NOVEL 3D Fe₂O₃@ZnBi₂O₄ n-p HETEROJUNCTION WITH HIGH PHOTOCATALYTIC ACTIVITY UNDER VISIBLE LIGHT

A novel n-p Fe₂O₃@ZnBi₂O₄ (FZB) heterojunction with a unique 3D structure was fabricated in two simple steps to break down MB under visible light. First, the polymer gel combustion technique was employed to fabricate a 3D Fe₂O₃ framework. Next, a microwave-assisted precipitation approach was used to incorporate 3D ZnBi₂O₄ flakes onto the framework surface. As a result, the n-p FZB, with a Fe₂O₃/ZnBi₂O₄ molar ratio of 2:1, showed the highest photocatalytic activity, increasing the reaction rate by 4.2 times compared to Fe₂O₃ and 2.8 times compared to ZnBi₂O4. Exposure to light for 100 min at a concentration of 0.7 g/L FZB catalyst and pH = 9 led to the breakdown of more than 95% of the 50 ppm MB solution. In addition, the photodegradation of MB by n-p FZB increased the reaction rate by 2.15 times by adding hydrogen peroxide (H2O2), which is known as the photo-Fenton reaction. The efficacy showed remarkable photocatalytic activity, which increased the reaction rate by 5.95 times when using persulfate was used. Finally, after an examination of the energy band structure of the materials and the findings regarding the function of the oxidizing sites in the photocatalytic process, a reaction mechanism was proposed.一种具有独特三维结构的新型n-p型Fe₂O₃@ZnBi₂O₄（简称FZB）异质结，通过两步简易法制备得到，可在可见光下降解亚甲基蓝（MB）。首先采用聚合物凝胶燃烧法制备三维Fe₂O₃骨架；随后通过微波辅助沉淀法将三维ZnBi₂O₄纳米片负载至该骨架表面。结果表明，当Fe₂O₃与ZnBi₂O₄的摩尔比为2:1时，该n-p型FZB异质结展现出最优的光催化活性，其反应速率分别为纯Fe₂O₃的4.2倍、纯ZnBi₂O₄的2.8倍。在催化剂投加浓度为0.7 g/L、pH=9的条件下光照100 min，可使50 ppm的MB溶液降解率超过95%。此外，向反应体系中添加过氧化氢（H₂O₂）后，n-p型FZB异质结对MB的光降解反应速率提升2.15倍，该体系即为光芬顿反应。当引入过硫酸盐时，该催化体系的反应速率进一步提升5.95倍，彰显出优异的光催化效能。最后，通过对材料能带结构以及光催化过程中氧化位点作用机制的分析，本文提出了该体系的光催化反应机理。