Facile Synthesis of 3D Hierarchical Flower-like Co3-xFexO4 ferrite on Nickel Foam as High-Performance Electrodes for Supercapacitors

Efficient electro-Fenton catalysis by self-supported CFP@CoFe2O4 electrode

In this work, the bimetallic iron oxide self-supported electrode was prepared by a simple solvothermal as well as thermal method. CoFe₂O₄ magnetic nanoparticles were grown in situ on the CFP surface and characterized to reveal the morphology, composition, and electrochemical properties of the electrode. Compared to CFP and CFP@Co-Fe, CFP@CoFe₂O₄ equipped more efficient mineralization current efficiency and lower energy consumption due to the improved electrocatalytic capacity of CoFe₂O₄ properly grown on the conductive substrate surface. Further studies showed that the manufactured electrode maintained a high level of stability after continuous operation. According to the free radical trapping experiment, EPR, and liquid mass spectrometry analysis, the rational reaction mechanism of p-nitrophenol was finally proposed, in which ·OH and SO₄·^- were considered as the main active oxidants. This work demonstrated the great potential of establishing an electro-Fenton system based on CoFe₂O₄ immobilized self-supporting cathode for environmental remediation.

Advanced materials and technologies for supercapacitors used in energy conversion and storage: a review

Supercapacitors are increasingly used for energy conversion and storage systems in sustainable nanotechnologies. Graphite is a conventional electrode utilized in Li-ion-based batteries, yet its specific capacitance of 372 mA h g−1 is not adequate for supercapacitor applications. Interest in supercapacitors is due to their high-energy capacity, storage for a shorter period and longer lifetime. This review compares the following materials used to fabricate supercapacitors: spinel ferrites, e.g., MFe2O4, MMoO4 and MCo2O4 where M denotes a transition metal ion; perovskite oxides; transition metals sulfides; carbon materials; and conducting polymers. The application window of perovskite can be controlled by cations in sublattice sites. Cations increase the specific capacitance because cations possess large orbital valence electrons which grow the oxygen vacancies. Electrodes made of transition metal sulfides, e.g., ZnCo2S4, display a high specific capacitance of 1269 F g−1, which is four times higher than those of transition metals oxides, e.g., Zn–Co ferrite, of 296 F g−1. This is explained by the low charge-transfer resistance and the high ion diffusion rate of transition metals sulfides. Composites made of magnetic oxides or transition metal sulfides with conducting polymers or carbon materials have the highest capacitance activity and cyclic stability. This is attributed to oxygen and sulfur active sites which foster electrolyte penetration during cycling, and, in turn, create new active sites.

Facile synthesis of Co3-xMnxO4/C nanocages as an efficient sulfur host for lithium-sulfur batteries with enhanced rate performance

Capacity reduction mainly caused by the shuttle effect and low conductivity restricts the commercial application of lithium-sulfur batteries (LSBs). Herein, we developed a method to overcome these two obstacles synchronously by designing nitrogenous carbon decorated hollow Co3-xMnxO4/C nanocages as hosts of sulfur. These hosts were derived from manganese doped ZIF-67 by a facile sintering method, which provided polar surface to anchor lithium polysulfides and considerable electronic conductivity. The polar material Co3-xMnxO4 and special hollow frame contribute to efficient synergistic sulfur-fixation, resulting in great cycling stabilities. The manganese elements ensure an efficient conversion among LSPs. At the same time, N-doped carbon provides excellent electrical conductivity, thereby leading to splendid rate performances. Thus, a battery with great stability and high capacity could be achieved. As a result, Co3-xMnxO4/C/S with 66 wt% sulfur content delivered a high initial capacity of 1082 mA h g-1 at 1C, together with a slow average capacity decay of 0.056% per cycle at 10C over 500 cycles. When the average sulfur loading is 1.3 mg cm-2, a capacity of 628 mA h g-1 can be maintained at 5C after 500 cycles.

Pulsed laser deposited CoFe2O4 thin films as supercapacitor electrodes

The influence of the substrate temperature on pulsed laser deposited (PLD) CoFe2O4 thin films for supercapacitor electrodes was thoroughly investigated. X-ray diffractometry and Raman spectroscopic analyses confirmed the formation of CoFe2O4 phase for films deposited at a substrate temperature of 450 °C. Topography and surface smoothness was measured using atomic force microscopy. We observed that the films deposited at room temperature showed improved electrochemical performance and supercapacitive properties compared to those of films deposited at 450 °C. Specific capacitances of about 777.4 F g-1 and 258.5 F g-1 were obtained for electrodes deposited at RT and 450 °C, respectively, at 0.5 mA cm-2 current density. The CoFe2O4 films deposited at room temperature exhibited an excellent power density (3277 W kg-1) and energy density (17 W h kg-1). Using electrochemical impedance spectroscopy, the series resistance and charge transfer resistance were found to be 1.1 Ω and 1.5 Ω, respectively. The cyclic stability was increased up to 125% after 1500 cycles due to the increasing electroactive surface of CoFe2O4 along with the fast electron and ion transport at the surface.

Designing positive electrodes based on 3D hierarchical CoMn2O4@NiMn-LDH nanoarray composites for high energy and power density supercapacitors

3D hierarchical CoMn₂O₄@NiMn-LDH core–shell nanowire arrays as positive electrodes for high energy and power density supercapacitors.

Nanostructured spinel manganese cobalt ferrite for high-performance supercapacitors

We report on the synthesis of manganese cobalt ferrite (MnCoFeO₄) nanoparticles via a simple one-pot co-precipitation method and their characterization through energy-dispersive spectroscopy (EDS), XRD, HR-TEM, FT-IR and N₂ adsorption/desorption techniques.

Mechanochemical growth of a porous ZnFe2O4 nano-flake thin film as an electrode for supercapacitor application

ZnFe₂O₄ nano-flake thin films prepared using a mechanochemical approach for supercapacitor applications showing excellent specific capacitance, stability, energy and power density.