Direct Electrophoretic Deposition of Binder-Free Co3O4/Graphene Sandwich-Like Hybrid Electrode as Remarkable Lithium Ion Battery Anode

Electrochemical energy storage enhanced by intermediate layer stacking of heteroatom-enriched covalent organic polymers in exfoliated graphene

Covalent organic polymers (COPs) have garnered attention as potential materials for various applications, including catalysis, gas storage, and energy production. Owing to their highly conjugated structures, chemical stability, adjustable band gap, and tunable functionality, COPs have emerged as a versatile material. However, their inherent structural rigidity and poor conductivity pose challenges for energy storage applications. To address these limitations, graphene has been incorporated as a conductive filler due to its exceptional conductivity and structural integrity. This study presents an innovative approach utilizing in situ electrophoretic exfoliation of a graphite strip to develop a COP-graphene nanohybrid system (RTh-COP-EGR) that enhances supercapacitor performance. Due to the synergistic effect of heteroatom-enriched RTh-COP and conductive graphene layers, the resulting RTh-COP-EGR nanohybrid exhibits a capacitance of 4.2 mF cm-2 at a current density of 70 μA cm-2, with an energy density of 0.4725 mW h cm-2 and a power density of 314.4 W cm-2 at higher current densities. Furthermore, this nanohybrid exhibits an impressive capacity retention of 82% over 10 000 cycles, showcasing its potential for advanced energy storage applications.

Bimetal Metal-Organic Framework-Derived Ni-Mn@Carbon/Reduced Graphene Oxide as a Cathode for an Asymmetric Supercapacitor with High Energy Density

As is known, metal-organic frameworks (MOFs) are a versatile class of materials in energy storage applications including supercapacitors. However, the individual kind of metal nodes connected by organic ligands to form a topological structure still limits the potential storage capacity of MOFs. Herein, a bimetal-based Ni-Mn MOF composite is configured with a one-pot hydrothermal method to derive a composite with a synergic effect to maximize the properties. Moreover, reduced graphene oxide (rGO) sheets are added as a conductive network to anchor the MOF-derived composite of Ni-Mn@C/rGO, which is expected to increase the conductivity of the materials system. The resulting composite exhibited a high specific capacitance of 1674 F g-1 at a current density of 0.3 A g-1, suggesting excellent energy storage performance. The composite was then integrated as the cathode in an asymmetrical supercapacitor with a 3D rGO aerogel anode, resulting in energy densities of 24.1 and 17.5 W h kg-1 at power densities of 88.9 and 444.4 W kg-1, respectively. Additionally, the device demonstrated remarkable long-term stability, with 90% capacitance retention after 10 000 charge-discharge cycles at 10 A g-1.

Electrophoretic Deposition of Co3O4 Particles/Reduced Graphene Oxide Composites for Efficient Non-Enzymatic H2O2 Sensing

In this work, the facile fabrication of Co₃O₄ particles/reduced graphene oxide (Co₃O₄/rGO) composites on Indium tin oxide (ITO) slide was achieved by an electrophoretic deposition and annealing process. The deposition time and ratio of the precursors were optimized. Structural characterization and chemical composition investigation indicated successful loading of Co₃O₄ particles on graphene sheets. When applied as a non-enzymatic H₂O₂ sensor, Co₃O₄/rGO showed significant electrocatalytic activity, with a wide linear range (0.1-19.5 mM) and high sensitivity (0.2247 mA mM^-1 cm^-2). The good anti-interference ability, reproducibility, and long-term stability of the constructed sensor were also presented. The application of Co₃O₄/rGO in real sample analysis was evaluated in human urine sample with satisfactory results, indicating the feasibility of the sensor in physiological and medical applications.

Reduced graphene oxide (rGO) supported and p yrolytic carbon (PC) coated γ-Fe2O3/PC-rGO composite anode material with enhanced Li-storage performance

As a high-capacity anode material for lithium ion batteries, γ-Fe 2 O 3 is a promising alternative to conventional graphite among multifarious transition metal oxides owing to its high theoretical specific capacity (1007 mAh g -1 ), abundant reserves, good safety and low cost. However, improving the electrical conductivity and overcoming the morphological damage caused by the severe volume expansion during cycling are still the tricky problems to be solved. Herein, a three-dimensional heterostructure composite (γ-Fe 2 O 3 /PC-rGO 60 ) was prepared by a facile solvothermal reaction followed by heat treatment in inert atmosphere. This composite material exhibits a reversible charge specific capacity of 1035 mAh g -1 at the current density of 0.1 A g -1 . After 100 cycles at 0.2 A g -1 , the capacity is increased from 966.2 to 1091.1 mAhg -1 . Even cycled for 200 cycles at 1 A g -1 , the capacity is only decreased from 751.4 to 670.6 mAh g -1 , giving capacity retention of 89.3%. The rGO network supported flexible composite architecture is beneficial for accommodating the volume expansion of the γ-Fe 2 O 3 active material during the lithiation/delithiation process. Besides, the conductive rGO network and the in-situ formed pyrolytic carbon (PC) can provide a smooth electron transmission path and a favorable lithium ion transport channel.

