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Developing oxygen evolution reaction (OER) electrocatalysts with high efficiency, low cost and good stability for water splitting is significant to relieve the energy crisis and environmental pollution. Herein, NiCo alloy (NC) nanoparticles (NPs) embedded N-doped carbon fibers (NCF) were prepared by electrospinning and carbonization. The surfaces of the NC@NCF were anchored with nanocrystalline NiCo 2 S 4 (NCS) in a following solvothermal process to form NCS-NC@NCF composite. Synergistic effect of the alloy (NC) and the semiconductor (NCS) was successfully stimulated, i.e., rapid charge separation and transfer was achieved during the OER process. In addition, the carbon fibers substrate is beneficial for good dispersion of the NC and NCS NPs as well as the conductivity improvement of the as-prepared NCS-NC@NCF catalyst. The prepared NCS-NC@NCF catalyst electrode owns good OER performances of a low overpotential of 291 mV, 342 mV and 376 mV to respectively deliver current densities of 10 mA cm−2, 50 mA cm−2 and 100 mA cm−2, which are respectively 19 mV, 82 mV and 116 mV lower than those of the RuO 2 electrode (310 mV, 424 mV and 492 mV), indicating the great potential of the catalyst in water splitting. Moreover, good durability of current density retention of 90.7 % is observed after 60 h of continuous OER polarization for the catalyst. Additionally, a two-electrode system composed of commercial Pt/C and the NCS-NC@NCF electrodes only needs a driven voltage of 1.51 V to afford 10 mA cm−2 for water splitting, which is superior to that (1.69 V) of the Pt/C||RuO 2 system. [Display omitted] • Needle-liked NiCo 2 S 4 particles adhered on the NiCo alloy embedded N-doped 3D carbon fibers were prepared as OER catalyst. • The catalyst presents a smaller overpotential of 342 mV and 376 mV at 50 mA cm−2 and 100 mA cm−2 for OER than those of RuO 2. • The water splitting device assembled with the as-prepared catalyst exhibits a small voltage of 1.51 V to obtain 10 mA cm−2. [ABSTRACT FROM AUTHOR]

Developing battery-type electrode materials with diverse core-shell heterostructures is the most crucial aspect in fabricating hybrid supercapacitors with high energy density and cycling stability. Additionally, mixed-metal sulfides are highly regarded due to their favorable theoretical specific capacity and conductivity. Here, we have devised hierarchical CoGa 2 O 4 −S@NiCo 2 S 4 core−shell heterostructures, featuring urchin−like and hexagonal morphologies. The needle−like shell significantly promotes the contact area with the electrolyte, facilitating OH− penetration to the core structure. This elevation improves both the diffusion−controlled process and reaction kinetics, thereby enhancing electrode material utilization and redox capability. Therefore, the optimized CoGa 2 O 4 −S@NiCo 2 S 4 exhibits a specific capacity of 959.0 C·g−1 (capacitance of 2131.1 F·g−1) at 1 A·g−1. The assembled CoGa 2 O 4 −S@NiCo 2 S 4 //AC hybrid supercapacitor delivers an energy density of 41.17 Wh kg−1 at 850 W kg−1, with a capacity retention rate of 93.60 % after 10,000 cycles. This study provides a novel approach to enhance the electrochemical performance of supercapacitors by optimizing reaction kinetics. • Urchin-like and hexagonal core−shell heterostructures were successfully synthesized. • The needle-like NiCo 2 S 4 facilitates the permeation of OH− into the CGOS core layer. • The diffusion−controlled processes of the composite electrode have been enhanced. [ABSTRACT FROM AUTHOR]

