Supporting Information for

Transcription

1 Supporting Information for Iridium-tungsten Alloy Nanodendrites as ph-universal Water Splitting Electrocatalysts Fan Lv, Jianrui Feng, Kai Wang, Zhipeng Dou, Weiyu Zhang, Jinhui Zhou, Chao Yang, Mingchuan Luo, Yong Yang, Yingjie Li, Peng Gao, and Shaojun Guo* & ѳ Department of Material Science and Engineering, College of Engineering, Peking University, Beijing , China. & BIC-ESAT, College of Engineering, Peking University, Beijing , China. Electron Microscopy Laboratory, and International Center for Quantum Materials, School of Physics, Peking University, Beijing , China Department of Energy and Resources Engineering, College of Engineering, Peking University, Beijing , P. R. China. ѳ Beijing Key Laboratory for Magnetoeletric Materials and Devices (BKL-MEMD), Peking University, Beijing , China. 1 / 30

2 Figures Figure S1. (a, b) Low-magnification TEM image and size distribution of IrW NDs. 2 / 30

3 Figure S2. HRTEM image and corresponding FFT patterns of the IrW NDs. 3 / 30

4 Figure S3. HAADF-STEM image of IrW NDs. 4 / 30

5 Figure S4. TEM images of IrW NDs with different diameters by changing the amount of glucose and keep other parameters consistent. (a) 10 mg glucose, (b) 80 mg glucose. 5 / 30

6 Figure S5. (a, b) TEM images of Ir nanoflowers synthesized without adding W(CO) 6. 6 / 30

7 a 0.1 b 0.1 c ECSA = 78.2 m 2 g -1 Pt ECSA = 58.2 m 2 g -1 Ir 0.1 ECSA = 38.7 m 2 g -1 Ir j(ma ) j(ma ) j(ma ) Pt/C IrW/C Ir/C E(V) vsrhe E(V) vsrhe E(V) vsrhe Figure S6. CVs of the (a) Pt/C, (b) IrW/C and (c) Ir/C in 0.1M HClO 4. The potential ranges are 0.05 V-1.05 V vs RHE for Pt/C, and 0.05 V-0.55V vs RHE for IrW/C and Ir/C. 7 / 30

8 Figure S7. The relationship between TOF and the measured potentials for Ir/C, Pt/C and IrW/C catalysts in 0.1 M HClO 4 (a) and 0.1 M KOH (b). 8 / 30

9 a j(ma cm -2 geo) IrW/C Intial IrW/C after 1000 cycles 0.1 M HClO 4 b j(ma cm -2 geo) IrW Intial IrW after 1000 cycles 0.1 M KOH E(V) vsrhe E(V) vsrhe Figure S8. HER polarization curves of IrW/C before and after durability test of 1000 cycles at the scan rate of 20 mv s -1 in 0.1 M HClO 4 (a) and 0.1 M KOH (b). 9 / 30

10 Figure S9. TEM images of IrW/C after HER durability test in 0.1 M HClO 4 (a, b) and 0.1 M KOH (c, d). 10 / 30

11 Figure S10. The Tafel slopes of Ir/C, Pt/C and IrW/C corresponds to the HER process in 0.1 M HClO 4 (a) and 0.1 M KOH (b). 11 / 30

12 Figure S11. Three different adsorption sites of H over IrW including top site of Ir, top site of W and the hollow site surrounded by two Ir atoms and one W atom. 12 / 30

13 Figure S12. The optimized adsorption structure of H atom over Pt and Ir for calculating free energy diagram in acid media. 13 / 30

14 Figure S13. The initial state, transition state and final state of the most advantageous path of water dissociation over Pt, Ir and IrW. 14 / 30

15 Figure S14. The initial state, transition state and final state of the disadvantageous path of water dissociation over IrW. 15 / 30

16 Figure S15. The initial state, transition state and final state of the Heyrovsky step over Pt, Ir and IrW. 16 / 30

17 0.2 IrW/C oxidation 0.2 Ir/C oxidation 0.1 H upd Oxidation 0.1 H upd Oxidation j(ma ) 0.0 j(ma ) Ir(III)/Ir(IV) -0.1 Ir(III)/Ir(IV) \ E(V) vsrhe E(V) vsrhe Figure S16. The oxidation process of IrW/C and Ir/C through potential cycles between 0.05 V and 1.5 V vs RHE before electrochemical activity test. 17 / 30

18 a 10 IrW/C Ir/C Pt/C 0.1 M HClO 4 b IrW/C Ir/C Pt/C 0.1 M KOH TOF (s -1 ) 1 TOF (s -1 ) E(V) vsrhe E(V) vsrhe Figure S17. The relationship between the TOF and the measured potentials for Ir/C, Pt/C and IrW/C catalysts in 0.1 M HClO 4 (a) and 0.1 M KOH (b). 18 / 30

19 a j(ma cm -2 geo) cj(ma cm-2 geo) IrW/C Ir/C Pt/C 0.1M KOH Overpotenial (mv) b mv dec mv dec mv dec E(V) vsrhe LogCurrent (ma cm -2 ) vs RHE 0.1 M KOH TOF (s -1 ) d j(ma cm -2 geo) IrW/C Initial IrW/C after 1000 cycles Ir/C Initial Ir/C after 1000 cycles 0.1 M KOH E(V) vsrhe Figure S18. OER activity and durability of IrW NDs in KOH. (a) OER polarization curves of IrW/C, Ir/C and Pt/C with 95% ir-compensation in 0.1 M KOH at the scan rate of 5 mv s -1 and (b) the corresponding Tafel slopes, (c) Current density (left) and TOFs normalized by the ECSA (right) at 1.53 V vs RHE of IrW/C, Ir/C and Pt/C in 0.1 M KOH, (d) OER polarization curves of IrW/C, and Ir/C before and after durability test of 1,000 cycles between 1.25 V and 1.7 V. 19 / 30