Controllable Synthesis of a Porous PEI-Functionalized Co3O4/rGO Nanocomposite as an Electrochemical Sensor for Simultaneous as Well as Individual Detection of Heavy Metal Ions

The present study focuses on the strategy of employing an electrochemical sensor with a porous polyethylenimine (PEI)-functionalized Co₃O₄/reduced graphene oxide (rGO) nanocomposite (NCP) to detect heavy metal ions (HMIs: Cd²⁺, Pb²⁺, Cu²⁺, and Hg²⁺). The porous PEI-functionalized Co₃O₄/rGO NCP (rGO·Co₃O₄·PEI) was prepared via a hydrothermal method. The synthesized NCP was based on a conducting polymer PEI, rGO, nanoribbons of Co₃O₄, and highly dispersed Co₃O₄ nanoparticles (NPs), which have shown excellent performance in the detection of HMIs. The as-prepared PEI-functionalized rGO·Co₃O₄·PEI NCP-modified electrode was used for the sensing/detection of HMIs by means of both square wave anodic stripping voltammetry (SWV) and differential normal pulse voltammetry (DNPV) methods for the first time. Both methods were employed for the simultaneous detection of HMIs, whereas SWV was employed for the individual analysis as well. The limits of detection (LOD; 3σ method) for Cd²⁺, Pb²⁺, Cu²⁺, and Hg²⁺ determined using the rGO·Co₃O₄·PEI NCP-modified electrode were 0.285, 1.132, 1.194, and 1.293 nM for SWV, respectively. Similarly, LODs of Cd²⁺, Pb²⁺, Cu²⁺, and Hg²⁺ were 1.069, 0.285, 2.398, and 1.115 nM, respectively, by DNPV during simultaneous analysis, whereas they were 0.484, 0.878, 0.462, and 0.477 nM, respectively, by SWV in individual analysis.

Hard template synthesis of 2D porous Co3O4 nanosheets with graphene oxide for H2O2 sensing

In this work, we used graphene oxide (GO) as a template that was removed by calcination to finally successfully prepare Co₃O₄ with 2D porous nanostructure. The results show that 2D porous structure Co₃O₄ nanosheets were only prepared at pH = 2. After electrochemical tests, the as-prepared Co₃O₄ nanosheets showed electrochemical properties that are highly suitable for H₂O₂ detection, such as high current response, short response time (less than 3 s), wide linear range (0.388-44.156 mM), low limit of detection (2.33 μM) and high sensitivity (0.0891 mA mM^-1 cm^-2). These excellent properties are mainly due to GO, as a 2D template, which connects Co₃O₄ nanoparticles to each other on a 2D plane, preventing the agglomeration of Co₃O₄ nanoparticles. The abundant pores between Co₃O₄ nanoparticles can greatly increase the reaction between the nanoparticles and H₂O₂ molecules.

One-Pot Efficient Catalytic Oxidation for Bio-Vanillin Preparation and Carbon Isotope Analysis

Vanillin (4-hydroxy-3-methoxybenzaldehyde) is one of the most widely used food spices. Aimed at bio-vanillin green production, the natural materials were directly catalytically oxidized efficiently in one pot under low O₂ pressure (0.035 MPa) in the presence of a non-noble metal oxidation combined catalyst (NiCo₂O₄/SiO₂ nanoparticles), which showed remarkable advantages of a short synthetic route and less industrial waste. The catalytic system showed good universality to many natural substrates with nearly 100% conversion and 86.3% bio-vanillin yield. More importantly, carbon isotope ratio investigations were employed to verify the origin of the organic matter. One hundred percent ¹⁴C content of the obtained vanillin was detected, which indicated that it was an efficient method to distinguish the vanillin from biomass or fossil materials. Furthermore, the ¹³C isotope examination showed effective distinguishing ability for the vanillin from a particular biomass source. The C isotope detection provides an effective method for commercial vanillin identification.