An efficient approach is developed to fabricate hybrid nanomaterials by anchoring in situ NiCo 2 S 4 components on hollow double-layered carbon nanospheres (DCs). NiCo(CO 3)(OH) 2 is deposited on DCs and then reacted with S ions to create NiCo 2 S 4 phase. Because of the homogeneous distribution of nanoparticles and well-developed interface, samples reveal excellent electrochemical activity. The compositions of NiCo 2 S 4 /hollow DCs (denoted as DCs-x-y, x and y are the molar ratios of Ni and Co in precursors) are adjusted to test the growth kinetics and morphology evolution. Under optimized conditions, the capabilities of composite sample DCs-0.20–0.30 outperform DCs and NiCo 2 S 4 alone, which is ascribed to the high specific surface area and the existence of monodispersed hollow carbon spheres improving the distribution of NiCo 2 S 4 and the overall conductivity to increase active sites. Especially, the optimized sample DCs-0.20–0.30 exhibits high performances and stability for enhanced hydrogen evolution reaction (HER) in both acidic and alkaline conditions and oxidation evolution reaction (OER) in alkaline electrolyte. Furthermore, using DCs-0.20–0.30 sample as both the cathode and anode in the alkaline electrolyzer, the current density of 10 and 100 mA cm−2 at 1.736 and 2.171 V are obtained. The sample also displays excellent durability for 20 h at 10 mA cm−2. • NiCo 2 S 4 nanoparticles were anchored homogeneously on hollow double-layered carbon nanospheres (DCs). • The nanoparticles and well-developed interface make samples with excellentelectrochemical activity. • NiCo 2 S 4 /hollow DCs revealed enhanced HER in acidic and alkaline conditions as well as OER in alkaline electrolyte. [ABSTRACT FROM AUTHOR]

Abstract In this work, NiCo 2 S 4 nanotube arrays are grown in suit on a Ni foam through a rapid microwave-assisted sulfidation process from analogous structure of Ni-Co precursors. This uniform nanotube array structure yields a high specific capacitance of 8.6 F cm−2 at 10 mA cm−2, and superb cycle property without loss of function after 48000 cycles at 50 mA cm−2. Benefitted by the nanotube structure and the unique triangular supporting system from the electrochemical activation, the cycling stability of ternary nickel cobalt sulfide is maintained at a high level with superior specific capacitance. Therefore, this novel structure has some reference significance for further research of supercapacitors. Highlights • A simple and fast microwave-assisted strategy of synthesizing NiCo 2 S 4 nanotube arrays on a Ni foam. • A novel triangular system was formed during the electrochemical reaction process. • An eminent cycling stability of approximately 100% retention after 48000 cycles. [ABSTRACT FROM AUTHOR]

Bimetallic sulfide NiCo 2 S 4 is a highly promising electrode material for applications in novel sustainable high-performance energy storage devices, but its poor rate capability and cycling life need to be enhanced. Herein, we report a novel self-supporting hierarchical porous NiCo 2 S 4 /RGO/CNTs nanohybrids (NCSRCs) by co-modification of NiCo 2 S 4 nanoparticles with RGO and CNTs. The synergistic effect of RGO and CNTs not only constructs a hierarchical porous conductive network that facilitates charge transport kinetic and ion diffusion kinetic, but also provides abundant induced sites for the dispersion anchoring of NiCo 2 S 4 nanoparticles due to their high specific surface area with rich functional groups, which reduces the stacking of NiCo 2 S 4 nanoparticles and provides abundant exposed electroactive redox sites. Therefore, the electrochemical performance test results demonstrate that the NCSRCs electrodes exhibit significantly enhanced charge storage performance, showing a high specific capacity of 257.1 mAh g−1 at 0.3 A g−1 and good rate capability. In addition, the optimal NCSRC-24//N-RGO aqueous hybrid supercapacitor delivered a high specific energy of 33.67 Wh kg−1 and ultra-long durability with 82.44% capacity retention after 22,000 cycles. These results provide a facile approach to design and synthesize novel NCSRCs nanohybrids with superior properties for high-safety, sustainable and efficient aqueous energy storage devices. [Display omitted] • The novel NCSRCs nanohybrids are rationally designed and synthesized. • The rich groups in RGO/GO induced dispersed growth and refinement of NiCo 2 S 4. • The hierarchical porous NCSRCs exhibit rich exposed electroactive redox sites. • The NCSRCs electrodes have enhanced specific capacity and rate capability. • The assembled HSC delivers excellent energy density and ultra-long durability. [ABSTRACT FROM AUTHOR]

