Self-supported core/shell Co3O4@Ni3S2 nanowires for high-performance supercapacitors

Efficient Activation of Peroxymonosulfate by Cobalt Supported Used Resin Based Carbon Ball Catalyst for the Degradation of Ibuprofen

The extensive use of ibuprofen (IBU) and other pharmaceuticals and personal care products (PPCPs) causes them widely to exist in nature and be frequently detected in water bodies. Advanced catalytic oxidation processes (AOPs) are often used as an efficient way to degrade them, and the research on heterogeneous catalysts has become a hot spot in the field of AOPs. Among transitional metal-based catalysts, metal cobalt has been proved to be an effective element in activating peroxymonosulfate (PMS) to produce strong oxidizing components. In this study, the used D001 resin served as the matrix material and through simple impregnation and calcination, cobalt was successfully fixed on the carbon ball in the form of cobalt sulfide. When the catalyst was used to activate persulfate to degrade IBU, it was found that under certain reaction conditions, the degradation rate in one hour could exceed 70%, which was far higher than that of PMS and resin carbon balls alone. Here, we discussed the effects of catalyst loading, PMS concentration, pH value and temperature on IBU degradation. Through quenching experiments, it was found that SO4− and ·OH played a major role in the degradation process. The material has the advantages of simple preparation, low cost and convenient recovery, as well as realizing the purpose of reuse and degrading organic pollutants efficiently.

Facile In Situ Synthesis of Co(OH)2-Ni3S2 Nanowires on Ni Foam for Use in High-Energy-Density Supercapacitors

Ni3S2 nanowires were synthesized in situ using a one-pot hydrothermal reaction on Ni foam (NF) for use in supercapacitors as a positive electrode, and various contents (0.3-0.6 mmol) of Co(OH)2 shells were coated onto the surfaces of the Ni3S2 nanowire cores to improve the electrochemical properties. The Ni3S2 nanowires were uniformly formed on the smooth NF surface, and the Co(OH)2 shell was formed on the Ni3S2 nanowire surface. By direct NF participation as a reactant without adding any other Ni source, Ni3S2 was formed more closely to the NF surface, and the Co(OH)2 shell suppressed the loss of active material during charging-discharging, yielding excellent electrochemical properties. The Co(OH)2-Ni3S2/Ni electrode produced using 0.5 mmol Co(OH)2 (Co0.5-Ni3S2/Ni) exhibited a high specific capacitance of 1837 F g-1 (16.07 F cm-2) at a current density of 5 mA cm-2, and maintained a capacitance of 583 F g-1 (16.07 F cm-2) at a much higher current density of 50 mA cm-2. An asymmetric supercapacitor (ASC) with Co(OH)2-Ni3S2 and active carbon displayed a high-power density of 1036 kW kg-1 at an energy density of 43 W h kg-1 with good cycling stability, indicating its suitability for use in energy storage applications. Thus, the newly developed core-shell structure, Co(OH)2-Ni3S2, was shown to be efficient at improving the electrochemical performance.

An enhancement on supercapacitor properties of porous CoO nanowire arrays by microwave-assisted regulation of the precursor

A microwave-assisted hydrothermal approach with a follow up thermal treatment was employed to prepare 1D porous CoO nanowires, which is constructed by numerous high crystallinity nanoparticles. A significant change in crystal structure of the precursor were observed, as position shift and absence of some diffraction peaks, which was induced by the microwave-assistance during hydrothermal process. Moreover, the precursor's purity was also effectively improved. As a result, the as-synthesized CoO annealed from the microwave-assisted precursor exhibited a morphology and phase structure significantly different from that of without microwave involvement. Benefiting from the 'microwave effect', the microwave-assisted as-fabricated porous CoO nanowires showed an enhanced specific capacitance (728.8 versus 503.7 F g^-1 at 1 A g^-1 ), strengthened rate performance (70.0% versus 53.2% maintenance at 15 A g^-1), reduced charge transfer resistance (1.06 Ω versus 2.39 Ω), enlarged window voltage (0.85 versus 0.7 V) and enhanced cycle performance (82.3% versus 76.5% retention after 5000 cycles at 15 A g^-1), compared with that of sample without microwave assistance. In addition, the corresponding electrochemical properties are also higher than those reported CoO sample prepared by solvothermal method. In conclusion, this work provides a practical way for enhancing electrochemical properties of supercapacitor materials through adjusting the precursor by microwave assistance into hydrothermal process.

