Carbocatalytic Oxidative Dehydrogenative Couplings of (Hetero)Aryls by Oxidized Multi-Walled Carbon Nanotubes in Liquid Phase.

HNO3 -oxidized carbon nanotubes catalyze oxidative dehydrogenative (ODH) carbon-carbon bond formation between electron-rich (hetero)aryls with O2 as a terminal oxidant. The recyclable carbocatalytic method provides a convenient and an operationally easy synthetic protocol for accessing various benzofused homodimers, biaryls, triphenylenes, and related benzofused heteroaryls that are highly useful frameworks for material chemistry applications. Carbonyls/quinones are the catalytically active site of the carbocatalyst as indicated by model compounds and titration experiments. Further investigations of the reaction mechanism with a combination of experimental and DFT methods support the competing nature of acid-catalyzed and radical cationic ODHs, and indicate that both mechanisms operate with the current material.

Comprehensive study to design advanced metal-carbide@garaphene and metal-carbide@iron oxide nanoparticles with tunable structure by the laser ablation in liquid.

Core-shell nanoparticles represent a class of materials that exhibit a variety of properties. By rationally tuning the cores and the shells in such nanoparticles (NPs), a range of materials with tailorable properties can be produced which are of interest for a wide variety of applications. Herein, experimental and theoretical approaches have been combined to show the structural transformation of NPs resulting to the formation of either NiFexCy encapsulated in ultra-thin graphene layer (NiFe@UTG) or Ni3C/FexCy@FeOx NPs with the universal one-step pulse laser ablation in liquid (PLAL) method. Analysis suggests that carbon in Ni3C is the source for the carbon shell formation, whereas the final carbon-shell thickness in the NPs originates from the difference between Ni3C and FexCy phases stability at room temperature. The ternary Ni-Fe-C phase diagram calculations reveal the competition between carbon solubility in the studied metals (Ni and Fe) and their tendency toward oxidation as the key properties to produce controlled core-shell NP materials. As an application example, the electrocatalytic hydrogen evolution current on the different NPs is measured. The electrochemical analysis of the NPs reveals that NiFe@UTG has the best performance amongst the NPs in this study in both alkaline and acidic media.

Catalyst Support Effect on the Activity and Durability of Magnetic Nanoparticles: toward Design of Advanced Electrocatalyst for Full Water Splitting.

Earth-abundant element-based inorganic-organic hybrid materials are attractive alternatives for electrocatalyzing energy conversion reactions. Such material structures do not only increase the surface area and stability of metal nanoparticles (NPs) but also modify the electrocatalytic performance. Here, we introduce, for the first time, multiwall carbon nanotubes (MWNTs) functionalized with nitrogen-rich emeraldine salt (ES) (denoted as ES-MWNT) as a promising catalyst support to boost the electrocatalytic activity of magnetic maghemite (γ-Fe2O3) NPs. The latter component has been synthesized by a simple and upscalable one-step pulsed laser ablation method on Ni core forming the core-shell Ni@γ-Fe2O3 NPs. The catalyst (Ni@γ-Fe2O3/ES-MWNT) is formed via self-assembly as strong interaction between ES-MWNT and Ni@γ-Fe2O3 results in NPs' encapsulation in a thin C-N shell. We further show that Ni does not directly function as an active site in the electrocatalyst but it has a crucial role in synthesizing the maghemite shell. The strong interaction between the NPs and the support improves notably the NPs' catalytic activity toward oxygen evolution reaction (OER) in terms of both onset potential and current density, ranking it among the most active catalysts reported so far. Furthermore, this material shows a superior durability to most of the current excellent OER electrocatalysts as the activity, and the structure, remains almost intact after 5000 OER stability cycles. On further characterization, the same trend has been observed for hydrogen evolution reaction, the other half-reaction of water splitting.