The charge storage mechanism of nanostructured intercalation materials such as anatase (TiO₂) is still a matter of intense research, because it provides the basis for designing electrochemical energy storage and conversion materials. In this work, we addressed the relationship between conductivity and the charge storage mechanism exemplified with nanostructured Nb-doped TiO₂. Nanoparticles of Nb-doped TiO₂ were prepared by a novel two-step solvothermal process based on tert-amyl alcohol as the solvent. Several state-of-the-art techniques, including X-ray diffraction along with Rietveld refinement and Raman and X-ray photoelectron spectroscopy, were used to analyze the phase composition, the chemical oxidation state and the structure after doping with different niobium contents. Mesoporous Nb-doped TiO₂ films with uniform pore sizes of 15 to 18 nm were produced by dip-coating employing these nanoparticles as building blocks. It is found that 5 at% Nb-doped TiO₂ exhibits the highest conductivity. The analysis of the peak currents in the cyclic voltammetry of the mesoporous films indicates that the pseudocapacitive current contribution varies with the conductivity in the same trend. This correlation can be described qualitatively by the changes in the space charge layer at the interface with varying carrier concentration. Such a finding implies that doping not only affects the charge storage in the bulk due to changes of kinetic parameters including the chemical diffusion coefficient and electronic conductivity, but also influences the surface-related storage mechanism of a given nanostructured material. These results further provide a valuable insight in searching for and designing materials applied in pseudocapacitors.

With the aid of ab initio molecular dynamics simulations, we investigate an ionic liquid (IL) mixture composed of three components 1-butyl-3-methylimidazolium [C₄C₁Im]⁺, tetrafluoroborate [BF₄]⁻, and chloride [Cl]⁻ without and with water. In the pure IL mixture, we observe an already complex network of interactions between cations and anions, and addition of water to the system even extends the complexity. Observed number integrals show that the coordination number between cations and anions is reduced in the system with water compared to that in the pure system. Further studies show that the Coulombic network of the strongly coordinating anion [Cl]⁻ is disturbed by water, while that of the weakly coordinating anion [BF₄]⁻ is not. These observations can also be confirmed by the Voronoi polyhedra analysis, which shows that the polar network of microheterogeneous IL collapses by the introduction of water. Hydrogen-acceptor interactions revealed that the [Cl]⁻ anions are transferred from being situated in the IL to the water continuum, while [BF₄]⁻ is almost unperturbed; these effects mainly influence the interplay of the ionic liquid network.

Imidazolium-based ionic liquids served to selectively methylate terminal chalcogenide ligands of chalcogenidometalate clusters [Sn ₁₀ S ₁₆ O ₄ (SMe) ₄ ] ⁴⁻ , [Mn ₄ Sn ₄ Se ₁₃ (SeMe) ₄ ] ⁶⁻ , and [Hg ₆ Te ₁₀ (TeMe) ₂ ] ⁶⁻ .