Preparation of anatase TiO2/Ti nanotube-like electrodes and their high photoelectrocatalytic activity for the degradation of PCP in aqueous solution

To further improve the photooxidation techniques for water and wastewater purification, we successfully prepared a new type of photoelectrode, a TiO2 nanotube electrode, first by a sol–gel method and then by treatment to form the tubular structure in NaOH aqueous solution. The structure, surface morphology and band gap energy of the Ti/TiO2 electrode were examined by X-ray diffraction (XRD), scanning electronic microscopy (SEM) and UV–vis absorption microscopy, respectively. The examination results indicated that anatase TiO2 was dominant in its composition and a significant blue-shift in the spectrum of UV–vis absorption was observed. The photoelectrochemical efficiency of the nanotube-like TiO2/Ti electrode has been determined in terms of photocurrent, degradation and mineralization of PCP. To investigate its potentials in environmental applications, we studied the degradation of pentachlorophenol (PCP) in aqueous solution using photoelectrocatalytic (PEC) processes. The results were compared with those of electrochemical process (EP) and photocatalysis (PC). A significant photoelectrochemical synergetic effect was observed. The kinetic constant of PEC degradation of PCP using TiO2 nanotube electrode was 64.7% higher than that using TiO2 film electrode. The dependences of the rate constants on various parameters in the photoelectrocatalytic process, such as applied potential, electrolyte and pH value were investigated in detail. Degradation efficiency increased with increasing applied bias potential and concentration of Na2SO4. PEC degradation of PCP was more favorable in acidic solution than in alkali solution. There was an optimum pH value in the PEC process.