Synthesis Of Carbon Doped Bismuth-Based Photocatalysts And Their Visible Light Driven NaPCP Degradation Performance

In recent years, more and more attention has been paid on the photocatalytic degradation of organic pollutants in water. Although titanium dioxide (TiO2) has a good activity and stability, it can only work under ultraviolet light (ca.4% of the solar spectrum). Therefore, many efforts have been dedicated to develop visible light photocatalytic materials for the better utilization of solar light. For instance, bismuth-based photocatalysts have received considerable attention as potential visible light photocatalytic materials.In this thesis, an effective carbon doping strategy was developed to modify bismuth oxide for its better visible light absorption, and more effective charge separation, as well as better performance in the photodegradation and complete mineralization of pollutants. We used bismuth nitrate and glucose as the precursors to prepare carbon-doped bismuth oxide with a mild solvothermal method. The effect of different doping amounts on the catalytic activity of photocatalyst was studied and further clarified through systematical characterizations. It was found that the carbon-doped bismuth oxide exhibited a broader visible light response than the undoped counterpart. We systematically studied the reactive species generation and the degradation path of NaPCP during the carbon-doped bismuth oxide photocatalysis. These results showed that the photogenerated holes were the major reactive species, while’OH also contributed to the NaPCP oxidation. The GC-MS analysis revealed the high yields of 2,3,5,6-tetrachloro-benzene-1,4-diol and 3, 4,5,6-tetrachloro-benzene-1,2-diol, suggesting that the hole-induced oxidative dechlorination was the major initial step of NaPCP decomposition. After being derivatized with silyl reagent, the small-molecule acids and alcohols as well as some intermediates of five-membered rings were detected.As a novel photocatalyst, bismuth oxychloride could only adsorb ultraviolet light. It is therefore of great significace to broaden its light responsive region for the purpose of organic pollutant removal under solar light. We employed NaPCP as the target pollutant to test the visible light photoreactivity of carbon doped bismuth oxychloride, and analyzed the intermediates with GC-MS. The intermediates included 2,3,5, 6-tetrachloro-benzene-1,4-diol,3,4,5,6-tetrachloro-benzene-1,2-diol,2,3,4, 6-tetrachloro-phenol,2,3,5,6-tetrachloro-phenol,2,3,4,5-tetrachloro-phenol,3, 4,5-trichloro-benzene-1,2-diol,3,4,6-trichloro-benzene-1,2-diol. When p-Benzoquinone was added as the ·O2- scavenger to probe the roles of ·O2- on the NaPCP degradation, the numbers of dechlorination products decreased and only 2,3,5, 6-tetrachloro-benzene-1,4-diol and 3,4,5,6-tetrachloro-benzene-1,2-diol were found. is interesting to find that the intermediates generated during the NaPCP degradation ove carbon doped bismuth oxychloride in the presence of ·O2- scavenger were the same a those over carbon doped bismuth oxide. We therefore conclude that superoxide anion ca promote NaPCP dechlorination effectively and change the pathway of degradation.The comparison between visible light driven NaPCP degradation over the tw samples revealed that the photogenerated hole mainly induced oxidative dechlorinatioi and subsequently oxidized the dechlorination intermediates, and hydroxyl radical coul also nonselectively oxidize these intermediates, while superoxide anion played a majo role in reductive dechlorination to increase the numbers of dechlorination products which would be easily oxidized by h+ and ·OH.