Formation of internal p-n junctions in Ta 3 N 5 photoanodes for water splitting

Yi Chieh Wang, Chih Yung Chang, Te Fu Yeh, Yuh-Lang Lee, Hsisheng Teng

Research output: Contribution to journalArticle

20 Citations (Scopus)

Abstract

Tantalum nitride photoanodes for water splitting are fabricated by anodizing tantalum foils, with subsequent nitridation of the foils in NH 3 . The as-synthesized Ta 3 N 5 film has n-type conductivity. Loading Co ions during and after the anodization process forms a Ta 3 N 5 :Co film consisting of p- and n-type Ta 3 N 5 domains. Both the Ta 3 N 5 and Ta 3 N 5 :Co electrodes have a band gap of 2.0 eV. The p-n junctions in the Ta 3 N 5 :Co electrode create an internal electrical field favorable for hole transfer from the n-type domains to the p-type domains. When the photoanodes are immersed in a 0.5 M KOH aqueous solution for water splitting with one-sun illumination, the Ta 3 N 5 :Co photoanode exhibits photocurrents an order of magnitude higher than those of the bare Ta 3 N 5 photoanode. AC impedance spectroscopy analysis reveals that the p-n junctions formed by Co-doping reduce the interfacial charge transfer resistance by an order of magnitude. The diffuse reflectance spectra of the electrodes indicate that Co incorporation minimizes the defect states in the bulk Ta 3 N 5 . Intensity-modulated photocurrent spectroscopy analysis reveals that the high electron transit rate of the Ta 3 N 5 :Co electrode can be attributed to its fewer defect states. A photoelectrochemical reaction using the Ta 3 N 5 :Co photoanode produces H 2 and O 2 at a ratio close to 2 : 1, and N 2 evolution from the reaction is negligible. The present study demonstrates the establishment of a p-n junction configuration that considerably enhances the performance of nitride anodes in photocatalyzed water splitting.

Original languageEnglish
Pages (from-to)20570-20577
Number of pages8
JournalJournal of Materials Chemistry A
Volume2
Issue number48
DOIs
Publication statusPublished - 2014 Dec 28

Fingerprint

Tantalum
Electrodes
Water
Photocurrents
Nitrides
Metal foil
Spectroscopy
Defects
Nitridation
Anodic oxidation
Sun
Charge transfer
Anodes
Energy gap
Lighting
Doping (additives)
Ions
Electrons

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Renewable Energy, Sustainability and the Environment
  • Materials Science(all)

Cite this

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title = "Formation of internal p-n junctions in Ta 3 N 5 photoanodes for water splitting",
abstract = "Tantalum nitride photoanodes for water splitting are fabricated by anodizing tantalum foils, with subsequent nitridation of the foils in NH 3 . The as-synthesized Ta 3 N 5 film has n-type conductivity. Loading Co ions during and after the anodization process forms a Ta 3 N 5 :Co film consisting of p- and n-type Ta 3 N 5 domains. Both the Ta 3 N 5 and Ta 3 N 5 :Co electrodes have a band gap of 2.0 eV. The p-n junctions in the Ta 3 N 5 :Co electrode create an internal electrical field favorable for hole transfer from the n-type domains to the p-type domains. When the photoanodes are immersed in a 0.5 M KOH aqueous solution for water splitting with one-sun illumination, the Ta 3 N 5 :Co photoanode exhibits photocurrents an order of magnitude higher than those of the bare Ta 3 N 5 photoanode. AC impedance spectroscopy analysis reveals that the p-n junctions formed by Co-doping reduce the interfacial charge transfer resistance by an order of magnitude. The diffuse reflectance spectra of the electrodes indicate that Co incorporation minimizes the defect states in the bulk Ta 3 N 5 . Intensity-modulated photocurrent spectroscopy analysis reveals that the high electron transit rate of the Ta 3 N 5 :Co electrode can be attributed to its fewer defect states. A photoelectrochemical reaction using the Ta 3 N 5 :Co photoanode produces H 2 and O 2 at a ratio close to 2 : 1, and N 2 evolution from the reaction is negligible. The present study demonstrates the establishment of a p-n junction configuration that considerably enhances the performance of nitride anodes in photocatalyzed water splitting.",
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Formation of internal p-n junctions in Ta 3 N 5 photoanodes for water splitting . / Wang, Yi Chieh; Chang, Chih Yung; Yeh, Te Fu; Lee, Yuh-Lang; Teng, Hsisheng.

In: Journal of Materials Chemistry A, Vol. 2, No. 48, 28.12.2014, p. 20570-20577.

Research output: Contribution to journalArticle

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AU - Chang, Chih Yung

AU - Yeh, Te Fu

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AU - Teng, Hsisheng

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AB - Tantalum nitride photoanodes for water splitting are fabricated by anodizing tantalum foils, with subsequent nitridation of the foils in NH 3 . The as-synthesized Ta 3 N 5 film has n-type conductivity. Loading Co ions during and after the anodization process forms a Ta 3 N 5 :Co film consisting of p- and n-type Ta 3 N 5 domains. Both the Ta 3 N 5 and Ta 3 N 5 :Co electrodes have a band gap of 2.0 eV. The p-n junctions in the Ta 3 N 5 :Co electrode create an internal electrical field favorable for hole transfer from the n-type domains to the p-type domains. When the photoanodes are immersed in a 0.5 M KOH aqueous solution for water splitting with one-sun illumination, the Ta 3 N 5 :Co photoanode exhibits photocurrents an order of magnitude higher than those of the bare Ta 3 N 5 photoanode. AC impedance spectroscopy analysis reveals that the p-n junctions formed by Co-doping reduce the interfacial charge transfer resistance by an order of magnitude. The diffuse reflectance spectra of the electrodes indicate that Co incorporation minimizes the defect states in the bulk Ta 3 N 5 . Intensity-modulated photocurrent spectroscopy analysis reveals that the high electron transit rate of the Ta 3 N 5 :Co electrode can be attributed to its fewer defect states. A photoelectrochemical reaction using the Ta 3 N 5 :Co photoanode produces H 2 and O 2 at a ratio close to 2 : 1, and N 2 evolution from the reaction is negligible. The present study demonstrates the establishment of a p-n junction configuration that considerably enhances the performance of nitride anodes in photocatalyzed water splitting.

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