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Summary: Doping Mn element into host material is an efficient approach to enhance the specific capacitance and cycling stability of supercapacitor. In this aspect, we fabricate Co‐Mn LDHs (CMLs) hollow polyhedron generated from ZIF‐67 via a template sacrifice method. Controllable doping of Mn element with gradient contents on the effect of electrochemical performance are investigated in detail. Moreover, in order to assemble a hybrid supercapacitor with superior energy and power output, a negative electrode based on MXene/rGO/V10O24 is synthesized considering the integration of EDLC and pseudocapacitance. As expected, the asymmetric supercapacitor of CMLs‐0.53//MXene/rGO/V10O24 delivers high energy density of 44.4 Wh kg−1, maximum power density of 12 750 W kg−1 and superior cycling life (91.6% capacitance retention after cycling 10 000 cycles). The special idea on the construction of CMLs with hollow structure can offer new insight to resolve the complicated steps during preparation procedure. The results also indicated that the device based on CMLs‐0.53 and MXene/rGO/V10O24 is a good candidate in the utilization of energy storage and conversion system in the future. [ABSTRACT FROM AUTHOR]

Summary: Transition metal sulfides show excellent performance in an aqueous supercapacitor. However, all‐solid‐state supercapacitors are attracting more and more interest because of thinner, lighter, and more flexible. Binary sulfides Ni3Co6S8 nanowire arrays (NCS) are directly grown on a nitrogen‐doped carbon foam (NCF) through hydrothermal reaction, which is applied as a binder‐free electrode for all‐solid‐state supercapacitor. The unique needlelike structure assembled by nanosheet effectively increases the utilization efficiency of active materials and promotes electrochemical performance. The NCS‐NCF electrode shows promising application potential for wearable electronic devices due to the flexibility of NCF. A high‐specific capacitance of 243 mAh g−1is delivered by NCS‐NCF electrode, which also exhibits good rate behavior along with outstanding cycle stability. The NCS‐NCF electrode (positive electrode) and NCF electrode (negative electrode) are employed to assemble asymmetric all‐solid‐state supercapacitor. When the high power density is 675 W kg−1, the energy density of supercapacitor reaches the maximum of 28.31 Wh kg−1. The specific capacitance of supercapacitors could maintain 84%, after 10 000 cycles of galvanostatic charge and discharge under 4 A g−1, indicating the potential application of NCS‐NCF electrode as an excellent supercapacitor electrode material in flexible, wearable energy storage systems. [ABSTRACT FROM AUTHOR]

Summary: The development of highly active, robust and cost‐effective noble metal‐free electrocatalysts for hydrogen evolution reaction (HER) in alkaline solution remains a severe challenge. In this work, a hollow structure CoSe2‐FeSe2 heterojunction electrocatalyst (denoted by "(Co,Fe)Se2") was designed by a simple anion exchange reaction and selenization. Benefiting from the unique hollow structure, the (Co,Fe)Se2 catalyst accelerates diffusion of electrolyte, besides, the CoSe2‐FeSe2 heterojunction could provide rapid interfacial charge transportation and more active sites for the HER reaction. The (Co,Fe)Se2 electrode material exhibits good performance for HER in 1 M KOH electrolyte. It needs an overpotential of 124 mV to obtain a current density of 10 mA cm−2, and the Tafel slope is 65 mV dec−1. Besides, (Co,Fe)Se2 has a smaller charge transfer resistance compared with CoSe2. At the same time, it has relatively large electrochemical active surface area due to the porosity. Most importantly, the (Co,Fe)Se2 electrode displays good stability in alkaline conditions for 15 hours, the linear sweep voltammetry curves are almost coincident before and after 1000 cycles, the overpotential with current density of 10 mA cm−2 increased by only 9.76% after 5000 cycles of CV. It shows great application potential in HER. [ABSTRACT FROM AUTHOR]

Summary: The development of highly active, robust and cost‐effective noble metal‐free electrocatalysts for hydrogen evolution reaction (HER) in alkaline solution remains a severe challenge. In this work, a hollow structure CoSe2‐FeSe2 heterojunction electrocatalyst (denoted by "(Co,Fe)Se2") was designed by a simple anion exchange reaction and selenization. Benefiting from the unique hollow structure, the (Co,Fe)Se2 catalyst accelerates diffusion of electrolyte, besides, the CoSe2‐FeSe2 heterojunction could provide rapid interfacial charge transportation and more active sites for the HER reaction. The (Co,Fe)Se2 electrode material exhibits good performance for HER in 1 M KOH electrolyte. It needs an overpotential of 124 mV to obtain a current density of 10 mA cm−2, and the Tafel slope is 65 mV dec−1. Besides, (Co,Fe)Se2 has a smaller charge transfer resistance compared with CoSe2. At the same time, it has relatively large electrochemical active surface area due to the porosity. Most importantly, the (Co,Fe)Se2 electrode displays good stability in alkaline conditions for 15 hours, the linear sweep voltammetry curves are almost coincident before and after 1000 cycles, the overpotential with current density of 10 mA cm−2 increased by only 9.76% after 5000 cycles of CV. It shows great application potential in HER. [ABSTRACT FROM AUTHOR]

Summary: Sodium‐ion hybrid capacitors are a prospective energy storage device candidate that couples the superiorities of battery‐type and capacitive storage mechanisms. In this study, we fabricate a composite of NiCo2O4 nanowires with carbon tubular bundles (CTBs) via a facile hydrothermal and annealing procedure. The density functional theory (DFT) calculations are performed to evaluate the bonding strength between the two components of the composite, the binding energy of the NiCo2O4 is calculated to be −0.952 J m−2, indicating that the NiCo2O4 nanowires can be stabilized on both sides of the carbon tubular bundles, which leads to a good cycling performance. Moreover, the composite in this work exhibits a metallic property because of the introduction of carbon material. As expected, when used for sodium storage, the NiCo2O4/CTBs shows a high capacity of 298 mA h g−1 at 1 A g−1 and high capacity retention of 92% after 500 cycles, which are superior than the bare NiCo2O4 electrode. Consequently, the sodium‐ion hybrid capacitor is also assembled with NiCo2O4/carbon tubular bundles and commercial activated carbon, which achieves high energy density of 99 Wh kg−1 in a wide potential range from 0.5 V to 4.0 V. [ABSTRACT FROM AUTHOR]