A Promising New Photo-Catalyst InVO 4 for Water Molecule Decomposition in the Visible Wavelength Region
- PDF / 122,651 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 64 Downloads / 167 Views
V5.8.1
A promising new photo-catalyst InVO4 for water molecule decomposition in the visible wavelength region M. Oshikiri1,2, A. P. Seitsonen2, M. Parrinello2, M. Boero3, J. Ye4 and Z. Zou5 Nanomaterials Laboratory, National Institute for Materials Science, 3-13 Sakura, Tsukuba, Ibaraki 305-0003, Japan 2 Swiss Center for Scientific Computing, Galleria 2, Via Cantonale, CH-6928 Manno, Switzerland 3 Institute of Physics, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8571, Japan 4 Materials Engineering Laboratory, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, Japan 5 Photoreaction Control Research Center, National Institute of Advanced Industrial Science and Technology, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan 1
ABSTRACT A promising vanadium-based photo-catalyst (InVO4) has been proposed recently by our group. This catalyst has been shown to be active in the visible light range, up to a wavelength of about 600 nm, and is able to promote the decomposition of water. In this paper, we focus on its electronic structure, computed via first principles calculations, in order to figure out analogies and differences with similar systems (InNbO4, InTaO4 and BiVO4) that have already been reported to act as photo-catalysts. An attempt is made to address the problem of the wavelength dependency of the photo catalytic activity of the InMO4 (M = V, Nb, Ta) family and how this is related to the crystal structure. Finally, by using an ab initio molecular dynamics approach, we inspect the relaxation/reconstruction phenomena occurring at the exposed surface of the InVO4 catalyst induced by the absorption of a water molecule, that represents a crucial step in the catalysis reaction.
INTRODUCTION It is well known that a photo-catalyst able to promote the hydrolysis of water molecules and operating in the visible and infra-red region is highly desired for solar energy storing. If we consider the redox level difference of H+/H2 and O2/H2O, which is about 1.2 eV (1.0 µm), the problem of finding a material with such properties does not seem a tough one: even an infra-red-active semiconductor catalyst should exist a priori. However, this naïve picture is in contrast with the experimental evidence: to date, most of the photo catalyst can work only in the UV region (< 420 nm). In an attempt to shed some light, we inspected the electronic structure of the most common photo-catalysts. As discussed later, the conduction band bottom (CBB) of the majority of the photo-catalysts consists of d orbitals of the transition metals (e.g. Zr, Ta, Nb, Ti) present in the structure, while the valence band top (VBT) is spanned by the 2p orbitals of the oxygen atoms. Given this scenario, an intuitive way to activate the catalyst in a longer wavelength range would be to substitute vanadium to either Zr, Ta, Nb or Ti. This idea is suggested by the lower position, on the energy axis, of the atomic 3d energy levels of V with respect to the other transition metals. Provided that this downward shift holds also
Data Loading...
