Graphene aerogel encapsulated Co3O4 microcubes derived from prussian blue analog as integrated anode with enhanced Li-ion storage properties

In lithium-ion batteries (LIB), cobalt oxide is considered an ideal anode material because of its theoretical specific capacity of up to 890 mAh g⁻¹, abundant resources, and low price. However, the volume expansion during the charging and discharging process and its lower conductivity have hindered its development. In this work, a metal-organic framework (MOF) was used as an initial template, encapsulated in graphene aerogels (GA) by hydrothermal and programmed temperature-controlled annealing and eventually formed into Co₃O₄ microcubes@GA composite. GA acts as a three-dimensional conductive network and mechanical skeleton, providing high electrical conductivity and structural stability to the composites. Moreover, the precursor's high porosity and stable structure are retained after annealing treatment. As an anode, the best long cycle life of Co₃O₄ microcubes@GA was achieved when the graphene oxide (GO) concentration was 3.0 mg ml⁻¹, reaching 1234.9 mAh g⁻¹ after 200 cycles at 1 A g⁻¹ with a coulomb efficiency (CE) of 98.97%.     

Fabrication of efficient nanostructured Co3O4-Graphene bifunctional catalysts: Oxygen evolution,hydrogen evolution,and H2O2 sensing

Nanostructured Co₃O₄-graphene hybrid catalysts are fabricated by a one-step vacuum kinetic spray technique from microparticles of Co₃O₄ and graphite powders. The Co₃O₄-graphene hybrid catalysts with various Co₃O₄ contents are studied concerning the oxygen evolution reaction (OER), and hydrogen evolution reaction (HER) in 1.0 M KOH, as well as, H₂O₂ sensing in 0.1 M NaOH. We find that increasing graphene content in the hybrid catalysts results in an overall improvement of the OER electrocatalytic activity due to the enhancement in the charge transfer kinetics. The hybrid catalyst with 25 wt% Co₃O₄ reveals the optimum electrocatalytic activity toward the OER with the lowest overpotential (η) of 283 mV@ 10 mA cm⁻² and superior reaction kinetics with a low Tafel slope of 25 mV dec⁻¹. Besides, the OER stability at 50 mA cm⁻² for 50 h in 1.0 M KOH was verified. The hybrid catalyst with 50 wt% Co₃O₄ revealed the highest activity toward the HER with η of 108 mV@ 10 mA cm⁻², Tafel slope of 90 mV.dec⁻¹, and stability at 50 mA cm⁻² for nearly 30 h. Moreover, it reveals ultrahigh H₂O₂ amperometric detection with superior sensitivity of 18,110 μA mM⁻¹ cm⁻², linear detection range from 20 μM to 1 mM, and a limit of detection of 0.14 μM.     

Polydopamine-assisted formation of Co3O4-nanocube-anchored reduced graphene oxide composite for high-performance supercapacitors

Tailoring transition-metal oxide nanoparticles with two-dimensional carbon has become a favorite way to improve their electrochemical performance. In this study, a composite of reduced graphene oxide was anchored by Co₃O₄ nanocubes and easily prepared with the assistance of polydopamine (PDA), using a combination of hydrothermal reaction and pyrolysis (Co₃O₄@PDA-rGO). Polydopamine, which possesses abundant catechol and amine groups, could be easily grafted onto graphene oxide to reduce the aggregation of graphene particles. Furthermore, PDA provided active sites, i.e., catechol and amine groups, which coordinated with Co²⁺, enabling enrichment of metal ions on the surface of graphene. After the pyrolysis of Co²⁺-containing PDA-grafted graphene at 400 °C, the Co²⁺ ions were converted into Co₃O₄ nanocubes, while the PDA carbonized to form N-doped porous carbon on the surface of graphene. The resulting product, Co₃O₄@PDA-rGO, demonstrated extraordinary supercapacitive behavior with good cycling stability owing to its unique porous structure as well as the intimate contact between Co₃O₄ and the carbon matrix.     

