Preparation And Performance Of One-dimensional Amorphous Co-B-N-H And CuB₂₃ Nano-catalysts

Because of their superior performance in such applications as catalysis, energy storage, sensors, transistors, and biochips, one-dimensional (1D) nanomaterials (e.g., nanowires, nanorods, nanotubes, and nanoribbons) have been widely studied in recent years. It is well known that materials in amorphous states have high concentrations of unsaturated coordination sites owing to their isotropic structures. As a result, the activities of amorphous catalysts are superior to those of crystalline ones. Some researchers have focused on the noncrystalline metal-boron (M-B) alloys. Therefore, preparing 1D materials and focusing on their possible applications will have great significance in the future development for 1D nanomaterials.In this paper, we report the development of a method for preparing amorphous alloys of ID nanomaterials. We also study the connection between the composition, morphology, structure, and surface properties and catalytic chemical reactions, and we explore the application of 1D amorphous alloy nanomaterials in catalyzing the decomposition of hydrazine hydrate (N2H·H2O) and Heck coupling of inactivated alkyl halides and alkenes. The deactivation mechanism of materials was also studied. The main findings are as follows:(1) We successfully prepared with high specific surface area and catalytic properties Co-B-N-H nanowires as catalysis on decomposition of hydrazine hydrate (N2H4·H2O) using Co(NH3)62+ as precursor and Brij-58 as assembly agent by SPP method. And we explored the synthesis mechanism of nanowires and catalytic decomposition of hydrogen hydrazine hydrate. The results show that: ① The average length and width of the Co-B-N-H nanowires are about 800 nm and 25 nm, respectively. Specific surface area is as high as 172.4 m2g-1,and chemical formula is CoBo.358No.286H0.251. The average pore size and pore volume of nanowires were estimated to be 2.6 nm and 0.28 cm2g-2, respectively. The hysteresis loop exhibited in the nitrogen adsorption-desorption isotherms of the Co-B-N-H nanowires, which resembles the type-H2 IUPAC (International Union of Pure and Applied Chemistry) classification; ② Mechanisms of synthesis indicated that the processing time of SPP, type and concentration of surfactant agent, have an effects on the structure of Co-B-N-H nanowires. And the best SPP treatment time is 5min. Brij-58 is necessary to induce nanostructure formation. The best concentration is 0.05 M compared with the rests; ③ The nanowires were stable catalysts for N2H4 hydrolytic dehydrogenation, providing 133020 total turnovers in 30 h. Without the promotion of NaOH, the activation energy of the Co-B-N-H nanowires was 39.9 ± 1.5 kJ mol-1. The turnover frequency (TOF) of the nanowire catalyst was 76.0 (mol of H2 (mol of active Co min)-1), exhibiting 100% H2 selectivity for the decomposition of N2H4·H2O; ④ The typical coercivity (Hc), saturation magnetization (Ms), and remnant magnetization (Mr) of the Co-B-N-H nanowires at 298 K were 240.1 Oe, 44.5 e mug-1, and 13.2 e mug-1, respectively. So, it’s easy to recycle; ⑤ After deactivation of the nanowires, SPP is a promising approach to reactivate catalysts.(2) Using the solution plasma processing (SPP) method, we successfully synthesized one-dimensional amorphous CuB23 short nanotubes by [Cu(NH3)4]2+ and KBH4(polyethylene glycol) solution. It can be used in Heck coupling of inactivated alkyl halides and alkenes. The results showed that: ① Amorphous alloy CuB23 short nanotube’s average length, diameter and wall thickness are 50 nm,10 nm and 2 nm, respectively. It’s specific surface area is about 84.7 m2g-1. significantly greater than the conventional irregular CuB23 alloy (23.2 m2g-1); ② Under the media of N-methyl-2-pyrrolidone and Na22CO3 substrate, CuB23 short nanotubes can replace Pd, Ni complex to catalyze Heck coupling of inactivated alkyl halides and alkenes at 80 ℃. What’s more, no ligand is needed in this case, and 2 mol% of the catalyst was sufficient to catalyze the reaction, reaching the yield of 91%; ③ Amorphous alloy CuB23 short nanotubes can also be applied to catalyze alkyl bromides; ④ After reused 10 times, CuB23 short nanotubes only a slight loss of activity (8%).