Rare Earth Doped Core-shell Structure Bismuth Vanadate Nanofibers with Enhanced Photocatalytic Performance
DescriptionEnvironmental pollution and energy crisis are major global challenges in the 21st century that need to be resolved. Conventional pollution treatment methods, such as direct incineration and microbial treatment, have low efficiencies and often have secondary pollution leading to incomplete decomposition of pollutants into harmless products. In contrast, photocatalysis has received much attention recently because it can utilize effectively clean and renewable solar energy, converting the energy directly into chemical energy to decompose organic pollutants. The photocatalytic reaction depends on the catalyst ability to create electron-hole pairs, which in turn generate free radical hydroxyl (∙OH) and radical oxygen (∙O2-) with very strong oxidation power, destroying bacteria and decompose other organic contaminants into carbon dioxide and water. The process is environmentally friendly, energy saving, relatively cheap, and sustainable, and has a wide range of applications, from water treatment, anti-bacteria, deodorization, dirtiness prevention, to energy conversion.Thus, investigation of the structure and development of photocatalyst has been an important strategic plan in many countries. Photocatalyst based on semiconductor material is attractive, and the ideal photocatalyst should be inexpensive, non-toxic, stable, and exhibit strong photosensitivity and photoactvity. Semiconductor with the required bandgap energy to catalyze the chemical reactions is the best compromise between catalytic performance and stability in an aqueous medium. Titanium dioxide (TiO2) and zinc oxide (ZnO) both exhibit high photosensitivity and large bandgap (~3.0 eV), and the characteristics of low price, strong oxidizing ability, non-toxicity, and are the mainstream photocatalysts studied and used in the control and degradation of several environmental contaminants. However, their uses have some drawbacks, such as short charge carrier recombination (nanoseconds), and limited driving reaction wavelength due to the band edge absorption threshold, utilizing only a few percent of the available solar energy. Also, the photocatalysts are in powder forms and can agglomerate easily, making recycling difficult and even cause secondary pollution.Recently, bismuth vanadate (BiVO4) has attracted much attention as a highly responsive and broad wavelength driving reaction range photocatalyst. BiVO4 is low cost, stable, non-toxic, resistance to photo-corrosion, and has good dispersibility and low bandgap (~2.4 eV) enabling good visible light absorption. However, up to now the efficiency obtained is below what is expected due to the slow electron mobility and fast recombination of the photogenerated electrons and holes. Hence, the undesirable electron-hole recombination must be suppressed in order to improve the performance, and this can be achieved by facilitating charge separation along the charge transfer pathways.In this project, pioneering work combining photocatalyst and nanotechnology to overcome the limitations will be developed. Coaxial electrospinning (CL) process will be used to fabricate coreshell structure nanofibers with BiVO4 as the base material. The core structure is a composite of rare earth (RE)-doped BiVO4 in polymethyl methacrylate (PMMA), and the shell structure is noble metal silver (Ag) nanoparticles in polyacrylonitrile (PAN). The photocatalytic activity and efficiency will be enhanced by the electrospun nanofibers with large specific surface area and high porosity; at the same time the porous structure can promote the enrichment of the reactant molecules on the catalyst surface and reduce secondary pollution. The incorporation of RE in BiVO4 and loading of Ag will further promote the separation of photogenerated electrons and holes and improve the photocatalytic performance. In particular, the RE can enrich the energy level structure and extend the wavelength driving reaction range. The composite Ag:RE-doped BiVO4 core-shell nanofibers will enhance the efficiency by as much as 70% compared to undoped BiVO4 powders, and provide new reference in the development of photocatalytic technology and application.
|Effective start/end date||1/01/20 → …|