Effect of Pr, Gd Coating on Photocatalytic Activity and Upconversion Behavior of Bismuth Oxide Powder

• Main Authors: Kuan-hung TU, 杜冠宏
• Other Authors: Chin-Yi Chen
• Format: Others
• Language: zh-TW
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/56970065914316459726

碩士 === 逢甲大學 === 材料科學與工程學系 === 103 === Semiconductors can be expected to exhibit excellent photocatalytic effects under light irradiation at a wavelength longer than 600 nm by coating lanthanide. In our study, bismuth oxide particles were first synthesized via thermal decomposition； and subsequently, lanthanides, such as praseodymium (Pr) and gadolinium (Gd), were coated in different concentrations (1 mol% and 3 mol%) onto the surface of the bismuth oxide by precipitation and photochemical reduction methods. Finally, the as-coated powders were calcined at 600°C in air for 1 h to improve the crystallinity of Pr and Gd. The material characteristics were determined by X-ray diffractometry (XRD), scanning electron microscopy (SEM), UV-visible, photoluminescence (PL). And, methylation reagent was used as an representative organic pollutant to evaluate the photocatalytic activity of the composite powders under visible light irradiation (λ>420 nm).The morphology of precipitated coatings was unevenly distributed；Whereas, the morphology of photoreduced coating exhibited a core shell structure. The photocatalytic activity of bismuth oxide powder can be expected to be increased by coating Pr and Gd to enhance the electron-hole pair separation. Highest photocatalytic activity of bismuth oxide was obtained by coating 1.0 mol% lanthanide. Coating higher concentration of lanthanides, however, was not useful for the powders to absorb light in the long-wavelength region to improve the photocatalytic activity. In addition strongest fluorescence emission intensity was obtained by calcining the powder at 600°C. By observing the microstructural change, diffusion of the coated Pr and Gd in grain boundary of bismuth oxide influenced the grain size and crystal structure when the calcination temperature was elevated.