Self-Supported Sheets-on-Wire CuO@Ni(OH)2/Zn(OH)2 Nanoarrays for High-Performance Flexible Quasi-Solid-State Supercapacitor

Transition metal hydroxides have attracted a lot of attention as the electrode materials for supercapacitors owing to their relatively high theoretical capacity, low cost, and facile preparation methods. However, their low intrinsic conductivity deteriorates their high-rate performance and cycling stability. Here, self-supported sheets-on-wire CuO@Ni(OH)2/Zn(OH)2 (CuO@NiZn) composite nanowire arrays were successfully grown on copper foam. The CuO nanowire backbone provided enhanced structural stability and a highly efficient electron-conducting pathway from the active hydroxide nanosheets to the current collector. The resulting CuO@NiZn as the battery-type electrode for supercapacitor application delivered a high capacity of 306.2 mAh g−1 at a current density of 0.8 A g−1 and a very stable capacity of 195.1 mAh g−1 at 4 A g−1 for 10,000 charge–discharge cycles. Furthermore, a quasi-solid-state hybrid supercapacitor (qss HSC) was assembled with active carbon, exhibiting 125.3 mAh g−1 at 0.8 A g−1 and a capacity of 41.6 mAh g−1 at 4 A g−1 for 5000 charge–discharge cycles. Furthermore, the qss HSC was able to deliver a high energy density of about 116.0 Wh kg−1. Even at the highest power density of 7.8 kW kg−1, an energy density of 20.5 Wh kg−1 could still be obtained. Finally, 14 red light-emitting diodes were lit up by a single qss HSC at different bending states, showing good potential for flexible energy storage applications.

Enhanced faradic activity by construction of p-n junction within reduced graphene oxide@cobalt nickel sulfide@nickle cobalt layered double hydroxide composite electrode for charge storage in hybrid supercapacitor

The intrinsic faradic reactivity is the uppermost factor determining the charge storage capability of battery material, the construction of p-n junction composing of different faradic components is a rational tactics to enhance the faradic activity. Herein, a reduced graphene oxide@cobalt nickle sulfide@nickle cobalt layered double hydroxide composite (rGO@CoNi₂S₄@NiCo LDH) with p-n junction structure is designed by deposition of n-type nickle cobalt layered double hydroxide (NiCo LDH) around p-type reduced graphene oxide@cobalt nickle sulfide (rGO@CoNi₂S₄), the charge redistribution across the p-n junction enables enhanced faradic activities of both components and further the overall charge storage capacity of the resultant rGO@CoNi₂S₄@NiCo LDH battery electrode. As expected, the rGO@CoNi₂S₄@NiCo LDH electrode can deliver high specific capacity (C_s, 1310 ± 26 C g^-1 at 1 A g^-1) and good cycleability (77% C_s maintaining ratio undergoes 5000 charge-discharge cycles). Furthermore, the hybrid supercapacitor (HSC) based on the rGO@CoNi₂S₄@NiCo LDH p-n junction battery electrode exports high energy density (E_cell, 57.4 Wh kg^-1 at 323 W kg^-1) and good durability, showing the prospect of faradic p-n junction composite in battery typed energy storage.

Rational design of self-supported Ni3S2 nanoparticles as a battery type electrode material for high-voltage (1.8 V) symmetric supercapacitor applications

We developed a high performance SSC device with excellent electrochemical performance in terms of specific capacitance, rate capability, energy density and power density which surpasses most of the reports.

