Cobalt Metal Nanoparticles Research Articles

Synthesis and Investigation of Catalytic Properties of Metal-Polymer Nanocomposites Based on Unsaturated Polyester Resins

This paper focuses on the hydrogenation process in metal-polymer complexes based on copolymers of polypropylene glycol fumarate phthalate and polypropylene glycol maleate phthalate, using acrylic acid and immobilized cobalt metal particles as catalysts. A classical reaction of the electrocatalytic hydrogenation of pyridine to piperidine was applied. SEM and dynamic light scattering were utilized to investigate the average size and dispersity of cobalt metal nanoparticles. The experimental findings show that the efficiency of hydrogenation can be improved by increasing the temperature from 25 to 40 °C and the current to 2 A. More specifically, increasing the temperature to 40 °C promotes swelling of the polymer and its transition from a globular collapsed state to an open one, which leads to an increase in the number of active catalytic centers and, as a consequence, acceleration of the hydrogenation process. Increasing the current strength to 2 A also helps to increase the rate of the hydrogenation process. Further increasing the current to 3 A is undesirable due to an increase in the yield of by-products and a decrease in the yield of the target product, piperidine. Based on a comparative analysis, it was established that the use of a copolymer of polypropylene glycol maleate phthalate with acrylic acid as the polymer matrix base is the most preferable for obtaining polymer-metal complexes with nanosized cobalt.

NiCo@EG-based composite PCMs with boosted thermal conductivity and photothermal conversion efficiency for solar energy harvesting

The application of phase change materials (PCMs) in solar energy is hampered by challenges such as insufficient photothermal conversion efficiency, low thermal conductivity and leakage. In this study, a novel composite PCMs based on NiCo@EG were prepared to solve the problems of low thermal conductivity, high leakage rate and inefficient photothermal performance. The NiCo@EG is obtained through calcination of the product of Ni-Co-BTC in-situ on expanded graphite (EG). In the composite PCMs, the octadecanol (OD) acts as a latent heat storage unit, the EG retains its porous network structure as an encapsulating skeleton. The nickel and cobalt nanoparticles derived from Ni-Co-BTC bimetallic organic frameworks are uniformly fixed on the surface of the EG, which could not only construct multiple thermal conduction pathways, but also enhance the photon-trapping ability. Benefiting from the synergy effect of nickel, cobalt metal nanoparticles and EG, the prepared OD/NiCo@EG-550 composite PCMs display high latent heat (168.3 J/g), excellent photothermal conversion efficiency (98.71 %), and improved thermal conductivity of 12.873 W/(m·K). Furthermore, the composite PCMs demonstrate exceptional shape stability, thermal stability, and robust thermal reliability. In summary, the high-efficiency photothermal composite PCMs display significant potential in improving the utilization of solar energy.

Furfural Hydrogenation Over Reduced Pure (LaBO3) and Substituted (LaB0.5B'0.5O3) (B, B': Fe, Co, Ni) Perovskites

AbstractA series of pure and 50 % substituted Fe‐containing (LaFeO3, LaFe0.5Ni0.5O3 and LaFe0.5Co0.5O3) and Co/Ni‐containing (LaCoO3, LaNiO3, and LaCo0.5Ni0.5O3) perovskites were used as precursors to synthesize metallic reduced catalysts to be tested for the liquid hydrogenation of furfural. The catalytic reaction was carried out in a batch reactor at 200 °C and 3.0 MPa of H2 pressure. The calcined perovskites and reduced catalysts were characterized by X‐ray diffraction (XRD), N2 physisorption at 77 K, temperature programmed reduction (H2‐TPR), temperature programmed CO2 and NH3 desorption (CO2‐TPD and NH3‐TPD), Atomic Absorption Spectroscopy (AAS) and X‐ray photoelectron spectroscopy (XPS) techniques. The LaCo0.5Ni0.5O3 reduced catalyst display the highest activity in furfural conversion, which was attributed to a cooperative effect between highly dispersed nickel and cobalt metal nanoparticles after reduction process. The effect of the nature of B‐cation have a high impact on the products selectivity in the hydrogenation of furfural, suggesting that enriched‐Ni metal surface was selectivity to tetrahydrofurfuryl alcohol, meanwhile enriched‐Co metal surface was selective to furfuryl alcohol formation, which was also supported with adsorption mode of furfural over the active sites obtained by quantum calculation.