A Low-Temperature Molecular Precursor Approach to Copper-Based Nano-Sized Digenite Mineral for Efficient Electrocatalytic Oxygen Evolution Reaction

In the urge of designing noble metal-free and sustainable electrocatalysts for oxygen evolution reaction (OER), herein, a mineral Digenite Cu9 S5 has been prepared from a molecular copper(I) precursor, [{(PyHS)2 CuI (PyHS)}2 ](OTf)2 (1), and utilized as an anode material in electrocatalytic OER for the first time. A hot injection of 1 yielded a pure phase and highly crystalline Cu9 S5 , which was then electrophoretically deposited (EPD) on a highly conducting nickel foam (NF) substrate. When assessed as an electrode for OER, the Cu9 S5 /NF displayed an overpotential of merely 298±3 mV at a current density of 10 mA cm-2 in alkaline media. The overpotential recorded here supersedes the value obtained for the best reported Cu-based as well as the benchmark precious-metal-based RuO2 and IrO2 electrocatalysts. In addition, the choronoamperometric OER indicated the superior stability of Cu9 S5 /NF, rendering its suitability as the sustainable anode material for practical feasibility. The excellent catalytic activity of Cu9 S5 can be attributed to the formation of a crystalline CuO overlayer on the conductive Cu9 S5 that behaves as active species to facilitate OER. This study delivers a distinct molecular precursor approach to produce highly active copper-based catalysts that could be used as an efficient and durable OER electro(pre)catalysts relying on non-precious metals.

MoS2 nanoflowers encapsulated into carbon nanofibers containing amorphous SnO2 as an anode for lithium-ion batteries

SnO₂ with high abundance, large theoretical capacity, and nontoxicity is considered to be a promising candidate for use as advanced electrodes. However, the poor electronic conductivity and large volume variations hinder the practical applications of SnO₂-based electrodes for use in lithium-ion batteries (LIBs). Herein, the MoS₂-SnO₂ heterostructures were encapsulated into carbon nanofibers (CNFs) via facile solvothermal and electrospinning methods. Remarkably, when the binder-free and robust MoS₂-SnO₂@CNF is employed as the anode for LIBs, such a clever structure yields a discharge capacity of 983 mA h g^-1 at a current density of 200 mA g^-1 after 100 cycles and a capacity of 710 mA h g^-1 after 800 cycles at a current density of 2000 mA g^-1. Moreover, full cells and flexible full cells were constructed, which exhibited high flexibility and delivered a high reversible capacity of 463 mA h g^-1 after 100 cycles at 500 mA g^-1. The exceptional performance of MoS₂-SnO₂@CNF could be attributed to the rational design of the electrode structure. On one hand, the robust structure of the amorphous SnO₂ and MoS₂ nanoflowers in the conductive carbon network not only provides direct current pathways, but also enhances electron transfer. On the other hand, the abundance of p-n heterogeneous interfaces considerably reduces the charge transfer resistance and enhances the surface reaction kinetics. This work proposes a feasible strategy to enhance the capacity and stability of SnO₂-based electrodes and opens up a new avenue for the potential applications of SnO₂ anode materials.

Nitrogen-Doped Porous Co3O4/Graphene Nanocomposite for Advanced Lithium-Ion Batteries

A novel approach is developed to synthesize a nitrogen-doped porous Co₃O₄/anthracite-derived graphene (Co₃O₄/AG) nanocomposite through a combined self-assembly and heat treatment process using resource-rich anthracite as a carbonaceous precursor. The nanocomposite contains uniformly distributed Co₃O₄ nanoparticles with a size smaller than 8 nm on the surface of porous graphene, and exhibits a specific surface area (120 m²·g⁻¹), well-developed mesopores distributed at 3~10 nm, and a high level of nitrogen doping (5.4 at. %). These unique microstructure features of the nanocomposite can offer extra active sites and efficient pathways during the electrochemical reaction, which are conducive to improvement of the electrochemical performance for the anode material. The Co₃O₄/AG electrode possesses a high reversible capacity of 845 mAh·g⁻¹ and an excellent rate capacity of 587 mAh·g⁻¹. Furthermore, a good cyclic stability of 510 mAh·g⁻¹ after 100 cycles at 500 mA·g⁻¹ is maintained. Therefore, this work could provide an economical and effective route for the large-scale application of a Co₃O₄/AG nanocomposite as an excellent anode material in lithium-ion batteries.

