Zuoliang Sha

Influence of anodic oxidation parameters of TiO 2 nanotube arrays on morphology and photocatalytic performance

Titanium dioxide nanotube arrays (TNTAs) were fabricated by electrochemical anodization of Ti foils. The effects of electrolyte, applied voltage, duration of anodic oxidation tomorphology, and photocatalytic performance of TNTAs were investigated. TNTAs formed in electrolyte of glycol and DMSO tend to grow along radial direction with flimsy tube wall and weak adhesion on Ti substrate. Those in glycerol, however, easily achieve balance between growth rate and corrosion rate, form orderly arranged array of nanotubes with uniform diameter, moderate length, and strong adhesiveness with substrates then. Although the photocatalytic activity of Rh B degradation on TNTAs prepared in glycol and DMSO is higher than those prepared in glycerol, their convenience of recycling and recovery shows the opposite. The optimality condition of anodic oxidation for TNTAs with good morphology and photocatalytic performance was present, which may have potential application in the synthesis of composite nanoarrays.

Prepared MnO2 with different crystal forms as electrode materials for supercapacitors: experimental research from hydrothermal crystallization process to electrochemical performances

The aim of this study was to prepare manganese dioxide with different crystal forms through hydrothermal treatment of MnSO4·H2O–KMnO4 precursors at various precursor ratios, temperatures, time periods, and pH values. The effect of the preparation parameters on the crystal structure and electrochemical performance of MnO2 was also studied. The conditions for the preparation of each crystal of MnO2 were experimentally optimized. The results indicate that the varied parameters affect the crystal form of MnO2; the ratio of the precursor and reaction temperature are the significant factors affecting the crystal form of MnO2, and the reaction time and pH value mainly affect the integrity of crystallization. Moreover, the presence of the cations K+ and NH4+ assists the crystallization of α-MnO2. δ-MnO2 and amorphous MnO2 have higher specific capacitance. The specific capacitance is determined not only by the crystal form, but also by the parameters of hydrothermal treatment.

Demonstration of Uninvolvement of Ions for Double Layer Capacitance by Use of Latex Suspensions

Abstract Water molecules in aqueous solutions were demonstrated to participate in formation of electric double layer capacitance, as partly agrees with the Stern–Gouy–Chapman theory, which is quite different from current fabrication techniques of industrial double layer capacitors. This conclusion was supported firstly by invariance of capacitance to ionic concentrations and secondly by exhibiting the same capacitance values in ionic latex suspensions without free ions as those in conventional ionic solutions. The latex particles used were mono-dispersed polystyrene sulfonic acid, 3.33 μm in diameter. The latex suspension was deionized to show low ionic concentration of less than 0.01 mM. Ac-impedance data were obtained at parallel platinum wires without insulating shield in order to avoid stray capacitance at cracks between electrodes and shields. They were analyzed through the equivalent circuit of a series combination of solution resistance and the double layer impedance. The latter was composed of a parallel combination of the capacitance and resistance, both of which depended on frequency. The solution resistance was inversely proportional to the concentration of the ionic latex particles, whereas the parallel capacitance was independent of the concentrations.