石墨型氮化碳对氨硼烷放氢性能的影响

利用石墨型氮化碳(C₃N₄)和氨硼烷(NH₃BH₃,AB)球磨制备了AB-C₃N₄体系,发现C₃N₄的加入使AB放氢反应温度明显降低,但是副产物氨气浓度有所升高. 因此,利用LiBH₄改性的C₃N₄(LC₃N₄)同AB球磨合成出了AB-LC₃N₄体系,并采用X射线衍射、程序升温脱附-质谱联用、热重-差热分析及核磁共振等技术考察了该体系的脱氢性能. 结果表明,由于LC₃N₄的加入,AB的放氢反应温度明显降低,放氢反应速率加快,放氢诱导期缩短,同时抑制了副产物无机苯的生成. 另外,C₃N₄的化学修饰也降低了AB-LC₃N₄放氢过程中生成氨气的浓度. 动力学分析和核磁共振结果表明,AB-LC₃N₄分解过程依然遵循NH₃BH₂NH₃BH₄诱导的氨硼烷自分解机理.

Effects of graphitic carbon nitride on the dehydrogenation of ammonia borane

By ball milling carbon nitride (C₃N₄) and ammonia borane (AB), the AB-C₃N₄ system was successfully synthesized. It is shown that the dehydrogenation temperature of the AB-C₃N₄ system was obviously decreased. However, the concentration of byproduct ammonia was much higher than that of pristine AB. Thus, LiBH₄-modified C₃N₄ (LC₃N₄) was produced and employed to synthesize a AB-LC₃N₄ system. The dehydrogenation of the AB-LC₃N₄ system was investigated using X-ray diffraction, temperature-programmed desorption-mass spectrometry, thermogravimetry-differential thermal analysis, and nuclear magnetic resonance. The results show that the dehydrogenation temperatures of the AB-LC₃N₄ systems were reduced to a lower region compared with pristine AB. Moreover, byproduct borazine and the induction period were significantly suppressed. After LiBH₄ modification on C₃N₄, the other byproduct ammonia was also reduced in the dehydrogenation process. Dynamic analysis and NMR characterization results show that the decomposition mechanism of AB-LC₃N₄ still follows the self-decomposition of AB, which is induced by the formation of NH₃BH₂NH₃BH₄.