Holey graphene interpenetrating networks for boosting high-capacitive Co3O4 electrodes via an electrophoretic deposition process

A composite of Co₃O₄/holey graphene (Co₃O₄/HG) was prepared via a facile hydrothermal route, and was then processed into an electrode by an electrophoretic deposition process. Holey graphene (HG) wrapped Co₃O₄ to form a 3D skeleton network, thereby providing high electrical conductivity, and the holes in HG could further shorten the electrolyte ion diffusion pathway. Therefore, by adjusting the mass ratio of Co₃O₄ to HG, the Co₃O₄/HG composite afforded an enhanced capacitance of 2714 F g⁻¹ (at a current density of 1 A g⁻¹), which is 20 times higher than that of pure Co₃O₄. To further explore the practical applications of Co₃O₄/HG, a symmetric supercapacitor employing Co₃O₄/HG was fabricated. The supercapacitor functioned stably at potentials up to 1.2 V, with an enhanced energy density of 165 Wh kg⁻¹ and a high power density of 0.6 kW kg⁻¹ at 1 A g⁻¹.     

Oxygen evolution on electrochemically generated cobalt spinel coating

The oxygen evolution reaction (OER) has been investigated in 40 wt % KOH at 80°C on a thick cobalt oxide coating obtained by potential cycling of a cobalt electrode for 0, 2, 4, 10 and 17h in the same electrolyte with and without dissolved strontium. The kinetic parameters of the OER were determined after preanodization for 1 h at 1 A cm^–2. Improved electrocatalytic activity for the OER, better mechanical strength of the coating and lower variation of the oxygen overpotential with time were noticed up to 70 h of polarization as the coating built up in the presence of dissolved strontium in the electrolyte. The beneficial effect of dissolved strontium on the electrocatalytic activity is ascribed to the accumulation of Co₃O₄, which results in a lower Tafel slope for the OER.     

Low-temperature growth of well-crystalline Co3O4 hexagonal nanodisks as anode material for lithium-ion batteries

Uniform hexagonal-shaped cobalt oxide (Co₃O₄) nanodisks were prepared in large scale via facile aqueous solution based hydrothermal process at 110 °C. The detailed structural characterizations confirmed that the synthesized products are hexagonal cobalt oxide nanodisks, possessing very well-crystalline cubic spinel structure. A coin cell of type −2032 was assembled using the synthesized Co₃O₄ nanodisks and its charge–discharge profile was analyzed between the voltages 0.01 and to 2.5 V vs. Li/Li⁺ reference electrode. The electrochemical cell composed of Li/Co₃O₄ delivered an initial lithium insertion capacity of 2039 mAh/g. Although the cell exhibited high irreversible capacity during the first four cycles, the columbic efficiency has been improved upon cycling.     

Effect of core-shell reversal on the structural,magnetic and adsorptive properties of Fe2O3-GO nanocomposites

Effect of core-shell reversal on the nanocomposites of graphene oxide (GO) and ferric oxide (Fe₂O₃) was studied. Fe₂O₃@GO core-shell nanosheets were synthesized by sonication method, while the GO@Fe₂O₃ core-shell nanospheres by employing N,N′-dicyclohexylcarbodimide as the binding agent for the wrapping of GO sheets on pre-formed Fe₂O₃ nanoparticles (NPs). The phase composition, crystallinity and morphology of the nanocomposites were characterized by FT-IR, TEM, SEM-EDS, VSM, BET surface area study and XRD techniques. The saturation magnetization (M_s) was 1.25 and 0.51 emu g⁻¹ for GO@Fe₂O₃ and Fe₂O₃@GO respectively owing to the dependence of magnetic properties on the reversal of core-shell. BET analysis revealed the surface area of 100.32 m² g⁻¹ and 45.69 m² g⁻¹ for GO@Fe₂O₃ and Fe₂O₃@GO nanocomposites respectively. The fabricated nanocomposites were analyzed as adsorbents for the uptake of Pb (II) ions. The impact of various factors affecting adsorption process such as pH, adsorbent dose, contact time, temperature and metal ion concentration was also investigated. GO@Fe₂O₃ core-shell nanospheres showed a higher adsorption capacity for Pb (II) ions as compared to Fe₂O₃@GO core-shell nanosheet with the maximum adsorption capacities (q_m) of 303.0 and 125.0 mg g⁻¹ respectively. The equilibrium data was estimated by Freundlich, Langmuir, D-R and Temkin isotherm models. Thermodynamic analysis confirmed the spontaneous and exothermic nature of the adsorption process. The adsorption kinetics was significantly fitted to pseudo-second order model. The results confirmed that core-shell reversal can significantly alter the adsorptive properties of Fe₂O₃-GO nanocomposite     

