Structure Of Co Nanoparticles Research Articles

Modulating metal-carrier interaction of high-loading Co-Al2O3-SiO2 catalysts for boosted N-propylcarbazole hydrogenation

We developed a series of high-loading Co-Al2O3-SiO2 catalysts to enhance the hydrogenation of N-propylcarbazole (NPCZ) by fine-tuning the Al/Si ratio. Our research reveals that adjusting this ratio can significantly modify the electronic structure of Co nanoparticles, as confirmed by XPS, H2-TPD, and CO-DRIFT analyses, thereby affecting the adsorption of hydrogen species and their interaction with unsaturated π-bonds of NPCZ intermediates. Optimal Al concentration promotes Co nanoparticles dispersion, while excessive Al leads to increased acidity and reduced surface area. The Co70/Al4Si1O catalyst, with an Al/Si ratio of 4, demonstrated superior hydrogenation efficiency by enabling fast and stable hydrogenation of NPCZ, achieving an activation energy of 64.53 kJ/mol and maintaining high performance over 10 cycles. Through DFT calculations, we explored the d-band center and Bader charge across 6 different Co10/Al-Si-O models and assessed the adsorption energies of NPCZ intermediates, along with the energetics of three stepwise reactions. The initial hydrogenation step from NPCZ to 4H-NPCZ is predominantly influenced by the catalyst's acidity/basicity, whereas the subsequent deeper hydrogenation steps of 4H-NPCZ and 8H-NPCZ are governed by the d-π feedback interaction between the metal and the adsorbate. This research offers critical guidance on selecting optimal supports for Co-based catalysts in LOHC hydrogenation.

Co/N-codoped carbon nanotube hollow polyhedron hybrid derived from salt-encapsulated core-shell ZIF-8@ZIF-67 for efficient oxygen reduction reaction

The rational design and construction of non-precious metal-based electrocatalysts with high activity and stability toward oxygen reduction reactions (ORR) are essential but challenging. In this work, a novel hybrid nanoporous structure of Co nanoparticles uniformly embedded in hollow porous carbon doped with nitrogen (CoNHPC) was constructed by a melt-evaporation-pyrolysis method, in which NaCl is utilized as an auxiliary template. The introduction to NaCl in this process served as the confining template to prevent nitrogen loss and promote graphitization, and the intercalating agent to form a mesoporous product. Due to the composite hierarchical porous structure, higher graphitization degree, and desirable nitrogen bonding type, the as-prepared CoNHPC-920 presents outstanding ORR electrocatalytic activity in terms of a half-wave potential of 0.87 V (vs. RHE) and onset potential of 0.97 V (vs. RHE). The composite material also shows higher selectivity and outstanding durability with most transition metal porous carbon materials reported. The strategy proposed in this study may provide ideas about metal nitrogen-carbon type catalysts enriched with carbon nanotubes and bare leaky hollow structures of the construction of advanced ORR electrocatalysts, opening up a new pathway.

One-dimensional metal-organic nanowires-derived catalyst of carbon nanobamboos with encapsulated cobalt nanoparticles for oxygen reduction

One-dimensional (1D) metal-organic nanostructures hold great promise for preparing various 1D carbon/metal derivatives toward various electrocatalysis including oxygen reduction reaction (ORR); but it is challenging to synthesize them. Herein, 1D cobalt(Co)-metal-organic nanowires are prepared using the complex of Co2+ and 1, 2, 4-triazole. Direct carbonization of the as-prepared nanowires affords a well-defined structure of Co nanoparticles encapsulated inside the bamboo-liked 1D carbon nanostructure, i.e., carbon nanobamboos (Co@CNB). Owing to the outstanding electronic transport in bamboo-liked carbon structure, strong electronic coupling between the N-doped carbon and Co nanoparticles, the Co@CNB catalyst exhibits an excellent ORR performance comparable to the commercial Pt/C in alkaline solution. Density functional theory (DFT) calculations reveal that the Co@CNB can strengthen the adsorption of all adsorbates (O*, OH* and OOH*) compared with a carbon nanotube, benifical for oxygen protonation and thus enhancing the ORR activity. Moreover, it is possible to outperform Pt intrinsically if the curvature of carbon shell is high enough in Co@CNB. Lastly, the zinc-air battery (ZAB) fabricated with Co@CNB as the cathode catalyst shows a higher peak power density and better cycling durability than those of the ZAB with Pt/C; suggesting the great potential of Co@CNB as efficient electrocatalysts for metal-air batteries.

