these at commercial Pt black (iPt). For
convenience, the specific peak current densities of methanol, ethanol, and 1-propanol
at commercial Pt black were normalized to 1. As observed, the value of the
ipdpt@ptpd/iPt decreases with increasing molecule size of alcohol. A smaller value of the
ipdpt@ptpd/iPt implies better alcohol tolerant ability, which further confirms
molecular-size dependent selectivity.
8
Initial
10000 cycle
i / mA cm
-2
0
-2
-4
-6
0.2
0.4
0.6
0.8
1.0
Potential / V (vs. RHE)
Figure S15. ORR polarization curves of commercial Pt black before and after 10000
potential sweeps in O2-saturated 0.5 M H2SO4 electrolyte at 5 mV s–1 and rotation rate
of 1600 rpm.
Figure S16. TEM image of PdPt@PtPd CSNDs after ADT.
9
E1/2=48 mV
-6
0
-2
E1/2=15 mV
-4
0.4
0.6
0.8
1.0
0.2
Potential / V (vs. RHE)
Initial
10000 cycles
-2
E1/2=22 mV
-4
-6
-6
0.2
c
-2
Initial
10000 cycles
i / mA cm
-2
-4
b
-2
i / mA cm
0
Initial
500 cycles
i / mA cm
a
-2
0
0.4
0.6
0.8
0.2
1.0
Potential / V (vs. RHE)
0.4
0.6
0.8
1.0
Potential / V (vs. RHE)
Figure S17. ORR polarization curves of (a) single-component Pd nanodendrites, (b)
single-component Pt nanodendrites, and (c) PdPt@PtPd CSNDs before and after
10000 potential sweeps in O2-saturated 0.5 M H2SO4 electrolyte at 5 mV s–1 and
rotation rate of 1600 rpm.
Intensity / a.u.
N 1s
405
400
395
Binding Energy /eV
390
Figure S18. N 1s XPS spectrum of PdPt@PtPd CSNDs after ADT experiment.
10