One-pot dual product synthesis of hierarchical Co3O4@N-rGO for supercapacitors,N-GDs for label-free detection of metal ion and bio-imaging applications

Cobalt oxide nanoparticles@nitrogen-doped reduced graphene oxide (Co₃O₄@N-rGO) composite and nitrogen-doped graphene dots (N-GDs) were synthesized by a one-pot simple hydrothermal method. The average sizes of the synthesized bare cobalt oxide nanoparticles (Co₃O₄ NPs) and Co₃O₄ NPs in the Co₃O₄@N-rGO composite were around 22 and 24 nm, respectively with an interlayer distance of 0.21 nm, as calculated using the XRD patterns. The Co₃O₄@N-rGO electrode exhibits superior capacitive performance with a high capability of about 450 F g^?1 at a current density of 1 A g^?1 and has excellent cyclic stability, even after 1000 cycles of GCD at a current density of 4 A g^?1. The obtained N-GDs exhibited high sensitivity and selectivity towards Fe²⁺ and Fe³⁺, the limit of detection was as low as 1.1 and 1.0 μM, respectively, representing high sensitivity to Fe²⁺ and Fe³⁺. Besides, the N-GDs was applied for bio-imaging. We found that N-GDs were suitable candidates for differential staining applications in yeast cells with good cell permeability and localization with negligible cytotoxicity. Hence, N-GDs may find dual utility as probes for the detection of cellular pools of metal ions (Fe³⁺/Fe²⁺) and also for early detection of opportunistic yeast infections in biological samples.     

Thermally reduced rGO‐wrapped CoP/Co2P hybrid microflower as an electrocatalyst for hydrogen evolution reaction

Cobalt phosphides (CoP_x) are potential candidates for use as high‐efficiency hydrogen evolution reaction electrocatalysts that can replace noble metals, such as Pt. Typically, CoP_x can be synthesized by phosphidation with Co‐based precursors such as oxides or hydroxides. In this study, we propose a new strategy for synthesizing CoP_x through the thermal reduction in cobalt phosphate (Co₃(PO₄)₂). A reduced graphene oxide‐wrapped CoP/Co₂P hybrid microflower was successfully synthesized by a facile coprecipitation method in a Co₃(PO₄)₂ matrix, followed by a thermal reduction process. Co₃(PO₄)₂ can be transformed to CoP/Co₂P by treatment at 700°C for 1 hour, maintaining the original particle morphology with the assistance of reduced graphene oxide (rGO). In a 0.5 mol/L H₂SO₄ solution, the rGO‐CoP/Co₂P microflower catalyzes the hydrogen evolution reaction with an overpotential of 156 mV at a current density of 10 mA cm^?2, a Tafel slope of 53.8 mV dec^?1, and good stability as observed through long‐term CV and chronoamperometry tests.     

Facile preparation of poly(ε-caprolactone)/Fe3O4@graphene oxide superparamagnetic nanocomposites

The main goal in this work was to prepare and characterize a kind of novel superparamagnetic poly(ε-caprolactone)/Fe₃O₄@graphene oxide (PCL/Fe₃O₄@GO) nanocomposites via facile in situ polymerization. Fabrication procedure included two steps: (1) GO nanosheets were decorated with Fe₃O₄ nanoparticles by an inverse co-precipitation method, which resulted in the production of the magnetite/GO hybrid nanoparticles (Fe₃O₄@GO); (2) incorporation of Fe₃O₄@GO into PCL matrix through in situ polymerization afforded the magnetic nanocomposites (PCL/Fe₃O₄@GO). The microstructure, morphology, crystallization properties, thermal stability and magnetization properties of nanocomposites were investigated with various techniques in detail. Results of wide-angle X-ray diffraction showed that the incorporation of the Fe₃O₄@GO nanoparticles did not affect the crystal structure of PCL. Images of field emission scanning electron microscope and transmission electron microscopy showed Fe₃O₄@GO nanoparticles evenly spread over PCL/Fe₃O₄@GO nanocomposites. Differential scanning calorimeter and polar optical microscopy showed that the crystallization temperature increased and the spherulites size decreased by the presence of Fe₃O₄@GO nanoparticles in the nanocomposites due to the heterogeneous nucleation effect. Thermogravimetric analysis indicated that the addition of Fe₃O₄@GO nanoparticles reduced the thermal stability of PCL in the nanocomposites. The superparamagnetic behavior of the PCL/Fe₃O₄@GO nanocomposites was testified by the superconducting quantum interference device magnetometer analysis. The obtained superparamagnetic nanocomposites present potential applications in tissue engineering and targeted drug delivery.     