β‐Cyclodextrin‐Modified Cobalt Nanoparticles as 5‐Fluorouracil Carriers

AbstractMetal nanoparticles having magnetic properties are exciting for application in the directed transport of anticancer drugs encapsulated in them. To ensure drug‐loading capacity and controlled release, surface modification with host molecules is a fascinating choice. In this paper, we report the synthesis and surface modification of magnetic cobalt metal nanoparticles with oligosaccharide host molecules (β‐cyclodextrin) tethered on the surface. A β‐cyclodextrin‐folate derivative is synthesized and characterized using Infrared‐, Nuclear Magnetic Resonance‐, and Matrix‐Assisted Laser Deposition Ionization‐Time of Flight mass spectrometry. The size of the cobalt nanoparticles carrying the host molecule on the surface is ~10 nm. The nanoparticles are characterized using X‐Ray Diffraction, Transmission Electron Microscopy, particle size analyzer, Energy‐Dispersive X‐ray, and X‐ray Photoelectron Spectroscopy. The bare magnetic nanoparticles also show a strong saturation magnetization of 142.21 emu g−1. The chemotherapeutic drug 5‐fluorouracil is loaded on the surface‐modified cobalt nanoparticles through host: guest complexation mode and its controlled release is measured in‐vitro. The slow release is spread over more than 14 days, and a complete release of the loaded therapeutic cargo is not reached. The release is pH‐dependent and changes with acidic levels of the medium. The anticancer activity of the drug‐loaded nanocarrier on MDA‐MB‐231 (breast cancer) cells is investigated. The mechanism of cell death is studied, and the cells are found inhibited in the synthesis phase. Flow cytometric analysis shows that 79.70 % of the empty nanocarrier‐treated and 74.86 % 5‐fluorouracil‐loaded nanocarrier‐treated MDA‐MB‐231 cells were in the early apoptosis phase. This new combination nanocarrier is intriguing owing to its structural and magnetic properties, and the action on cell lines.

Ferromagnetism and two magnetic phases in rutile (TiO<sub>2</sub>) implanted with cobalt ions: effect of substrate temperature and orientation

Room-temperature ferromagnetism and two magnetic phases: cobalt metal nanoparticles and a solid solution of divalent cobalt ions have been observed in single-crystal rutile (TiO2) implanted with cobalt ions to high dose level. Here we present the results of our structural and magnetic studies showing an influence both the temperature and the orientation of TiO2 substrate during a cobalt ion implantation, as well the effect of post-implantation thermal annealing (in air or in vacuum) on ferromagnetism value and magnetic phase composition of Co-implanted rutile.

Graphene-supported cobalt nanoparticles used to activate SiO2-based anode for lithium-ion batteries

Although SiO2-based anode is a strong competitor to supersede graphite anode for lithium-ion batteries, it still has problems such as low electrochemical activity, enormous loss of active lithium, and serious volume expansion. In order to solve these problems, we used a graphene network loaded with cobalt metal nanoparticles (rGO–Co) to coat SiO2 porous hollow spheres (SiO2@rGO–Co). The construction of porous hollow structure and graphene network can shorten the lithium-ion (Li+) diffusion distance and enhance the conductivity of the composite, which improves the electrochemical activity of SiO2 effectively. They also alleviate the volume expansion of the anode in the cycling process. Moreover, nano-scale cobalt metal particles dispersed on graphene catalyze the conversion reaction of SiO2 and activate the locked Li+ in Li2O through a reversible reaction, which improves the charge and discharge capacity of the anode. The capacity of SiO2@rGO–Co reaches 370.4 mAh/g after 100 cycles at 0.1 A/g, which is 6.19 times the capacity of pure SiO2 (59.8 mAh/g) under the same circumstance. What is more, its structure also exhibits excellent cycle stability, with a volume expansion rate of only 13.0% after 100 cycles at a current density of 0.1 A/g.

