The transition metal nitrides are promising catalyst in catalytic fields. The decrease of particle size is favourable to improve the catalytic ability, but its synthesis remains a challenge due to high calcination temperature in the synthesis. Here, we have reported the designed synthesis of cluster-like Co 4 N paticles (NPs) uniformly embedded in N-doped carbon microsphere (Co 4 N@NC) by controllable nitridation of a spherical Co-HQÀ S composed of Co 2 + and 8-hydroxy quinoline (8-HQ), and its used as efficient hydrogenation catalyst. The Co 4 N have less size about 3 nm benefited the confined effect of carbon matrix. The small size is favorable to develop the catalytic ability of Co 4 N and a protection by carbon can enhance its stability. The test indicated that Co 4 N/NC can act effective catalysts for the hydrogenation by taking the conversion of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) as model. The rate constant of 4-NP conversion is 1.14 min À 1 at 25°C (5 mg of catalyst), much higher than many non-noble metal catalyst and even comparable to noble metal catalysts. The Co 4 N/NC can be easily separated by a external magnet with good reuse performance. Importantly, the catalytic ability can be further enhanced by slight increase of the dose of catalyst, and/or reaction temperature. The combination of magnetic property and good catalytic ability makes the Co 4 N/NC large promising in catalytic fields.
A single-source precursor route is presented to prepare smallsized Ni particles (∼ 5 nm) uniformly embedded into SiO 2 sheet (Ni/SiO 2). The synthetic process involved the coordination of APTES (3-aminopropyltriethoxysilane) with Ni 2 + to form NiÀ Si precursor in high yield, followed by pyrolysis under NH 3 atmosphere. During the heating, the Si component in the NiÀ Si precursor was transformed into SiO 2 , which could restrict the in-situ generated Ni from aggregation, resulting in the formation of the small-sized Ni particles. Small size is conducive to promoting the catalytic performance, and meanwhile SiO 2 protection plays a vital role in improving stability. During aromatic nitro reduction, Ni/SiO 2 shows excellent catalytic performance, which can be separated conveniently by an external magnet after use. The route is indicative of designing other catalysts protected by SiO 2 due to the versatile coordination ability of APTES with other metal ions (Fe, Co, Cu, etc).
The effective catalysts for the liquid‐phase catalytic (reduction) reaction are constant pursued. Traditional powder catalysts usually suffered from the separation from reaction medium, the aggregation at higher temperature, and poor reused stability, which are not favorable for the practical application. Here, we have shown the cobalt‐nickel nitrides anchored on Nickel foam (NF) as low‐cost catalysts overcoming above disadvantages by taking the reduction of 4‐nitrophenol to 4‐aminophenol as model. The conversion can reach to 97.6% after the reaction for 5 minutes at 25 °C, being comparable to most non‐noble metal based catalysts. Notably, the catalyst can be manually separated from reaction medium benefited from anchoring nitrides on macroscopical NF substrate. The anchoring can endow the high stability and avoid loss during separation process, thus is especially favorable to give good recycled ability and to use at higher temperature. Indeed, the catalyst can be used at higher temperature (75 °C) to accelerate dramatically reaction (conversion close to 100% within 20 s). Moreover, the activity can be remained after sequential 20 times of catalytic reaction, which is superior to the catalysts ever reported. The catalyst is promising for the practical catalytic application.
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