Metal organic framework (ZIF-67)-derived Co nanoparticles/N-doped carbon nanotubes composites for electrochemical detecting of tert-butyl hydroquinone

In this work, the framework of Co nanoparticles and nitrogen-doped carbon nanotubes (Co/NCNTs) derived from metal–organic frameworks (MOFs) through solid pyrolysis was successfully synthesized in the atmosphere of H2 and Ar gases. The Co/NCNTs composites exhibited superior electrocatalytic performance for tert-butyl hydroquinone (TBHQ) oxidation due to the synergistic effect between chemical composition and the specific structure of Co nanoparticles and nitrogen-doped carbon nanotubes. It was found that the reaction underwent a quasi-reversible redox reaction with 37-fold higher anodic current for TBHQ at Co/NCNT-modified electrode when compared to bare glassy carbon electrode (GCE). In optimal condition, Co/NCNTs/GCE exhibited a linear range of 0.05–80.00 μmol·L−1 for detecting TBHQ, and the limit of detection (LOD) was estimated to be as low as 10 nmol·L−1 (signal/noise of S/N = 3). Moreover, the as-obtained modified electrode was successfully used to assay the content of TBHQ in edible oil samples.

Cobalt nanoparticles for biomedical applications: Facile synthesis, physiochemical characterization, cytotoxicity behavior and biocompatibility

Cobalt (Co) nanoparticles (NPs) were produced by a simple, one step hydrothermal method with the capping of oleic acid. Intrinsic structural, physiochemical and magnetic properties of Co NPs were investigated and demonstrated their applicability in biomedicine. X-ray diffraction, Raman spectroscopy and infrared (IR) spectroscopic studies confirm the single phase Co NPs with a high structural quality. The IR data revealed the capping of oleic acid via monodentate interaction. Small angle scattering studies suggest the existence of sticky hard sphere type of interaction among the Co NPs because of magnetic interaction which is further evidenced by electron microscopy imaging analyses. The Co NPs exhibit a ferromagnetic character over a wide range of temperature (20–300K). The temperature dependence of magnetic parameters namely, saturation magnetization, remanent magnetization, coercivity and reduced remanent magnetization were determined and correlated with structure of Co NPs. The Cytotoxicity studies demonstrate that these Co NPs exhibit the mild anti-proliferative character against the cancer cells (cisplatin resistant ovarian cancer (A2780/CP70)) and safe nature towards the normal cells. Haemolytic behavior of human red blood cells (RBC) revealed (<5%) haemolysis signifying the compatibility of Co NPs with human RBC which is an essential feature in vivo biomedical applications without creating any harmful effects in the human blood stream.

Self-Organization and/or Nanocrystallinity of Co Nanocrystals Effects on the Oxidation Process Using High-Energy Electron Beam

The enhanced stability of Co nanocrystals (NCs) when they are highly ordered at both nanometer and micrometer scales is reported. For the first time, it is shown that both the crystalline structure of Co nanoparticles (NPs) and their 2D hexagonal organization have a significant impact on the oxidation process rate enabling to produce various types of nanostructures including core-shell NPs. The Co core can be either polycrystalline or hexagonal close-packed (hcp) single-crystalline, whereas the oxide shell is composed either of CoO or of the spinel structrure Co3O4. The present results are evidenced through a careful high-resolution transmission electron microscopy (HRTEM) study and are highly reproducible.

Formation of Co nanoparticles in metal-carbon composites

The effect of the IR-pyrolysis intensity on the phase formation and structure of Co nanoparticles in a matrix of IR-pyrolyzed polyacrylonitrile has been investigated.

Synthesis and characterization of cobalt/gold bimetallic nanoparticles

Cobalt/gold (Co/Au) bimetallic nanoparticles are prepared by chemically reducing gold (III) chloride to gold in the presence of pre-synthesized Co nanoparticles. Transmission electron microscopy (TEM), ultraviolet-visible (UV-vis) absorption spectrometry, and a superconducting quantum interference device (SQUID) magnetometer have been used to characterize as-prepared bimetallic nanoparticles. Our findings demonstrate Au not only grows onto Co nanoparticles, forming a surface coating, but also diffuses into Co nanoparticles. The introduction of Au alters the crystalline structure of Co nanoparticles and changes their magnetic properties. Dodecanethiols induce a reorganization of as-prepared Co/Au bimetallic nanoparticles.