The flexible porous skeleton of S/N co-doped graphene aerogel (SNGA) can not only provide abundant ion transport channels but also improve the rate capability of graphene. Herein, taking the advantage of SNGA structure, NiCoO 2 and NiCo 2 S 4 were loaded onto the surface of SNGA (denoted as NiCoO 2 /SNGA-X and NiCo 2 S 4 /SNGA-X) via two-step hydrothermal and one-step hydrothermal method, respectively. The results show that NiCoO 2 and NiCo 2 S 4 particle agglomeration can be successfully mitigated since the Ni-Co binding process is influenced by the high specific surface area carbon source of SNGA. In addition, the NiCo 2 S 4 prepared by one-step hydrothermal process plays the role of intercalation support during the formation of SNGA, which makes the porous structure of NiCo 2 S 4 /SNGA-X more compact and coherent. Benefiting from adequate active sites and porous structure, NiCoO 2 /SNGA-X and NiCo 2 S 4 /SNGA-X show high reversible capacity as anode materials for lithium energy storage. NiCoO 2 /SNGA-0.4 exhibits superior stability of 356.3 mA h g−1 at the current density of 1 A g−1 after 300 cycles, NiCo 2 S 4 /SNGA-0.3 exhibits excellent rate capability of 259.7 mA h g−1 at the current density of 5 A g−1. Lithium ion battery anode materials with high reversible specific capacity under high current density were successfully prepared. The research would provide a theoretical guidance for further application of SNGA skeletons. [Display omitted] • The surface-distributed N atoms with the metal ions and the presence of sulfur-metal bonds improve the stability of material. • NiCo 2 S 4 /SNGA-0.3 shows excellent rate capability (259.7 mA h g−1 at 5 A g−1). • NiCoO 2 /SNGA-0.4 shows superior stability (356.3 mA h g−1 at 1 A g−1 after 300 cycles). • The rich pore structure helps to slow down the accumulation of graphene flakes and to reduce the volume expansion. [ABSTRACT FROM AUTHOR]

Abstract Although supercapacitors have been extensively investigated due to the good electrochemical performance, the awful energy density, poor cycle stability and low rate performance still remain challenges in applications. In this article, we successfully design and synthesize the hierarchical NiCo 2 O 4 @NiCo 2 S 4 core/shell nanowire arrays on Ni foam by a special interface ion-exchange process. As supercapacitor material, it exhibits a high specific capacitance of 3176 F g−1 at a current density of 2 A g−1 and can retain 86.52% at a high current density of 10 A g−1, indicating excellent rate capability. In addition, an asymmetric supercapacitor is assembled with NiCo 2 O 4 @NiCo 2 S 4 as the cathode electrode and porous carbon as the anode electrode and KOH solution as the electrolyte, showing a super energy density of 196.8 Wh kg−1 at 752.33 W kg−1 and a high power density of 5625.12 W kg−1 at 162.45 Wh kg−1. After 15000 cyclic voltammetry cycles at a scan rate of 60 mV s−1, 137% of initial capacitance is maintained. Theoretical analysis reveals that the diffusion-controlled reaction is dominant in the total capacitance of NiCo 2 O 4 @NiCo 2 S 4 electrode, which may be the reason for the high specific capacitance and excellent rate capability. Thereby, these electrochemical performances demonstrate that the as-fabricated NiCo 2 O 4 @NiCo 2 S 4 core/shell nanowire arrays are the promising candidates for high-performance supercapacitors. Highlights • The method was hydrothermal and ion-exchange route process. • They showed high specific capacitance of 3176 F g−1 at a current density of 2 A g−1 • The high capacitance can retain 86.52% even at a current density of 10 A g−1 • The diffusion-controlled process was dominant in the total capacitance. • The asymmetric supercapacitor device exhibited high energy density of 196.8 Wh kg−1 at 752.33 W kg−1 [ABSTRACT FROM AUTHOR]

