Excellent Interfacial Contact Research Articles

Carbon nanofiber–RuO2–poly(benzimidazole) ternary hybrids for improved supercapacitor performance

Carbon nanofiber–RuO2–poly(benzimidazole) ternary hybrid electrode material which integrates dual wall decoration and interfacial area tuning for supercapacitor applications has been devised based on a simple approach. This is achieved by decorating RuO2 nanoparticles of size ca. 2–3 nm along the inner and outer walls of a hollow carbon nanofiber (CNF) support (F-20RuO2). In the next step, a proton conducting polymer, phosphoric acid doped polybenzimidazole (PBI-BuI), interface is created along the inner and outer surfaces of this material. A 103% increase in the specific capacitance is obtained for RuO2–PBI hybrid material as compared to that of F-20RuO2 at the optimum level of the polymer wrapping. Apart from the high specific capacitance, the RuO2–PBI hybrid materials exhibit enhanced rate capability and excellent electrochemical stability of 98% retention in the capacitance. Such a remarkably high activity can be primarily attributed to the efficient dispersion of active sites achieved by properly utilizing inner and outer surfaces of CNF. Apart from this, the facile routes for ion transport created as a result of PBI incorporation coupled with excellent interfacial contact between the RuO2 and the electrolyte resulting in the improved utilization of the active material also contribute to the improved activity. In addition to this, the synergistic effects of pseudocapacitive contribution from both the PBI-BuI and RuO2 also contribute to the redefined performance characteristics.

Rapid Fabrication of an Inverse Opal TiO2 Photoelectrode for DSSC Using a Binary Mixture of TiO2 Nanoparticles and Polymer Microspheres

AbstractA rapid fabrication method of highly reflective TiO2 inverse opal (IO) film exhibiting controllable thickness, high TiO2 content, and excellent interfacial contact with glass substrate is presented. By inducing accelerated solvent evaporation during the colloidal self‐assembly process, a composite film of polystyrene (PS)/TiO2 has been directly fabricated on a fluorine doped tin oxide (FTO) glass substrate, which exhibits the highly ordered opaline structure of PS embedded into the TiO2 matrix. This hybrid fabrication path leads to the formation of layers with the preferred {111} face‐centered cubic (FCC) orientation parallel to the substrate and to produce a 1 cm2‐wide well‐ordered composite colloidal crystal film in less than 30 min. The film showed highly ordered FCC structure, particularly at the upper region, due to the induced solvent evaporation and exhibited a reliable light modulation at a reflectance mode. Regardless of the size of sacrificial PS microspheres, TiO2 IO films of controllable thickness were successfully formed by varying the moving speed of the fabrication cell. The binary aqueous dispersion of tailor‐made anatase TiO2 nanoparticles and monodisperse PS microspheres showed a high degree of dispersion stability under basic conditions. Hydrothermal treatment of the TiO2 dispersion favored the crystallinity of the coated film and provided small volume contraction after thermal calcinations. The high degree of dispersion stability enabled to increase TiO2 content in a binary mixture, which is more favorable toward the robust and large‐area IO film. The calcined films exhibited excellent mechanical robustness and intimate interfacial contact with the glass substrate. which in turn resulted in higher TiO2 content near the glass substrate. The TiO2 IO film was tested as a dye‐sensitized solar cell (DSSC) photoelectrode, and a single cell showed a relatively high photon‐to‐current conversion efficiency of 4.2%. The high TiO2 content of IO film and its good adhesion to the FTO subratrate remarkably improved in the performance of the solar cell compared to the previous investigations where post‐infiltration of TiO2 had been employed.

Chemical Stability of ZnO Nanostructures in Simulated Physiological Environments and Its Application in Determining Polar Directions

The in vitro chemical stability and etching of ZnO nanostructures in simulated physiological solution (SPS) were studied using electron microscopy. Calcium hydrogen phosphate thin layers were observed to be uniformly deposited on the surfaces of ZnO nanomaterials in SPS. Electron diffraction and high-resolution transmission electron microscopy revealed that the calcium hydrogen phosphate layers were amorphous and had excellent interfacial contact with the nanocrystals. ZnO nanostructures fabricated by thermal evaporation were found to survive much longer in SPS than those fabricated using a hydrothermal solution method. The shapes of the voids formed in the ZnO nanostructures by the etching in SPS can be used to deduce the polar directions of ZnO nanostructures.