Bismuth mobile promoter and cobalt-bismuth nanoparticles in carbon nanotube supported Fischer-Tropsch catalysts with enhanced stability

Metal nanoparticles on the surface of porous supports have found numerous applications in different areas of science. Fischer-Tropsch synthesis, which proceeds on the surface of cobalt metal nanoparticles, is an efficient way to convert renewables and fossil feedstocks into alternative fuels. The stability of cobalt catalysts is an essential and even crucial parameter and can be significantly improved by promotion.In this paper, a combination of operando Quick-XAS, NAP-XPS, high resolution electron microscopy imaging, DFT modeling alongside with Fischer-Tropsch catalytic experiments has provided deep insights into the evolution of bismuth promoter and structure of cobalt-bismuth nanoparticles in the catalysts supported by carbon nanotubes. We uncovered noticeable migration of metallic bismuth occurring during the reduction step, which leads to bismuth redispersion over the surface of cobalt nanoparticles. Cobalt reduction is facilitated in the presence of bismuth. The working Fischer-Tropsch catalyst contains cobalt-bismuth bimetallic nanoparticles, with bismuth located in the nanoparticle shell. The promotion with bismuth has resulted in a noticeable increase in catalyst stability. Characterization and DFT modeling suggest preferential localization of bismuth mobile promoter at the steps and edges of cobalt nanoparticles, which hinders cobalt sintering and carbon deposition and improves the catalyst stability.

Hierarchical Carbon/Metal Nanostructure with a Combination of 0D Nanoparticles, 1D Nanofibers, and 2D Nanosheets: An Efficient Bifunctional Catalyst for Zinc‐Air Batteries

AbstractMulti‐dimensional hierarchical nanostructures can efficiently promote the mass transportation and electron transfer of electrocatalysts, which can boost the electrocatalytic performance. In this study, we report the design of a hierarchical carbon/metal nanostructure (Co@CNFs) with the combination of 0D cobalt metal nanoparticles, 1D carbon nanofibers, and 2D carbon nanosheets as a bifunctional oxygen reduction/evolution reaction (ORR/OER) catalyst. The Co@CNF catalysts are prepared by using a facile approach of combining electrospinning, impregnation growth of ZIF‐67 nanosheets, and high‐temperature carbonization. Through rationally optimizing the synthesis conditions, including the chemical concentration and carbonization temperature, the optimal catalyst of Co@CNFs‐50‐800 features a hierarchical structure of continuous carbon nanofibers (CNFs)‐anchored carbon nanosheets wrapping Co nanoparticles, which holds decent catalytic activities in term of a half‐wave potential of 0.8 V for the ORR and a potential of 1.54 V for the OER at 10 mA cm−2. A rechargeable Zn‐air battery is set up using the catalyst as the air cathode, which exhibits a high specific capacity of 809 mAh g−1 and a peak power density of 165.5 mW cm−2, as well as a good durability up to 1000 charging‐discharging cycles (>160 h), which is even better than the benchmark Pt/C+RuO2 catalyst. This study provides a rational strategy to design hierarchically nanostructural catalysts to boost the mass transportation and electron transfer of electrocatalytic reactions.

Mechanical dry method for synthesis of cobalt metal nano particles

Cobalt-chloride coordination used as simple solid state method to synthesized in the solid phase, product of magnetic cobalt nano hybride was produce, the complexes undergoes a reversible phase transition, changing color at room temperature. The structure and the morphology of the produced materials was studied using FTIR, SEM and XRD spectroscopy, magnetic susceptibility measurements was done, the need of new magnetic materials is distinct interest of researchers on the study of magnetic materials, complexes transform to nanoparticles electromagnetic Cobalt metals were successfully synthesized by dry mechano method, decomposition synthesis was successfully occur . Structure morphology and magnetic properties were studied and reported. properties are characterized by X-ray diffract metric and scanning electronic microscope, SEM

Assessing Cobalt Metal Nanoparticles Uptake by Cancer Cells Using Live Raman Spectroscopy.