Abstract In this work, we report the synthesis of NiCo 2 S 4 nanosheets network and its application as electrode material for hybrid supercapacitors. The synthesis involves two-steps. Firstly, a precursor nanowires array is synthesized by a hydrothermal process. Then, the reaction between precursor and sodium sulfide through a vapor-phase diffusion process under hydrothermal condition leads to NiCo 2 S 4 nanosheets network. The unique network structure can prevent NiCo 2 S 4 nanosheets from aggregation and overlap. When act as an electrode material for supercapacitors, the NiCo 2 S 4 nanosheets network exhibits specific capacitances of 1956 F g−1 at 1 A g−1 and 1622 F g−1 at 20 A g−1. Cycling test shows 91.6% capacitance retention after 5000 charge–discharge cycles. The specific capacitance and rate capability of the NiCo 2 S 4 nanosheets network are higher than that of the NiCo 2 S 4 nanotubes array which was obtained from the direct reaction of precursor and sodium sulfide in solution. In addition, a hybrid supercapacitor device is assembled by using the NiCo 2 S 4 nanosheets network as positive electrode and porous carbon as negative electrode. The device exhibits an energy density of 27.5 W h kg−1 at a power density of 0.747 kW kg−1, and a power density of 6.03 kW kg−1 at an energy density of 18.75 W h kg−1. The results indicate that the NiCo 2 S 4 nanosheets network is an excellent electrode material candidate for high-performance supercapacitors. Highlights • NiCo 2 S 4 with a unique nanosheets network structure is prepared. • A vapor-phase diffusion process is involved during the synthesis process. • The NiCo 2 S 4 nanosheets network can be used as supercapacitor electrode material. • The NiCo 2 S 4 nanosheets network exhibit excellent capacitive activities. [ABSTRACT FROM AUTHOR]

Reduced graphdiyne oxide/NiCo 2 S 4 hierarchical nanosheet array (r-GDYO/NiCo 2 S 4) electrodes are successfully synthesized by electrodeposition and hydrothermal method. The r-GDYO/NiCo 2 S 4 electrode has high capacity, high rate and high stability. At 30 mA cm−2, the area-specific capacity is 3.09 F cm−2, and the capacitance retention rate is 93.10% after 5000 cycles. Density functional theory can reveal the mechanism of graphdiyne enhancing pseudocapacitance of NiCo 2 S 4 electrode. On the one hand, carbon repulsion promotes hydroxyl ion (OH−) to approach cobalt atoms (Co), which enhances NiCo 2 S 4 's binding ability to OH−. On the other hand, the strong electronegativity of the carbon layer enhances the binding ability of NiCo 2 S 4 to external electrons and increases the surface reactivity, thus accelerating the redox reaction and improving the charge storage capacity. Finally, r-GDYO/NiCo 2 S 4 is the positive electrode, activated carbon (AC) is the negative electrode, and melamine foam is assembled as a membrane and storage electrolyte container to form a small volume and light weight aqueous asymmetric supercapacitor. This work not only provides ideas for the design of high-performance NiCo 2 S 4 electrode materials, but also provides a new direction for the application of supercapacitors. [Display omitted] • Flexible r-GDYO/NiCo 2 S 4 electrodes with high capacity, high rate and long cycle stability were prepared by electrodeposition. • The pioneering use of melamine foam as a storage device for water system electrolyte. • MFAASCs devices have high area capacity, high energy density and long cycle stability. [ABSTRACT FROM AUTHOR]

