Improved Interfacial Charge Transfer Dynamics and Onset Shift in Nanostructured Hematite Photoanodes via Efficient Ti                         4+                         /Sn                         4+                          Heterogeneous Self-Doping Through Controlled TiO                         2                          Underlayers

Jin Woo Park; Mahadeo A. Mahadik; Haiqing Ma; Gil Woo An; Hyun Hwi Lee; Sun Hee Choi; Weon Sik Chae; Hee Suk Chung; Jum Suk Jang

doi:10.1021/acssuschemeng.8b06544

Improved Interfacial Charge Transfer Dynamics and Onset Shift in Nanostructured Hematite Photoanodes via Efficient Ti ⁴⁺ /Sn ⁴⁺ Heterogeneous Self-Doping Through Controlled TiO ₂ Underlayers

Jin Woo Park
, Mahadeo A. Mahadik^*
, Haiqing Ma
, Gil Woo An
, Hyun Hwi Lee
, Sun Hee Choi
, Weon Sik Chae
, Hee Suk Chung
, Jum Suk Jang

^*Corresponding author for this work

Environmental Biotechnology

Jeonbuk National University
Pohang University of Science and Technology
Korea Basic Science Institute

Research output: Contribution to journal › Journal article › peer-review

34 Scopus citations

Abstract

We introduce a simple strategy to unintentional heterogeneous Ti ⁴⁺ /Sn ⁴⁺ doping and surface passivation of hematite via TiO ₂ underlayers at high temperature quenching. The effects of the controlled TiO ₂ underlayer thickness and high temperature quenching process on the interfacial diffusion of Ti ⁴⁺ /Sn ⁴⁺ and TiO ₂ passivation of hematite nanorod arrays have been carefully studied. The improved photoelectrochemical water oxidation performance of the TiO ₂ underlayered hematite nanorod photoanodes after high-temperature quenching (800 °C for 10 min) suggests enhanced interfacial Ti ⁴⁺ diffusion, blocking of electron back transfer, and reduced interfacial charge recombination. The TiO ₂ underlayers led to more inclined growth of hematite (α-Fe ₂ O ₃ ) nanorods on the fluorine-doped tin oxide (FTO) substrates. Ti ⁴⁺ and Sn ⁴⁺ diffusion and formation of the TiO ₂ passivation layer on the α-Fe ₂ O ₃ surface are confirmed by HRTEM and X-ray photoelectron spectroscopy (XPS) analyses. As a result, the TU2 photoanode displayed higher donor density and enhanced photocurrent density of (1.45 mA·cm ^-2 ) than the pristine hematite photoelectrode (1.0 mA·cm ^-2 ). The improved photoelectrochemical performance of TU2 is attributed to the high separation efficiency of photoinduced carriers via TiO ₂ underlayer, the Ti ⁴⁺ /Sn ⁴⁺ diffusion, and surface passivation of hematite at high-temperature annealing. The thickness of the TiO ₂ underlayer has great influence on the surface passivation as well as resistance on FTO/hematite interfaces than the diffused Sn.

Original language	English
Pages (from-to)	6947-6958
Number of pages	12
Journal	ACS Sustainable Chemistry and Engineering
Volume	7
Issue number	7
DOIs	https://doi.org/10.1021/acssuschemeng.8b06544
State	Published - 2019.04.1

Keywords

FTO deformation
Hematite; Ti /Sn diffusion
Onset potential
Surface passivation
TiO underlayer

Quacquarelli Symonds(QS) Subject Topics

Environmental Sciences
Engineering - Electrical & Electronic
Engineering - Petroleum
Engineering - Chemical
Chemistry

Access to Document

10.1021/acssuschemeng.8b06544

Cite this

Park, J. W., Mahadik, M. A., Ma, H., An, G. W., Lee, H. H., Choi, S. H., Chae, W. S., Chung, H. S., & Jang, J. S. (2019). Improved Interfacial Charge Transfer Dynamics and Onset Shift in Nanostructured Hematite Photoanodes via Efficient Ti ⁴⁺ /Sn ⁴⁺ Heterogeneous Self-Doping Through Controlled TiO ₂ Underlayers ACS Sustainable Chemistry and Engineering, 7(7), 6947-6958. https://doi.org/10.1021/acssuschemeng.8b06544

Park, Jin Woo ; Mahadik, Mahadeo A. ; Ma, Haiqing et al. / Improved Interfacial Charge Transfer Dynamics and Onset Shift in Nanostructured Hematite Photoanodes via Efficient Ti ⁴⁺ /Sn ⁴⁺ Heterogeneous Self-Doping Through Controlled TiO ₂ Underlayers In: ACS Sustainable Chemistry and Engineering. 2019 ; Vol. 7, No. 7. pp. 6947-6958.

