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Manganese dioxide (MnO 2) and NiFe-layered double hydroxide (LDH) nanosheets were deposited on bimetallic metal sulfide (NiCo 2 S 4) by hydrothermal reaction method, and MnO 2 /NiFe-LDH@NiCo 2 S 4 was applied as cathode catalyst in microbial fuel cell (MFC). The combination of lamellar MnO 2 with NiFe-LDH coated on NiCo 2 S 4 achieved a typical core-double shell structure. The unique core-double shell structure created a rapid pathway for electron transport and reduced interfacial impedance. The MnO 2 /NiFe-LDH@NiCo 2 S 4 -MFC exhibited the maximum power density of 80 mW/m2, approximately 2.16 times that of the MnO 2 -MFC (37 mW/m2). Additionally, the maximum voltage was around 200 mV, with good stability maintained for approximately 10 d. The material exhibited excellent electrochemical properties and possessed great potential for application as cathode catalysts of MFC. [Display omitted] • MnO 2 /NiFe-LDH@NiCo 2 S 4 was prepared by simple hydrothermal method. • Maximum power density of MnO 2 /NiFe-LDH@NiCo 2 S 4 -MFC was 80 mW/m2. • Modification of MnO 2 , NiFe-LDH and NiCo 2 S 4 improved ORR ability. [ABSTRACT FROM AUTHOR]

NiCo2S4@PPy core–shell nanotube arrays have been successfully prepared through three facile steps: solvothermal synthesis, solvothermal sulphurisation and subsequentin situelectropolymerisation of polypyrrole (PPy). Their structure and morphology were studied by XRD, FTIR, SEM and TEM. The results suggest that a thin layer of PPy with 8 nm in thickness is wrapped on the surface of NiCo2S4nanotubes. The coating PPy strong promotes pseudo-capacitance reaction of NiCo2S4nanotube arrays. NiCo2S4@PPy shows lower charge plateau and IR drop, higher discharge plateau and Coulombic efficiency. Rate performance is improved remarkably. Average specific capacitance at 24 mA cm−2is even two times that of the uncoated NiCo2S4. The galvanostatic cycling tests at 4 mA cm−2indicate NiCo2S4@PPy exhibit the highest specific capacitance of 1524 F g−1and improved capacitance retention to 78.5% after 3000 cycles. The corresponding values of the uncoated NiCo2S4nanotube arrays are only 1410 F g−1and 22%. The improved electrochemical performance is mainly attributed to unique core–shell nanotube array structure and the key assistant effect of the coating PPy which remarkably improves the conductive property of NiCo2S4long nanotubes and effectively enhances structure stability and cycling stability of NiCo2S4nanotubes. [ABSTRACT FROM PUBLISHER]

As a metallic cocatalyst, the photothermal effect of NiCo 2 S 4 in the process of photocatalytic hydrogen evolution has not been deeply discussed elsewhere. It has been well known that how to intrinsically speed the photogenerated electrons transfer and active absorbed Water (*H 2 O) to release more hydrogen proton (*H) are extremely meaningful to photocatalytic hydrogen evolution improvement. Herein, a convenient and mild two-step solvothermal strategy was developed to meticulously design the intimate contact structure between a noble-metal-free cocatalyst NiCo 2 S 4 and semiconductor ZnIn 2 S 4 nanoflower, which facilitates the charge rearrangement at the interface to boost the separation of photogenerated carriers. Importantly, photothermal effect induced by NiCo 2 S 4 was demonstrated to ameliorate slow kinetics of water spilling with the apparent activation energy reduction form 50.5 kJ·mol−1 to 38.8 kJ·mol−1, which was responsible for improving photocatalytic hydrogen evolution rate of 6834.6 μmol·g−1·h−1 accompanied by apparent quantum efficiency of 13.0% at 400 nm. The electron transfer was accelerated due to localized electric field enhancement determined by Finite difference time domain (FDTD) simulations. The decline of Gibbs free energy barrier of adsorbed water from 2.94 eV on ZIS to 1.62 eV on NCS/ZIS resulted in H-OH bond activating was demonstrated using density functional theory (DFT). This work will provide an effective pathway to design semiconductor-metal-based photothermal assisted photocatalytic system and expand the application of metallic NiCo 2 S 4 in solar-to-fuel conversion. [Display omitted] • The mechanism of NiCo 2 S 4 -induced photothermal effect was investigated systematically for the first time. • The kinetic studies were carried out to pursuit the contribution of photothermal effect for H-OH bond activation. • NiCo 2 S 4 was responsible for accelerating the electron transfer due to localized electric field enhancement. [ABSTRACT FROM AUTHOR]

• Key strategies for improving electrochemical properties of NiCo 2 S 4 -based electrodes are proposed. • This work provides one specific perspective for the development of NiCo 2 S 4 -based composites used in energy storage devices. • This work is helpful to researchers around the world who are working on the synthesis and application of nanostructure TMSs. NiCo 2 S 4 has received wide attention as a promising electrode material for supercapacitors (SCs), Li-ion batteries (LIBs), and Na-ion batteries (SIBs) in the past few years because of its excellent mechanical property, low cost, and rich redox chemistry. In addition, NiCo 2 S 4 has higher electronic conductivity than the corresponding nickel cobaltite oxide (NiCo 2 O 4) and higher redox ability than the corresponding single-phase sulfide. Nevertheless, the actual applications of pristine NiCo 2 S 4 without unique morphology have been restrained on account of the small specific surface area, agglomeration, and big volume change during cycling, resulting in low reversible specific capacity (capacitance) and poor cycle stability at high rates. Constructing NiCo 2 S 4 with novel nanostructures and heterogeneous core-shell structures have been considered as one of the most promising strategy to solve these problems. In the present review, the recent research developments in the electrochemical reaction mechanisms, preparation methods, morphology control, and electrochemical property of NiCo 2 S 4 -based composites as electrode materials for SCs and secondary batteries are summarized. The main focus is to discuss the dominant factors affecting the electrochemical properties of NiCo 2 S 4 -based materials, and then highlight hopeful strategies to improve specific capacitances/capacities and cycling stability, especially at high current densities. Finally, several insights into the future developments, challenges, and prospects of NiCo 2 S 4 -based composites for SCs, LIBs, and SIBs are proposed. [ABSTRACT FROM AUTHOR]