Electrophoretic Deposition for Lithium-Ion Battery Electrode Manufacture

Electrophoretic deposition (EPD) has received increasing attention as an alternative manufacturing approach to slurry casting for the production of battery and supercapacitor electrodes. This process is of relevance for industrial scalability as evidently seen in the current electrophoretic paints industry. Nevertheless, the reported work so far have only concentrated on thin films of electrophoretically deposited electrodes for energy storage. Here, the electrochemical performance of thick films (up to tens of μm) as lithium-ion battery electrodes produced by EPD is reported. A commercially sourced LiN1/3M1/3C1/3O2 (5 to 25 μm particle size) was used in this exemplary investigation. This work shows the production of binder-free high density active material (>90 %) electrodes. Coin cells were assembled and the battery performance was measured. Tests included: cyclic voltammetry, C-rate vs capacity, battery cycling and electrochemical impedance spectroscopy. Other investigations also studied: colloidal electrolyte formulation, electrode manufacture, microstructure characterisation and elemental mapping analysis. In short, EPD electrode manufacture can be applied as a platform technology for any battery and supercapacitor material, and the reported manufacturing processes and methodologies represent direct relevance to produce energy storage electrodes useful to practical applications.

Recent Advances and Perspectives of Carbon-Based Nanostructures as Anode Materials for Li-ion Batteries

Rechargeable batteries are attractive power storage equipment for a broad diversity of applications. Lithium-ion (Li-ion) batteries are widely used the superior rechargeable battery in portable electronics. The increasing needs in portable electronic devices require improved Li-ion batteries with excellent results over many discharge-recharge cycles. One important approach to ensure the electrodes' integrity is by increasing the storage capacity of cathode and anode materials. This could be achieved using nanoscale-sized electrode materials. In the article, we review the recent advances and perspectives of carbon nanomaterials as anode material for Lithium-ion battery applications. The first section of the review presents the general introduction, industrial use, and working principles of Li-ion batteries. It also demonstrates the advantages and disadvantages of nanomaterials and challenges to utilize nanomaterials for Li-ion battery applications. The second section of the review describes the utilization of various carbon-based nanomaterials as anode materials for Li-ion battery applications. The last section presents the conclusion and future directions.

Enhanced Roles of Carbon Architectures in High-Performance Lithium-Ion Batteries

Lithium-ion batteries (LIBs), which are high-energy-density and low-safety-risk secondary batteries, are underpinned to the rise in electrochemical energy storage devices that satisfy the urgent demands of the global energy storage market. With the aim of achieving high energy density and fast-charging performance, the exploitation of simple and low-cost approaches for the production of high capacity, high density, high mass loading, and kinetically ion-accessible electrodes that maximize charge storage and transport in LIBs, is a critical need. Toward the construction of high-performance electrodes, carbons are promisingly used in the enhanced roles of active materials, electrochemical reaction frameworks for high-capacity noncarbons, and lightweight current collectors. Here, we review recent advances in the carbon engineering of electrodes for excellent electrochemical performance and structural stability, which is enabled by assembled carbon architectures that guarantee sufficient charge delivery and volume fluctuation buffering inside the electrode during cycling. Some specific feasible assembly methods, synergism between structural design components of carbon assemblies, and electrochemical performance enhancement are highlighted. The precise design of carbon cages by the assembly of graphene units is potentially useful for the controlled preparation of high-capacity carbon-caged noncarbon anodes with volumetric capacities over 2100 mAh cm^-3. Finally, insights are given on the prospects and challenges for designing carbon architectures for practical LIBs that simultaneously provide high energy densities (both gravimetric and volumetric) and high rate performance.

3D plum candy-like NiCoMnO4@graphene as anodes for high-performance lithium-ion batteries

3D plum candy-like NiCoMnO4 microspheres have been prepared via ultrasonic spraying and subsequently wrapped by graphene through electrostatic self-assembly. The as-prepared NiCoMnO4 powders show hollow structures and NiCoMnO4@graphene exhibits excellent electrochemical performances in terms of rate performance and cycling stability, achieving a high reversible capacity of 844.6 mA h g-1 at a current density of 2000 mA g-1. After 50 cycles at 1000 mA g-1, NiCoMnO4@graphene delivers a reversible capacity of 1045.1 mA h g-1 while the pristine NiCoMnO4 only has a capacity of 143.4 mA h g-1. The hierarchical porous structure helps to facilitate electron transfer and Li-ion kinetic diffusion by shortening the Li-ion diffusion length, accommodating the mechanical stress and volume change during the Li-ion insertion/extraction processes. Analysis from the electrochemical performances reveals that the enhanced performances could be also attributed to the reduced charge-transfer resistance and enhanced Li-ion diffusion kinetics because of the graphene-coating. Moreover, Schottky electric field, due to the difference in work function between graphene and NiCoMnO4, might be favorable for the redox activity of the NiCoMnO4. In light of the excellent electrochemical performance and simple preparation, we believe that 3D plum candy-like NiCoMnO4@graphene composites are expected to be applied as a promising anode materials for high-performance lithium ion batteries.

