六面体形Ta₂O₅@Ta₃N₅的熔盐辅助高温氮化控制合成及可见光解水析氢性能

Controlled Synthesis of Hexahedron Ta₂O₅@Ta₃N₅ by Molten-Salt-Assisted High-Temperature Nitridation and the Performance for Hydrogen Evolution from Water-Splitting by Visible Light

摘要: 利用混合熔盐辅助高温氮化成功制备了六面体形Ta₂O₅@Ta₃N₅光催化剂。调控助熔剂种类、混合熔盐配比、Ta₂O₅与混合熔盐比例等工艺条件，制备出六面体形Ta₂O₅，确定最佳制备条件为NaCl和Na₂CO₃混合熔盐(摩尔比为1:1)作为助熔剂，Ta₂O₅和混合熔盐比例为1:3 (质量比)，再经过800℃氮化处理3 h，仍保持六面体拓扑结构，建立了分步控制合成工艺。以水热合成的无规则形貌Ta₂O₅为前驱体，利用混合熔盐辅助技术，经800℃氮化4 h制备出核壳异质结构的六面体形Ta₂O₅@Ta₃N₅，建立了晶面控制与异质结构建同步控制合成工艺；其光电流密度达到0.57 μA∙cm⁻²，是前者(0.28 μA∙cm⁻²)的2.03倍，比课题组前期制备的无规则形貌Ta₂O₅@Ta₃N₅提高了一个数量级，产氢活性为(709 μmol∙g⁻¹∙h⁻¹)，也远远高于无规则形貌Ta₂O₅@Ta₃N₅ (21.75 μmol∙g⁻¹∙h⁻¹)。六面体形貌的棱角改变体相电荷分布，以及Ta₃N₅/Ta₂O₅异质结构的构筑有效促进了光生电子空穴分离，提升了载流子分离效率，为进一步实现表面空间选择性修饰助催化剂奠定了实验基础。

Abstract: Hexahedral Ta₂O₅@Ta₃N₅ photocatalyst was successfully prepared by high temperature nitriding assisted by mixed molten salt. Hexahedral Ta₂O₅ was prepared by adjusting the flux type, the ratio of mixed molten salt and the ratio of Ta₂O₅ to mixed molten salt and other technological conditions. The optimal preparation conditions were as follows: NaCl and Na₂CO₃ mixed molten salt (molar ratio: 1:1) as flux, and the ratio of Ta₂O₅ to mixed molten salt was 1:3 (mass ratio). After being nitridated at 800˚C for 3 h, the hexahedral topological structure was still maintained. A step-by-step controlled synthesis process was established. Using the irregular morphology of Ta₂O₅ synthesized by hydrothermal method as precursor, the hexahedron Ta₂O₅@Ta₃N₅ with core-shell heterostructure was prepared by nitridation at 800˚C for 4 h using mixed molten salt assisted technology. The synthesis process of crystal plane control and heterostructure construction was established. The photocurrent density reached 0.57 μA∙cm⁻², which was 2.03 times that of the former (0.28 μA∙cm⁻²), and was an order of magnitude higher than that of the previous irregular morphologies Ta₂O₅@Ta₃N₅. The activity of hydrogen production was 709 μmol∙g⁻¹∙h⁻¹, which was much higher than that of the irregular morphology (21.75 μmol∙g⁻¹∙h⁻¹). The edges and angles of the hexahedral morphology change the volume phase charge distribution, and the construction of Ta₃N₅/Ta₂O₅ heterostructure effectively promotes the hole separation of photogenerated electrons, improves the efficiency of carrier separation, and lays the experimental foundation for the further realization of surface space selective modification of co-catalyst.