摘要/Abstract
具有可控配位环境的高催化活性和选择性的稳定单金属位点催化剂的合成仍然具有挑战性. 本工作采用阳离子交换策略合成了两种具有不同配位结构的Cu单原子催化材料. 该策略主要依赖于硫化物的阴离子骨架和富含 N 的聚合物壳在高温退火过程中产生大量的S和N缺陷, 精确合成了富边缘S和N双修饰的单金属Cu位点催化材料. 在这两种材料, 一种Cu单原子具有硫(S)、氮(N)双配位, 一种Cu单原子只有单一的S配位. Cu中心原子的第一壳层配位数为4, Cu-S/N-C的结构为Cu-S1N3, Cu-S-C的结构为Cu-S4. 实验表明, S、N双修饰的Cu单原子材料在室温下催化硝基苯加氢过程中表现出较高活性. 反应20 min后, 在Cu-S/N-C催化下, 硝基苯加氢转化率达到100%, 循环使用5次后活性未见显著下降. 该发现为调节中心金属配位环境以提高单原子催化材料的性能提供了一种可行的方法.
关键词: 单原子催化材料, 铜掺杂碳材料, 催化加氢, 非均相催化
The synthesis of stable single-metal site catalysts with high catalytic activity and selectivity with a controllable coordination environment is still challenging. Due to the different electronegativity of different coordination atoms (N, P, S, etc.), adjusting the coordination atom type of the active metal center is an effective and wise strategy to break the symmetry of the electron density. We adopted a cation exchange strategy to synthesize two Cu single-atom catalytic materials with different coordination structures. This strategy can change the coordination environment of Cu single atom by changing the different organics wrapped around Cu-CdS. This strategy mainly relies on the anion skeleton of sulfide and the N-rich polymer shell to produce a large number of S and N defects during the high-temperature annealing process, and the precise synthesis of a single-metal Cu site catalyst material with rich edge S and N double modification. In these two materials, one single Cu atom has double coordination of sulfur (S) and nitrogen (N), and the other single Cu atom has only a single S coordination. The first shell coordination number of Cu central atom is 4, the structure of Cu-S/N-C is Cu-S1N3, and the structure of Cu-S-C is Cu-S4. The results show that the catalytic performance of Cu-S/N-C in the hydrogenation of nitrobenzene compounds is much better than that of Cu-S-C, that is, the Cu monoatomic materials with S and N double-modified metal sites has better hydrogenation activity than single S-modified metal sites. After 20 min of reaction, under the catalysis of Cu-S/N-C, the conversion rate of nitrobenzene reached 100%, and the activity did not decrease significantly after being recycled for 5 times. It shows that the Cu-S/N-C catalytic material with a single-atom structure we synthesized has good stability. This discovery not only provides a feasible method for adjusting the coordination environment of the central metal to improve the performance of single-atom catalytic materials, but also provides an understanding of the catalytic performance of heteroatom modification.
Key words: single-atom catalytic material, copper-doped carbon material, catalytic hydrogenation, heterogeneous catalysis
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