Three-dimensional porous Co3O4-CoO@GO composite combined with N-doped carbon for superior lithium storage

Synergistic enhanced activation of peroxymonosulfate by heterojunction Co3O4-CuO@CN for removal of oxytetracycline: Performance, mechanism, and stability

Metal-organic frameworks (MOFs) as precursors for catalysts has drawn growing attentions. In this study, heterojunction Co3O4-CuO doped carbon materials (noted as Co3O4-CuO@CN) were prepared by direct carbonization of CuCo-MOF in air. It was found that the Co3O4-CuO@CN-2 exhibited excellent catalytic activity with the highest Oxytetracycline (OTC) degradation rate of 0.0902 min-1 at 50 mg/L of Co3O4-CuO@CN-2 dosage, 2.0 mM of PMS and 20 mg/L of OTC, which was 4.25 and 4.96 times that of CuO@CN and Co3O4@CN, respectively. Furthermore, Co3O4-CuO@CN-2 was efficient over a wide pH range (pH 1.9-8.4), and possessed good stability and reusability without OTC degradation decrease after five consecutive uses at pH 7.0. In a comprehensive analysis, the rapid regeneration of Cu(II) and Co(II) is responsible for their excellent catalytic performance, and the p-p heterojunction structure formed between Co3O4 and CuO acts as an intermediary of electron transfer to accelerate PMS decomposition. Moreover, it was interesting to find that Cu rather than Co species played a vital role in the PMS activation. The quenching experiments and electron paramagnetic resonance demonstrated that .OH, SO4•-, and 1O2 were the reactive species responsible for oxidation of OTC and the non-radical pathway triggered by 1O2 was dominant.

Hollow Porous CoO@Reduced Graphene Oxide Self-Supporting Flexible Membrane for High Performance Lithium-Ion Storage

We report an environment-friendly preparation method of rGO-based flexible self-supporting membrane electrodes, combining Co-MOF with graphene oxide and quickly preparing a hollow CoO@rGO flexible self-supporting membrane composite with a porous structure. This unique hollow porous structure can shorten the ion transport path and provide more active sites for lithium ions. The high conductivity of reduced graphene oxide further facilitates the rapid charge transfer and provides sufficient buffer space for the hollow Co-MOF nanocubes during the charging process. We evaluated its electrochemical performance in a coin cell, which showed good rate capability and cycling stability. The CoO@rGO flexible electrode maintains a high specific capacity of 1103 mAh g^-1 after 600 cycles at 1.0 A g^-1. The high capacity of prepared material is attributed to the synergistic effect of the hollow porous structure and the 3D reduced graphene oxide network. This would be considered a promising new strategy for synthesizing hollow porous-structured rGO-based self-supported flexible electrodes.

A g-C3N4 self-templated preparation of N-doped carbon nanosheets@Co-Co3O4/Carbon nanotubes as high-rate lithium-ion batteries' anode materials

A novel N-doped graphene-like carbon nanosheets (CNs) and carbon nanotubes (CNTs)-encapsulated Co-Co₃O₄ nanoparticles (NPs) (CN@Co-Co₃O₄/CNTs) were synthesized successfully by a simple hydrothermal and annealing method with graphite carbon nitride (g-C₃N₄) as self-template. By annealing Co²⁺/g-C₃N₄ under N₂ atmosphere, g-C₃N₄ was transformed into CN/CNTs, and Co²⁺ was reduced into CoNPs which were embedded in CNs. Further annealing in air, a shell of Co₃O₄ was formed around CoNPs. The amount of CNs, CNTs, and CoNPs can be adjusted by changing the ratio of Co²⁺ in Co²⁺/g-C₃N₄. The graphene-like CNs provided a large number of active sites and a large specific surface area for loading lots of small CoNPs uniformly. The CNTs with a diameter of 100 nm could not only improve the conductivity but also provide a buffer space for the aggregation and volume expansion of Co₃O₄. CNTs also enlarged the interlayer distance of CNs, which prevented the re-stacking of CNs and provided great convince for the intercalation and de-intercalation of Li⁺. When applied for anode material of lithium-ion batteries, CN@Co-Co₃O₄/CNTs exhibited a high discharge capacity of 460.0 mAh g^-1 at 5000 mA g^-1 after 300 cycles with a Coulombic efficiency of 98% and excellent higher-rate capacity (401.0 mAh g^-1 at 2000 mA g^-1 and 329.0 mAh g^-1 at 5000 mA g^-1).

Study of solvent variation on controlled synthesis of different nanostructured NiCo2O4 thin films for supercapacitive application

The present investigation deals with controlled synthesis of nanostructured NiCo₂O₄ thin films directly on stainless steel substrates by facile and economical chemical bath deposition technique, without adding a surfactant or a binder. The consequences of different compositions of solvents on morphological and electrochemical properties have been studied systematically. We used different solvent composition as Double Distilled Water (DDW), DDW:Ethanol (1:1) and DDW: N, N dimethylformamide (1:1). The films have been named as NCO-W for DDW, NCO-WE for DDW: Ethanol (1:1) solvent and NCO-WD for DDW: N, N dimethylformamide (1:1) solvent. The morphologies of NiCo₂O₄ thin films modify substantially with change in a solvent. NCO-W exhibited the spikes of Crossandra infundibuliformis like nanostructures. The NCO-WE favored the formation of uniformly distributed leaf-like nanostructure whereas NCO-WD showed randomly oriented nanoplates all over the surface area. The Electrochemical performance of these NiCo₂O₄ thin films were studied using cyclic voltammetry, chronopotentiometry, and electrochemical impedance spectroscopy techniques. The NCO-W, NCO-WE and NCO-WD electrodes showed specific capacitance values of 271, 553 and 140 F/g respectively at the current density of 0.5 mA/cm² and excellent capacitance retention of 90%, 91% and 80% after 2000 cycles for NCO-W, NCO-WE and NCO-WD samples respectively. This result reveals that NiCo₂O₄ is a prominent electrode material for supercapacitor application.

CuCo2O4 nanoparticles wrapped in a rGO aerogel composite as an anode for a fast and stable Li-ion capacitor with ultra-high specific energy

To meet practical application requirements, high specific energy and specific power and excellent cyclability are highly desired.

Synthesis of hierarchically porous MnO/C composites via a sol–gel process followed by two-step combustion for lithium-ion batteries

Hierarchically porous MnO/C composites with interconnected macropores and co-continuous skeletons were fabricated via a sol–gel process combined with phase separation, followed by a two-step combustion.