PurposeNanotechnology applied to cancer treatment is a growing area of research in nanomedicine with magnetic nanoparticle-mediated anti-cancer drug delivery systems offering least possible side effects. To that end, both structural and chemical properties of commercial cobalt metal nanoparticles were studied using label-free confocal Raman spectroscopy.Materials and MethodsCrystal structure and morphology of cobalt nanoparticles were studied by XRD and TEM. Magnetic properties were studied with SQUID and PPMS. Confocal Raman microscopy has high spatial resolution and compositional sensitivity. It, therefore, serves as a label-free tool to trace nanoparticles within cells and investigate the interaction between coating-free cobalt metal nanoparticles and cancer cells. The toxicity of cobalt nanoparticles against human cells was assessed by MTT assay.ResultsSuperparamagnetic Co metal nanoparticle uptake by MCF7 and HCT116 cancer cells and DPSC mesenchymal stem cells was investigated by confocal Raman microscopy. The Raman nanoparticle signature also allowed accurate detection of the nanoparticle within the cell without labelling. A rapid uptake of the cobalt nanoparticles followed by rapid apoptosis was observed. Their low cytotoxicity, assessed by means of MTT assay against human embryonic kidney (HEK) cells, makes them promising candidates for the development of targeted therapies. Moreover, under a laser irradiation of 20mW with a wavelength of 532nm, it is possible to bring about local heating leading to combustion of the cobalt metal nanoparticles within cells, whereupon opening new routes for cancer phototherapy.ConclusionLabel-free confocal Raman spectroscopy enables accurately localizing the Co metal nanoparticles in cellular environments. The interaction between the surfactant-free cobalt metal nanoparticles and cancer cells was investigated. The facile endocytosis in cancer cells shows that these nanoparticles have potential in engendering their apoptosis. This preliminary study demonstrates the feasibility and relevance of cobalt nanomaterials for applications in nanomedicine such as phototherapy, hyperthermia or stem cell delivery.

A short review on biosynthesis of cobalt metal nanoparticles

Nanotechnology is study of nanoscale material properties dependent on their size, shape, and morphology. The establishment of this area will have a numerous advantage towards world industry and technology because it can be utilized globally for various application such as healthcare, electronic, cosmetics, chemical, energy and composites. Along with the time, various of synthesis method such as chemical and physical methods emerging. Somehow these method starts to show its limitations. Thus, the requirement to find another alternative way to synthesis nanoparticles that are not going to cause environmental hazards are urgently needed. A development of eco-friendly approach for synthesis of nanoparticles mainly are desirable in order to move forwards towards green chemistry. At present, plants have shown to be proven and efficiently applied for the extraction method for cobalt oxide nanoparticles. Therefore, this short review includes methodologies and benefit as well as recent studies to produce cobalt oxide nanoparticles using green synthesis.

Co-substituted Sr2Fe1.5Mo0.5O6-δ as anode materials for solid oxide fuel cells: Achieving high performance via nanoparticle exsolution

Co-Substituted Sr2Fe1.5Mo0.5O6-δ (Sr2Fe1.3Co0.2Mo0.5O6-δ) double perovskite oxides have been prepared and evaluated as anode materials of solid oxide fuel cells (SOFCs). In reducing atmosphere, active cobalt metal nanoparticles are in situ exsolved from the parent double perovskite oxides, which are characterized by XRD, XPS, SEM and TEM. Sr2Fe1.3Co0.2Mo0.5O6-δ show the highest electrical conductivity of 13.9 S cm−1 at 600 °C and the lowest polarization resistance of 0.15 Ω cm2 at 850 °C in 5% H2–95% N2. When hydrogen, syngas and methane are filled as fuel, a maximum power density of 1.09, 0.981 and 0.29 W cm−2 could be achieved at 850 °C, respectively. Further, after continuously operated in hydrogen for 115 hs, in syngas for 190 hs and in methane for 300 hs, there are no negligible degradations. Synergistic effect between perovskite oxide and exsolved Co nanoparticles contributes to the improved SOFCs performances. The protocol developed in this research provides a new strategy to optimize anodic activities of double perovskite oxides, and broadens our horizons in rational design of heterogeneous ceramics for other applications.

Metal-organic-framework-derived formation of Co–N-doped carbon materials for efficient oxygen reduction reaction

Abstract Non-precious metal nitrogen-doped carbonaceous materials have attracted tremendous attention in the field of electrochemical energy storage and conversion. Herein, we report the designed synthesis of a novel series of Co-N-C nanocomposites and their evaluation of electrochemical properties. Novel yolk-shell structured Co nanoparticles@polymer materials are fabricated from the facile coating polymer strategy on the surface of ZIF-67. After calcination in nitrogen atmosphere, the Co–N–C nanocomposites in which cobalt metal nanoparticles are embedded in the highly porous and graphitic carbon matrix are successfully achieved. The cobalt nanoparticles containing cobalt metal crystallites with an oxidized shell and/or smaller (or amorphous) cobalt-oxide deposits appear on the surface of graphitic carbons. The prepared Co–N–C nanoparticles showed favorable electrocatalytic activity for oxygen reduction reactions, which is attributed to its high graphitic degree, large surface area and the large amount existence of Co–N active sites.

