title: The potential of imogolite nanotubes as (co-)photocatalysts: a linear-scaling density functional theory study.
abstract: We report a linear-scaling density functional theory (DFT) study of the structure, wall-polarization absolute band-alignment and optical absorption of several, recently synthesized, open-ended imogolite (Imo) nanotubes (NTs), namely single-walled (SW) aluminosilicate (AlSi), SW aluminogermanate (AlGe), SW methylated aluminosilicate (AlSi-Me), and double-walled (DW) AlGe NTs. Simulations with three different semi-local and dispersion-corrected DFT-functionals reveal that the NT wall-polarization can be increased by nearly a factor of four going from SW-AlSi-Me to DW-AlGe. Absolute vacuum alignment of the NT electronic bands and comparison with those of rutile and anatase TiO2 suggest that the NTs may exhibit marked propensity to both photo-reduction and hole-scavenging. Characterization of the NTs' band-separation and optical properties reveal the occurrence of (near-)UV inside-outside charge-transfer excitations, which may be effective for electron-hole separation and enhanced photocatalytic activity. Finally, the effects of the NTs' wall-polarization on the absolute alignment of electron and hole acceptor states of interacting water (H2O) molecules are quantified and discussed.
authors.affiliation: Stephenson Institute for Renewable Energy and Department of Chemistry, University of Liverpool, Liverpool L69 3BX, UK.
authors.forename: E
authors.initials: E
authors.lastname: Poli
authors.forename: J D
authors.initials: JD
authors.lastname: Elliott
authors.forename: L E
authors.initials: LE
authors.lastname: Ratcliff
authors.forename: L
authors.initials: L
authors.lastname: Andrinopoulos
authors.forename: J
authors.initials: J
authors.lastname: Dziedzic
authors.forename: N D M
authors.initials: ND
authors.lastname: Hine
authors.forename: A A
authors.initials: AA
authors.lastname: Mostofi
authors.forename: C-K
authors.initials: CK
authors.lastname: Skylaris
authors.forename: P D
authors.initials: PD
authors.lastname: Haynes
authors.forename: G
authors.initials: G
authors.lastname: Teobaldi
mesh_terms: D000538:Aluminum Silicates / Q000737:chemistry*; D002384:Catalysis; D002627:Chemistry, Physical; D004583:Electrons; D005857:Germanium / Q000737:chemistry*; D006801:Humans; D008958:Models, Molecular; D015394:Molecular Structure; D043942:Nanotubes / Q000737:chemistry*; D011789:Quantum Theory; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry*; D014466:Ultraviolet Rays; D014867:Water / Q000737:chemistry
chemical_list: D000538:Aluminum Silicates; D005857:Germanium; D014867:Water; C009495:titanium dioxide; C049037:aluminosilicate; D014025:Titanium