Synthesis of PbS/TiO2 nano-tubes photoelectrode and its enhanced visible light driven photocatalytic performance and mechanism for purification of 4-chlorobenzoic acid

In this study, highly ordered TiO2 nano-tubes (TiO2 NTs) were synthesized by anodization. Subsequently, PbS nanoparticles were successfully decorated onto the surface of TiO2 NTs by successive ionic layer adsorption and reaction strategy in the presence of lead acetate (Pb(Ac)(2)) and thiourea. Afterwards, morphologies and chemical structures of PbS/TiO2 NTs photoelectrode were systematically studied by scanning electron microscope (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Results showed that PbS nanoparticles were uniformly dispersed on the surface of TiO2 NTs, and a small amount of PbS nanoparticles gathered together. Besides, their optical properties were investigated by ultraviolet visible diffuse reflectance spectroscopy (DRS), transient photocurrent density, open potentials, electrochemical impedance spectroscopy (EIS) and Mott-schottky measurements. Compared with the pristine TiO2 NTs photoelectrode that only could utilize ultraviolet light, The PbS/TiO2 NTs photoelectrode presented absorption properties of visible light, which improved the utilization of solar energy. What's more, the photocatalytic degradation performance of PbS/TiO2 NTs photo electrode was studied by using 4-chlorobenzoic acid as the target pollutant, finding that 80.37% of 4-chlorobenzoic acid could be removed within 7 h. After these, based on the electrochemical and fluorescence spectra, the enhanced photocatalytic performance mechanism of PbS/TiO2 NTs was proposed. In addition, the PbS/TiO2 NTs possessed excellent stability for 4-chlorobenzoic acid degradation after consecutive utilization for five cycles. This study illustrated that the novel PbS/TiO2 NTs photoelectrode was a promising photocatalyst with many potential applications, which could be used in sewage treatment process. Most importantly, this study provided a theoretical support for the practical application of photocatalytic technology.