@article{5280b4f3412e4749b1d7b3404100100b,

title = " Improved Interfacial Charge Transfer Dynamics and Onset Shift in Nanostructured Hematite Photoanodes via Efficient Ti 4+ /Sn 4+ Heterogeneous Self-Doping Through Controlled TiO 2 Underlayers ",

abstract = " We introduce a simple strategy to unintentional heterogeneous Ti 4+ /Sn 4+ doping and surface passivation of hematite via TiO 2 underlayers at high temperature quenching. The effects of the controlled TiO 2 underlayer thickness and high temperature quenching process on the interfacial diffusion of Ti 4+ /Sn 4+ and TiO 2 passivation of hematite nanorod arrays have been carefully studied. The improved photoelectrochemical water oxidation performance of the TiO 2 underlayered hematite nanorod photoanodes after high-temperature quenching (800 °C for 10 min) suggests enhanced interfacial Ti 4+ diffusion, blocking of electron back transfer, and reduced interfacial charge recombination. The TiO 2 underlayers led to more inclined growth of hematite (α-Fe 2 O 3 ) nanorods on the fluorine-doped tin oxide (FTO) substrates. Ti 4+ and Sn 4+ diffusion and formation of the TiO 2 passivation layer on the α-Fe 2 O 3 surface are confirmed by HRTEM and X-ray photoelectron spectroscopy (XPS) analyses. As a result, the TU2 photoanode displayed higher donor density and enhanced photocurrent density of (1.45 mA·cm -2 ) than the pristine hematite photoelectrode (1.0 mA·cm -2 ). The improved photoelectrochemical performance of TU2 is attributed to the high separation efficiency of photoinduced carriers via TiO 2 underlayer, the Ti 4+ /Sn 4+ diffusion, and surface passivation of hematite at high-temperature annealing. The thickness of the TiO 2 underlayer has great influence on the surface passivation as well as resistance on FTO/hematite interfaces than the diffused Sn.",

keywords = "FTO deformation, Hematite; Ti /Sn diffusion, Onset potential, Surface passivation, TiO underlayer",

author = "Park, \{Jin Woo\} and Mahadik, \{Mahadeo A.\} and Haiqing Ma and An, \{Gil Woo\} and Lee, \{Hyun Hwi\} and Choi, \{Sun Hee\} and Chae, \{Weon Sik\} and Chung, \{Hee Suk\} and Jang, \{Jum Suk\}",

note = "Publisher Copyright: {\textcopyright} 2019 American Chemical Society.",

year = "2019",

month = apr,

day = "1",

doi = "10.1021/acssuschemeng.8b06544",

language = "English",

volume = "7",

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Park, JW, Mahadik, MA, Ma, H, An, GW, Lee, HH, Choi, SH, Chae, WS, Chung, HS & Jang, JS 2019, ' Improved Interfacial Charge Transfer Dynamics and Onset Shift in Nanostructured Hematite Photoanodes via Efficient Ti ⁴⁺ /Sn ⁴⁺ Heterogeneous Self-Doping Through Controlled TiO ₂ Underlayers ', ACS Sustainable Chemistry and Engineering, vol. 7, no. 7, pp. 6947-6958. https://doi.org/10.1021/acssuschemeng.8b06544

Improved Interfacial Charge Transfer Dynamics and Onset Shift in Nanostructured Hematite Photoanodes via Efficient Ti ⁴⁺ /Sn ⁴⁺ Heterogeneous Self-Doping Through Controlled TiO ₂ Underlayers . / Park, Jin Woo; Mahadik, Mahadeo A.; Ma, Haiqing et al.
In: ACS Sustainable Chemistry and Engineering, Vol. 7, No. 7, 01.04.2019, p. 6947-6958.

Research output: Contribution to journal › Journal article › peer-review

TY - JOUR

T1 - Improved Interfacial Charge Transfer Dynamics and Onset Shift in Nanostructured Hematite Photoanodes via Efficient Ti 4+ /Sn 4+ Heterogeneous Self-Doping Through Controlled TiO 2 Underlayers

AU - Park, Jin Woo

AU - Mahadik, Mahadeo A.

