Qing Zheng

Photoelectrocatalytic COD determination method using highly ordered TiO2 nanotube array

This work focuses on the experimental studies of a photoelectrocatalytic method for COD determination in a thin-cell reactor based on a highly effective TiO(2) nanotube array electrode. The effect of preparation parameters on the photoelectrocatalytic performance of TiO(2) nanotube array electrodes including the electrolyte, anodic potential, anodic time, solution pH, calcination temperature and time was examined. The TiO(2) nanotube array electrode prepared in preparation parameters at 1% HF electrolyte solution, anodic potential 20V, anodic time 5min, calcination temperature 450 degrees C with highly photoelectrocatalytic performance was chosen as the working electrode. When it is used in a thin-cell photoeletrocatalytic reactor for COD determination, it requires about 1-5min to complete the oxidation of organics without further titration, much faster than the standard K(2)Cr(2)O(7) method (2-4h). It consumes very limited harmless and inexpensive supporting electrolyte, free from secondary pollution. A wide dynamic working range of 0-850mg/L can be achieved by this method, much wider than any other photoeletrocatalytic methods using TiO(2) nanoparticles or nanofilms in the reported literature. The effects of the water components were studied to propose the TiO(2) nanotube array method. Real sample analyses were also carried out and the COD value of real samples determined by this method agreed well with the standard dichromate method, and it shows good accuracy, stability and reproducibility.

Kinetics and Mechanisms for Photoelectrochemical Degradation of Glucose on Highly Effective Self-Organized TiO2 Nanotube Arrays

The kinetics and mechanisms of photoelectrochemical catalytic degradation of glucose on self-organized TiO2 nanotube arrays (TNAs) were investigated. A thin-layer cell was used to obtain an exhausted reaction condition with which an overall degradation process of glucose could be identified including surface reaction on TNAs and mass transfer from body solution to the diffuse layer. Current-time (Iph-t) and the corresponding differential coefficient profiles were used to analyze the micro-processes of photoelectrochemical catalytic degradation. The initially generated photocurrents on glucose degradation versus glucose concentrations fits well with Langmuir adsorption isotherm, I0ph = 0.00008c0/(1+0.69274c0)+0.00034. This confirmed the adsorption of glucose on TNAs film catalyst was a single molecule layer adsorption, and the photoelectrochemical catalytic degradation reaction kinetics on TNAs surface belonged to a first-order reaction. After the initial quick reaction, three consecutive micro kinetic processes were revealed by the differential coefficient profiles (dIph/dt-t) of the glucose degradation profiles (Iph-t).

Characterization and Mechanism of the Photoelectrocatalytic Oxidation of Organic Pollutants in a Thin-Layer Reactor

Abstract The characterization and mechanism of the photoelectrocatalytic oxidation of a typical endocrine disrupting chemical, bisphenol-A (BPA), on TiO2 nanotube arrays (TNAs) were investigated using a thin-layer reactor where BPA was rapidly and exhaustively oxidized. Physical parameters such as the photocurrent, the initial peak photocurrent, the exhaustive charge quantity, and the blank photocurrent were found to be related to the degradation rate and the reaction mechanism. The Langmuir equation was used to fit the relationship between the initial peak photocurrent response and the BPA concentration indicating the proportionality between the photocurrent responses and the adsorbed organic concentration. A first-order exponential decay fitting of transient photocurrent profiles indicated the validity of first-order organic degradation kinetics for the photoelectrocatalysis. These relationships were found to be valid for many other organics including urea, glycol, glumatic acid, tartaric acid, methanol, and diethanolamine. The quantitative relationship found in this study provides a theoretical foundation for the real-time determination of the degradability of toxic organics by photoelectrocatalytic sensors.

Photoelectrochemical degradation of methyl orange by TiO2 nanopore arrays electrode and its comparison with TiO2 nanotube arrays electrode.

Highly ordered TiO(2) nanopore arrays (TNPs) electrode was applied as an electrode material for photoelectrochemical (PEC) degradation of methylic orange (MO). As a comparison, the self-organized TiO(2) nanotube arrays (TNAs) electrode about 500 nm in length was fabricated by Ti anodization in 0.5 wt% HF-H(2)O solution. The COD removal rate and color removal rate for PEC degradation of MO using the TNPs electrode was found to be 9 and 7%, respectively, as high as that obtained for TNAs electrode when biased at 0.5 V. The results indicate that the fast electron separation and transport properties of TNPs electrode makes it possesses enhanced PEC performance for the degradation of MO. In addition, the color removal rate of MO by TNPs PEC process increased with increasing bias potential and electrolyte concentration, but decreased with the increasing pH value and initial concentration of the reaction solution.