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Electronic Supplementary Information

Stabilization of Pt Nanoparticles at Ta2O5–TaC Binary Junction: An

Effective Strategy to Achieve High Durability for Oxygen Reduction

Wenbin Gao,ab Tongtong Liu,ab Zhengping Zhang,ab Meiling Dou,*ab and Feng Wang*ab

a State Key Laboratory of Chemical Resource Engineering, Beijing Key Laboratory of

Electrochemical Process and Technology for Materials, Beijing University of Chemical

Technology, Beijing 100029, P. R. China

b Beijing Advanced Innovation Center for Soft Matter Science and Engineering, Beijing

University of Chemical Technology, Beijing 100029, P. R. China

* Corresponding author: E–mail: wangf@mail.buct.edu.cn (F. Wang);

douml@mail.buct.edu.cn (M. L. Dou); Tel. / Fax: +86–10–64451996.

Electronic Supplementary Material (ESI) for Journal of Materials Chemistry A.This journal is © The Royal Society of Chemistry 2020

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Electrochemical measurement

Preparation of electrocatalyst slurry: 30 mg mixture of Pt/Ta2O5–TaC/C and Vulcan XC–72

(mass ratio = 2:1) were dispersed in n-hexane (10 mL) solution and stirred at ambient

temperatures for 3 h. After that, the product was dried at 40 °C and re-dispersed in 10 mL of

acetic acid by heating at 70 °C for 6 h to clean its surface. Then, it was filtered and washed

with ethanol. After drying, 3 mg of final product was re-dispersed in the blending (1 mL of

ethanol and 20 μL of 5% Nafion) under ultrasonication for 30 min. A certain volume of catalyst

slurry required was then pipetted onto the polished GCE to act as the working electrode, to

give a Pt loading of 15 μg cm−2. For commercial Pt/C electrode, 2 mg of Pt/C was dispersed in

1 mL of ethanol containing 20 μL of 5% Nafion under ultrasonication for 30 min. A certain

volume of Pt/C slurry was dropped on the GCE and kept the Pt loading of 20 μg cm−2.

The kinetic current density (Jk) was calculated from the ORR polarization curves using

the Koutecky−Levich equation: 1/J = 1/Jk+ 1/Jd (where J is the current density at 0.9 V and Jd

is the diffusion-limiting current density). The electron transfer number (n) and hydrogen

peroxide production yield (H2O2%) were evaluated according to the listed formulas:

(1) 𝑛 =

4𝐼𝑑

𝐼𝑑 + (𝐼𝑟/𝑁)

(2) 𝐻2𝑂2% = 100 ×

4 ‒ 𝑛2

where Id, Ir, and N refer to the disk current, ring current, and current collection efficiency (0.37),

respectively.

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Fig. S1 (a) (b) SEM and (c) TEM images of the products via a solvothermal process using PS

spheres as templates prepared without the addition of crosslinker.

Fig. S2 SEM images of (a) PS−DVB and (b) SPS−DVB spheres. (c) (d) FT−IR spectra of

PS−DVB and SPS−DVB.

SEM images (Fig. S2a and b) show that the PS−DVB spheres before and after sulfonation

are both well-monodispersed and the surface morphology of the spheres changes from smooth

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to rough with the increase of average particle size from 520 to 542 nm. The FT−IR spectra of

PS−DVB and SPS−DVB spheres were shown in Fig. S2c and d. Compared with PS−DVB

spheres, new absorption peaks for SPS−DVB spheres at 1220, 1180, 1125, 1040 and 1010 cm−1

are observed, assigned to the stretching vibration of −SO3− groups.1,2 The increased intensity

of the broad peak at 3435 cm−1 (derived from the O−H stretching vibrations in both residual

water and the −SO3H groups) can also comfirm the presence of −SO3− groups. These results

indicate that the sulfonic acid groups have been introduced onto the PS−DVB surface after the

treatment of concentrated sulfuric acid.

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Fig. S3 (a) TG-DTA and (b) DTG curves of TaOx@SPS−DVB precursor in Ar atmosphere.

Fig. S4 Quantitative phase analysis of Ta2O5–TaC/C (900) and Ta2O5–TaC/C (1000) carried

out by the Rietveld refinement method using MAUD.

