Crystal Engineering of Bi₂WO₆ to Polar Aurivillius-Phase Oxyhalides

Abstract

Crystal Engineering of Bi2WO6 to Polar Aurivillius-Phase Oxyhalides. ChemRxiv. Preprint. The Aurivillius phases of complex bismuth oxides have attracted considerable attention due to their lattice polarization (ferroelectricity) and photocatalytic activity. We report a first-principles exploration of Bi 2 WO 6 and download file view on ChemRxiv manuscript_Aurivillius.pdf (5.84 MiB) download file view on ChemRxiv SI_Aurivillius.pdf (5.34 MiB)

Anisotropic Electron Transport Limits Performance of Bi2WO6 Photoanodes

“…This coupling of Bi 6s and O 2p orbitals leads to an upward dispersion of the VB and a narrower band gap than would otherwise be expected . Consistent with the results of a previous theoretical study screening Aurivillius oxides, the conduction band (CB) minimum projects predominantly on W 5d states with some O 2p density. The CB exhibits a strong spatial anisotropy, illustrated by the isosurface shown in Figure b.…”

“…2 The layered structure of these materials implies a vast library of possible subphases, each with a distinct set of optoelectronic properties, while studies of B site substitution demonstrate the possibility of band gap engineering to enhance solar harvesting. 12,13 Preliminary studies indicate that some members show promise in photocatalytic and photoelectrochemical applications. 14−16 However, relatively little is known about the factors which govern water oxidation efficiency in even the simplest examples of this diverse and complex family of materials.…”

“…The search for efficient, low-cost metal oxides with improved visible light-harvesting characteristics has resulted in an expanding library of ternary and quaternary metal oxides, some of which show promise as photoanodes for the rate-limiting water oxidation half-reaction. , An unexplored and potentially versatile group of ternary/quaternary oxides is the family of Aurivillius oxides: (Bi 2 O 2 ) 2+ (A m–1 B m O 3m + 1 ) . The layered structure of these materials implies a vast library of possible subphases, each with a distinct set of optoelectronic properties, while studies of B site substitution demonstrate the possibility of band gap engineering to enhance solar harvesting. , Preliminary studies indicate that some members show promise in photocatalytic and photoelectrochemical applications. − However, relatively little is known about the factors which govern water oxidation efficiency in even the simplest examples of this diverse and complex family of materials.…”

Symmetry and the Role of the Anion Sublattice in Aurivillius Oxyfluoride Bi2TiO4F2

“…It is timely to reconsider these materials and, in particular, the anion ordering possibilities and their consequences for symmetry and polar properties. 49 Our experimental work (based on property measurements as well as neutron powder diffraction (NPD) and electron diffraction) is consistent with earlier studies, 39 and our symmetry analysis demonstrates that it is possible to break inversion symmetry in these systems by ordering of O 2− and F − ions over the anion sites and in combination with octahedral rotations. We explore an experimental method that may be applied more widely to investigate anion order in oxyfluorides based on the Rietveld method combined with global instability index (GII) calculations to introduce structural strain information into structural refinements.…”

“…This sensitivity may result from the complexity of the anion sublatticeboth in terms of the distribution of O 2– and F – ions over the anion sites and any displacive disorder of the anion positions. It is timely to reconsider these materials and, in particular, the anion ordering possibilities and their consequences for symmetry and polar properties . Our experimental work (based on property measurements as well as neutron powder diffraction (NPD) and electron diffraction) is consistent with earlier studies, and our symmetry analysis demonstrates that it is possible to break inversion symmetry in these systems by ordering of O 2– and F – ions over the anion sites and in combination with octahedral rotations.…”