The Preparation Of Wide Spectral Response TiO₂ And Their Electrophotocatalytic Performance

Titanium dioxide (TiO2) has been extensively investigated as a photoanode for photoelectrocatalytic (PEC) organic pollution abatement owing to its high activity, good chemical and photonic stability, and low cost.However, a drawback, regarding commercially available TiO2, is that it is mainly active in the UV that accounts for less than 5% of the total solar radiation. However, most reported surface-modified TiO2 photocatalysts for removal of recalcitrant organic pollutants were used in the format of suspensions mediated by powder species. In this case, technical problems arising from hard particle-fluid separation after photocatalytic reaction, difficult reuse and costly post processing limit its industrialization. Recently, TiO2-films are put into use frequently as for practical application. Furthermore, the application of an additional bias voltage can further accelerate charge separation and reduce unwanted charge recombination processes, and consequently promoting the photocatalytic oxidation degradation efficiency of pollutants, and the details are as follows:1. In this study, C@TiO2 nanoparticles were prepared by smoldering combustion sol-gel synthesis using urea as carbon source. The result indicated that an amorphous shell covering the crystalline core of the TiO2 nanoparticles developed a core/shell structure. The thickness of this shell is approximately 1 nm or even smaller. Visible-light driven C@TiO2 electrode films on a conducting substrate were fabricated and studied as photoanode for degradation of organic pollutant. The C@TiO2 films exhibited multiporous structure, extended visible light-harvesting, low electron transfer resistance, and promoted photocurrent response. As a proof-of-concept, we demonstrated that C@TiO2 photoanodes exhibited excellent PEC performance toward the degradation of organic pollutants such as rhodamine B (RhB) and 1-naphthol (1-NP) under visible light by applying a small bias voltage (1.0 V). In addition, the photocatalytic activity for RhB was retained after five cycles, implying the stability of the film and strong adhesion to the substrate.2. A simple chemical reduction method has been applied to synthesize of uniformly decorated Au/C@TiO2 nanoparticles. The morphology, composition and structure of nanoparticles were analyzed using various methods. It is noted that Au nanoparticles with the diameter of 2-9 nm were deposited on the surface of TiO2. As compared to C@TiO2, approximately 20-fold enhancement in the photocatalytic degradation rate for RhB was achieved over the optimized Au/C@TiO2 (the amount of Au:1.0 wt%). The remarkable enhancement of degradation rate can be attributed to some reasons:(1) Au nanoparticles generate a new absorption band in the visible region due to the surface plasmon resonance; (2) Au nanoparticles could act as an electron acceptor, thereby suppresse the photogenerated electron-hole recombination effectively; (3) It could reduce the redox potential and thus degradation activity was significantly enhanced. Moreover, the RhB removal rate for Au/C@TiO2 was well-maintained after five cycles under visible light irradiation, implying the stability and reusability of the material.