Synthesis of Co3O4 nanotubes and their catalytic applications in CO oxidation

Co₃O₄ nanotubes with the inner of about 8 nm and the length of 200–500 nm were synthesized by oxidizing Co nanowires. Analyses on the structural evolution of the intermediates at different intervals identified that the formation of Co₃O₄ nanotubes followed a nanoscale Kirkendall effect. The outward diffusion of cobalt species was faster than the inward diffusion of oxygen species, resulting in the formation of nanovoids at the initial stage and subsequently the tubular structure. The Co₃O₄ nanotubes showed a higher activity and stability than the spherical nanoparticles in CO oxidation, primarily due of the facile redox feature.     

Encapsulated Cobalt Oxide on Carbon Nanotube Support as Catalyst for Selective Continuous Hydrogenation of the Showcase Substrate 1‐Iodo‐4‐nitrobenzene

A carbon nanotube supported catalyst containing cobalt/cobalt oxide (Co/Co₃O₄) nanoparticles encapsulated within a shell of nitrogen‐doped graphene layers (Co₃O₄/NGr@CNT) was prepared. It shows excellent chemoselectivity in the hydrogenation of 1‐iodo‐4‐nitrobenzene, which contains an iodine substituent highly sensitive against hydrodehalogenation. In contrast to traditional activated charcoal‐supported catalysts such as Pt‐V/C or the closely related Vulcan carbon black supported Co₃O₄/NGr@C, the advantageous morphological properties of the CNT support allow for the application of the new Co₃O₄/NGr@CNT as a fixed bed catalyst in a continuous flow reactor. Under optimized conditions, no dehalogenation side products could be detected. This remarkable selectivity in combination with its mechanical stability under operation conditions render Co₃O₄/NGr@CNT a catalyst particularly relevant for application in continuous processes based on a packed bed reactor.

     

Controllable Fabrication of Co3−xMnxO4 with Tunable External Co3+/Co2+ Ratio for Promoted Oxygen Reduction Reaction

Co_3?xMn_xO₄ is a bimetal oxide with excellent electrochemical activity in alkaline solution, has been regarded as a promising alternative in the field of ion-air batteries and proton exchange membrane fuel cell (PEMFC). Herein, we report a simple solvothermal-calcination method to fabricate Co_3?xMn_xO₄ with tunable external Co³⁺/Co²⁺ and Mn³⁺/Mn²⁺ ratio. The tunable ratio of element valence in the bimetal results in a higher exposure of active center for oxygen redox reaction (ORR), and thus lead to a better ORR activity, which was confirmed by X-ray photoelectron spectroscopy characterizations and electrochemical measurements. Specially, Co_1.8Mn_1.2O₄ with a Co³⁺/Co²⁺ ratio of 2.08 showed an overpotential of 0.37 V at benchmark ORR current density of 3 mA/cm² in 0.1 M KOH, which is lower than that of pure oxide (Mn₃O₄ 0.53 V and Co3O4 0.56 V). In addition, the as prepared Co_1.8Mn_1.2O₄ exhibited a positive half-wave potential (0.83 V vs RHE) due to their more active sites, promotes charge transfer, adsorption and desorption of oxygen species. This work provides a strategy for the design and fabrication of earth-abundant, low-cost electrocatalysts for PEMFC in practical applications.

Graphic Abstract

Co_3?xMn_xO₄ was fabricated by tuning external Co³⁺/Co²⁺ and Mn³⁺/Mn²⁺ ratio, and the activity initially shows a positive correlation with the ration of Co³⁺/Co²⁺ in Co_3?xMn_xO₄.

