title: Localized photoelectrochemistry on a tungsten oxide-iron oxide thin film material library.
abstract: A WO3-Fe2O3 thin film combinatorial library was fabricated using a vapor phase co-deposition method followed by a combined thermal annealing and oxidation process. The scanning electron microscopy (SEM) analysis of the library microstructure combined with X-ray diffraction (XRD) investigations suggested that α-Fe2O3 grains preferentially grow from boundaries of domains, containing finer grains of WO3 and Fe2WO6, forming filiform networks on the surface. The surface density of the hematite networks depends on the amount of Fe present in the library. Photocurrents measured at different applied biases using Photo Electrochemical Scanning Droplet Cell Microscopy (PE-SDCM) were analyzed and mapped along the entire compositional spread. A distinctive photocurrent peak was detected at 21.9 atom % Fe, and its appearance was correlated to the higher amount of hematite present in the library at this specific composition together with a specific WO3 crystallographic orientation ((222) orthorhombic or (400) monoclinic). This finding is confirmed by qualitative and quantitative XPS surface analysis at the photocurrent peak position in the material library. Thus the enhancement of the photocurrent cannot be exclusively attributed to certain surface modifications since only hematite was found on the library surface at the peak composition.
authors.affiliation: Institute for Chemical Technology of Inorganic Materials, and ‡Christian Doppler Laboratory for Combinatorial Oxide Chemistry at Institute for Chemical Technology of Inorganic Materials, Johannes Kepler University Linz , Altenberger Strasse 69, 4040 Linz, Austria.
authors.forename: Jan Philipp
authors.initials: JP
authors.lastname: Kollender
authors.forename: Andrei Ionut
authors.initials: AI
authors.lastname: Mardare
authors.forename: Achim Walter
authors.initials: AW
authors.lastname: Hassel
mesh_terms: D004563:Electrochemistry / Q000295:instrumentation; D004867:Equipment Design; D005290:Ferric Compounds / Q000737:chemistry*; D008853:Microscopy / Q000295:instrumentation; D008855:Microscopy, Electron, Scanning; D010084:Oxidation-Reduction; D010087:Oxides / Q000737:chemistry*; D055668:Photochemical Processes; D014414:Tungsten / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D005290:Ferric Compounds; D010087:Oxides; C000499:ferric oxide; C511604:tungsten oxide; D014414:Tungsten