ARTICLE NUMBER: 17045 | DOI: 10.1038/NENERGY.2017 · PDF fileYanhao Yu, 1, † Zheng...
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In the format provided by the authors and unedited. © 2017 Macmillan Publishers Limited, part of Springer Nature. All rights reserved. Enhanced Photoelectrochemical Efficiency and Stability Using A Conformal TiO2 Film on A Black Silicon Photoanode Yanhao Yu, 1,† Zheng Zhang, 2, † Xin Yin, 1 Alexander Kvit, 4 Qingliang Liao, 2 Zhuo Kang, 2 Xiaoqin Yan, 2 Yue Zhang, 2,3,* Xudong Wang 1,* 1. Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI 53706, USA, 2. Department of Materials Physics, School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China, 3. Beijing Municipal Key Laboratory of Advanced Energy Materials and Technologies, University of Science and Technology Beijing, Beijing 100083, China 4. Materials Science Center, University of Wisconsin-Madison, Madison, WI 53706, USA † These authors contribute equally to this work * Email: XW: [email protected]; YZ: [email protected] SUPPLEMENTARY INFORMATION ARTICLE NUMBER: 17045 | DOI: 10.1038/NENERGY.2017.45 NATURE ENERGY | www.nature.com/natureenergy 1
Transcript of ARTICLE NUMBER: 17045 | DOI: 10.1038/NENERGY.2017 · PDF fileYanhao Yu, 1, † Zheng...
In the format provided by the authors and unedited.
© 2017 Macmillan Publishers Limited, part of Springer Nature. All rights reserved.
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Supplementary Information
Enhanced Photoelectrochemical Efficiency and Stability Using A Conformal TiO2
Film on A Black Silicon Photoanode
Yanhao Yu,1,† Zheng Zhang,2, † Xin Yin,1 Alexander Kvit,4 Qingliang Liao,2 Zhuo Kang,2 Xiaoqin Yan,2
Yue Zhang,2,3,* Xudong Wang1,*
1. Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI
53706, USA,
2. Department of Materials Physics, School of Materials Science and Engineering, University of Science
and Technology Beijing, Beijing 100083, China,
3. Beijing Municipal Key Laboratory of Advanced Energy Materials and Technologies, University of
Science and Technology Beijing, Beijing 100083, China
4. Materials Science Center, University of Wisconsin-Madison, Madison, WI 53706, USA
† These authors contribute equally to this work
* Email: XW: [email protected]; YZ: [email protected]
SUPPLEMENTARY INFORMATIONARTICLE NUMBER: 17045 | DOI: 10.1038/NENERGY.2017.45
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Supplementary Figures
Supplementary Figure 1. (a) Top view SEM image of b-Si/TiO2/Co(OH)2. (b-d) EDS characterizations of highlight regions in white dashed boxes of (b) Figure S1a, (c) Figure 1f at position 1 and (d) Figure 1f at position 2.
Supplementary Figure 2. Cross-sectional STEM image of b-Si/Co(OH)2. Inset is the EELS spectrum showing the presence of Co inside the channel.
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Supplementary Figure 3. Representative TEM image of the electrodeposited Co(OH)2 thin film.
Supplementary Figure 4. XPS full survey scan of b-Si, b-Si/TiO2 and b-Si/TiO2/Co(OH)2.
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Supplementary Figure 5. Optimization of CoCl2 concentration for Co(OH)2 electrodeposition. (a-c) Top view SEM images of Co(OH)2 and Co metal particles on b-Si/TiO2 surface obtained in (a) 1 mM, (b) 10 mM and (c) 50 mM CoCl2 electrolytes. (d) XPS Co 2p spectra of samples corresponding to Figure S3a-c. (e) Jph-V curves of PEC water oxidation for b-Si/TiO2/Co(OH)2 electrodes deposited in CoCl2 electrolytes with various concentrations.
