The efficient preparation of non-precious metal nanocatalysts embedded in carbon nano/microtubes remains a considerable challenge. Herein, we report a facile self-template and carbonization strategy to fabricate nickel nanoparticle (NP) supporting N-doped carbon microtubes. Firstly, molybdenum trioxide (a-MoO₃) microrods are coated with polypyrrole (MoO₃@PPy) by a simple in situ polymerization route. Then, PPy@PDA-Ni²⁺ microtubes with a hollow structure are obtained by further coating the PDA-Ni²⁺ complex in ammonia solution. In contrast, the direct coating of MoO₃ microrods with PDA-Ni²⁺ under the same experimental conditions only leads to aggregated PDA-Ni²⁺ spheres. Moreover, nickel/N-doped carbon microtubes (Ni/NCMTs) can be obtained by a further heating treatment and highly graphitic carbon microtubes are achieved by etching the nickel nanoparticles. The hollow Ni/NCMTs exhibit excellent reduction activity on 4-nitrophenol (4-NP). Moreover, the size of Ni nanoparticles (Ni NPs) which can effectively control the catalytic performance of the as-prepared nanocomposites is facilely adjusted via changing the roasting temperature. Benefitting from the highly exposed surface, short diffusion distance, and homogeneous Ni NP dispersion, the Ni/NCMT catalyst exhibits an improved activity on 4-NP. This novel structure is helpful for further applications in hydrogen evolution reaction, supercapacitors and batteries.

中文翻译：

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用于制造支持N掺杂碳微管的镍纳米粒子的便捷自我模板和碳化策略†

高效嵌入碳纳米/微管中的非贵金属纳米催化剂的制备仍然是一个巨大的挑战。在这里，我们报告了一种简便的自我模板和碳化策略，以制造支持N掺杂碳微管的镍纳米颗粒（NP）。首先，通过简单的原位聚合途径用聚吡咯（MoO ₃ @PPy）涂覆三氧化钼（a-MoO ₃）微棒。然后，通过在氨溶液中进一步涂覆PDA-Ni ²⁺络合物，获得具有空心结构的PPy @ PDA-Ni ²⁺微管。相比之下，用PDA-Ni ²⁺直接涂覆MoO _3微棒在相同的实验条件下，只会导致PDA-Ni ²⁺球团聚。此外，可以通过进一步的热处理获得镍/ N掺杂的碳微管（Ni / NCMT），并且通过蚀刻镍纳米颗粒而获得高度石墨化的碳微管。中空的Ni / NCMT对4-硝基苯酚（4-NP）表现出优异的还原活性。此外，可以通过以下方法轻松调整可以有效控制所制备纳米复合材料催化性能的镍纳米颗粒（Ni NPs）的尺寸：改变烘烤温度。受益于高度暴露的表面，较短的扩散距离和均匀的Ni NP分散，Ni / NCMT催化剂对4-NP的活性有所提高。这种新颖的结构有助于在析氢反应，超级电容器和电池中的进一步应用。