Fang Tao, Huang Huiting, Feng Jianyong, Hu Yingfei, Guo Yongsheng, Zhang Shiying, Li Zhaosheng, Zou Zhigang
Collaborative Innovation Center of Advanced Microstructures, National Laboratory of Solid State Microstructures, Department of Physics, Nanjing University, Nanjing 210093, China.
College of Engineering and Applied Sciences, Nanjing University, Nanjing 210093, China.
Sci Bull (Beijing). 2018 Nov 15;63(21):1404-1410. doi: 10.1016/j.scib.2018.10.005. Epub 2018 Oct 12.
Metal nitrides are widely studied due to their outstanding physical properties, including high hardness, high thermal and chemical stability, low electrical resistivity etc. Generally, metal nitrides can be obtained from the direct reaction of metal and ammonia/nitrogen. However, some of the metal nitrides, such as TaN, cannot be synthesized by direct nitridation of metals. To achieve TaN, high-oxidation-state Ta precursors like TaO, NaTaO, TaS, KTaO, Ta(N(CH)) and TaCl have to be employed, which is a time-consuming and laborious process with the possibility of introducing undesirable impurities. Here taking TaN as an example, a facile carbonate-assisted one-step nitridation method is proposed, which enables the direct synthesis of high-oxidation-state metal nitride films from metal precursors under ammonia flow. The mechanism of the nitridation process has been studied, which carbon dioxide released from carbonates decomposition reacts with metallic Ta and assists the one-step conversion of metallic Ta to TaN. The as-prepared TaN film, after modified with NiFe layered double hydroxide, exhibits promising water splitting performance and stability. This method avoids the preoxidation process of metal precursors in high-oxidation-state metal nitride synthesis, and may facilitate the direct fabrication of other important metal nitrides besides TaN.
金属氮化物因其出色的物理性能而被广泛研究，这些性能包括高硬度、高热稳定性和化学稳定性、低电阻率等。一般来说，金属氮化物可通过金属与氨/氮的直接反应获得。然而，一些金属氮化物，如氮化钽，无法通过金属的直接氮化反应合成。为了制备氮化钽，必须使用高氧化态的钽前驱体，如氧化钽、偏钽酸钠、硫化钽、钽酸钾、三甲基钽和五氯化钽，这是一个耗时费力的过程，而且可能会引入不需要的杂质。这里以氮化钽为例，提出了一种简便的碳酸盐辅助一步氮化法，该方法能够在氨气流下由金属前驱体直接合成高氧化态金属氮化物薄膜。对氮化过程的机理进行了研究，碳酸盐分解产生的二氧化碳与金属钽反应，辅助金属钽一步转化为氮化钽。制备的氮化钽薄膜经镍铁层状双氢氧化物修饰后，表现出良好的析氢性能和稳定性。该方法避免了高氧化态金属氮化物合成中金属前驱体的预氧化过程，并且可能有助于除氮化钽之外的其他重要金属氮化物的直接制备。