Controllable synthesis of hydrangea-like NixSy hollow microflower all-solid-state asymmetric supercapacitor electrodes with enhanced performance by the synergistic effect of multiphase nickel

In this work, through controlling the urea content in the synthesis system, the nucleation rate of Ni_xS_y can be adjusted, and a series of Ni_xS_y with multiphase nickel and various sizes and surface morphologies can be achieved.

Synergistic effect of MoS2 and Fe3O4 decorated reduced graphene oxide as a ternary hybrid for high-performance and stable asymmetric supercapacitors

Today, two-dimensional materials for use in energy devices have attracted the attention of researchers. Molybdenum disulfide is promising as an electrode material with unique physical properties and a high exposed surface area. However, there are still problems that need to be addressed. In this study, we prepared a hybrid containing MoS₂, Fe₃O₄, and reduced graphene oxide (rGO) by a two-step hydrothermal method. This nanocomposite is well structurally and morphologically identified, and its electrochemical performance is then evaluated for use in supercapacitors. According to the galvanostatic charge-discharge results, this nanocomposite shows a good specific capacity, equivalent to 527 F g^-1 at 0.5 mA cm^-2. The results of the multi-cycle stability test (5000 cycles) indicate a significant stability rate capability, with 93% of the electrode capacity remaining after 5000 cycles. The reason for this could be the synergistic effect between rGO and MoS₂ as well as between molybdenum and iron in the faradic reaction in the charge storage process. Fe₃O₄ and MoS₂ provide electroactive sites for the faradic process and electrolyte accessibility and rGO supply conductivity.

2D nanosheet/3D cubic framework Ni-Co sulfides for improved supercapacitor performance via structural engineering

The construction of multi-dimensional structured battery-type electrode materials is a promising strategy to develop high performance electrodes for supercapacitors. Herein, a series of battery-type Ni3S2@Co3S4 electrodes with different morphologies are synthesized by controlling the hydrothermal reaction time. Owing to the unique structure with independent but interconnected 2D nanosheets and 3D cubic frameworks, NCS-60 displays high conductivity, numerous active sites and good wettability behavior. It can deliver a high specific capacity of 388.9 mA h g-1 (3500 F g-1) at 1 A g-1, an outstanding rate capacity of maintaining 88.6% at 10 A g-1 and long cycle stability. The battery-type supercapacitor hybrid (BSH) device with active carbon (AC) as the negative electrode delivers an energy density of 41.8 W h kg-1 at the power density of 800 W kg-1. This study provides a feasible route for regulating the morphologies of in situ growth materials that improve the electrochemical performance of supercapacitors.

3D hierarchical porous nitrogen-doped carbon/Ni@NiO nanocomposites self-templated by cross-linked polyacrylamide gel for high performance supercapacitor electrode

Three-dimensional nitrogen-doped carbon network incorporated with nickel@nickel oxide core-shell nanoparticles composite (3D NC/Ni@NiO) has been facilely prepared, self-templated by the cross-linked polyacrylamide aerogel precursor containing NiCl₂. Characterizations reveal that the Ni@NiO nanoparticles distribute homogeneously in the 3D nitrogen-doped carbon matrix and the composite is of hierarchical porous structure. When used as supercapacitor electrode in a three-electrode system, the 3D NC/Ni@NiO exhibits enhanced electrical conductivity and excellent electrochemical performance, presenting a high specific capacitance (389F g^-1 at 5 mV s^-1), good rate capability (276 F g^-1 at 100 mV s^-1) and outstanding cycling performance (with the capacitance retention of 70.2% after 5000 charge-discharge cycles). This is due to the synergistic effects of conductive metallic nickel, pseudocapacitive nickel oxide as well as in situ nitrogen doping of carbon network. Moreover, an asymmetric supercapacitor (ASC) was fabricated with NC/Ni@NiO as positive electrode and active carbon as negative electrode. The ASC device exhibits a maximum energy density of 19.4 W h kg^-1 at a power density of 700 W kg^-1 and shows good cycling stability (73.8% capacity retention after 3000 cycles), indicating that it has great promise for practical energy storage and conversion application.