In Situ Synthesis and Unprecedented Electrochemical Performance of Double Carbon Coated Cross-Linked Co3O4

Improving the structural stability and the electron/ion diffusion rate across whole electrode particles is crucial for transition metal oxides as next-generation anodic materials in lithium-ion batteries. Herein, we report a novel structure of double carbon-coated Co₃O₄ cross-linked composite, where the Co₃O₄ nanoparticle is in situ covered by nitrogen-doped carbon and further connected by carbon nanotubes (Co₃O₄ NP@NC@CNTs). This double carbon-coated Co₃O₄ NP@NC@CNTs framework not only endows a porous structure that can effectively accommodate the volume changes of Co₃O_4, but also provides multidimensional pathways for electronic/ionic diffusion in and among the Co₃O₄ NPs. Electrochemical kinetics investigation reveals a decreased energy barrier for electron/ion transport in the Co₃O₄ NP@NC@CNTs, compared with the single carbon-coated Co₃O₄ NP@NC. As expected, the Co₃O₄ NP@NC@CNT electrode exhibits unprecedented lithium storage performance, with a high reversible capacity of 1017 mA h g^-1 after 500 cycles at 1 A g^-1, and a very good capacity retention of 75%, even after 5000 cycles at 15 A g^-1. The lithiation/delithiation process of Co₃O₄ NP@NC@CNTs is dominated by the pseudocapacitive behavior, resulting in excellent rate performance and durable cycle stability.

Self-supporting Co3O4/Graphene Hybrid Films as Binder-free Anode Materials for Lithium Ion Batteries

A self-supporting Co₃O₄/graphene hybrid film has been constructed via vacuum filtration of Co(OH)₂ nanosheet and graphene, followed by a two-step thermal treatment. Within the hybrid film, Co₃O₄ nanoparticles with size of 40~60 nm uniformly in-situ grew on the surface of graphene, forming a novel porous and interleaved structure with strong interactions between Co₃O₄ nanoparticles and graphene. Such fascinating microstructures can greatly facilitate interfacial electron transportation and accommodate the volume changes upon Li ions insertion and extraction. Consequently, the binder-less hybrid film demonstrated extremely high reversible capacity (1287.7 mAh g⁻¹ at 0.2 A g⁻¹), excellent cycling stability and rate capability (1110 and 800 mAh g⁻¹ at 0.5 and 1.0 A g⁻¹, respectively).

Cobalt Nanoparticles Chemically Bonded to Porous Carbon Nanosheets: A Stable High-Capacity Anode for Fast-Charging Lithium-Ion Batteries

A two-dimensional electrode architecture of ∼25 nm sized Co nanoparticles chemically bonded to ∼100 nm thick amorphous porous carbon nanosheets (Co@PCNS) through interfacial Co-C bonds is reported for the first time. This unique 2D hybrid architecture incorporating multiple Li-ion storage mechanisms exhibited outstanding specific capacity, rate performance, and cycling stabilities compared to nanostructured Co₃O₄ electrodes and Co-based composites reported earlier. A high discharge capacity of 900 mAh/g is achieved at a charge-discharge rate of 0.1C (50 mA/g). Even at high rates of 8C (4 A/g) and 16C (8 A/g), Co@PCNS demonstrated specific capacities of 620 and 510 mAh/g, respectively. Integrity of interfacial Co-C bonds, Co nanoparticles, and 90% of the initial capacity are preserved after 1000 charge-discharge cycles. Implementation of Co nanoparticles instead of Co₃O₄ restricted Li₂O formation during the charge-discharge process. In situ formed Co-C bonds during the pyrolysis steps improve interfacial charge transfer, and eliminate particle agglomeration, identified as the key factors responsible for the exceptional electrochemical performance of Co@PCNS. Moreover, the nanoporous microstructure and 2D morphology of carbon nanosheets facilitate superior contact with the electrolyte solution and improved strain relaxation. This study summarizes design principles for fabricating high-performance transition-metal-based Li-ion battery hybrid anodes.

A ratiometric photoelectrochemical immunosensor based on g-C3N4@TiO2 NTs amplified by signal antibodies–Co3O4 nanoparticle conjugates

Herein, we report a ratiometric photoelectrochemical (PEC) immunosensor coupled with secondary antibodies–Co₃O₄ nanoparticle conjugates (Ab₂–Co₃O₄ NPs) for signal amplification.