In recent years, transition metal sulfides have been regarded as a promising energy storage material for supercapacitors, due to their high theoretical specific capacity and conductivity compared with other similar metal oxides and hydroxides. However, the sluggish diffusion dynamics and low capacitance impede its practical implement application. Herein, an advanced 3D nanocomposite of NiCo 2 S 4 /CuCo 2 S 4 heterostructure was designed via a time-saving, safe and efficient approach. The mass transfer kinetics of NiCo 2 S 4 /CuCo 2 S 4 nanocomposite has been significantly promoted owing to this novel heterostructure. Therefore, the NiCo 2 S 4 /CuCo 2 S 4 electrode materials reveal a superior specific capacitance (180.8 mAh g−1 at 2 A g−1) and excellent rate properties (84.7% capacitance retention from 2 to 20 A g−1). The asymmetric supercapacitor device assembled with NiCo 2 S 4 /CuCo 2 S 4 and activated carbon has an energy density of 37.0 Wh kg−1 at 400 W kg−1 and outstanding cyclic stability (93.3% remained after 10,000 cycles at 10 A g−1). Density functional theory (DFT) calculation further proves the electronic structure and the charge transfer can be tuned by the heterostructure of NiCo 2 S 4 and CuCo 2 S 4. This work offers a new perspective to design a high-performance electrode material in the field of supercapacitors. [Display omitted] • A 3D NiCo 2 S 4 /CuCo 2 S 4 nanoparticles composite was synthesized by a time-saving chemical deposition method. • NiCo 2 S 4 /CuCo 2 S 4 composite has a larger specific surface area than NiCo 2 S 4 or CuCo 2 S 4. • The heterostructure of NiCo 2 S 4 /CuCo 2 S 4 improves charge transport capacity. • The materials reveal a capacitance (180.8 mAh g−1 at 2 A g−1), rate properties (84.7% retention from 2 to 20 A g−1). [ABSTRACT FROM AUTHOR]

This work reports a simple, eco-benign, pollution-free two-step electrodeposition technology to prepare NiCo 2 S 4 /MoS x composites on nickel foam (NF). It was then employed as electrodes for all-solid symmetric supercapacitors. The NiCo 2 S 4 / MoS x /NF composite can provide a superior specific capacity of 1494.52 F/g at 1 A/g, and also deliver good stability of ∼93.03% after 1000 cycles. The NiCo 2 S 4 /MoS x /NF was assembled as the positive and negative electrodes of an all-solid symmetric supercapacitor (NiCo 2 S 4 /MoS x /NF // NiCo 2 S 4 /MoS x /NF). This assembly exhibits an energy density of 32.54 Wh/kg with the power density 285.72 W/kg, and superior cycle life retention rate of 84.46% and Coulombic efficiency of 100% after 1000 charge-discharge cycles, respectively. The excellent electrochemical property of the NiCo 2 S 4 /MoS x /NF composite is ascribed to the synergistic effect between the MoS x and NiCo 2 S 4 , suggesting it has excellent prospects as an electrode for supercapacitors. • The NiCo 2 S 4 /MoS x /NF electrode was successfully prepared by two-step electrochemical deposition. • The NiCo 2 S 4 /MoS x /NF electrode exhibits a specific capacitance of 1494.52 F/g at 1 A/g in a three-electrode system. • The NiCo 2 S 4 /MoS x /NF // NiCo 2 S 4 /MoS x /NF device exhibits a high energy density of 32.54 Wh/kg and excellent power density of 285.72 W/kg. [ABSTRACT FROM AUTHOR]

