Effect of calcination temperature on the structure of a Pt/TiO2 (B) nanofiber and its photocatalytic activity in generating H2

Chiu-Hsun Lin, Jiunn Hsing Chao, Chun Hsuan Liu, Jui Chun Chang, Feng Chieh Wang

Research output: Contribution to journalArticle

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Abstract

Hydrogen trititanate (H2Ti3O7) nanofibers were prepared by a hydrothermal method in 10 M NaOH at 403 K, followed by acidic rinsing and drying at 383 K. Calcining H2Ti3O7 nanofibers at 573 K led to the formation of TiO2 (B) nanofibers. Calcination at 673 K improved the crystallinity of the TiO2 (B) nanofibers and did not cause any change in the morphology and dimensions of the nanofibers. TiO2 (B) and H2Ti3O7 nanofibers are 10-20 nm in diameter and several micrometers long, but FE-SEM reveals that several of these nanofibers tend to bind tightly to each other, forming a fiber bundle. Calcination at 773 K transformed TiO2 (B) nanofibers into a TiO2 (B)/anatase bicrystalline mixture with their fibrous morphology remaining intact. Upon increasing the calcination temperature to 873 K, most of the TiO2 (B) nanofibers were converted into anatase nanofibers and small anatase particles with smoother surfaces. In the photocatalytic dehydrogenation of neat ethanol, 1% Pt/TiO2 (B) nanofiber calcined at 673 K was the most active catalyst and generated about the same amount of H2 as did 1 % Pt/P-25. TPR indicated that the calcination of 1 % Pt/TiO2 (B) nanofiber at 573 K produced a poor Pt dispersion and poor activity. Calcination at a temperature higher than 773 K (in ambient air) resulted in an SMSI effect similar to that observed over TiO2 in the reductive atmosphere. As suggested by XPS, such an SMSI effect decreased the surface concentration of Pt metal and created Ptδ- sites, preventing Pt particles from functioning as a Schottky barrier and leading to a lower activity. Because of the synergetic effect between TiO2 (B) and anatase phases, the bicrystalline mixture, produced by calcining at 773 K, was able to counter negative effects such as the reduction in surface area and the SMSI effect and maintained its photocatalytic activity.

Original languageEnglish
Pages (from-to)9907-9915
Number of pages9
JournalLangmuir
Volume24
Issue number17
DOIs
Publication statusPublished - 2008 Sep 2

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Nanofibers
Calcination
roasting
anatase
Titanium dioxide
Temperature
temperature
dehydrogenation
drying
bundles
micrometers
crystallinity
counters
ethyl alcohol
catalysts
atmospheres
scanning electron microscopy
fibers
causes
air

All Science Journal Classification (ASJC) codes

  • Materials Science(all)
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Spectroscopy
  • Electrochemistry

Cite this

Lin, Chiu-Hsun ; Chao, Jiunn Hsing ; Liu, Chun Hsuan ; Chang, Jui Chun ; Wang, Feng Chieh. / Effect of calcination temperature on the structure of a Pt/TiO2 (B) nanofiber and its photocatalytic activity in generating H2. In: Langmuir. 2008 ; Vol. 24, No. 17. pp. 9907-9915.
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abstract = "Hydrogen trititanate (H2Ti3O7) nanofibers were prepared by a hydrothermal method in 10 M NaOH at 403 K, followed by acidic rinsing and drying at 383 K. Calcining H2Ti3O7 nanofibers at 573 K led to the formation of TiO2 (B) nanofibers. Calcination at 673 K improved the crystallinity of the TiO2 (B) nanofibers and did not cause any change in the morphology and dimensions of the nanofibers. TiO2 (B) and H2Ti3O7 nanofibers are 10-20 nm in diameter and several micrometers long, but FE-SEM reveals that several of these nanofibers tend to bind tightly to each other, forming a fiber bundle. Calcination at 773 K transformed TiO2 (B) nanofibers into a TiO2 (B)/anatase bicrystalline mixture with their fibrous morphology remaining intact. Upon increasing the calcination temperature to 873 K, most of the TiO2 (B) nanofibers were converted into anatase nanofibers and small anatase particles with smoother surfaces. In the photocatalytic dehydrogenation of neat ethanol, 1{\%} Pt/TiO2 (B) nanofiber calcined at 673 K was the most active catalyst and generated about the same amount of H2 as did 1 {\%} Pt/P-25. TPR indicated that the calcination of 1 {\%} Pt/TiO2 (B) nanofiber at 573 K produced a poor Pt dispersion and poor activity. Calcination at a temperature higher than 773 K (in ambient air) resulted in an SMSI effect similar to that observed over TiO2 in the reductive atmosphere. As suggested by XPS, such an SMSI effect decreased the surface concentration of Pt metal and created Ptδ- sites, preventing Pt particles from functioning as a Schottky barrier and leading to a lower activity. Because of the synergetic effect between TiO2 (B) and anatase phases, the bicrystalline mixture, produced by calcining at 773 K, was able to counter negative effects such as the reduction in surface area and the SMSI effect and maintained its photocatalytic activity.",
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Effect of calcination temperature on the structure of a Pt/TiO2 (B) nanofiber and its photocatalytic activity in generating H2. / Lin, Chiu-Hsun; Chao, Jiunn Hsing; Liu, Chun Hsuan; Chang, Jui Chun; Wang, Feng Chieh.

