具有光催化与光芬顿反应协同作用的2D/2Dα-Fe_(2)O_(3)/g-C_(3)N_(4)S型异质结用于高效降解四环素

Efficient Degradation of Tetracycline via Coupling of Photocatalysis and Photo-Fenton Processes over a 2D/2Dα-Fe_(2)O_(3)/g-C_(3)N_(4)S-Scheme Heterojunction Catalyst

构建具有高效电荷迁移效率和丰富活性位点的异质结光催化体系是提升光芬顿反应速率的有效途径。本研究通过简单的水热法合成了2D/2D结构的α-Fe_(2)0_(3)/g-C3N S型异质结光芬顿催化剂,并使用X射线衍射仪技术(XRD).透射电子显微镜(TEM).傅立叶变换红外吸收光谱(FTIR)和紫外-可见吸收光谱(UV-Vis)等分析手段对α-Fe_(2)0_(3)/g-C_(3)N_(4)的晶体结构、微观结构、化学组分和光学性质进行了详细的表征。通过在可见光照射下降解四环素,评测了α-Fe_(2)O_(3)/g-C_(3)N_(4)的催化活性。结果表明,光催化反应与芬顿反应的协同作用使α-Fe_(2)0_(3)/g-C_(3)N_(4)(1:1)展现出了优异的光芬顿催化活性:在可见光照射下,仅加入微量的双氧水便可辅助催化剂在20min内对四环素的降解率达到78%,其降解速率分别是单一的α-Fe_(2)0_(3)和g-C_(3)N_(4)的3.5倍和5.8倍。α-Fe_(2)0_(3)/g-C_(3)N_(4)复合材料优异的催化活性得益于在2D/2D S型电荷迁移机制上构建的光芬顿催化体系。2D/2D S型异质结能够显著促进电子和空穴的传输与分离,并为催化剂提供较大的比表面积和丰富的活性位点,同时还能保持复合材料最佳的氧化还原能力。此外,光催化反应促进了Fe^(3+)的还原,从而加速了芬顿反应中羟基自由基的产生。总之,本研究为构建高效、稳定的光芬顿催化体系提供了-条简单有效的途径。

Graphitic carbon nitride(g-C_(3)N_(4))has been widely used as a potential photocatalytic material for the removal of tetracycline from water.However,the poor visible light absorption ability and high recombination rate of the photogenerated charge significantly inhibit the catalytic activity of g-C_(3)N_(4).Therefore,facile methods to improve the photocatalytic efficiency of g-C_(3)N_(4)need to be developed.Hematite(α-Fe_(2)O_(3)),which has a good visible light absorption and corrosion resistance,is often used for photocatalysis and photo-Fenton reactions.Therefore,a two-dimension/two-dimension(2D/2D)S-scheme heterojunction constructed of g-C_(3)N_(4)andα-Fe_(2)O_(3)nanosheets could be expected to improve the degradation efficiency of tetracycline.In this study,2D/2D S-schemeα-Fe_(2)O_(3)/g-C_(3)N_(4)photo-Fenton catalysts were prepared using a hydrothermal strategy.The photo-Fenton catalytic activity ofα-Fe_(2)O_(3)/g-C_(3)N_(4)(α-Fe_(2)O_(3)50%(w))was significantly improved by the addition of a small amount of H2O2,removing 78%of tetracycline within 20 min,which was approximately 3.5 and 5.8 times the removal achieved usingα-Fe_(2)O_(3)and g-C_(3)N_(4),respectively.The high catalytic activity was attributed to the synergy between the photocatalysis and Fenton reaction promoted by the continuous Fe3+/Fe2+conversion over the 2D/2D S-scheme heterojunction.The 2D/2D S-scheme heterojunction was crucial in the fabrication of theα-Fe_(2)O_(3)/g-C_(3)N_(4)photocatalyst with a large surface area,adequate active sites,and strong oxidation-reduction capability.Furthermore,the photo-Fenton reaction provided additional hydroxyl radicals for the degradation of tetracycline with the aid of H2O2.The excess reaction product(Fe3+)was reduced to Fe2+by the photogenerated electrons from the conduction band ofα-Fe_(2)O_(3).The resulting Fe2+could participate in the photo-Fenton reaction.The morphological structures ofα-Fe_(2)O_(3)/g-C_(3)N_(4)were analyzed using transmission electron microscopy to demonstrate the formation of a 2D/2D structure with face-to-face contact,and the optical properties of the composites were measured using ultraviolet-visible diffuse reflectance spectroscopy.α-Fe_(2)O_(3)/g-C_(3)N_(4)possessed a significantly improved visible light absorption compared to g-C_(3)N_(4).Five sequential cyclic degradation tests and X-ray diffraction(XRD)patterns obtained before and after the reaction showed that theα-Fe_(2)O_(3)/g-C_(3)N_(4)composites possessed stable photo-Fenton catalytic activity and crystal structures.Transient photocurrent responses ofα-Fe_(2)O_(3)/g-C_(3)N_(4)demonstrated that the prepared composites exhibited a higher charge transfer efficiency compared to that of singleα-Fe_(2)O_(3)and g-C_(3)N_(4).In addition,according to the photoluminescence analysis and active species trapping experiments,a possible S-scheme heterojunction charge transfer process in the photo-Fenton catalytic reaction was proposed.This study provided a promising method for the construction of a high-performance photo-Fenton catalytic system to remove antibiotics from wastewater.