Table S1 Quantitative phase analysis of Ta2O5–TaC/C (900) and Ta2O5–TaC/C (1000) samples

carried out by MAUD.

Samples Rwp% Rexp% Ta2O5% TaC%

Ta2O5–TaC/C (900) 4.31 1.40 82.64 17.36

Ta2O5–TaC/C (1000) 6.14 1.56 44.06 55.94

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Fig. S5 (a) Raman spectra and (b) TG-DTA curves in the air atmosphere of TaOx@SPS−DVB

precursor calcinated at different temperatures.

Table S2 Composition analyses for TaOx@SPS−DVB precursor calcinated at different

temperatures according to TG-DTA in air and XRD analysis.

Sample Ta2O5 (wt.%) TaC (wt.%) C (wt.%)

TaOx/C 57.9 — 42.1

Ta2O5/C 56.7 — 43.3

Ta2O5–TaC/C (900) 50.1 0.1 49.8

Ta2O5–TaC/C (1000) 24.9 31.7 43.4

TaC/C — 55.5 44.5

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Fig. S6 SEM images of TaOx@SPS−DVB precursor calcinated at different temperatures of (a)

700, (b) 800, (c) 900, (d) 1000 and (e) 1100 ºC.

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Fig. S7 TEM images of TaOx@SPS−DVB precursor calcinated at different temperatures of (a)

700, (b) 800, (c) 900, (d) 1000 and (e) 1100 ºC.

Table S3 Specific surface area of TaOx@SPS−DVB precursor calcinated at different

temperatures from 700 to 1100 ºC.

Sample Surface area (m2 g−1)

TaOx/C 206.6

Ta2O5/C 249.1

Ta2O5–TaC/C (900) 387.6

Ta2O5–TaC/C (1000) 470.9

TaC/C 442.5

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Fig. S8 XPS survey spectra for TaOx@SPS−DVB precursor calcinated at different

temperatures.

Fig. S9 High-resolution XPS spectra of C 1s and O 1s for TaOx@SPS−DVB precursor

calcinated at different temperatures.

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Table S4 Elemental content of Ta analyzed by XPS.

% of total Ta 4fSample

Ta5+ Ta4+ Ta2+

TaOx/C 100 —— ——

Ta2O5/C 90.8 4.1 5.1

Ta2O5–TaC/C (900) 50.7 9.0 40.4

Ta2O5–TaC/C (1000) 35.4 19.0 45.6

TaC/C 24.8 17.6 57.6

Table S5 Elemental content of Ta analyzed by XPS.

Table S6 Elemental content of O analyzed by XPS.

% of total O 1s

Sample Ta−O/Pt−O Ta−OH −OH H2O

Lattice O

Ta2O5−TaC/C 26.9 27.8 27.4 17.9 54.7

Pt/Ta2O5−TaC/C 44.7 22.1 19.4 13.8 66.8

% of total Ta 4fSample

Ta5+ Ta4+ Ta2+

Ta2O5−TaC/C 35.4 19.0 45.6

Pt/Ta2O5−TaC/C 78.4 9.0 12.7

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Fig. S10 (a) CV curves of the Pt-based electrocatalysts and (b) the corresponding ECSA values

in N2-saturated 0.1 M HClO4.

Fig. S11 The calculated peroxide yield (H2O2%) and n number using the rotating ring disk

electrode technique.

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Table S7 Comparison of ORR performance in 0.1 M HClO4 solution.

Catalyst

Cycling

test

(cycles)

Potential

range

(V)

E1/2

(V vs

RHE)

E1/2

Loss

(mV)

ECSA

(m2 g–

1Pt)

ECSA

loss

MA

(A mg−1Pt)

(At 0.9 V vs.

RHE)

MA

loss Ref.