20 Figure S19. TEM images of Ir/C before (a) and after (b) OER durability test. 20 / 30

21 Figure S20. EDS mapping images of IrW/C after OER durability test. 21 / 30

22 Figure S21. XPS spectra of and IrW/C (a) and Ir/C (b) before and after OER durability test in HClO / 30

23 Figure S22. Optimized clean surface of the model of IrO 2 (110) and W-IrO 2 (110). 23 / 30

24 Figure S23. Optimized adsorption structure of OH, O and OOH on IrO 2 and W-IrO / 30

25 Tables Table S1. Summary and comparisons of some recently reported representative HER electrocatalysts in acidic electrolytes Sample IrW/C Mass Loading electrolyte Current Density/mA cm -2 Overpotential (mv) 10.2 µg Ir /cm M HClO TOF 3.35 s 10 mv References This work Ru@C 2 N mg cm M H 2 SO s 25 mv Nature Nano. 12, (2017) SV-MoS M H 2 SO s 0 mv Nature Mater. 15, (2016) CoPS nanoplates M H 2 SO Nature Mater. 14, (2015) CoMoS x 50 µg cm M HClO Nature Mater. 15, (2016) [Mo 3 S 13 ] -2 clusters 0.1 mg cm M H 2 SO Nature Chem. 6, (2014) M-MoS 2 43 µg cm M H 2 SO A-Ni C mg cm M H 2SO Nature Comm. 7, (2016) Nature Comm. 7, (2016) MoS 2 /CoSe mg cm M H 2SO Nature Comm. 6, 5982 (2015) Rh/Si mg cm M H 2 SO Nature Comm. 7, (2016) 25 / 30

26 Table S2. Summary and comparisons of some recently reported representative HER electrocatalysts in alkaline electrolytes. Sample Mass Loading electrolyte Current Density/mA cm-2 Overpotential (mv) TOF Reference IrW/C 10.2 µg /cm M KOH s 10 mv This work Ru@C 2 N mg cm 2 1 M KOH s 25 mv Nat. Nano. 12, (2017) CoMoS x 50 µg cm M KOH Ni(OH) 2 / Pt-islands/ Pt(111) surface Co(OH) 2 /Pt( 111) M KOH 0.1 M KOH 5 ~ ~ ~248 - Nat. Mater. 15, (2016) Science 334, 1256 (2011) Nat. Mater. 11, (2012) MoNi 4 /MoO mg cm -2 1 M KOH mv Nat. Comm. 8, (2017). Pt NWs/SL - Ni(OH) 2 16 µg /cm M KOH Nat. Common. 6, 6430 (2015) np-cuti M KOH Nat. Commun. 6, 6567 (2015) NiO/Ni -CNT 0.28 mg cm -2 1 M KOH Nat. Commun. 5, 4695 (2014) Pt 3 Ni 2 -NWs -S/C 15 µg /cm M KOH Nat Commun. 8, (2017) 26 / 30

27 Table S3. Dissolved amount of Ir from IrW/C and Ir/C catalysts in electrolyte after durability test examined by ICP-AES. Sample Dissolved Ir (µg) Percentage of dissolved Ir from the initial mass IrW/C % Ir/C % 27 / 30

28 Table S4. Adsorption energies of OH, O and OOH on IrO 2 (110) and W-IrO 2 (110) with corresponding d-band centers (Integrated from -5 ev to 0 ev vs. Fermi level). Model d-band center (ev vs. Fermi level) Intermediate Adsorption energy (ev) OH IrO 2 (110) O OOH OH W-IrO 2 (110) O OOH / 30

29 Table S5. Summary and comparison of some recently reported representative overall water-splitting electrocatalysts in acidic or alkaline electrolytes. Sample Mass Loading electrolyte Current density ma cm -2 ) Overpotential (mv) References IrW/C 30 µg cm M H 2 SO This work Ni-Co complexes /1T MoS2 1 mg cm -2 1 M KOH Nat. Commun. 8, (2017) NiFe-MOF M KOH Nat. Commun.8, (2017) IrNi NCs 12.5 µg cm M H 2 SO Adv. Funct. Mater. 27, (2017) Ir/GF 0.82 mg cm M H 2 SO Nano Energy 40, (2017) NiFeOx 0.6 mg cm -2 1 M KOH Nat. Commun. 6, 7261 (2015) Co 0.85 Se/NiFe- LDH 2.7 mg cm -2 1 M KOH Energy Environ. Sci. 9, (2016) NiCoP ~1.6 mg cm M KOH Nano Lett (2016) Hierarchical NiCo 2 O 4 hollow microcuboids 1 mg cm -2 1 M KOH Angew. Chem. Int. Ed. 55, (2016) 29 / 30

30 Table S6. Frequencies of HER and OER intermediates. IS, TS and FS represent for initial state, transition state and final state. Model Intermediate Frequency (cm -1 ) H 2 O (IS) , , , , , 83.49, 51.74, 12.35, 7.13 *H + OH (TS) , , , , , , , 85.29, i IrW (HER) *H + OH (FS) *H + H 2 O (IS) , , , , 97.72, 94.21, 93.46, 13.49, , , , , , , , , , , 47.58, * + H2 + OH (TS) , , , , , , , , 74.33, 17.60, 8.51, i * + H2 + OH (FS) , , , , , 98.27, 56.60, 33.23, 25.76, 11.50, 9.23, 1.47 OH , , , , 88.50, W-IrO 2 (OER) O 87.49, 22.83, OOH , , , , 90.27, 61.25, 38.49, 15.37, / 30