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Ferric cobalt sulfide/silver nanowires/graphene (FeCo2S4/Ag NWs/G) ternary nanocomposites with hierarchical honeycomb-like morphology have been obtained through hydrothermal synthesis. In the FeCo2S4/Ag NWs/G composite electrode, the Ag NWs provide effective electron transport channels and prevent the graphene and FeCo2S4 nanosheets from aggregating. The graphene sheets can not only provide connected channels for ion transportation and charge transfer but also significantly buffer the volume change of electrode. As a result, the as-prepared FeCo2S4/Ag NWs/G composite electrode exhibits a high specific capacitance of 2689.2 F/g at a current density of 1 A/g, and excellent capacitance retention of 96.1% after 5000 charge–discharge cycles. In addition, an asymmetric supercapacitor was fabricated using FeCo2S4/Ag NWs/G as positive electrode and flower-like hierarchical porous nitrogen-doped carbon sphere as negative electrode. The assembled supercapacitor delivered a high energy density of 80.6 Wh/kg at a power density of 806 W/kg. These results demonstrate that such FeCo2S4/Ag NWs/G nanocomposites have widespread application prospects in the field of electrochemical energy storage.

Bimetallic sulfides are potential and attractive electrode materials for high-performance supercapacitors. In this study, the manganese-cobalt sulfide/silver nanowires/graphene (MnCo2S4/Ag NWs/G) ternary nanocomposites with a hierarchical honeycomb-like nanoarchitecture have been successfully synthesized through a facile two-step hydrothermal route. Due to the unique compositional and structural advantages, the obtained MnCo2S4/Ag NWs/G composite electrode delivers a superior electrochemical capacitive performance than pure MnCo2S4 electrode and other reported MnCo2S4-based electrode materials, exhibiting a large specific capacity of 2193.6 F/g at the current density of 1 A/g, a high rate capability of 59.6% capacitance retention at 20 A/g, and a long-term cycling stability of 94.7% at 10 A/g after 3000 charge–discharge cycles. The outstanding supercapacitive performance suggests that MnCo2S4/Ag NWs/G ternary nanocomposites are promising electrode materials for high performance energy storage devices.

In this paper, the hierarchical porous carbon coated nickel cobalt sulphide (NiCo2S4@HPC) nanowire composites in situ grown on Ni foam have been fabricated by a facile two-step hydrothermal method. The HPC with three-dimensional interconnected macroporous framework not only improves the structural stability subject to repeated charge-discharge cycles, but also enhances the conductivity and facilitates the rapid charge storage of NiCo2S4. When evaluated as an electrode material for supercapacitor, the NiCo2S4@HPC composite electrode exhibits a superior specific capacitance (1682.5 F/g at the current density of 1 A/g) and high cycling stability of 93.7 % capacitance retention after 2000 cycles at 1 A/g, which are superior to most reported NiCo2S4-based electrode materials, confirming the outstanding electrochemical performance of the NiCo2S4@HPC composite electrode. The present work not only proves the NiCo2S4@HPC nanowire composite to be an excellent electrode material for supercapacitors, but also promotes the practical applications of NiCo2S4-based composite materials in high-performance energy storage devices.

In this work, the ferric cobalt sulfide/aminated graphene quantum dots (FeCo2S4/NH2-GQDs) nanoflowers grown on Ni foam substrate have been successfully fabricated via a facile two-step hydrothermal method. The as-prepared FeCo2S4/NH2-GQDs nanoflowers can expose plenty of electroactive sites, provide fast charge transfer paths and buffer the drastic volume change during long-term charge–discharge cycles. Therefore, the FeCo2S4/NH2-GQDs nanoflowers exhibit excellent supercapacitive performance, including high specific capacitance, excellent rate capability and cycling stability. The specific capacitance of FeCo2S4/NH2-GQDs composite electrode reaches 2314.8 and 1802.5 F g−1 at the current density of 1 and 10 A g−1, respectively, while maintaining superior cycling stability with 95.1% capacitance retention after 5000 cycles. This study proves that NH2-GQDs are promising materials to enhance the electrochemical performance of bimetallic sulfides, providing a new insight for the design and fabrication of novel electrode materials for high-performance supercapacitors.

Flexible piezoelectric nanogenerator (PENG) has been regarded as one of the promising solutions to harvesting mechanical energy, as a sustainable energy source for wearable devices, etc. Here, a universal strategy of carbon coating modulation is proposed to synthesis carbon coated 0-D piezoceramics nanoparticles (NPs). Owing to the good electric conductivity of carbon shell, the redistribution and accumulation of mobile charges in carbon layer gives rise to reinforcement of electric field, results in the much-enhanced piezoelectric effect. Polydimethylsiloxane (PDMS) composites with those 0-D piezoceramics NPs are used to fabricate PENGs. The peak power density of BT@C, PZT@C and KNN@C based PENGs reaches up to 45.4 μW/cm2, 59.8 μW/cm2 and 9.9 μW/cm2, that are 20, 20.4 and 13.4 times larger than those of control PENGs incorporated with bare 0-D piezoceramic NPs, respectively. A theoretical model based on Lewis diffusion theory is constructed to reveal the mechanism of piezoelectric enhancement in the poling process. This research provides a new strategy for synthesis of high piezoelectric characteristic composites by embedding carbon coated 0-D piezoceramic NPs.

In this work, nitrogen-doped, yolk–shell-structured CoSe/C mesoporous dodecahedra are successfully prepared by using cobalt-based metal–organic frameworks (ZIF-67) as sacrificial templates. The CoSe nanoparticles are in situ produced by reacting the cobalt species in the metal–organic frameworks with selenium (Se) powder, and the organic species are simultaneously converted into nitrogen-doped carbon material in an inert atmosphere at temperatures between 700 and 900 °C for 4 h. For the composite synthesized at 800 °C, the carbon framework has a relatively higher extent of graphitization, with high nitrogen content (17.65%). Furthermore, the CoSe nanoparticles, with a size of around 15 nm, are coherently confined in the mesoporous carbon framework. When evaluated as novel anode materials for sodium ion batteries, the CoSe/C composites exhibit high capacity and superior rate capability. The composite electrode delivers the specific capacities of 597.2 and 361.9 mA h g–1 at 0.2 and 16 A g–1, respectively.