Well-ordered and nanoporous anodic aluminum oxide (AAO) templates are fabricated through an anodization process by varying cell potentials. The pores of AAO templates are widened by etching in phosphoric acid for different times. Next, carbon nanotubes (CNTs) are directly grown on nanoporous alumina templates by chemical vapor deposition. Subsequently, aluminum is sputtered onto the nanoporous alumina templates with grown CNTs and then aluminum oxide is formed by anodizing. Finally, alumina is annealed at different temperatures. The longer the widening pore time, the larger the pore diameter and the higher the initial current density of depositing Co. The longer the widening pore time, the higher the capacitance; however, the operation voltage almost remains constant.

View full abstract

Anodic polarization of aluminum in three kinds of ionic liquids was studied by the constant-voltage rising rate method and constant-current method, with characterization by X-ray photoelectron spectroscopy. Both the capacity for passive-layer formation and the composition varied depending on the ionic liquid, applied voltage and holding time. A passive film consisting of Al₂O₃ and AlF₃ in which the concentration of AlF₃ became the highest at the Al₂O₃/Al interface was formed in 1-butyl-3-methylimidazolium trifluoromethylacetate (BMIm-TFA) at 40 V. In the case of 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide (BMIm-TFSA), no passive film was formed at 40 V. However, a passive film in which the concentration of AlF₃ reached its maximum at the electrolyte/Al₂O₃ interface was formed at 10 V, and the layer composition changed to pure Al₂O₃ when held at 10 V for 20 min. On the contrary, pure homogeneous Al₂O₃ film was formed in 1-ethyl-3-methylimidazolium lactate (EMIm-LAC) at 40 V. Although the oxygen source of the oxidation reaction was thought to be the small amount of water contained in the ionic liquids, the anion component of the ionic liquids appears to have had an important effect on the ability to form a passive layer and its composition.

View full abstract

In our previous paper (J. Power Sources, 183, 344 (2008)), we proposed the application of a pre-cycling treatment to a Li-rich solid-solution layered cathode (xLi₂MnO₃·yLi[Ni_0.5Mn_0.5]O₂·zLi[Co_1/3Ni_1/3Mn_1/3]O₂ where (x + y + z = 1)) before the charge/discharge cycling process to obtain enhanced capacities stable above 250 mAh g⁻¹. The aim of the present work is to reduce the duration of this pre-cycling process. The cycling performance dependence of Li_1−α[Ni_0.18Li_0.20+αCo_0.03Mn_0.58]O₂ on the pre-cycling processing parameters, such as the number of cycles, voltage limits, and current density was explored. The processing conditions were then optimized, which ultimately reduced the pre-cycling treatment time from one week to 6.5 h.

View full abstract

Internal reforming reaction at low temperature in micro tubular solid oxide fuel cell (SOFC) was investigated by electrochemical impedance spectroscopy and numerical simulation using FLUENT. A micro tubular cell was composed of NiO/(ZrO₂)_0.9(Y₂O₃)_0.1 anode-substrate, La_0.8Sr_0.2Ga_0.8Mg_0.2O_2.8 electrolyte, and La_0.6Sr_0.4Co_0.2Fe_0.8O₃ cathode. It was suggested that cell performance became lower in supplied 50% reforming gas composition at 873 K because of variation of current density and hydrogen partial pressure distribution along the cell axis direction. The reason was that steam reforming reaction rate was slow along the cell axis direction and shift reaction occurred mainly without CO electrochemical oxidation owing to heat radiation of the cell at lower temperature.

View full abstract

Supersaturated hydrogen and oxygen solutions of pH-neutral tap water were created through electrolysis and subsequently blended back together. The blended solution was monitored as a function of time with dissolved gas meters and time-lapse photography. While the pH of the blended anodic and cathodic electrolysis streams returned to neutral pH within seconds, the blended solution was observed to retain significantly elevated dissolved gas concentrations on a timescale of hours. The analysis of dynamic bubble formation along the surfaces of the container, along with dissolved gas measurements, indicates that exsolution of dissolved hydrogen gas takes place on a very similar timescale. The measured total mass balance of gas produced electrolytically suggests that while a significant fraction of gas is exsoluted immediately before mixing of the anodic and cathodic streams, there are dissolved gases that take hours to exsolute completely from an undisturbed solution. Additionally, these signatures were studied as a function of electrolysis current.

View full abstract