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Supplementary Figure 6. Optimization of Co(OH)2 electrodeposition. (a) Cyclic voltammetry of b-Si with a high cathodic bias (up to -3 V vs. SCE) in 10 mM CoCl2 solution. Two main chemical reactions were identified at bias regions of -1.0 to -1.6 V and -2.0 to 3.0 V, corresponding to the Co2+ and H+ reductions, respectively. (b) J-t curve during Co(OH)2 deposition. Three deposition times (2 s, 8 s and 20 s) were selected and indicated by crosses. (c) Jph-V curves of PEC water oxidation for b-Si/TiO2/Co(OH)2 electrodes deposited under various deposition times.
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Supplementary Figure 7. (a) XPS Co 2p spectrum and (b) top view SEM image of Co(OH)2 on planar Si substrate under optimized electrodeposition condition (8 s and 10 mM CoCl2).
Supplementary Figure 8. (a) XPS Co 2p spectrum and (b) top view SEM image of Co(OH)2 on b-Si substrate under optimized electrodeposition condition (8 s and 10 mM CoCl2).
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Supplementary Figure 9. Mott-Schottky plots of b-Si/TiO2/Co(OH)2 and b-Si/Co(OH)2, showing almost identical EFB at ~0.49 V vs. RHE.
The dopant concentration can be calculated using the equation:
1
2
0
1( )2d
d CNe dV
where Nd is the dopant concentration, C is the capacitance between the sample and electrolyte,
21( )d CdV
is the slope of the sharp increase from 0.5-0.6 V region in Figure S9, ε is the dielectric
constant of silicon, ε0 is the permittivity of vacuum, e is the single electron charge. According to the
measured Mott-Schottky data, 2
1( )d CdV
was calculated to be 2.01016 and 1.91016 cm4F-2V-1 for
b-Si/Co(OH)2 and b-Si/TiO2/Co(OH)2, respectively. With ε=11.68, ε0=8.8510-14 Fcm-1 and e=1.610-19 C, Nd of b-Si/Co(OH)2 and b-Si/TiO2/Co(OH)2 were calculated to be 6.051014 and 6.361014 cm-3. These values were consistent with the resistance of the silicon wafer 1-10 cm, corresponding to the Nd of 51015-51014 cm-3.
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Supplementary Figure 10. Top view SEM images of (a) b-Si/Co(OH)2 and (b) Si/TiO2/Co(OH)2.
Supplementary Figure 11. Light reflectance + scattering of b-Si/TiO2/Co(OH)2 sample.
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Supplementary Figure 12. (a) UV-visible absorption spectra of planar Si, b-Si and b-Si/TiO2 derived from reflectance spectra in Figure 2d through the relation absorption = 100 – transmittance – reflectance, assuming zero transmittance. (b) The light harvesting efficiencies (ηLHE) of planar Si, b-Si and b-Si/TiO2. ηLHE was calculated from the absorbance data (ηABS) shown in Figure S7a via the equation ηLHE = (1-10-ηABS) × 100%. (c) Electron flux of AM 1.5G solar spectrum. (d) Electron flux of planar Si, b-Si and b-Si/TiO2. The electron flux of the photoanode was the product of the AM 1.5G electron flux and ηLHE. Photocurrent density (Jabs) under 100% absorbed photon conversion efficiency can be estimated by integrating the electron flux at the photoanodes across 300-1200 nm wavelength range.
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Supplementary Figure 13. Electrochemical impedance spectroscopy (EIS) plots of b-Si/Co(OH)2 and b-Si/TiO2/Co(OH)2.
Supplementary Figure 14. Top view SEM images of (a) b-Si/Co(OH)2 after 3 hours PEC water oxidation and (b) b-Si/TiO2/Co(OH)2 after 4 hours PEC water oxidation.
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Supplementary Figure 15. XPS Co 2p spectra of b-Si/Co(OH)2 after 0.5 hour water oxidation.
Supplementary Figure 16. XPS Co 2p spectra of freshly built b-Si/TiO2/Co(OH)2 and the same device after 4 hours PEC water oxidation.
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