Pt/Nb–TiO2 nanofiber 6000 (O2) 0.6–1.1 0.896 17 – 32% 0.081 35.8% 3

Pt–WN/CNTs–M 4000 (N2) 0–1.1 – – – 23.7% 0.045 5.0% 4

Pt/V–TiO2 4000 (N2) 0.6–1.1 0.873 – 13 23% 0.074 34.3% 5

Pt/TiN NTs 10000 (N2) 0.6–1.2 – – 61.3 3% 0.207 16.1% 6

35ALD–TaOx–Pt/C 10000 (N2) 0.6–1.0 0.92 2 60.6 – 0.246 7.5% 7

Pt/N–ALDTa2O5/C 10000 (N2) 0.6–1.0 0.908 4 70.3 14.9% 0.280 10.0% 8

Pt−Ta2O5/CNT 10000 (N2) 0.6–1.0 0.892 16 78.4 3.4% 0.23 – 9

Pt/C–TiO2 10000 (N2) 0.6–1.0 0.876 1 81.67 0.8% 0.205 0.9% 10

Pt/Ta2O5–TaC/C 10000 (N2) 0.6–1.1 0.893 3 70 5.7% 0.297 7.4% This work

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Table S8 The changes of ECSAs, E1/2 values, mass and specific activities at 0.9 V of Pt/C and

Pt/Ta2O5−TaC/C before and after ADTs in 0.1 M HClO4.

Fig. S12 TEM images before and after ADTs for (a) Pt/C and (b) Pt/Ta2O5−TaC/C.

Pt/C Pt/Ta2O5−TaC/C

SampleInitial

After 5000

cycles

After 10000

cyclesInitial

After 5000

cycles

After 10000

cycles

ECSAs (m2 g−1Pt) 62 44 34 70 68 66

E1/2 (V) 0.861 0.791 0.754 0.893 0.892 0.890

Jk (mA cm−2) 1.63 0.58 0.15 4.45 4.35 4.13

MA (A mg−1Pt) 0.081 0.029 0.008 0.297 0.290 0.275

SA (mA cm−2) 0.131 0.066 0.024 0.424 0.426 0.417

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Fig. S13 The high-resolution XPS Pt 4f spectra for Pt/Ta2O5–TaC/C before and after ADTs.

Fig. S14 CVs of Vulcan XC−72 and Ta2O5−TaC/C before (a) and after (b) potential step

corrosion test in N2-saturated 0.1 M HClO4. The shaded areas in CVs show the pseudo-

capacitive gravimetric charge.

Table S9 Pseudo-capacitive gravimetric charge (between 0.4-0.9 V) for Vulcan XC−72 and

Ta2O5−TaC/C.

Sample Before corrosion

Qi (C g-1)

After corrosion

Qf (C g-1)

Increase

ΔQf-i (C m-2)

Vulcan XC−72 15 17.8 0.014

Ta2O5−TaC/C 0.4 1.6 0.003

Note: Qi and Qf is the pseudo-capacitive gravimetric charge before and after the test,

respectively; ΔQf-i is the change of pseudo-capacitive gravimetric charge normalized by BET

specific surface areas after the test.

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Reference

1 S. B., Brijmohan, S. Swier, R. A. Weiss and M. T. Shaw, Ind. Eng. Chem. Res., 2005, 44,

8039-8045.

2 G. Fan, C. Liao, T. Fang, M. Wang and G. Song, Fuel Process. Technol., 2013, 116, 142-

148.

3 M. Kim, C. Kwon, K. Eom, J. Kim and E. Cho, Scientific reports, 2017, 7, 44411.

4 S. Jing, L. Luo, S. Yin, F. Huang, Y. Jia, Y. Wei, Z. Sun and Y. Zhao, Appl. Catal. B:

Environ., 2014, 147, 897-903.

5 J. Kim, G. Kwon, H. Lim, C. Zhu, H. You and Y.-T. Kim, J. Power Sources, 2016, 320,

188-195.

6 H. Shin, H. Kim, D. Chung, J. Yoo, S. Weon, W. Choi and Y. Sung, ACS Catal., 2016, 6,

3914-3920.

7 Z. Song, B. Wang, N. Cheng, L. Yang, D. Banham, R. Li, S. Ye and X. Sun, J. Mater.

Chem. A, 2017, 5, 9760-9767.

8 Z. Song, M. N. Banis, L. Zhang, B. Wang, L. Yang, D. Banham, Y. Zhao, J. Liang, M.

Zheng, R. Li, S. Ye and X. Sun, Nano Energy, 2018, 53, 716-725.

9 W. Gao, Z. Zhang, M. Dou and F. Wang, ACS Catal., 2019, 9, 3278-3288.

10 J. Wang, M. Xu, J. Zhao, H. Fang, Q. Huang, W. Xiao, T. Li and D. Wang, Appl. Catal.

B: Environ., 2018, 237, 228-236.