A soft X-ray spectroscopic perspective of electron localization and transport in tungsten doped bismuth vanadate single crystals

Vedran Jovic, Alexander J E Rettie, Vijay R Singh, Jianshi Zhou, Bethany Lamoureux, C Buddie Mullins, Hendrik Bluhm, Jude Laverock, Kevin E Smith

Research output: Contribution to journalArticle (Academic Journal)

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Abstract

Doped BiVO4 is a promising photoelectrochemical water splitting anode, whose activity is hampered by poor charge transport. Here we use a set of X-ray spectroscopic methods to probe the origin and nature of localized electron states in W:BiVO4. Furthermore, using the polarized nature of the X-rays, we probe variations in the electronic structure along the crystal axes. In this manner, we reveal aspects of the electronic structure related to electron localization and observations consistent with conductivity anisotropy between the ab-plane and c-axis. We verify that tungsten substitutes as W(6+) for V(5+) in BiVO4. This is shown to result in the presence of inter-band gap states related to electrons at V(4+) sites of e symmetry. The energetic position of the states in the band gap suggest that they are highly localized and may act as recombination centres. Polarization dependent X-ray absorption spectra reveal anisotropy in the electronic structure between the ab-plane and c-axis. Results show the superior hybridization between V 3d and O 2p states, higher V wavefunction overlap and broader conduction bands in the ab-plane than in the c-axis. These insights into the electronic structure are discussed in the context of existing experimental and theoretical reports regarding charge transport in BiVO4.

Original languageEnglish
Pages (from-to)31958-31965
Number of pages8
JournalPhysical Chemistry Chemical Physics
Volume18
Issue number46
Early online date9 Nov 2016
DOIs
Publication statusPublished - 14 Dec 2016

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