     

ZIF-derived wrinkled Co3O4 polyhedra supported on 3D macroporous carbon sponge for supercapacitor electrode

Co₃O₄/melamine-derived carbon sponge (MCS) nanocomposite in which wrinkled ball-in-dodecahedral Co₃O₄ nanoparticles derived from ZIF-67 were homogeneously dispersed on the interconnected MSC was fabricated via a simple immersion and thermolysis route. As-prepared ultralight Co₃O₄/MCS possessed mechanically robust characteristic and unique 3D macroporous framework anchored with corrugated Co₃O₄ dodecahedra. Utilized as a pseudocapacitor electrode, Co₃O₄/MCS hybrid exhibited a great specific capacitance of 1409.5 F g⁻¹ at the current density of 0.5 A g⁻¹ and excellent long-term cycling stability of 93.2% after 1000 charge/discharge cycles, which might be ascribed to the synergistic effect of the inherent high redox activity from Co₃O₄ polyhedra combined with excellent electrical conductivity of MCS. This work demonstrates that tunable structure design and rational morphology control are efficient approaches for manufacturing novel electrode materials with extraordinary electrochemical performance.     

Achieving ultra-high electromagnetic wave absorption by anchoring Co0.33Ni0.33Mn0.33Fe2O4 nanoparticles on graphene sheets using microwave-assisted polyol method

The Co_0.33Ni_0.33Mn_0.33Fe₂O₄/graphene nanocomposite for electromagnetic wave absorption was successfully synthesized from metal chlorides solutions and graphite powder by a simple and rapid microwave-assisted polyol method via anchoring the Co_0.33Ni_0.33Mn_0.33Fe₂O₄ nanoparticles on the layered graphene sheets. The Fe³⁺, Co²⁺, Ni²⁺ and Mn²⁺ ions in the solutions were attracted by graphene oxide obtained from graphite and converted to the precursors Fe(OH)₃, Co(OH)₂, Ni(OH)₂, and Mn(OH)₂ under slightly alkaline conditions. After the transformations of the precursors to Co-Ni-Mn ferrites and conversion of graphene oxide to graphene under microwave irradiation at 170?°C in just 25?min, the Co_0.33Ni_0.33Mn_0.33Fe₂O₄/graphene nanocomposite was prepared. The composition and structure of the nanocomposite were characterized by X-ray diffraction (XRD), inductive coupled plasma emission spectroscopy (ICP), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy (RS), transmission electron microscopy (TEM), etc. It was found that with the filling ratio of only 20?wt% and the thickness of 2.3?mm, the nanocomposite showed an ultra-wide effective absorption bandwidth (less than ?10?dB) of 8.48?GHz (from 9.52 to 18.00?GHz) with the minimum reflection loss of ??24.29?dB. Compared to pure graphene sheets, Co_0.33Ni_0.33Mn_0.33Fe₂O₄ nanoparticles and the counterparts reported in literature, the nanocomposite exhibited much better electromagnetic wave absorption, mainly attributed to strong wave attenuation, as a result of synergistic effects of dielectric loss, conductive loss and magnetic loss, and to good impedance matching. In view of its thin thickness, light weight and outstanding electromagnetic wave absorption property, the nanocomposite could be used as a very promising electromagnetic wave absorber.     

Monolithic Fe2O3/graphene hybrid for highly efficient lithium storage and arsenic removal

We fabricated a monolithic Fe₂O₃/graphene hybrid directly by hydrothermal reaction of ferrous oxalate dihydrate and graphene oxide without using a reducing agent. The reduced graphene oxide formed an interconnected network structure that can be used as a support for homogeneous distribution of active Fe₂O₃ nanoparticles. The graphene network and the pore channels in the hybrid facilitate fast electron transfer and ion transport. This hybrid can be directly used as a free-standing anode for lithium ion batteries, which simplifies the fabrication procedure of electrodes, and also exhibited a high capacity of 1062 mA h g⁻¹ at 100 mA g⁻¹, high rate capability and excellent cyclic stability over 100 cycles. Furthermore, as a self-supported adsorbent, it provides a new idea on loading active materials to the suitable substrate, which can be used as a promising material for water purification due to its easy collection and excellent capability in removing As(V) from water. The results demonstrate the promising applications of bulk reduced assembly of graphene with functional metal oxides, which will be helpful for future development of graphene-based multifunctional materials.     

