| Photocatalysis of TiO2has been considered as one of the most promising techniques for environmental elimination in the twenty-first century by using solar energy directly, which could not only solve the predicament of energy crisis, but also meet the urgent demand of pollution prevention. Compared with the thin film electrode, TiO2nano-tubes (TiO2NTs) originated from anodization was attractive due to the high ratio of surface and volume, exceptional size effect and intense light harvesting properties and possessed wide prospects in the field of solar energy conversion, water splitting and pollutants elimination. In this dissertation, several photoelectrodes based on the as-anodized TiO2NTs were fabricated by modification with noble Pd nano-crystallite and reduced graphene oxide, and N, S codoped TiO2nano-particle. Meanwhile, physicochemical properties, photoelectrochemical performances and photoelectrocatalytic activities of the modified TiO2NTs photoelectrodes were systematically investigated. In this dissertation, based on the aforementioned research contents, some mainly works were carried out.In order to solve the hard-separation and reuse of catalyst, well-aligned and highly-ordered TiO2NTs photoelectrode was fabricated by in-situ anodization of Ti foil through orthogonal experiment in this study. Subsequently, some critical fabricating parameters were systematically analyzed. Meanwhile, the effects of annealing temperature on the apparent morphologies, crystal structures, surface compositions and photoelectrochemical properties of TiO2NTs photoelectrode were investigated in detail. Furthermore, the enhanced mechanism for the photocatalytic degradation of methyl blue was proposed and discussed in detail. It was found that the optimized anodization potential, concentration of ammonium fluoride, anodization time, content of water in the electrolyte, reaction temperature and post-annealing temperature were20V,2h,0.5wt%,40%(V/V),40℃and500℃, respectively. Under the optimized conditions, a48.7%of photocatalytic efficiency for the degradation of methyl blue could be achieved within120min under35W Xenon light irradiation. Furthermore, the photocurrent density and photoconversion efficiency of TiO2NTs photlelectrode in the sodium sulfate electrolyte (0.1mol·L-1) containing methyl blue solution (5mg·L-1) were1.34and1.26times higher than those of TiO2NTs photoelectrode in singlet sodium sulfate electrolyte, respectively. Besides these,·OH was the dominate active species during the photocatalytic process, in which the contribution of·OH and h+were approximately95%and0.21%, respectively。In order to improve the separation efficiency of photogenerated charge carriers and visible light response, noble palladium nano-crystallite and reduced graphene oxide co-modified TiO2NTs (Pd-RGO/TiO2NTs) photoelectrode was successfully constructed by anodization method, followed by two-step electrodeposition strategy. Subsequently, scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron microscopy (XPS) and Ultraviolet-visible diffuse reflection spectrum (UV-vis DRS) were applied to study the apparent morphologies, crystal structures, surface compositions and light absorbance of Pd-RGO/TiO2NTs photoelectrode. Furthermore, photoelectrochemical properties of Pd-RGO/TiO2NTs photoanode were investigated through electrochemical workstation. Meanwhile, the evolvement rate of·OH radicals at photo-illuminated Pd-RGO/TiO2NTs photoelectrode/water interface has been detected by measuring the fluorescence derived by the reaction with terephthalic acid. Results showed that the optimized anodic electrodeposition potential and deposition time of RGO were+0.8V and10min, respectively, while for cathodic electrodeposition of Pd nano-crystallite were-0.8V and10min, respectively. Under the optimized conditions, a73.6%of photocatalytic efficiency for the degradation of methyl blue could be achieved. In addition, the photocurrent density, concentration of charge carriers and photoelectrocatalytic performance of TiO2NTs photoelectrode were significantly improved by modification with noble palladium nano-crystallite and RGO, which was ascribed to the enhancement of light absorbance and separation efficiency of photogenerated charge carriers.In order to further enhance the range of visible light response and separation efficiency of charge carriers, N, S codoped TiO2nano-particle decorated TiO2NTs photoelectrode has been successfully fabricated through anodization, followed by evaporation induced self-assembly (EISA) strategy. Subsequently, the apparent morphologies, crystal structures, surface compositions and light absorbance of N, S-TiO2/TiO2NTs photoelectrode were characterized by SEM, XRD, XPS and UV-vis DRS. In addition, the photoelectrochemical properties of N, S-TiO2/TiO2NTs photoelectrode were systematically investigated through electrochemical workstation. Furthermore, the evolvement rate of·OH radicals at photoilluminated N, S-TiO2/TiO2NTs photoelectrode/water interface was detected by measuring the fluorescence derived by the reaction with terephthalic acid. In addition, the enhanced mechanism for photocatalytic degradation of methyl blue was clarified in detail. It was found that the optimized additive concentration of thiourea, impregnation times and annealing temperature were1.25%,3times and500℃, respectively. Under the optimized conditions, a59.7%of photocatalytic efficiency for the degradation of methyl blue could be achieved. Besides these, the intense light absorbance, photoelectrochemical properties and separation efficiency of photogenerated charge carriers of TiO2NTs photoelectrode were greatly increased by modification with N, S-TiO2nano-particle, thereby leading to an improved photoelectrocatalytic performance.Finally, Pharmaceuticals and personal care products, such as diclofenac in aquatic environment, was selected and served as the target contaminant to evaluate the photoelectrocatalytic performances of the as-modified TiO2NTs photoelectrode. Results revealed that photocatalytic efficiencies of diclofenac were58.4%and61.4%for Pd-RGO/TiO2NTs and N, S-TiO2/TiO2NTs photoelectrode, respectively. Furthermore, photoelectrocatalytic performance of the as-fabricated N, S-TiO2/TiO2NTs photoelectrode could be clearly improved by posing an external potential of+0.4V. In addition, the photoelectrocatalytic degradations of diclofenac fitted well with the pseudo-first-order kinetics formula according to the Langmuir-Hinshelwood (L–H) model, in which the as-fabricated N, S-TiO2/TiO2NTs photoanode exhibited the highest photocatalytic efficiency with an apparent rate constant of0.1009h-1. Besides these,·OH, H2O2,·O2-and h+could all participated in the photoelectrocatalytic degradation of diclofenac, in which·OH radicals was the dominated active species. |
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