Graphitic carbon nitride (g-C 3 N 4) with high nitrogen contents and excellent thermal/chemical stability is widely applied as active material of supercapacitors (SC). Small surface area and electrical conductivity of g-C 3 N 4 lead to poor electrochemical performance, which can be improved by heteroatom doping and metal compound incorporation. In this work, it is the first time to fabricate NiCo 2 S 4 /S-doped g-C 3 N 4 (NCS-C) composite using thermal polymerization and hydrothermal reaction as active material of SC. The S-g-C 3 N 4 electrode shows a higher specific capacitance (C sp) of 72.4 mF/g at 20 mV/s than that of 49.5 mF/g of g-C 3 N 4 electrode. Using sulfur as doping source and anion in metal compound favors for improving compatibility of composites. NCS-C composite shows favorable S-g-C 3 N 4 nanosheets-covered NCS flower-like structures. The NCS-C electrode presents a higher C sp value of 351.0 F/g at 1 A/g (886.2 F/g at 20 mV/s) than that of 348.9 F/g at 1 A/g (794.2 F/g at 20 mV/s) of NCS electrode, due to sulfur and nitrogen-rich carbon of S-g-C 3 N 4 and abundant redox reactions of NCS. The symmetric SC with NCS/C electrodes delivers potential window of 1.0 V, maximum energy density of 9.7 Wh/kg at 0.65 kW/kg, and C sp retention of 97.6% and Coulombic efficiency of 90% after 10,000 charge/discharge cycles. [Display omitted] • NiCo 2 S 4 /S-g-C 3 N 4 (NCS/C) is firstly got as active material for supercapacitor(SC). • Optimal NCS/C electrode shows specific capacitance (C sp) of 886.2 F/g at 20 mV/s. • The pristine g-C 3 N 4 electrode only shows a C sp value of 49.5 mF/g at 20 mV/s. • Sulfur as dopant and anion in metal compound favors for composite compatibility. • SC shows C sp retention of 98.4% and Coulombic efficiency of 90% after 10,000 cycle. [ABSTRACT FROM AUTHOR]

• NiCo 2 S 4 NWs/GF and CoNi 2 S 4 NAs/GF were successfully synthesized. • NiCo 2 S 4 NWs/GF anode was tested in DEGDME electrolyte at 0.3–3.0 V. • The NiCo 2 S 4 NWs/GF showed better electrochemical performance than CoNi 2 S 4 NAs/GF. • NiCo 2 S 4 NWs/GF anode with more Co content shortens diffusion length of Na+ and e-. [Display omitted] Bimetallic Ni x Co 3−x S 4 (x = 1 or 2) with synergistic effect is a promising candidate material for sodium-ion battery (SIB) anodes because of its higher electrical conductivity than monometallic sulfides owing to its lower bandgap. In this study, samples of bimetallic sulfide Ni x Co 3−x S 4 with tunable chemical Ni/Co components are successfully grown on graphene foam (GF), forming free-standing Chinese knot-like nanowires (NiCo 2 S 4 NWs/GF) and Chinese lantern-like nanoarrays (CoNi 2 S 4 NAs/GF). When evaluate as anodes for SIBs at 0.3–3.0 V in ether-based electrolytes, the NiCo 2 S 4 NWs/GF electrodes offer superior rate performance and cycling stability than the CoNi 2 S 4 NAs/GF electrodes. More specifically, the NiCo 2 S 4 NWs/GF electrode has a high capacity of 650–556 mAh g−1 at 0.1–2.0 A g−1 and 457 mAh g−1 after 200 cycles at 0.5 A g−1 with a high initial coulombic efficiency (ICE) of 95.6%. And its rate performance outperforms most existing electrodes those contain NiS x , CoS x , or NiCo 2 S 4. The excellent electrochemical performance of the NiCo 2 S 4 NWs/GF electrode is attributed to its unique composition, smaller size, and porous nanowires that can reduce the diffusion length of e- and Na+, and enhance reaction kinetics. [ABSTRACT FROM AUTHOR]

