Crack-free TiO(2) nanotube (NT) membranes were obtained by short time re-anodization of a sintered TiO(2) NT array on Ti foil, followed by dilute HF etching at room temperature. The resulting freestanding TiO(2) membranes were opaque with a slight yellow color having one end open and another end closed. The membranes were then fixed on transparent fluorine-tin-oxide glass using a thin layer of screen-printed TiO(2) nanoparticles (NPs) as a binding medium. It was found that low temperature treatment of the resulting NT/NP film under appropriate pressure before sintering at 450 °C was critical for successful fixation of the NT membrane on the NP layer. The resulting films with open-ends of NT membranes facing the NP layer (open-ends down, OED, configuration) exhibited better interfacial contact between NTs and NPs than those with closed-ends facing the NP layer (closed-ends down, CED, configuration). The cells with an OED configuration exhibit higher external quantum efficiency, greater charge transfer resistance from FTO/TiO(2) to electrolyte, and better dye loading compared to CED configurations. The solar cells with the OED configuration gave 6.1% energy conversion efficiency under AM1.5G condition when the commercial N719 was used as a dye and I(-)/I(3)(-) as a redox couple, showing the promise of this method for high efficiency solar cells.

Plasma electrolysis (PE) combines the characteristics of electrolysis and plasma discharges, creating high-energy-density plasmas that lead to intensive physical processes and chemical reactions on the working electrode. The authors have found that the physical processes and the chemical reactions could be decoupled under certain conditions, and a textured electrode surface could be created through a chemical-reaction-dominated process instead of an irregular porous surface produced by the physical-dominated interactions. A plasma fluid model for the chemical-reaction-dominated discharge is established with constraint conditions obtained from the experiments. This study aims to elucidate the plasma characteristics and the chemical reactions in cathodic PE. The modeling reveals that the plasma is highly electronegative, and the dominant neutral species are H ₂ and O ₂ dissociated from water vapor. The decoupling mechanism is attributed to the low surface tension, high viscosity and high boiling point of glycerol in the electrolyte, which suppress the localized intensive physical interactions and promote the formation of a stable vapor layer. The formation of textured surface is attributed to the anisotropic chemical etching by the reactive species generated in the plasmas.