Sodium-doped carbon nitride nanotubes (Na_x-CNNTs) were prepared by a green and simple two-step method and applied in photocatalytic water splitting for the first time. Transmission electron microscopy (TEM) element mapping and X-ray photoelectron spectroscopy (XPS) measurements confirm that sodium was successfully introduced in the carbon nitride nanotubes (CNNTs), and the intrinsic structure of graphitic carbon nitride (g-C₃N₄) was also maintained in the products. Moreover, the porous structure of the CNNTs leads to relatively large specific surface areas. Photocatalytic tests indicate that the porous tubular structure and Na⁺ doping can synergistically enhance the hydrogen evolution rate under visible light (λ > 420 nm) irradiation in the presence of sacrificial agents, leading to a hydrogen evolution rate as high as 143 μmol·h⁻¹ (20 mg catalyst). Moreover, other alkali metal-doped CNNTs, such as Li_x-CNNTs and K_x-CNNTs, were tested; both materials were found to enhance the hydrogen evolution rate, but to a lower extent compared with the Na_x-CNNTs. This highlights the general applicability of the present method to prepare alkali metal-doped CNNTs; a preliminary mechanism for the photocatalytic hydrogen evolution reaction in the Na_x-CNNTs is also proposed.

中文翻译：

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钠掺杂的氮化碳纳米管，用于高效可见光驱动的制氢

采用绿色，简单的两步法制备了钠掺杂的碳氮化碳纳米管（Na _x -CNNTs），并首次将其应用于光催化水分解中。透射电子显微镜（TEM）元素映射和X射线光电子能谱（XPS）测量证实，已成功将钠引入了氮化碳纳米管（CNNTs）中，并且还保持了石墨碳氮化物（gC ₃ N ₄）的固有结构。在产品中。而且，CNNT的多孔结构导致相对大的比表面积。光催化实验表明，多孔管状结构和Na ⁺掺杂可以协同增强可见光下氢的析出率（λ> 420 nm）在牺牲剂的存在下照射，导致析氢速率高达143μmol·h ^-1（20 mg催化剂）。此外，还测试了其他掺杂碱金属的CNNT，例如Li _x -CNNT和K _x -CNNT。两种材料均被发现可以提高氢的释放速率，但与Na _x -CNNTs相比，程度较低。这突出了本方法制备碱金属掺杂的CNNTs的普遍适用性。还提出了Na _x -CNNTs中光催化氢释放反应的初步机理。