• A shell-strengthened hollow structure of NiCo 2 S 4 is built by a hydrothermal method. • The hollowing process follows an in-situ reaction Ostwald Ripening mechanism. • Rich pores, hollow structure and cobalt ions lead to excellent high-rate performance. • The mechanically strengthened shell of NiCo 2 S 4 prolongs its cycling life. For Faraday supercapacitors, some battery-type electrode materials such as nickel-based materials attract intensive attention by virtue of their high theoretical capacity. However, it is quite difficult for these materials to achieve the satisfied high-rate performance and cycling life concurrently due to the contradiction of their individual requirements to the microscopic structure of materials. In this work, we build a hollow architecture of NiCo 2 S 4 at hydrothermal condition following an in-situ reaction Ostwald Ripening mechanism. The as-prepared NiCo 2 S 4 presents a shell-strengthened hollow structure, satisfying the as-mentioned two requirements: (1) the rich pores in shell and hollow structure plus structural cobalt ions lead to the excellent high-rate performance of NiCo 2 S 4 ; (2) the dense particulate layer in shell with additional mechanical strength prolongs the cycling life of NiCo 2 S 4. Consequently, the asymmetrical supercapacitors assembled with NiCo 2 S 4 as positive electrode material show both high energy and power densities, and excellent cycling stability. [ABSTRACT FROM AUTHOR]

The development of low-cost cocatalysts is desirable for photocatalytic H 2 generation. Here, we are the first to demonstrate the in situ hydrothermal growth of NiCo 2 S 4 nanosheets on g-C 3 N 4 surfaces to construct a "sheet-on-sheet" heterostructure. The as-prepared NiCo 2 S 4 /CN heterostructured nanohybrid exhibits remarkably enhanced rates of visible-light-driven photocatalytic H 2 evolution without using a noble metal cocatalyst, such as Pt. Notably, the optimum loading of NiCo 2 S 4 nanosheets is 10 wt%, providing the best H 2 performance rate of 293.4 μmolh−1g−1, which is approximately 7 times higher than that of the single-component bulk CN. This result suggested that the improved photocatalytic activity can be primarily ascribed to the efficient interfacial transfer of the photogenerated charge pairs from CN to the NiCo 2 S 4 nanosheets. These nanosheets serve as temporary electron reservoirs, resulting in a reduced charge recombination rate on the CN surfaces and increasing the amount of photogenerated charge pairs in the NiCo 2 S 4 nanosheets. Furthermore, the increased potential of reactive surface sites, together with the extended light absorption range after the introduction of NiCo 2 S 4 nanosheets on the CN substrate, may also play a certain role in improving the photocatalytic performance. This study reveals a promising and efficient route for using CN-based photocatalysts incorporated with a ternary transition metal sulfide cocatalyst, which have been prepared by the nanoarchitecture engineering of noble metal-free heterostructured interfaces for use in renewable energy production. Novel sheet on sheet NiCo 2 S 4 /CN heterostructure catalyst for efficient solar hydrogen production based on photogenerated interfacial charge transfer. Image 1 • NiCo 2 S 4 /CN sheet on sheet heterostructure was fabricated by facile in-situ hydrothermal method. • 2D NiCo 2 S 4 /CN heterostructure efficiently promoted the electron-hole pair separation. • NiCo 2 S 4 nanosheets as low-cost synergist significantly accelerated the hydrogen reduction process. • The origin of superior H 2 evolution rate by 2D NiCo 2 S 4 /CN heterostructure was proposed. [ABSTRACT FROM AUTHOR]

Bimetallic transition metal sulfides (TMSs) hold great promise as electrode materials for supercapacitive energy storage devices compared with their monometallic counterparts. However, it is still necessary to develop efficient synthetic protocols for favorable electrode architecture in order to further improve the electrochemical performance. This study presents a facile and controllable method to construct NiCo 2 S 4 heterostructure based on electrochemically exfoliated graphene with good adhesion, which involves the growth of bimetallic MOF precursor and in-situ conversion into NiCo 2 S 4 nanoparticles. This integrated architecture was found to be efficient for supercapacitive energy storage, as evident by the improved utilization of NiCo 2 S 4 and excellent electrochemical performance including high capacity of 1802.5 F g−1 at 1 A g−1 and good rate capability (86.1% capacity retention at 10 A g−1). Additionally, N-doped mesoporous carbon spheres (NMCS) were synthesized by sacrificial template method and used as anode for practical application. Benefiting from good charge balance and compatibility, the assembled EEG@NiCo 2 S 4 //NMCS hybrid supercapacitor (HSC) exhibited outstanding energy density (30.4 Wh kg−1 at 800.0 W kg−1) and excellent cycling stability (80.1% capacitance retention after 9000 cycles). • Advanced NiCo 2 S 4 /graphene heterostructure is created by conversion of MOF based on electrochemically exfoliated graphene. • The heterostructure is of importance to promote electrochemical performance compared with NiCo 2 S 4 and Ni 3 S 4 /NiS counterparts. • The N-doped mesoporous carbon anode with multidimensional transport pathways allows for efficient electrical/ionic transfer. [ABSTRACT FROM AUTHOR]