Preparation of Three-Dimensional Co3O4/graphene Composite for High-Performance Supercapacitors

Here, we developed a simple and efficient route for the preparation of three-dimensional (3D) Co₃O₄-anchored graphene composites using the sacrificial template-assisted method and the subsequent deposition process of Co₃O₄ nanoparticles. As structural guiding materials, polystyrene (PS) spheres provide 3D porous architectures with a high surface area. 3D porous graphene materials serve as conductive supporters for the deposition of Co₃O₄ nanoparticles through precipitation growth. The 3D porous composite structures of Co₃O₄/graphene composites were intensively investigated using scanning electron microscope, transmission electron microscope, and X-ray diffraction. The 3D Co₃O₄/graphene composites show a high specific capacitance of 328?F?g^?1 with efficient and fast charge–discharge process in aqueous 6?M KOH electrolyte. In addition, the composites provide a good cycle lifetime, which retained 98% capacitance retention over 2000 cycles.     

One-step hydrothermal synthesis of hybrid core-shell Co3O4@SnO2–SnO for supercapacitor electrodes

We successfully synthesized a novel core-shell hybrid metal oxide via a simple one-step hydrothermal method without annealing. This composite of Co₃O₄ particles covered with SnO₂–SnO (Co₃O₄@SnO₂–SnO) predicted better performance compared to pure Co₃O₄, which strongly depends on the synthetic temperature. The Co₃O₄@SnO₂–SnO prepared at a temperature of 250 °C (labeled Co₃O₄@SnO₂–SnO-250) exhibited an outstanding specific capacitance of 325 F g⁻¹ under the current density of 1 A g⁻¹, which was much higher than those of Co₃O₄ (12.6 F g⁻¹) and other composites. Additionally, the sample also exhibited good cycle stability performance with a retention rate of 100% after 5000 cycles at a current density of 5 A g⁻¹. Through X-ray photoelectron spectroscopy analysis, the presumed mechanism was that Sn-O_x decreases the surface electron densities of Co₃O₄, which is beneficial to OH⁻ adsorption and specific capacitance improvement, and the synthetic temperature had a strong impact on the microstructure and thus on the surface electron densities. The most.obvious finding to emerge from this study is that the specific capacitance can be improved through adjusting the surface electron densities of transition metal oxides.     

Towards high purity graphene/single-walled carbon nanotube hybrids with improved electrochemical capacitive performance

CoMgAl layered double hydroxides were prepared as catalysts for the in situ synchronous growth of graphene and single-walled carbon nanotubes (SWCNTs) from methane by chemical vapor deposition. The as-calcined CoMgAl layered double oxide (LDO) flakes served as the template for the deposition of graphene, and Co nanoparticles (NPs) embedded on the LDOs catalyzed the growth of SWCNTs. After the removal of CoMgAl LDO flakes, graphene (G)/SWCNT/Co₃O₄ hybrids with SWCNTs directly grown on the surface of graphene and 27.3 wt.% Co₃O₄ NPs encapsulated in graphene layers were available. Further removal of the Co₃O₄ NPs by a CO₂-oxidation assistant purification method induced the formation of G/SWCNT hybrids with a high carbon purity of 98.4 wt.% and a high specific surface area of 807.0 m²/g. The G/SWCNT/Co₃O₄ hybrids exhibited good electrochemical performance for pseudo-capacitors due to their high Co₃O₄ concentration and the high electrical conductivity of SWCNTs and graphene. In another aspect, the G/SWCNT hybrids can be used as excellent electrode materials for double-layer capacitors. A high capacity of 98.5 F/g_electrode was obtained at a scan rate of 10 mV/s, 78.2% of which was retained even when the scan rate increased to 500 mV/s.     

Highly reversible Co3O4/graphene hybrid anode for lithium rechargeable batteries

A Co₃O₄/graphene hybrid material was fabricated using a simple in situ reduction process and demonstrated as a highly reversible anode for lithium rechargeable batteries. The hybrid is composed of 5 nm size Co₃O₄ particles uniformly dispersed on graphene, as observed by transmission electron microscopy, atomic force microscopy, Raman spectroscopy and X-ray diffraction analysis. The Co₃O₄/graphene anode can deliver a capacity of more than 800 mA h g⁻¹ reversibly at a 200 mA g⁻¹ rate in the voltage range between 3.0 and 0.001 V. The high reversible capacity is retained at elevated current densities. At a current rate as high as 1000 mA g⁻¹, the Co₃O₄/graphene anode can deliver more than 550 mA h g ⁻¹, which is significantly higher than the capacity of current commercial graphite anodes. The superior electrochemical performance of the Co₃O₄/graphene is attributed to its unique nanostructure, which intimately combines the conductive graphene network with uniformly dispersed nano Co₃O₄ particles.