Phase Controlled Synthesis of Pt Doped Co Nanoparticle Composites Using a Metal-Organic Framework for Fischer–Tropsch Catalysis

Recently, metal nanoparticles embedded in porous carbon composite materials have been playing a significant role in a variety of fields as catalyst supports, sensors, absorbents, and in energy storage. Porous carbon composite materials can be prepared using various synthetic methods; recent efforts provide a facile way to prepare the composites from metal-organic frameworks (MOFs) by pyrolysis. However, it is usually difficult to control the phase of metal or metal oxides during the synthetic process. Among many types of MOF, recently, cobalt-based MOFs have attracted attention due to their unique catalytic and magnetic properties. Herein, we report the synthesis of a Pt doped cobalt based MOF, which is subsequently converted into cobalt nanoparticle-embedded porous carbon composites (Pt@Co/C) via pyrolysis. Interestingly, the phase of the cobalt metal nanoparticles (face centered cubic (FCC) or hexagonal closest packing (HCP)) can be controlled by tuning the synthetic conditions, including the temperature, duration time, and dosage of the reducing agent (NaBH4). The Pt doped Co/C was characterized using various techniques including PXRD (powder X-ray diffraction), XPS (X-ray photoelectron spectroscopy), gas sorption analysis, TEM (transmission electron microscopy), and SEM (scanning electron microscopy). The composite was applied as a phase transfer catalyst (PTC). The Fischer-Tropsch catalytic activity of the Pt@Co/C (10:1:2.4) composite shows 35% CO conversion under a very low pressure of syngas (1 MPa). This is one of the best reported conversion rates at low pressure. The 35% CO conversion leads to the generation of various hydrocarbons (C1, C2–C4, C5, and waxes). This catalyst may also prove useful for energy and environmental applications.

In-situ X-Ray Absorption Near Edge Structure Spectroscopy of a Solid Catalyst using a Laboratory-Based Set-up.

An in‐situ laboratory‐based X‐ray Absorption Near Edge Structure (XANES) Spectroscopy set‐up is presented, which allows performing long‐term experiments on a solid catalyst at relevant reaction conditions of temperature and pressure. Complementary to research performed at synchrotron radiation facilities the approach is showcased for a Co/TiO2 Fischer‐Tropsch Synthesis (FTS) catalyst. Supported cobalt metal nanoparticles next to a (very small) fraction of cobalt(II) titanate, which is an inactive phase for FTS, were detected, with no signs of re‐oxidation of the supported cobalt metal nanoparticles during FTS at 523 K, 5 bar and 200 h, indicating that cobalt metal is maintained as the main active phase during FTS.

MOF-derived nickel and cobalt metal nanoparticles in a N-doped coral shaped carbon matrix of coconut leaf sheath origin for high performance supercapacitors and OER catalysis

Coconut leaf sheath-derived nitrogen doped carbon framework is developed and incorporated with nickel and cobalt metal nanoparticles in the carbon matrix by a facile process of growing ZIF-67 metal organic framework particles on the graphitised carbon, followed by annealing it in inert atmosphere. Various parameters are modified to obtain three different samples. These samples are tested for high performance supercapacitors and oxygen evolution reaction (OER) catalysts. The optimised sample NiCoC-1 gave a high specific capacity of 308 mAh g−1 at a current density of 1 A g−1 in a 2 M KOH electrolyte. An asymmetric supercapacitor assembly prepared from NiCoC-1 as the positive electrode and the nitrogen-doped carbon as the negative electrode, exhibited an energy density of up to 31.8 Wh Kg−1 for a high power density of 6.2 kW kg−1 over a potential window of 0–1.55 V. Two of our best samples were also tested for OER, giving good water oxidation kinetics, revealed by their lower Tafel slopes of around 107 mV and a low over potential (η) of around 420 mV at a current density of 10 mA cm−2. Hence, this work opens great avenues for biomass-derived materials for high performance supercapacitors and catalysis.

Aligned cobalt-based Co@CoOx nanostructures for efficient electrocatalytic water oxidation.

