磁性Co/TiB2室温高效催化氨硼烷产氢及串联降解有机污染物

通过熔盐法制备TiB₂载体，并采用简单的沉淀-沉积法制备了Co/TiB₂磁性可回收纳米催化剂，用于室温催化氨硼烷（NH₃BH₃）溶液产氢及串联降解对硝基苯酚（4-NP）及偶氮染料酸性橙7（AO7）、酸性红1（AR1）和甲基橙（MO）等有机污染物。采用X射线衍射、扫描电子显微镜、透射电子显微镜、X射线光电子能谱、振动样品磁强计等表征方法对催化剂的微观形貌和结构等进行分析。结果表明，Co纳米粒子均匀地分布在TiB₂载体表面，晶粒尺寸约为40 nm，并且被TiB₂载体包覆，具有典型的金属-载体强相互作用。Co/TiB₂表现出优异的室温催化NH₃BH₃溶液产氢活性，产氢速率为565.8 mol_H2·mol_cat^-1·h^-1。在串联降解有机污染物反应中，Co/TiB₂在7 min内催化4-NP氨基化的转化率接近100%，反应速率常数高达0.72 min^-1；降解AO7的反应速率常数在3种偶氮染料中最高（0.34 min^-1）。通过EPR-DMPO（EPR=电子顺磁共振，DMPO=5，5-二甲基-1-吡咯啉-N-氧化物）自由基捕获实验检测出Co/TiB₂+NH₃BH₃催化体系中产生大量的氢自由基（·H）。得益于·H的强还原性，Co/TiB₂+NH₃BH₃催化体系能够将4-NP氨基化为具有更高价值的对氨基苯酚（4-AP），同时能够还原偶氮染料分子中的显色基团偶氮基（—N=N—）。

Magnetic Co/TiB2 for Efficient Catalytic Hydrogen Production from Ammonia Borane and Tandem Degradation of Organic Pollutants at Room Temperature

TiB₂ support was prepared by molten salt method and Co/TiB₂ magnetic recyclable nano-catalyst was prepared by simple precipitation-deposition method, which was used for catalytic hydrogen evolution in ammonia borane (NH₃BH₃) solution at room temperature and synergistic degradation of p-nitrophenol (4-NP) and azo dye such as acid orange 7 (AO7), acid red 1 (AR1), methyl orange (MO), without light, heat, other external energy, and additives. The catalyst was characterized by X-ray diffraction, scanning electron microscope, transmission electron microscope, X-ray photoelectron spectroscopy, vibrating sample magnetometer, and other characterization methods. The results showed that Co nanoparticles were uniformly distributed on the surface of TiB₂ support, and the grain size was about 40 nm, which was coated by TiB₂ support with a typical strong metal-support interaction. Co/TiB₂ exhibited excellent catalytic activity for hydrogen evolution from NH₃BH₃ solution at room temperature, with a rate of hydrogen evolution at 565.8 mol_H2·mol_cat^-1·h^-1. In the cascade reaction of degrading organic pollutants, 4-NP amination was catalyzed by Co/TiB₂ with nearly 100% conversion within 7 min, and the reaction rate constant was up to 0.72 min^-1. The reaction rate constant of degrading AO7 was the highest among the three azo dyes (0.34 min^-1). A large number of hydrogen radicals (·H) was detected in the catalytic system of Co/TiB₂/NH₃BH₃ by EPR-DMPO (EPR=electron paramagnetic resonance, DMPO=5, 5-dimethyl-1-pyrroline N-oxide) free radical capture experiment. Due to the strong reducibility of ·H radical, the catalytic system of Co/TiB₂/NH₃BH₃ can aminate 4-NP into p-aminophenol (4-AP) and reduce the azo chromogen group (-N=N-) in azo dye molecules. At the end of the reaction, the catalyst could be recycled by introducing an external magnetic field to avoid secondary pollution to the water body.