Three dimensional Ni3S2 nanorod arrays as multifunctional electrodes for electrochemical energy storage and conversion applications

The increasing demand for energy and environmental protection has stimulated intensive interest in fundamental research and practical applications. Nickel dichalcogenides (Ni3S2, NiS, Ni3Se2, NiSe, etc.) are promising materials for high-performance electrochemical energy storage and conversion applications. Herein, 3D Ni3S2 nanorod arrays are fabricated on Ni foam by a facile solvothermal route. The optimized Ni3S2/Ni foam electrode displays an areal capacity of 1602 µA h cm-2 at 5 mA cm-2, excellent rate capability and cycling stability. Besides, 3D Ni3S2 nanorod arrays as electrode materials exhibit outstanding performances for the overall water splitting reaction. In particular, the 3D Ni3S2 nanorod array electrode is shown to be a high-performance water electrolyzer with a cell voltage of 1.63 V at a current density of 10 mA cm-2 for overall water splitting. Therefore, the results demonstrate a promising multifunctional 3D electrode material for electrochemical energy storage and conversion applications.

An autocatalytic route of CuO/Co3O4@SiO2 nanocapsules as excellent performance supercapacitor materials

Nanocapsules prepared with silica as a carrier and coated with Co₃O₄ and CuO nanoparticles are used for high-performance supercapacitors.

CuCo2O4 nanoneedle array with high stability for high performance asymmetric supercapacitors

Cycling performance is very important to device application. Herein, a facile and controllable approach is proposed to synthesize high stability CuCo₂O₄ nanoneedle array on a conductive substrate. The electrode presents excellent performances in a large specific capacitance up to 2.62 F cm⁻² (1747 F g⁻¹) at 1 mV s⁻¹ and remarkable electrochemical stability, retaining 164% even over 70 000 cycles. In addition, the asymmetric supercapacitor assembled with the optimized CuCo₂O₄ nanoneedle array (cathode) and active carbon (anode), which exhibits superior specific capacity (146 F g⁻¹), energy density (57 W h kg⁻¹), and cycling stability (retention of 83.9% after 10 000 cycles). These outstanding performances are mainly ascribed to the ordered binder-free nanoneedle array architecture and holds great potential for the new-generation energy storage devices.

The CuCo₂O₄ nanoneedle array with enhanced electrochemical performance especially high stability is due to the hierarchical porosity framework with the high mesoporous nanoneedle array.

PVP-Assisted Synthesis of Self-Supported Ni2P@Carbon for High-Performance Supercapacitor

Highly conductive and stable electrode materials are usually the focus of high-performance supercapacitors. In this work, a unique design of Ni₂P@carbon self-supported composite nanowires directly grown on Ni foam was applied for a supercapacitor. The Co₃O₄ nanowire array was first synthesized on the Ni foam substrate, and the resulting Ni₂P@carbon nanocomposite was obtained by hydrothermally coating Co₃O₄ with the Ni-ethylene glycol complex followed by gaseous phosphorization. We have discovered that the molecular weight of surfactant polyvinylpyrrolidone (PVP) used in the hydrothermal step, as well as the temperature for phosphorization, played very important roles in determining the electrochemical properties of the samples. Specifically, the sample synthesized using PVP with 10 k molecular weight and phosphorized at 300°C demonstrated the best supercapacitive performance among the different samples, with the highest capacitance and most stable cyclic retention. When an asymmetric supercapacitor (ASC) was assembled with this Ni₂P@carbon sample as the cathode and activated carbon (AC) as the anode, the ASC device showed excellent capacitances of 3.7 and 1.6 F cm⁻² at 2 and 50 mA cm⁻², respectively, and it kept a high capacitance of 1.2 F cm⁻² after 5000 cycles at a current rate of 25 mA cm⁻². In addition, the ASC could reach a high energy density of about 122.8 Wh kg⁻¹ at a power density of 0.15 kW kg⁻¹ and 53.3 Wh kg⁻¹ at the highest power density of 3.78 kW kg⁻¹. Additionally, this device also had the ability to power up 16 red LEDs effortlessly, making it a strong candidate in electrochemical energy storage for practical usage.