Carbon-Encapsulated Co 3 O 4 @CoO@Co Nanocomposites for Multifunctional Applications in Enhanced Long-life Lithium Storage, Supercapacitor and Oxygen Evolution Reaction

Unraveling the Electrochemical Insights of Cobalt Oxide/Conducting Polymer Hybrid Materials for Supercapacitor, Battery, and Supercapattery Applications

This review article focuses on the potential of cobalt oxide composites with conducting polymers, particularly polypyrrole (PPy) and polyaniline (PANI), as advanced electrode materials for supercapacitors, batteries, and supercapatteries. Cobalt oxide, known for its high theoretical capacitance, is limited by poor conductivity and structural degradation during cycling. However, the integration of PPy and PANI has been proven to enhance the electrochemical performance through improved conductivity, increased pseudocapacitive effects, and enhanced structural integrity. This synergistic combination facilitates efficient charge transport and ion diffusion, resulting in improved cycling stability and energy storage capacity. Despite significant progress in synthesis techniques and composite design, challenges such as maintaining structural stability during prolonged cycling and scalability for mass production remain. This review highlights the synthesis methods, latest advancements, and electrochemical performance in cobalt oxide/PPy and cobalt oxide/PANI composites, emphasizing their potential to contribute to the development of next-generation energy storage devices. Further exploration into their application, especially in battery systems, is necessary to fully harness their capabilities and meet the increasing demands of energy storage technologies.

Polymer-assisted synthesis of Co3O4/CoO microballs decorated N-doped carbon for symmetric supercapacitor

Cobalt oxide (Co) and cobalt oxide/N-doped carbon composites (Co-NC) were synthesized and applied as electrode materials for supercapacitors. The pristine cobalt oxide was prepared hydrothermally at 160 °C (CoH160) and further calcined at three different temperatures of 300, 400, and 500 °C (CoC300, CoC400, and CoC500). The cobalt oxide prepared at 300 °C was composited with N-doped carbon prepared from g-C3N4 at four different weight ratios 1 : 0.03, 1 : 0.06, 1 : 0.15, and 1 : 0.30 (Co-NC1, Co-NC2, Co-NC3, and Co-NC4). X-ray diffraction analysis (XRD) confirms the phase and product formation. Among all the composites, Co-NC2 showed the microball structure decorated on N-doped carbon with an average size of 4.2 μm. The X-ray photoelectron spectroscopy (XPS) of Co-NC2 confirms the presence of Co2+, Co3+, C, N, and O. The Brunauer-Emmett-Teller analysis (BET) of Co-NC2 showed a surface area of 73.06 m2 g-1 with a pore diameter of 3.39 nm. The energy storage performance of Co-NC2 exhibits a high specific capacitance of 774.38 F g-1 at a current density of 1 A g-1 in 1 M KOH electrolyte. The fabricated symmetric device showed a specific capacitance of 84.60 F g-1 at a current density of 1 A g-1. The fabricated device showed good cyclic stability with a coulombic efficiency of 92.55% and capacitance retention of 97.75% up to 4000 cycles.

The Review of Hybridization of Transition Metal-Based Chalcogenides for Lithium-Ion Battery Anodes

Transition metal chalcogenides as potential anodes for lithium-ion batteries have been widely investigated. For practical application, the drawbacks of low conductivity and volume expansion should be further overcome. Besides the two conventional methods of nanostructure design and the doping of carbon-based materials, the component hybridization of transition metal-based chalcogenides can effectively enhance the electrochemical performance owing to the synergetic effect. Hybridization could promote the advantages of each chalcogenide and suppress the disadvantages of each chalcogenide to some extent. In this review, we focus on the four different types of component hybridization and the excellent electrochemical performance that originated from hybridization. The exciting problems of hybridization and the possibility of studying structural hybridization were also discussed. The binary and ternary transition metal-based chalcogenides are more promising to be used as future anodes of lithium-ion batteries for their excellent electrochemical performance originating from the synergetic effect.

High Cycle Stability of Hybridized Co(OH)2 Nanomaterial Structures Synthesized by the Water Bath Method as Anodes for Lithium-Ion Batteries

Cobalt oxides have been intensely explored as anodes of lithium-ion batteries to resolve the intrinsic disadvantages of low electrical conductivity and volume change. However, as a precursor of preparing cobalt oxides, Co(OH)₂ has rarely been investigated as the anode material of lithium-ion batteries, perhaps because of the complexity of hydroxides. Hybridized Co(OH)₂ nanomaterial structures were synthesized by the water bath method and exhibited high electrochemical performance. The initial discharge and charge capacities were 1703.2 and 1262.9 mAh/g at 200 mA/g, respectively. The reversible capacity was 1050 mAh/g after 150 cycles. The reversible capability was 1015 mAh/g at 800 mA/g and increased to 1630 mAh/g when driven back to 100 mA/g. The electrochemical reaction kinetics study shows that the lithium-ion diffusion-controlled contribution is dominant in the energy storage mechanism. The superior electrochemical performance could result from the water bath method and the hybridization of nanosheets and nanoparticles structures. These hybridized Co(OH)₂ nanomaterial structures with high electrochemical performance are promising anodes for lithium-ion batteries.

