Observatorio de I+D+i UPM

Memorias de investigación
Communications at congresses:
Vanadium-Doped In and Sn Sulphides: Photocatalysts able to use the whole visible light spectrum
Year:2012
Research Areas
  • Chemistry,
  • Electric engineers, electronic and automatic (eil),
  • Materials for electric engineering and electronics,
  • Technology of devices for engineering
Information
Abstract
Using photocatalysis for energy applications depends, more than for environmental purposes or selective chemical synthesis, on converting as much of the solar spectrum as possible; the best photocatalyst, titania, is far from this. Many efforts are pursued to use better that spectrum in photocatalysis, by doping titania or using other materials (mainly oxides, nitrides and sulphides) to obtain a lower bandgap, even if this means decreasing the chemical potential of the electron-hole pairs. Here we introduce an alternative scheme, using an idea recently proposed for photovoltaics: the intermediate band (IB) materials. It consists in introducing in the gap of a semiconductor an intermediate level which, acting like a stepstone, allows an electron jumping from the valence band to the conduction band in two steps, each one absorbing one sub-bandgap photon. For this the IB must be partially filled, to allow both sub-bandgap transitions to proceed at comparable rates; must be made of delocalized states to minimize nonradiative recombination; and should not communicate electronically with the outer world. For photovoltaic use the optimum efficiency so achievable, over 1.5 times that given by a normal semiconductor, is obtained with an overall bandgap around 2.0 eV (which would be near-optimal also for water phtosplitting). Note that this scheme differs from the doping principle usually considered in photocatalysis, which just tries to decrease the bandgap; its aim is to keep the full bandgap chemical potential but using also lower energy photons. In the past we have proposed several IB materials based on extensively doping known semiconductors with light transition metals, checking first of all with quantum calculations that the desired IB structure results. Subsequently we have synthesized in powder form two of them: the thiospinel In2S3 and the layered compound SnS2 (having bandgaps of 2.0 and 2.2 eV respectively) where the octahedral cation is substituted at a â?10% level with vanadium, and we have verified that this substitution introduces in the absorption spectrum the sub-bandgap features predicted by the calculations. With these materials we have verified, using a simple reaction (formic acid oxidation), that the photocatalytic spectral response is indeed extended to longer wavelengths, being able to use even 700 nm photons, without largely degrading the response for above-bandgap photons (i.e. strong recombination is not induced) [3b, 4]. These materials are thus promising for efficient photoevolution of hydrogen from water; work on this is being pursued, the results of which will be presented.
International
Si
Congress
2012 MRS Spring Meeting & Exhibit
960
Place
San Francisco, CA (EEUU)
Reviewers
Si
ISBN/ISSN
000-0000-000-000
Start Date
09/04/2012
End Date
13/04/2012
From page
1
To page
2
Proc. 2012 MRS Spring Meeting & Exhibit
Participants
  • Autor: R. Lucena
  • Autor: F. Fresno
  • Autor: Pablo Palacios Clemente (UPM)
  • Autor: Yohanna Seminóvski Pérez (UPM)
  • Autor: Perla Wahnon Benarroch (UPM)
  • Autor: J.C. Conesa
Research Group, Departaments and Institutes related
  • Creador: Centro o Instituto I+D+i: Instituto de Energía Solar
  • Departamento: Física y Química Aplicadas a la Técnica Aeronáutica
  • Departamento: Tecnologías Especiales Aplicadas a la Telecomunicación
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