Details
| Original language | English |
|---|---|
| Pages (from-to) | 8844-8855 |
| Number of pages | 12 |
| Journal | ACS catalysis |
| Volume | 8 |
| Issue number | 9 |
| Early online date | 14 Aug 2018 |
| Publication status | Published - 7 Sept 2018 |
Abstract
The rich crystal chemistry of mullite-type Bi 2M 4O 9 (M = Fe, Al, Ga) offers multiple potential applications. In particular, the strong absorption of visible light shown by Bi 2Fe 4O 9 has led to an influx of research on its photocatalytic properties. However, most of the published studies involve the decolorization of dyes and take it as proof of its photocatalytic activity; furthermore, there are no reports on its conduction and valence band edges, and, thus, the actual redox characteristics of the photogenerated charge carriers have not been determined. Here, we evaluate the photocatalytic activity toward methanol oxidation under monochromatic visible light (= 450 nm) irradiation of 12 different members of the Bi 2(Al 1-xFe x) 4O 9 (x = 0-1) series of compounds. The reaction rate reaches its highest value at an iron fraction of x = 0.1, while the compounds with the highest iron fractions present negligible activity. Based on an extensive characterization, which included the Rietveld refinement of the XRD patterns, the measurement of the specific surface areas by the BET method, and the determination of the flat-band potentials by the Mott-Schottky method, we rationalize the results on the basis of two opposing factors: the incorporation of iron narrows the fundamental bandgap and thus improves light capture, but at the same time it lowers the conduction band edge, hindering the oxygen reduction half-reaction and thus promoting electron-hole recombination. Our work highlights the importance of a proper band edge engineering for photocatalytic applications and underlines the inadequacy of dye decolorization tests for visible-light-active materials.
Keywords
- band-edge tuning, bandgap narrowing, heterogeneous photocatalysis, methanol oxidation, mullite-type materials
ASJC Scopus subject areas
- Chemical Engineering(all)
- Catalysis
- Chemistry(all)
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In: ACS catalysis, Vol. 8, No. 9, 07.09.2018, p. 8844-8855.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - Visible-Light Photocatalysis with Mullite-Type Bi2(Al1–xFex)4O9
T2 - Striking the Balance between Bandgap Narrowing and Conduction Band Lowering
AU - Curti, Mariano
AU - Kirsch, Andrea
AU - Granone, Luis I.
AU - Tarasi, Facundo
AU - López-Robledo, Germán
AU - Bahnemann, Detlef W.
AU - Murshed, M. Mangir
AU - Gesing, Thorsten M.
AU - Mendive, Cecilia B.
N1 - © 2018 American Chemical Society
PY - 2018/9/7
Y1 - 2018/9/7
N2 - The rich crystal chemistry of mullite-type Bi 2M 4O 9 (M = Fe, Al, Ga) offers multiple potential applications. In particular, the strong absorption of visible light shown by Bi 2Fe 4O 9 has led to an influx of research on its photocatalytic properties. However, most of the published studies involve the decolorization of dyes and take it as proof of its photocatalytic activity; furthermore, there are no reports on its conduction and valence band edges, and, thus, the actual redox characteristics of the photogenerated charge carriers have not been determined. Here, we evaluate the photocatalytic activity toward methanol oxidation under monochromatic visible light (= 450 nm) irradiation of 12 different members of the Bi 2(Al 1-xFe x) 4O 9 (x = 0-1) series of compounds. The reaction rate reaches its highest value at an iron fraction of x = 0.1, while the compounds with the highest iron fractions present negligible activity. Based on an extensive characterization, which included the Rietveld refinement of the XRD patterns, the measurement of the specific surface areas by the BET method, and the determination of the flat-band potentials by the Mott-Schottky method, we rationalize the results on the basis of two opposing factors: the incorporation of iron narrows the fundamental bandgap and thus improves light capture, but at the same time it lowers the conduction band edge, hindering the oxygen reduction half-reaction and thus promoting electron-hole recombination. Our work highlights the importance of a proper band edge engineering for photocatalytic applications and underlines the inadequacy of dye decolorization tests for visible-light-active materials.
AB - The rich crystal chemistry of mullite-type Bi 2M 4O 9 (M = Fe, Al, Ga) offers multiple potential applications. In particular, the strong absorption of visible light shown by Bi 2Fe 4O 9 has led to an influx of research on its photocatalytic properties. However, most of the published studies involve the decolorization of dyes and take it as proof of its photocatalytic activity; furthermore, there are no reports on its conduction and valence band edges, and, thus, the actual redox characteristics of the photogenerated charge carriers have not been determined. Here, we evaluate the photocatalytic activity toward methanol oxidation under monochromatic visible light (= 450 nm) irradiation of 12 different members of the Bi 2(Al 1-xFe x) 4O 9 (x = 0-1) series of compounds. The reaction rate reaches its highest value at an iron fraction of x = 0.1, while the compounds with the highest iron fractions present negligible activity. Based on an extensive characterization, which included the Rietveld refinement of the XRD patterns, the measurement of the specific surface areas by the BET method, and the determination of the flat-band potentials by the Mott-Schottky method, we rationalize the results on the basis of two opposing factors: the incorporation of iron narrows the fundamental bandgap and thus improves light capture, but at the same time it lowers the conduction band edge, hindering the oxygen reduction half-reaction and thus promoting electron-hole recombination. Our work highlights the importance of a proper band edge engineering for photocatalytic applications and underlines the inadequacy of dye decolorization tests for visible-light-active materials.
KW - band-edge tuning
KW - bandgap narrowing
KW - heterogeneous photocatalysis
KW - methanol oxidation
KW - mullite-type materials
UR - http://www.scopus.com/inward/record.url?scp=85052292008&partnerID=8YFLogxK
U2 - 10.1021/acscatal.8b01210
DO - 10.1021/acscatal.8b01210
M3 - Article
VL - 8
SP - 8844
EP - 8855
JO - ACS catalysis
JF - ACS catalysis
SN - 2155-5435
IS - 9
ER -