Noble-Metal-Free Multicomponent Nanointegration for Sustainable Energy Conversion

Global energy and environmental crises are among the most pressing challenges facing humankind. To overcome these challenges, recent years have seen an upsurge of interest in the development and production of renewable chemical fuels as alternatives to the nonrenewable and high-polluting fossil fuels. Photocatalysis, photoelectrocatalysis, and electrocatalysis provide promising avenues for sustainable energy conversion. Single- and dual-component catalytic systems based on nanomaterials have been intensively studied for decades, but their intrinsic weaknesses hamper their practical applications. Multicomponent nanomaterial-based systems, consisting of three or more components with at least one component in the nanoscale, have recently emerged. The multiple components are integrated together to create synergistic effects and hence overcome the limitation for outperformance. Such higher-efficiency systems based on nanomaterials will potentially bring an additional benefit in balance-of-system costs if they exclude the use of noble metals, considering the expense and sustainability. It is therefore timely to review the research in this field, providing guidance in the development of noble-metal-free multicomponent nanointegration for sustainable energy conversion. In this work, we first recall the fundamentals of catalysis by nanomaterials, multicomponent nanointegration, and reactor configuration for water splitting, CO₂ reduction, and N₂ reduction. We then systematically review and discuss recent advances in multicomponent-based photocatalytic, photoelectrochemical, and electrochemical systems based on nanomaterials. On the basis of these systems, we further laterally evaluate different multicomponent integration strategies and highlight their impacts on catalytic activity, performance stability, and product selectivity. Finally, we provide conclusions and future prospects for multicomponent nanointegration. This work offers comprehensive insights into the development of cost-competitive multicomponent nanomaterial-based systems for sustainable energy-conversion technologies and assists researchers working toward addressing the global challenges in energy and the environment.

Facile Synthesis of Co3O4@CoO@Co Gradient Core@Shell Nanoparticles and Their Applications for Oxygen Evolution and Reduction in Alkaline Electrolytes

We demonstrate a facile fabrication scheme for Co₃O₄@CoO@Co (gradient core@shell) nanoparticles on graphene and explore their electrocatalytic potentials for an oxygen evolution reaction (OER) and an oxygen reduction reaction (ORR) in alkaline electrolytes. The synthetic approach begins with the preparation of Co₃O₄ nanoparticles via a hydrothermal process, which is followed by a controlled hydrogen reduction treatment to render nanoparticles with radial constituents of Co₃O₄/CoO/Co (inside/outside). X-ray diffraction patterns confirm the formation of crystalline Co₃O₄ nanoparticles, and their gradual transformation to cubic CoO and fcc Co on the surface. Images from transmission electron microscope reveal a core@shell microstructure. These Co₃O₄@CoO@Co nanoparticles show impressive activities and durability for OER. For ORR electrocatalysis, the Co₃O₄@CoO@Co nanoparticles are subjected to a galvanic displacement reaction in which the surface Co atoms undergo oxidative dissolution for the reduction of Pt ions from the electrolyte to form Co₃O₄@Pt nanoparticles. With commercial Pt/C as a benchmark, we determine the ORR activities in sequence of Pt/C > Co₃O₄@Pt > Co₃O₄. Measurements from a rotation disk electrode at various rotation speeds indicate a 4-electron transfer path for Co₃O₄@Pt. In addition, the specific activity of Co₃O₄@Pt is more than two times greater than that of Pt/C.

Ultrasound-treated metal-organic framework with efficient electrocatalytic oxygen evolution activity

Metal-organic frameworks (MOFs) and their derivatives are excellent candidates for electrocatalysts profiting from their unique structures and accessible active sites. Generally, due to the weak poor conductivity and catalytic activity when used as OER electrocatalysts, MOFs are more likely to be used as precursors to obtain composite catalysts through further pyrolysis treatment, rather than directly applied as OER electrocatalysts. But heat treatment usually results in structural collapse and loss of active sites. Specially, as a kind of two-dimensional (2D) materials with rapid electron transfer, metal-organic framework nanosheets (MONs) have great application potential in various fields, especially in the field of catalysis, due to the advantages of both MOFs and 2D materials. Here, we have reported a simple top-down approach to synthesize Co-MONs which can be directly adopted as efficient OER catalysts. Ultrasonic bath (40 KHz, 100 W) was employed to control the exposing of the preponderant lattice plane, which can offer plentiful active catalytic sites and accelerate ions transport. The optimized Co-MONs attain 10 mA cm^-2 at an overpotential of 309 mV with a small Tafel slope of 75.71 mV dec^-1.