In: Langmuir, Vol. 24, No. 17, 02.09.2008, p. 9907-9915.

Research output: Contribution to journalArticle

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T1 - Effect of calcination temperature on the structure of a Pt/TiO2 (B) nanofiber and its photocatalytic activity in generating H2

AU - Lin, Chiu-Hsun

AU - Chao, Jiunn Hsing

AU - Liu, Chun Hsuan

AU - Chang, Jui Chun

AU - Wang, Feng Chieh

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N2 - Hydrogen trititanate (H2Ti3O7) nanofibers were prepared by a hydrothermal method in 10 M NaOH at 403 K, followed by acidic rinsing and drying at 383 K. Calcining H2Ti3O7 nanofibers at 573 K led to the formation of TiO2 (B) nanofibers. Calcination at 673 K improved the crystallinity of the TiO2 (B) nanofibers and did not cause any change in the morphology and dimensions of the nanofibers. TiO2 (B) and H2Ti3O7 nanofibers are 10-20 nm in diameter and several micrometers long, but FE-SEM reveals that several of these nanofibers tend to bind tightly to each other, forming a fiber bundle. Calcination at 773 K transformed TiO2 (B) nanofibers into a TiO2 (B)/anatase bicrystalline mixture with their fibrous morphology remaining intact. Upon increasing the calcination temperature to 873 K, most of the TiO2 (B) nanofibers were converted into anatase nanofibers and small anatase particles with smoother surfaces. In the photocatalytic dehydrogenation of neat ethanol, 1% Pt/TiO2 (B) nanofiber calcined at 673 K was the most active catalyst and generated about the same amount of H2 as did 1 % Pt/P-25. TPR indicated that the calcination of 1 % Pt/TiO2 (B) nanofiber at 573 K produced a poor Pt dispersion and poor activity. Calcination at a temperature higher than 773 K (in ambient air) resulted in an SMSI effect similar to that observed over TiO2 in the reductive atmosphere. As suggested by XPS, such an SMSI effect decreased the surface concentration of Pt metal and created Ptδ- sites, preventing Pt particles from functioning as a Schottky barrier and leading to a lower activity. Because of the synergetic effect between TiO2 (B) and anatase phases, the bicrystalline mixture, produced by calcining at 773 K, was able to counter negative effects such as the reduction in surface area and the SMSI effect and maintained its photocatalytic activity.

AB - Hydrogen trititanate (H2Ti3O7) nanofibers were prepared by a hydrothermal method in 10 M NaOH at 403 K, followed by acidic rinsing and drying at 383 K. Calcining H2Ti3O7 nanofibers at 573 K led to the formation of TiO2 (B) nanofibers. Calcination at 673 K improved the crystallinity of the TiO2 (B) nanofibers and did not cause any change in the morphology and dimensions of the nanofibers. TiO2 (B) and H2Ti3O7 nanofibers are 10-20 nm in diameter and several micrometers long, but FE-SEM reveals that several of these nanofibers tend to bind tightly to each other, forming a fiber bundle. Calcination at 773 K transformed TiO2 (B) nanofibers into a TiO2 (B)/anatase bicrystalline mixture with their fibrous morphology remaining intact. Upon increasing the calcination temperature to 873 K, most of the TiO2 (B) nanofibers were converted into anatase nanofibers and small anatase particles with smoother surfaces. In the photocatalytic dehydrogenation of neat ethanol, 1% Pt/TiO2 (B) nanofiber calcined at 673 K was the most active catalyst and generated about the same amount of H2 as did 1 % Pt/P-25. TPR indicated that the calcination of 1 % Pt/TiO2 (B) nanofiber at 573 K produced a poor Pt dispersion and poor activity. Calcination at a temperature higher than 773 K (in ambient air) resulted in an SMSI effect similar to that observed over TiO2 in the reductive atmosphere. As suggested by XPS, such an SMSI effect decreased the surface concentration of Pt metal and created Ptδ- sites, preventing Pt particles from functioning as a Schottky barrier and leading to a lower activity. Because of the synergetic effect between TiO2 (B) and anatase phases, the bicrystalline mixture, produced by calcining at 773 K, was able to counter negative effects such as the reduction in surface area and the SMSI effect and maintained its photocatalytic activity.

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