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Title: Cobalt-Doped Black TiO 2 Nanotube Array as a Stable Anode for Oxygen Evolution and Electrochemical Wastewater Treatment

Abstract

TiO2 has long been recognized as a stable and reusable photocatalyst for water splitting and pollution control. However, it is an inefficient anode material in the absence of photoactivation due to its low electron conductivity. To overcome this limitation, a series of conductive TiO2 nanotube array electrodes have been developed. Even though nanotube arrays are effective for electrochemical oxidation initially, deactivation is often observed within a few hours. To overcome the problem of deactivation, we have synthesized cobalt-doped Black-TiO2 nanotube array (Co-Black NTA) electrodes that are stable for more than 200 h of continuous operation in a NaClO4 electrolyte at 10 mA cm-2. Using X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, electron paramagnetic resonance spectroscopy, and DFT simulations, we are able to show that bulk oxygen vacancies (Ov) are the primary source of the enhanced conductivity of Co-Black. Cobalt doping both creates and stabilizes surficial oxygen vacancies, Ov, and thus prevents surface passivation. The Co-Black electrodes outperform dimensionally stable IrO2 anodes (DSA) in the electrolytic oxidation of organic-rich wastewater. Increasing the loading of Co leads to the formation of a CoOx film on top of Co-Black electrode. The CoOx/Co-Black composite electrode was found to have a lower OER overpotential (352 mV)more » in comparison to a DSA IrO2 (434 mV) electrode and a stability that is greater than 200 h in a 1.0 M KOH electrolyte at a current density of 10 mA cm-2.« less

Authors:
ORCiD logo [1];  [2]; ORCiD logo [3];  [1];  [4]; ORCiD logo [5];  [2];  [1]
  1. California Inst. of Technology (CalTech), Pasadena, CA (United States)
  2. National Taiwan Univ., Taipei (Taiwan)
  3. Univ. of Texas, Austin, TX (United States)
  4. Dalian Univ., Dalian (China)
  5. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of California, Santa Cruz, CA (United States)
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES). Scientific User Facilities Division
OSTI Identifier:
1506308
Grant/Contract Number:  
AC02-05CH11231
Resource Type:
Accepted Manuscript
Journal Name:
ACS Catalysis
Additional Journal Information:
Journal Volume: 8; Journal Issue: 5; Journal ID: ISSN 2155-5435
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 54 ENVIRONMENTAL SCIENCES; cobalt oxide; conductive TiO2 nanotube array; oxygen evolution reaction; oxygen vacancies; wastewater treatment

Citation Formats

Yang, Yang, Kao, Li Cheng, Liu, Yuanyue, Sun, Ke, Yu, Hongtao, Guo, Jinghua, Liou, Sofia Ya Hsuan, and Hoffmann, Michael R. Cobalt-Doped Black TiO 2 Nanotube Array as a Stable Anode for Oxygen Evolution and Electrochemical Wastewater Treatment. United States: N. p., 2018. Web. https://doi.org/10.1021/acscatal.7b04340.
Yang, Yang, Kao, Li Cheng, Liu, Yuanyue, Sun, Ke, Yu, Hongtao, Guo, Jinghua, Liou, Sofia Ya Hsuan, & Hoffmann, Michael R. Cobalt-Doped Black TiO 2 Nanotube Array as a Stable Anode for Oxygen Evolution and Electrochemical Wastewater Treatment. United States. https://doi.org/10.1021/acscatal.7b04340
Yang, Yang, Kao, Li Cheng, Liu, Yuanyue, Sun, Ke, Yu, Hongtao, Guo, Jinghua, Liou, Sofia Ya Hsuan, and Hoffmann, Michael R. Tue . "Cobalt-Doped Black TiO 2 Nanotube Array as a Stable Anode for Oxygen Evolution and Electrochemical Wastewater Treatment". United States. https://doi.org/10.1021/acscatal.7b04340. https://www.osti.gov/servlets/purl/1506308.
@article{osti_1506308,
title = {Cobalt-Doped Black TiO 2 Nanotube Array as a Stable Anode for Oxygen Evolution and Electrochemical Wastewater Treatment},
author = {Yang, Yang and Kao, Li Cheng and Liu, Yuanyue and Sun, Ke and Yu, Hongtao and Guo, Jinghua and Liou, Sofia Ya Hsuan and Hoffmann, Michael R.},
abstractNote = {TiO2 has long been recognized as a stable and reusable photocatalyst for water splitting and pollution control. However, it is an inefficient anode material in the absence of photoactivation due to its low electron conductivity. To overcome this limitation, a series of conductive TiO2 nanotube array electrodes have been developed. Even though nanotube arrays are effective for electrochemical oxidation initially, deactivation is often observed within a few hours. To overcome the problem of deactivation, we have synthesized cobalt-doped Black-TiO2 nanotube array (Co-Black NTA) electrodes that are stable for more than 200 h of continuous operation in a NaClO4 electrolyte at 10 mA cm-2. Using X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, electron paramagnetic resonance spectroscopy, and DFT simulations, we are able to show that bulk oxygen vacancies (Ov) are the primary source of the enhanced conductivity of Co-Black. Cobalt doping both creates and stabilizes surficial oxygen vacancies, Ov, and thus prevents surface passivation. The Co-Black electrodes outperform dimensionally stable IrO2 anodes (DSA) in the electrolytic oxidation of organic-rich wastewater. Increasing the loading of Co leads to the formation of a CoOx film on top of Co-Black electrode. The CoOx/Co-Black composite electrode was found to have a lower OER overpotential (352 mV) in comparison to a DSA IrO2 (434 mV) electrode and a stability that is greater than 200 h in a 1.0 M KOH electrolyte at a current density of 10 mA cm-2.},
doi = {10.1021/acscatal.7b04340},
journal = {ACS Catalysis},
number = 5,
volume = 8,
place = {United States},
year = {2018},
month = {4}
}

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Figures / Tables:

Figure 1 Figure 1: (a) NTA electrode preparation procedures. (b, c) Cyclic voltammograms of NTA electrodes in 100 mM KPi buffer at pH 7.2.

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