TY - JOUR

T1 - Solid State Fluorination on the Minute Scale: Synthesis of WO3−xFx with Photocatalytic Activity

AU - Lange, Martin Alexander

AU - Krysiak, Yaşar

AU - Hartmann, Jens

AU - Dewald, Georg

AU - Cerretti, Giacomo

AU - Tahir, Muhammad Nawaz

AU - Panthöfer, Martin

AU - Barton, Bastian

AU - Reich, Tobias

AU - Zeier, Wolfgang G.

AU - Mondeshki, Mihail

AU - Kolb, Ute

AU - Tremel, Wolfgang

N1 - Funding information: M.A.L. is recipient of a Carl?Zeiss?fellowship. This research was supported by a grant from the Deutsche Forschungsgemeinschaft within the priority program Manipulation of Matter Controlled by Electric and Magnetic Fields: Towards Novel Synthesis and Processing Routes of Inorganic Materials (SPP 1959). Use of the Advanced Photon Source at Argonne National Laboratory was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE?AC02?06CH11357. M.A.L. is recipient of a Carl-Zeiss-fellowship. This research was supported by a grant from the Deutsche Forschungsgemeinschaft within the priority program Manipulation of Matter Controlled by Electric and Magnetic Fields: Towards Novel Synthesis and Processing Routes of Inorganic Materials (SPP 1959). Use of the Advanced Photon Source at Argonne National Laboratory was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.

PY - 2020/3/1

Y1 - 2020/3/1

N2 - Solid state reactions are notoriously slow, because the rate-limiting step is diffusion of atoms or ions through reactant, intermediate, and product crystalline phases. This requires days or even weeks of high temperature treatment, consuming large amounts of energy. Metal oxides are particularly difficult to react, because they have high melting points. The study reports a high-speed solid state fluorination of WO3 with Teflon to the oxyfluorides WO3–xFx on a minute (<10 min) scale by spark plasma sintering, a technique that is used typically for a high-speed consolidation of powders. Automated electron diffraction analysis reveals an orthorhombic ReO3-type structure of WO3–xFx with F atom disorder as demonstrated by 19F magic angle spinning nuclear magnetic resonance spectroscopy. The potential of this new approach is demonstrated by the following results. i) Mixed- valent tungsten oxide fluorides WO3–xFx with high F content (0 < x < 0.65) are obtained as metastable products in copious amounts within minutes. ii) The spark plasma sintering technique yields WO3–xFx nanoparticles with high photocatalytic activity, whereas the corresponding bulk phases obtained by conventional solid-state (ampoule) reactions have no photocatalytic activity. iii) The catalytic activity is caused by the microstructure originating from the processing by spark plasma sintering.

AB - Solid state reactions are notoriously slow, because the rate-limiting step is diffusion of atoms or ions through reactant, intermediate, and product crystalline phases. This requires days or even weeks of high temperature treatment, consuming large amounts of energy. Metal oxides are particularly difficult to react, because they have high melting points. The study reports a high-speed solid state fluorination of WO3 with Teflon to the oxyfluorides WO3–xFx on a minute (<10 min) scale by spark plasma sintering, a technique that is used typically for a high-speed consolidation of powders. Automated electron diffraction analysis reveals an orthorhombic ReO3-type structure of WO3–xFx with F atom disorder as demonstrated by 19F magic angle spinning nuclear magnetic resonance spectroscopy. The potential of this new approach is demonstrated by the following results. i) Mixed- valent tungsten oxide fluorides WO3–xFx with high F content (0 < x < 0.65) are obtained as metastable products in copious amounts within minutes. ii) The spark plasma sintering technique yields WO3–xFx nanoparticles with high photocatalytic activity, whereas the corresponding bulk phases obtained by conventional solid-state (ampoule) reactions have no photocatalytic activity. iii) The catalytic activity is caused by the microstructure originating from the processing by spark plasma sintering.

KW - automated diffraction tomography

KW - fluorination

KW - photocatalysis

KW - spark plasma synthesis

KW - tungsten oxyfluoride

UR - http://www.scopus.com/inward/record.url?scp=85079439465&partnerID=8YFLogxK

U2 - 10.1002/adfm.201909051

DO - 10.1002/adfm.201909051

M3 - Article

AN - SCOPUS:85079439465

VL - 30

JO - Advanced functional materials

JF - Advanced functional materials

SN - 1616-301X

IS - 13

M1 - 1909051

ER -