Bridging experiment and theory: enhancing the electrical conductivities of soft-templated niobium-doped mesoporous titania films

Abstract

Combined experimental & theoretical approach for the elucidation of structure–property relations in niobium-doped mesoporous titania.

ALD‐Coated Mesoporous Iridium‐Titanium Mixed Oxides: Maximizing Iridium Utilization for an Outstanding OER Performance

“…Impedance spectroscopy is a powerful tool to assess the electrical conductivities of thin films deposited on insulating substrates. [31,49] In accordance with our previous results [20,30] for as-prepared mesoporous films prior to catalytic testing, the addition of 15 mol% Ir to TiO x leads to well-conductive materials (≈10 -2 S cm -1 for mp. IrTiO x ), which enables efficient charge transfer kinetics at the electrode during OER catalysis.…”

“…[26,27] The general synthesis concept relies on the application of a soft template, e.g., an amphiphilic blockcopolymer, as a porogen to produce fully interconnected pore networks with adjustable pore diameters. [26][27][28] The EISA method is well-established and has been previously used to synthesize various mesoporous metal oxides such as SiO 2 , [26] TiO 2 , [29] IrO x , [10] mixed metal oxides such as IrTiO x [20,30] or Nb-doped TiO x , [31] and composite materials such as Pd/TiO 2 , [32] among others.…”

Effect of Doping on Rutile TiO2 Surface Stability and Crystal Shapes

“…Ti substitution leads to defect states that may cross the Fermi level so that the doped systems have a conducting ground state. Experimentally, highest conductivity was observed for 25–33 % Nb/Ti substitution, which was also confirmed by theoretical calculations [38] . In our models, 50 % of the Ti atoms of rutile are substituted by M=Sc, Y, V, Nb, or Ta, so that the primitive bulk unit cells have the composition MTiO 4 .…”

“…Experimentally, it was observed that 25-33 % Nb/Ti substitution leads to the highest electrical conductivity. [38] In order to reduce the number of possible cation configurations in our models, we replaced every second Ti atom by the previously mentioned transition metals M and obtained primitive unit cells with MTiO 4 stoichiometry, compare Figure 1, or, for the primitive unit cells, Figure S1 in the Supporting Information. Even though methods for modeling random cation distributions exist, for example, special quasirandom structures, [43] we decided to apply symmetry restrictions to our surface models in order to avoid artificial dipole moments.…”

Influence of Phase Composition and Pretreatment on the Conversion of Iron Oxides into Iron Carbides in Syngas Atmospheres

“…Briefly, the model-type oxide films are prepared using the well-established EISA approach with block-copolymer micelles as soft template for the introduction of a mesoporous structure [22,23]. It enables synthesis of well-ordered mesoporous thin films with tunable composition, crystallite size and wall thickness [24,25]. The as-synthesized ordered mesoporous films enable a precise investigation of bulk-averaged information (e.g., XRD) and study of local changes in the phase composition, i.e., domain growth on the nanometer scale using microscope methods such as SEM, TEM, and SAED.…”