Influence of post-treatment temperature of TNTa photoelectrodes on photoelectrochemical properties and photocatalytic degradation of 4-nonylphenol

TiO2/Ti Nanotube array (TNTa) photoelectrodes were prepared by galvanostatic and potentiostatic anodization technique, and annealed at different temperature. The morphology and structure were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman spectra. Optical properties and photoelectrochemical (PECH) properties were investigated by surface photovoltage (SPV), ultra UV–vis diffuse reflectance spectra (UV/vis/DRS), open-circuit potential (OCP) and transient photocurrent. Photodecomposition performances were evaluated by the yield of
• OH radicals and photocatalytic (PC) degradation rate of 4-nonylphenol (4-NP) under xenon light. The results showed that with the increase of post-treatment temperature, PECH and PC properties increased gradually and then decreased. The photocurrent densities, yield of ⁎OH radicals and photodecomposition rates of 4-NP were following the trend of TNT-823>TNT-873>TNT-773>TNT-673>TNT-973>TNT-298. When the annealing temperature was 823 K, the photoelectrodes were composed of mixed crystal structure and ordered nanotube array, which exhibited superior PECH properties. When the annealed temperature arrived to 973 K, the nanotube collapsed and the PECH and PC properties of TNTa photoelectrodes decreased. For TNT-823 photoelectrodes, after the assistant potential was applied, the degradation rate of 4-NP increased significantly from 77% to 97% after 120 min illumination.

Photophysical chemistry processes and the degradation of 4-NP on TNTa photoelectrodes was showed in the graphical. The overall scheme of TNTa photoelectrodes (A) movement of photoelectrons and holes without bias potentials;(B) movement of photoelectrons and holes at applied bias potentials; the local enlargement of the part in black open circle of (A) showed the mixed crystal effect. The number refers (1) transmission process of photoelectrons and holes; (2) Recombination process of photoelectrons and holes; Arrow represent move direction of photoelectons. A-anatase TiO2, R-rutile TiO2.Figure optionsDownload as PowerPoint slideHighlights
► Effect of annealed temperature on Morphology of TNTa photoelectrodes.
► Effect of annealed temperature on crystal structure of TNTa photoelectrodes.
► Effect of annealed temperature on Optical and PECH properties.
► PC and PEC degradation activity of 4-NP by TNTa photoelectrodes.
► Analysis of degradation mechanism of 4-NP on TNTa photoelectrodes.