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Titanium dioxide (TiO(2)) has often served as a model substrate for experimental sorption studies of environmental contaminants. However, various forms of Ti-oxide have been used, and the different sorption properties of these materials have not been thoroughly studied. We investigated uranium sorption on some thoroughly characterized TiO(2) surfaces with particular attention to the influence of surface area, surface charge, and impurities. The sorption of U(VI) differed significantly between samples. Aggressive pretreatment of one material to remove impurities significantly altered the isoelectric point, determined by an electroacoustic method, but did not significantly impact U sorption. Differences in sorption properties between the various TiO(2) materials were related to the crystallographic form, morphology, surface area, and grain size, rather than to surface impurities or surface charge. In-situ attenuated total reflection Fourier-transform infrared (ATR FT-IR) spectroscopic studies showed that the spectra of the surface species of the TiO(2) samples are not significantly different, suggesting the formation of similar surface complexes. The data provide insights into the effect of different source materials and surface properties on radionuclide sorption.

The race for better electrochemical energy storage systems has prompted examination of the stability in the molybdate framework (MMoO; M = Mn, Co, or Ni) based on a range of transition metal cations from both computational and experimental approaches. Molybdate materials synthesized with controlled nanoscale morphologies (such as nanorods, agglomerated nanostructures, and nanoneedles for Mn, Co, and Ni elements, respectively) have been used as a cathode in hybrid energy storage systems. The computational and experimental data confirms that the MnMoO crystallized in β-form with α-MnMoO type whereas Co and Ni cations crystallized in α-form with α-CoMoO type structure. Among the various transition metal cations studied, hybrid device comprising NiMoO vs activated carbon exhibited excellent electrochemical performance having the specific capacitance 82 F g at a current density of 0.1 A g but the cycling stability needed to be significantly improved. The specific capacitance of the NiMoO electrode material is shown to be directly related to the surface area of the electrode/electrolyte interface, but the CoMoO and MnMoO favored a bulk formation that could be suitable for structural stability. The useful insights from the electronic structure analysis and effective mass have been provided to demonstrate the role of cations in the molybdate structure and its influence in electrochemical energy storage. With improved cycling stability, NiMoO can be suitable for renewable energy storage. Overall, this study will enable the development of next generation molybdate materials with multiple cation substitution resulting in better cycling stability and higher specific capacitance.

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