Shenghan Zhang

Photocurrent response and semiconductor characteristics of Ce-Ce2O3-CeO2-modified TiO2 nanotube arrays

We reported Ce and its oxide-modified TiO2 nanotube arrays (TNTs) and their semiconductor properties. The TNTs were prepared by anodic oxidation on pure Ti and investigated by electrochemical photocurrent response analysis. Then, the TNT electrodes were deposited of Ce by cathodic reduction of Ce(NO3)3 6H2O. After deposition, the TNT electrodes were fabricated by anodic oxidation at Eu2009=u20091.0 V(SCE) for various electricity as Ce-Ce2O3-CeO2 modification. The Ce-deposited TNTs (band gap energy Egu2009=u20092.92 eV) exhibited enhanced photocurrent responses under visible light region and indicated more negative flat band potential (Efb) compared with the TNTs without deposition. After anodic oxidation, the mixed Ce and its oxide (Ce2O3-CeO2)-modified TNT photoelectrodes exhibited higher photocurrent responses under both visible and UV light regions than the TNTs without deposition. The photocurrent responses and Efb were found to be strongly dependent on the contents of Ce2O3 and CeO2 deposited on TNTs. A new characteristic of Egu2009=u20092.1u2009±u20090.1 eV was investigated in the Ce2O3- and CeO2-modified photoelectrodes. X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) were also employed to characterize various modified TNTs photoelectrodes.

Comparison of the Solubility of ZnFe2O4, Fe3O4 and Fe2O3 in High Temperature Water

As the solubility is a direct measure of stability, this study compares the solubilities of ZnFe2O4, Fe3O4 and Fe2O3 in high temperature water. Through literature analysis and formula derivation, it is shown that it is reasonable to assume ZnFe2O4 and Fe(OH)3 coexist when ZnFe2O4 is dissolved in water. Results indicated that the solubility of ZnFe2O4 is much lower than that of Fe2O3 or Fe3O4. The low solubility of ZnFe2O4 indicates that it is more protectively stable as an anticorrosion phase. Moreover, the gap between the solubility of ZnFe2O4 and that of Fe3O4 or Fe2O3 was enlarged with an increase of temperature. This means that ZnFe2O4 is more protective at higher temperatures. Further analysis indicated that with the increase of temperature, the solubility of ZnFe2O4 changed little while those of Fe2O3 or Fe3O4 changed a lot. Little change of the solubility of ZnFe2O4 with increase of temperature showed that ZnFe2O4 is stable. The very low and constant solubility of ZnFe2O4 suggests that it is more protective than Fe2O3 and Fe3O4, especially in water at higher temperature.

Photoelectrochemical characterization of TiO 2 nanotube array for ammonia degradation by electrochemical impedance spectroscopy

Well-ordered TiO2 nanotube arrays are prepared by the electrochemical anodization on pure Ti surfaces in organic solution. TiO2 nanotube arrays have good photo response by the photocurrent tests. Photoelectrochemical characteristics of the TiO2 nanotube arrays are investigated by electrochemical impedance spectroscopy (EIS) in the ammonia degradation cell system. The extra bias potential can decrease the values of the electron-transfer resistance and increase the separation efficiency of photogenerated electron-hole pairs. The photoelectrocatalytic rate is highest at the bias potential of 0.1V. The detailed dynamics information of TiO2 nanotube arrays electrode concerning the double charged layer at the semiconductor/electrolyte interface are obtained by equivalent electrical circuit fitting to EIS spectra. The results reveal that the surface reaction step is the rate limiting step for the photoelectron-catalytic process of ammonia degradation.

Electrochemistry study on the environmental factors of pitting corrosion of type 304 stainless steel

The pitting breaking potential (Eb) and repassivation potential (Ep) of 304 stainless steel were studied by electrochemistry method. These potentials were highly affected by the concentration of chloride solution, pH and buffer capacity, which defined as environmental factors. The buffer capacity and the concentration of non-aggressive anions in the solutions show some effects on the pitting initiation and repassivation of stainless steel. The pitting Eb and Ep show a strong dependence on a parameter J as general environmental factor, which is defined as the product of concentration of aggressive anions and buffer capacity. Electrochemistry study on the environmental factors on pitting corrosion of 304 stainless steel is a new method to investigate the anti-corrosion ability of stainless steel.