AU - Ma, Haiqing

AU - An, Gil Woo

AU - Lee, Hyun Hwi

AU - Choi, Sun Hee

AU - Chae, Weon Sik

AU - Chung, Hee Suk

AU - Jang, Jum Suk

PY - 2019/4/1

Y1 - 2019/4/1

N2 - We introduce a simple strategy to unintentional heterogeneous Ti 4+ /Sn 4+ doping and surface passivation of hematite via TiO 2 underlayers at high temperature quenching. The effects of the controlled TiO 2 underlayer thickness and high temperature quenching process on the interfacial diffusion of Ti 4+ /Sn 4+ and TiO 2 passivation of hematite nanorod arrays have been carefully studied. The improved photoelectrochemical water oxidation performance of the TiO 2 underlayered hematite nanorod photoanodes after high-temperature quenching (800 °C for 10 min) suggests enhanced interfacial Ti 4+ diffusion, blocking of electron back transfer, and reduced interfacial charge recombination. The TiO 2 underlayers led to more inclined growth of hematite (α-Fe 2 O 3 ) nanorods on the fluorine-doped tin oxide (FTO) substrates. Ti 4+ and Sn 4+ diffusion and formation of the TiO 2 passivation layer on the α-Fe 2 O 3 surface are confirmed by HRTEM and X-ray photoelectron spectroscopy (XPS) analyses. As a result, the TU2 photoanode displayed higher donor density and enhanced photocurrent density of (1.45 mA·cm -2 ) than the pristine hematite photoelectrode (1.0 mA·cm -2 ). The improved photoelectrochemical performance of TU2 is attributed to the high separation efficiency of photoinduced carriers via TiO 2 underlayer, the Ti 4+ /Sn 4+ diffusion, and surface passivation of hematite at high-temperature annealing. The thickness of the TiO 2 underlayer has great influence on the surface passivation as well as resistance on FTO/hematite interfaces than the diffused Sn.

AB - We introduce a simple strategy to unintentional heterogeneous Ti 4+ /Sn 4+ doping and surface passivation of hematite via TiO 2 underlayers at high temperature quenching. The effects of the controlled TiO 2 underlayer thickness and high temperature quenching process on the interfacial diffusion of Ti 4+ /Sn 4+ and TiO 2 passivation of hematite nanorod arrays have been carefully studied. The improved photoelectrochemical water oxidation performance of the TiO 2 underlayered hematite nanorod photoanodes after high-temperature quenching (800 °C for 10 min) suggests enhanced interfacial Ti 4+ diffusion, blocking of electron back transfer, and reduced interfacial charge recombination. The TiO 2 underlayers led to more inclined growth of hematite (α-Fe 2 O 3 ) nanorods on the fluorine-doped tin oxide (FTO) substrates. Ti 4+ and Sn 4+ diffusion and formation of the TiO 2 passivation layer on the α-Fe 2 O 3 surface are confirmed by HRTEM and X-ray photoelectron spectroscopy (XPS) analyses. As a result, the TU2 photoanode displayed higher donor density and enhanced photocurrent density of (1.45 mA·cm -2 ) than the pristine hematite photoelectrode (1.0 mA·cm -2 ). The improved photoelectrochemical performance of TU2 is attributed to the high separation efficiency of photoinduced carriers via TiO 2 underlayer, the Ti 4+ /Sn 4+ diffusion, and surface passivation of hematite at high-temperature annealing. The thickness of the TiO 2 underlayer has great influence on the surface passivation as well as resistance on FTO/hematite interfaces than the diffused Sn.

KW - FTO deformation

KW - Hematite; Ti /Sn diffusion

KW - Onset potential

KW - Surface passivation

KW - TiO underlayer

UR - https://www.scopus.com/pages/publications/85063132335

U2 - 10.1021/acssuschemeng.8b06544

DO - 10.1021/acssuschemeng.8b06544

M3 - Journal article

AN - SCOPUS:85063132335

SN - 2168-0485

VL - 7

SP - 6947

EP - 6958

JO - ACS Sustainable Chemistry and Engineering

JF - ACS Sustainable Chemistry and Engineering

IS - 7

ER -

Park JW, Mahadik MA, Ma H, An GW, Lee HH, Choi SH et al. Improved Interfacial Charge Transfer Dynamics and Onset Shift in Nanostructured Hematite Photoanodes via Efficient Ti ⁴⁺ /Sn ⁴⁺ Heterogeneous Self-Doping Through Controlled TiO ₂ Underlayers ACS Sustainable Chemistry and Engineering. 2019 Apr 1;7(7):6947-6958. doi: 10.1021/acssuschemeng.8b06544