TiO₂-QDs/Nb₄N₅纳米花的控制合成及太阳光催化全解水析氢性能

Controllable Synthesis of TiO₂-QDs/Nb₄N₅ Nanoflowers and Its Property for Solar Photocatalytic Overall Water Splitting into Hydrogen

摘要: 本文以NbCl₅为前驱体，利用水热技术制备了Ti⁴⁺掺杂Nb₂O₅纳米花，再经高温氮化制得TiO₂-QDs/Nb₄N₅纳米花。考查Ti⁴⁺掺杂量、水热时间、氮化温度对样品光生载流子分离效率的影响规律，建立了TiO₂-QDs/Nb₄N₅纳米花的优化工艺，在Ti⁴⁺掺杂量1 wt%、水热时间3 h、氮化温度800℃时样品光电流为0.035 μA•cm⁻²，是Nb₄N₅纳米花(0.014 μA•cm⁻²)的2.5倍，载流子分离效率显著提升。在500 W氙灯模拟太阳光照射下，样品光催化全解水产氢活性为109.9 μmol•g⁻¹•h⁻¹，明显高于未修饰的Nb₄N₅样品(87.9 μmol•g⁻¹•h⁻¹)。2~3 nm TiO₂量子点修饰在Nb₄N₅表面形成TiO₂/Nb₄N₅局域异质结构，增强了从紫外到整个可见光区域的光吸收性能，促进了载流子高效分离，增大了比表面积及2~17 nm微介孔数量，增加了表面催化活性点位，协同提升样品太阳光催化全解水产氢活性。本文为进一步开发高性能Nb₄N₅基纳米光催化材料奠定了实验技术基础。

Abstract: TiO₂-QDs/Nb₄N₅ nanoflowers were obtained by high-temperature nitriding Ti⁴⁺-doped Nb₂O₅ nanoflowers prepared by hydrothermal synthesis method, using NbCl₅ as a precursor. Based on the effects of Ti⁴⁺-doping amount, hydrothermal time, and nitriding temperature on the separation efficiency of photogenerated carriers, an optimized process for TiO₂/Nb₄N₅ nanoflowers was constructed. When the condition of Ti⁴⁺-doping amount was 1 wt%, and the hydrothermal time was 3 h, and the nitridation temperature was 800˚C, the photocurrent density of the sample reached to 0.035 μA•cm⁻², which was 2.5 times that of Nb₄N₅ nanoflowers (0.014 μA•cm⁻²). The separation efficiency of charged carriers was improved significantly. Under simulated sunlight irradiation of 500 W Xenon lamp, the photocatalytic overall water splitting into hydrogen activity of TiO₂/Nb₄N₅ was 109.9 μmol•g⁻¹•h⁻¹, significantly higher than that of the unmodified Nb₄N₅ sample (87.9 μmol•g⁻¹•h⁻¹). 2~3 nm TiO₂-QDs modification formed TiO₂/Nb₄N₅ local hetero-structures, which enhanced the light absorption capability from UV to entire visible region, promoted the efficient separation of charged carriers, and increased the specific surface area and micro-mesopores of 2~17 nm. The surface catalytic active sites were increased. All the above factors led to an enhanced photocatalytic activity for overall water-splitting into hydrogen under simulated sunlight irradiation. This work lays an experimental technical foundation for further developing high-performance Nb₄N₅-based nanophotocatalysts.