Supercapacitors suffer from lack of energy density and impulse the energy density limit, so a new class of hybrid electrode materials with promising architectures is strongly desirable. Here, the rational design of a 3D hierarchical sandwich Co S /α-MnS@N-C@MoS nanowire architecture is achieved during the hydrothermal sulphurization reaction by the conversion of binary mesoporous metal oxide core to corresponding individual metal sulphides core along with the formation of outer metal sulphide shell at the same time. Benefiting from the 3D hierarchical sandwich architecture, Co S /α-MnS@N-C@MoS electrode exhibits enhanced electrochemical performance with high specific capacity/capacitance of 306 mA h g /1938 F g at 1 A g , and excellent cycling stability with a specific capacity retention of 86.9% after 10 000 cycles at 10 A g . Moreover, the fabricated asymmetric supercapacitor device using Co S /α-MnS@N-C@MoS as the positive electrode and nitrogen doped graphene as the negative electrode demonstrates high energy density of 64.2 Wh kg at 729.2 W kg , and a promising energy density of 23.5 Wh kg is still attained at a high power density of 11 300 W kg . The hybrid electrode with 3D hierarchical sandwich architecture promotes enhanced energy density with excellent cyclic stability for energy storage.
By changing the mixed metal sulfide composition, morphology tuning of an active electrode material can be possible, which can have a huge impact on its electrochemical performance. Here, effective morphology tuning of Ni−Co layered double hydroxide (LDH)/MMoS x (M = Co, Ni, and Zn) heteronanostructures is demonstrated by varying the composition of MMoS x . Taking advantage of the benefits associated with Kirkendall growth and Ostwald ripening, tunable morphologies were successfully achieved. Among the Ni−Co LDH/MMoS x (M = Co, Ni, and Zn) heteronanostructures, a Ni−Co LDH/NiMoS x core−shell structured electrode delivered a high specific capacity of 404 mAh g −1 at 3 mA cm −2 and an extraordinary cycling stability (after 10 000 cycles) of 93.2% at 50 mA cm −2 . In addition, an asymmetric supercapacitor (ASC) device coupled with Ni−Co LDH/ NiMoS x as the cathode and Fe 2 O 3 /reduced graphene oxide as the anode exhibited excellent cell capacity and extraordinary cycling stability. Moreover, the ASC device provided a very high specific energy of 72.6 Wh kg −1 at a specific power of 522.7 W kg −1 and maintained the specific power of 23.5 Wh kg −1 at 5357.6 W kg −1 , demonstrating its high applicability to energy storage devices.
A thin layer of N–C sandwiched between an electroactive MnCo2O4 core and MnO2 shell results in sophisticated, robust core@sandwich@shell as a highly efficient energy storage material.
SiO2@Co3O4 coreshell nanorattles with different Co3O4 shell thickness have been successfully synthesized by the calcination of SiO2@-Co(OH)2 at 500 o C. The synthetic approach is facile, economical, and requires no surface modification. The synthesized materials were thoroughly characterized using powder Xray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA), BrunauerEmmettTeller (BET) analysis, field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and diffuse reflectance spectroscopy (DRS). SEM analysis indicates hierarchical coreshell morphology for SiO2@Co3O4 and the TEM results indicate the coreshell nanorattle morphology. Diffuse reflectance spectroscopy studies indicate that the SiO2@Co3O4 coreshell nanorattles show two absorption bands in the range 420450 nm and 700750 nm related to ligand to metal charge transfer transitions (O 2 → Co 2+ and O 2 → Co 3+ ). The SiO2@Co3O4 coreshell nanorattles act as an artificial peroxidase enzyme mimic with enhanced intrinsic peroxidaselike activity compared to pure Co3O4 nanoparticles and horseradish peroxidase (HRP), a natural enzyme. The SiO2@Co3O4 coreshell nanorattles show higher kcat and kcat/Km values compared to pure Co3O4 and HRP indicating their applicability as artificial enzyme mimic in biomedicine and biosensing.
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