Seaweed-Liked WS₂/rGO Enabling Ultralong Cycling Life and Enhanced Rate Capability for Lithium-Ion Batteries

WS₂ is considered as a potential anode material for lithium ion batteries (LIBs) with superior theoretical capacity and stable structure with two-dimensional which facilitates to the transportation and storage of lithium ion. Nevertheless, the commercial recognition of WS₂ has been impeded by the intrinsic properties of WS₂, including poor electrical conductivity and large volume expansion. Herein, a seaweed-liked WS₂/reduced graphene oxide (rGO) composites has been fabricated through a procedure involving the self-assembling of WO₄2-, hexadecyl trimethyl ammonium ion with graphene oxide (GO) and the subsequent thermal treatment. The WS₂/rGO nanocomposite exhibited the outstanding electrochemical property with a stable and remarkable capacity (507.7 mAh·g-1) at 1.0 A·g-1 even after 1000 cycles. This advanced electrochemical property is due to its seaweed-liked feature which can bring in plentiful active sites, ameliorate the stresses arisen from volume variations and increase charge transfer rate.

Metal-Oleate Complex-Derived Bimetallic Oxides Nanoparticles Encapsulated in 3D Graphene Networks as Anodes for Efficient Lithium Storage with Pseudocapacitance

In this manuscript, we have demonstrated the delicate design and synthesis of bimetallic oxides nanoparticles derived from metal-oleate complex embedded in 3D graphene networks (MnO/CoMn₂O₄ ⊂ GN), as an anode material for lithium ion batteries. The novel synthesis of the MnO/CoMn₂O₄ ⊂ GN consists of thermal decomposition of metal-oleate complex containing cobalt and manganese metals and oleate ligand, forming bimetallic oxides nanoparticles, followed by a self-assembly route with reduced graphene oxides. The MnO/CoMn₂O₄ ⊂ GN composite, with a unique architecture of bimetallic oxides nanoparticles encapsulated in 3D graphene networks, rationally integrates several benefits including shortening the diffusion path of Li⁺ ions, improving electrical conductivity and mitigating volume variation during cycling. Studies show that the electrochemical reaction processes of MnO/CoMn₂O₄ ⊂ GN electrodes are dominated by the pseudocapacitive behavior, leading to fast Li⁺ charge/discharge reactions. As a result, the MnO/CoMn₂O₄ ⊂ GN manifests high initial specific capacity, stable cycling performance, and excellent rate capability.

Engineering Cu2O/Cu@CoO hierarchical nanospheres: synergetic effect of fast charge transfer cores and active shells for enhanced oxygen evolution reaction

An OER catalyst that has a high conductivity Cu₂O/Cu core and a strong bonding interface with the active CoO shell was constructed.

Bioinspired Cobalt-Citrate Metal-Organic Framework as an Efficient Electrocatalyst for Water Oxidation

Efficient and cost-effective oxygen evolution reaction (OER) electrocatalysts are closely associated with many important energy conversion technologies. Herein, we first report an oxygen-evolving cobalt-citrate metal-organic framework (MOF, UTSA-16) for highly efficient electrocatalytic water oxidation. Benefiting from synergistic cooperation of intrinsic open porous structure, in situ formed high valent cobalt species, and existing Co₄O₄ cubane, the UTSA-16 exhibits excellent activity toward OER catalysis in alkaline medium. The UTSA-16 needs only 408 mV to offer a current density of 10 mA cm^-2 for OER catalysis, which is superior to that of most MOF-based electrocatalysts and the standard Co₃O₄ counterpart. The present finding provides a better understanding of electroactive MOFs for water oxidation.

Well-Dispersed Co/CoO/C Nanospheres with Tunable Morphology as High-Performance Anodes for Lithium Ion Batteries

Well-dispersed Co/CoO/C nanospheres have been designed and constructed through a facile electrospinning method with a strategy controlling the morphology of nanocomposites via adjusting the pre-oxidized and heat treatments. Scanning electron microscopy results reveal that the as-synthesized sample pre-oxidized at 275 °C shows better spherical morphology with a diameter of around 300 nm without conspicuous agglomeration. X-ray diffraction analysis confirms the coexistence of cobalt and cobalt monoxide in the sample. Furthermore, the electrochemical tests reveal that the sample pre-oxidized at 275 °C displays excellent cycling stability with only 0.016% loss per cycle even after 400 cycles at 1000 mA·g^-1 and enhanced high-rate capability with a specific discharge capacity of 354 mA·g^-1 at 2000 mA·g^-1. Besides, the sample pre-oxidized at 275 °C shows a specific capacity of 755 mA·g^-1 at 100 mA·g^-1 after 95 cycles. The improved electrochemical performance has been ascribed to the well dispersion of nanospheres, the improved electronic conductivity, and the structural integrity contribution from the carbon and cobalt coexisting nanocomposite. The strategy for preparing well-dispersed nanospheres by adjusting pre-oxidized and annealing processes could have insight for other oxide nanosphere synthesis.