Room-Temperature Synthesis of Ni and Pt-Co Alloy Nanoparticles Using a Microreactor

Metal nanoparticles (NPs) are key materials used in a broad range of industries. Among the various synthetic routes of NPs, liquid-phase chemical reactions are promising because of their versatility in reaction conditions as well as their potential productivity. However, because the synthesis of NPs involves not only chemical reactions but also nucleation and growth processes, which are typically higher-order reactions in terms of the concentration, a small degree of nonuniformity in the concentration during mixing of reaction solutions can easily result in a wide size distribution of the resultant particles. A typical solution to this problem is to slow the rate of reactions compared with that of mixing; however, as a result, the synthetic processes often require long reaction periods and complex procedures. In this study, we applied a microreactor with excellent mixing performance to NP synthesis to simplify and intensify the processes. We synthesized nickel and platinum-cobalt alloy NPs as model materials. For the Ni NP synthesis, we demonstrated that the quick mixing provided by the microreactor enabled the precise control of the residence time, and consequently, monodispersed Ni NPs with an average size of 3.8 nm were synthesized. For the Pt-Co bimetallic system, the microreactor successfully produced Pt-Co alloy NPs, while batch-type synthesis with weaker mixing intensity resulted in a bimodal mixture of larger Pt NPs and smaller Co NPs. For both Ni and Pt-Co, monodispersed NPs were synthesized by simply mixing the reaction solutions in the microreactor at room temperature. These results demonstrate that the mixing process plays a key role in NP synthesis, and application of a microreactor enables the establishment of a facile and robust synthetic process.

Hydroxylamine Accelerates the Cycle of Fe(III)/Fe(II)-Cu(II)/Cu(I) to Enhance the Ability of Fe-Cu Bimetallic System to Activate Peroxymonosulfate to Degrade AO7

In this study, a new type of iron/copper bimetallic combined with hydroxylamine (HA) activated peroxymonosulfate (PMS) was constructed to treat organic pollutants. Selecting the azo dye AO7 as the representative of organic pollutants, the new system can achieve nearly 100% degradation of AO7 within 5 minutes. The Fe(Ⅲ)/Cu(Ⅱ)/HA/PMS system mainly generates SO4·- to achieve the degradation of AO7 in acidic environment, while neutral and alkaline environments rely on ·OH. The presence of hydroxylamine accelerates the cycle of Fe(Ⅲ)/Fe(Ⅱ) and Cu(Ⅱ)/Cu(Ⅰ) in the system, and enhances the degradation ability of the system for organic pollutants. The addition of trace Cu(Ⅱ) (1 μM) enhances the ability of a single Fe(Ⅲ)/HA/PMS system to degrade AO7 in neutral and alkaline environments without causing secondary copper pollution. The common inorganic anions Cl- and NO3- in water have almost no effect on the degradation of AO7 in the system. The constructed Fe(Ⅲ)/Cu(Ⅱ)/HA/PMS system is an efficient and clean organic pollutant wastewater treatment process, which has very promising application prospects.

Nickel-catalyzed Homo-coupling of Aryl Ethers with Magnesium Anthracene Reductant

Nickel-catalyzed reductive homo-coupling of aryl ethers has been achieved with Mg(anthracene)(thf)3 as a readily available low-cost reductant. DFT calculations provided a rationale for the specific efficiency of the diorganomagnesium-type two-electron reducing agent. The calculations showed that the dianionic anthracene-9,10-diyl ligand reduces the two aryl ether substrates resulting in the homo-coupling reaction through supplying the electrons to the Ni-Mg bimetallic system to form organomagnesium nickel(0)-ate complexes, which cause two sequential C–O bond cleavage reactions. The calculations also showed cooperative actions of Lewis-acidic magnesium atoms and electron-rich nickel atoms in the C–O cleavage reactions.

Bimetallic Metal-Organic Framework Mediated Synthesis of Ni-Co Catalysts for the Dry Reforming of Methane

Dry reforming of methane (DRM) involves the conversion of CO2 and CH4, the most important greenhouse gases, into syngas, a stoichiometric mixture of H2 and CO that can be further processed via Fischer–Tropsch chemistry into a wide variety of products. However, the devolvement of the coke resistant catalyst, especially at high pressures, is still hampering commercial applications. One of the relatively new approaches for the synthesis of metal nanoparticle based catalysts comprises the use of metal-organic frameworks (MOFs) as catalyst precursors. In this work we have explored MOF-74/CPO-27 MOFs as precursors for the synthesis of Ni, Co and bimetallic Ni-Co metal nanoparticles. Our results show that the bimetallic system produced through pyrolysis of a Ni-Co@CMOF-74 precursor displays the best activity at moderate pressures, with stable performance during at least 10 h at 700 °C, 5 bar and 33 L·h−1·g−1.