Aligned cobalt metal nanoparticles were prepared from the pyrolysis of cobalt oxalate nanoplate precursors for efficient electrocatalytic water oxidation. The 2D morphology of the precursor guided the 2D alignment of the derived cobalt metal nanoparticles. The as-prepared Co@CoOx electrocatalyst requires an ultra-low overpotential of 289 mV to achieve a current density of 10 mA cm-2 on a simple glassy carbon (GC) electrode in a 1 M KOH aqueous solution. The metallic nature of the bulk of the electrocatalyst and the compact alignment of the nanoparticles can facilitate the inner- and inter-particulate charge transfers.

Cobalt Nanoparticle-Embedded Porous Carbon Nanofibers with Inherent N- and F-Doping as Binder-Free Bifunctional Catalysts for Oxygen Reduction and Evolution Reactions.

Efficient, low-cost, non-precious metal-based, and stable bifunctional electrocatalysts are key to various energy storage and conversion devices such as regenerative fuel cells and metal-air batteries. In this work, we report cobalt nanoparticle-embedded porous carbon nanofibers with inherent N- and F-doping as binder-free bifunctional electrocatalysts with excellent activity for both the oxygen reduction and oxygen evolution reaction (ORR/OER) in an alkaline medium. Single-step electrospinning of a solution of the polymer mixture (carbon precursor) and the cobalt precursor followed by controlled pyrolysis with an intermediate reduction step in H2 (to reduce cobalt oxides to cobalt) was utilized to synthesize an integrated freestanding catalyst. The fabricated catalyst with effective structural and electronic interaction between the cobalt metal nanoparticles and the N- and F-doped carbon defect sites showed enhanced catalytic properties compared to the benchmark catalysts for ORR and OER (Pt, Ir, and Ru). The ORR potential at the current density of -3 mA cm-2 was 0.81 VRHE and the OER potential at a current density of 10 mA cm-2 was 1.595 VRHE , resulting in a ΔE of only 0.785 V.

Magnetic Coupling of Dissimilar ZnO–Co Granular Films Through a ZnO Spacer

An all-oxide granular film (GF) with a sandwich structure containing cobalt metal nanoparticles embedded in ZnO is fabricated by magnetron sputtering. Large and small Co particles can be obtained simultaneously in a sample by depositing nanostructured ZnO–Co layers at high and low temperatures, respectively. The two ZnO–Co layers couple with each other through a ZnO spacer layer, whose thickness tunes the strength of the coupling. Both the magnetic properties and the magnetoresistance (MR) of the samples depend on the sandwich structure. Magnetic interactions can be transferred through the polycrystalline pure ZnO spacer layer even when the layer is as thick as 40[Formula: see text]nm due to the long spin coherence length. An analysis of the data found that the spin coherence length was greater than [Formula: see text]17[Formula: see text]nm at room temperature (RT) in a polycrystalline film with very small grains. Tuning the resistance of the ZnO–Co layer deposited at a low temperature by adding aluminum so that it more nearly matches the resistance of the ZnO–Co layer deposited at a high temperature, dramatically enhances the MR of the sandwich sample. This study illustrates the power of combining films containing different sizes of nanoparticles in order to optimize the MR and so make the ZnO-based films more suitable for applications in spintronics.

The size-dependent site composition of FCC cobalt nanocrystals

Cobalt-based Fischer–Tropsch (FT) catalysts typically contain reactive cobalt metal nanoparticles on support materials. Such metal nanoparticles are expected to have properties that are strongly size-dependent. Noting the size-dependence of the Co FT rate for particle diameters below 10nm, we aimed to see whether the FCC Co nanoparticle site composition exhibits a corresponding size-dependence. This aim was realised by: building and optimising realistic and representative close-packed Co nanoparticle models at various sizes; defining, identifying and counting the exposed surface sites; generalising these findings based on the small subset of simulated nanocrystal models. Using this approach, the site composition of five defined sites with increasing size up to 8nm was obtained. The three defined defect/step sites increased in concentration with increasing size, with the B5-A site and the B6 site reaching a stable value at about 4nm, while the B5-B site still increased somewhat even at 8nm. This confirms the size-dependent change in the surface site composition for FCC Co nanocrystals. The shape and site composition ranges were also compared to previously calculated Wulff shapes and showed good agreement. Implications of the size-dependent FCC Co site composition on the FT catalysis process are also discussed.