Although potassium ion batteries (KIBs) have been invested in development as an emerging low-cost, high-content energy storage system at present. However, the large ionic radius of K+-ion lead to poor rate performance and low cycle life. Therefore, it is extremely necessary to develop a new type of potassium storage material. Here, we report a novel three-dimensional (3D) structural self-supported anode composite material for KIBs, which consists of tapered rod-shaped nanomaterial NiCo 2 S 4 and nitrogen-doped hollow carbon nanofibers (NiCo 2 S 4 @N-HCNFs). Then, the composite material was obtained by high temperature carbonization and hydrothermal reaction process. The prepared electrode materials were used to assemble K half-cells for electrochemical performance measurement, achieved the capacity of 263.7 mAh g−1 after 200 cycles at a current density of 100 mA g−1 and an outstanding stability of retaining 134.3 mAh g−1 at 3200 mA g−1 after 600 cycles. It has superior performance and convenient synthesis process over other reported metal sulfides self-supported anode materials for KIBs so far. The novel structure not only shorten the ion transmission distance, but also increase the contact area with the electrolyte. It can improve electrochemical performance effectively. Image 1 • 3D composite NiCo 2 S 4 @N-HCNFs self-supported anode was successfully fabricated. • The synthetic sample exhibits excellent potassium-storage performance. • The excellent performance thanks to the special structure of NiCo 2 S 4 @N-HCNFs. [ABSTRACT FROM AUTHOR]

The activated carbon prepared from gasified rice husk carbon by gasification power generation (or RHAC), has been researched as a promising electrode materials for supercapacitors. In this work, we show a simple one-step solvothermal synthesis of flower-like RHAC/NiCo 2 S 4 composite nanomaterials by an in-situ growth. Moreover, the RHAC/NiCo 2 S 4 electrode demonstrates a capacitance of 1680 Fg-1 and 1118.4 Fg-1 at current densities of 1 A g−1 and 12 A g−1, respectively, which has excellent Rate performance. In order to improve the energy density of the supercapacitor, the asymmetric supercapacitors were assembled by a RHAC/NiCo 2 S 4 electrode and RHAC electrode. The asymmetric supercapacitor delivers super great properties with a specific capacitance of 133.3 F g−1 at the current density of 0.2 A g−1 and the energy density of 41.6 Wh Kg−1 at the power density is 150 W kg−1. Furthermore, the energy density was maintained 29.2 Wh Kg−1 at a high power density of 1500 W kg−1, demonstrating superior rate capability. Additionally, the asymmetric supercapacitor also exhibits better cycling stability with 86% capacitance retention at current density of 1 A g−1 after 5000 cycles. In view of environment-friendly and well capacitance, such RHAC/NiCo 2 S 4 electrode would hold a promising application as candidate materials in next-generation high-performance supercapacitor. • The flower-like RHAC/NiCo 2 S 4 composite was synthesized by one-step solvothermal. • Gasified rice husk porous carbon RHAC is used as substrate disperse NiCo 2 S 4 nanosheet. • The multi-component reduce the band gap of the material and improve the conductivity. • The synergistic effect of bimetallic sulfides improve the electrochemical properties. [ABSTRACT FROM AUTHOR]