Vertical Graphene-Supported NiMo Nanoparticles as Efficient Electrocatalysts for Hydrogen Evolution Reaction under Alkaline Conditions.

Water electrolysis as an important and facile strategy to generate hydrogen has attracted great attention, and efficient electrocatalysts play a key role in hydrogen evolution reaction (HER). Herein, vertical graphene (VG)-supported ultrafine NiMo alloy nanoparticles (NiMo@VG@CC) were fabricated successfully via electro-depositing as efficient self-supported electrocatalysts for HER. The introduction of metal Mo optimized the catalytic activity of transition metal Ni. In addition, VG arrays as the three-dimensional (3D) conductive scaffold not only ensured high electron conductivity and robust structural stability, but also endowed the self-supported electrode large specific surface area and exposed more active sites. With the synergistic effect between NiMo alloys and VG, the optimized NiMo@VG@CC electrode exhibited a low overpotential of 70.95 mV at 10 mA cm-2 and a remarkable stable performance over 24 h. This research is anticipated to offer a powerful strategy for the fabrication of high-performance hydrogen evolution catalysts.

Scalable CNTs/NiCoSe2 Hybrid Films for Flexible All-Solid-State Asymmetric Supercapacitors.

The rapidly developing wearable flexible electronics makes the development of high-performance flexible energy storage devices, such as all-solid-state supercapacitors (SCs), particularly important. Herein, we report the fabrication of CNTs/NiCoSe2 hybrid films on carbon cloth (CC) through a facile co-electrodeposition method based on flexible electrodes for all-solid-state SCs. The NiCoSe2 sheets grown on CNTs uniformly with a diameter of 50-100 nm act as the active materials. The CNTs in the hybrid films act as the scaffold to offer more deposition sites for NiCoSe2 and provide a conductive network to facilitate the transfer of electrons. Moreover, the one-step electrodeposition process avoids the usage of any organic binders. Benefiting from the high intrinsic reactivity and unique 3D architecture, the obtained CNTs/NiCoSe2 electrode delivers high specific capacity (218.1 mA h g-1) and satisfactory durability (over 5000 cycles). Remarkably, the CNTs/NiCoSe2//AC flexible all-solid-state (FASS) ASC provides remarkable energy density (112.2 W h kg-1) within 0-1.7 V and maintains 98.1% of its initial capacity after 10,000 cycles. In addition, this flexible ASC device could be fabricated at a large scale (5 × 6 cm2), and the LED arrays (>3.7 V) can be easily lighted up by three ASCs in series, showing its potential practical application.

Free-standing NiCoSe2 nanostructure on Ni foam via electrodeposition as high-performance asymmetric supercapacitor electrode.

Designing a high-energy-density and power-density electrode for supercapacitors has become an increasingly important concept in the energy storage community. In this article, NiCoSe2 nanostructures were electrodeposited on nickel (Ni) foam and directly used as electrodes for supercapacitors. The effect on the morphology and electrochemical performance of NiCoSe2 prepared under different scan rates was measured through scanning electron microscopy and various electrochemical measurements. The resultant NiCoSe2 prepared with 5 mV s-1 exhibits a cross-linked porous nanostructure and a high specific capacitance of 2185 F g-1 at a current density of 1 A g-1. Taking advantage of these features, an ASC is constructed by using NiCoSe2 on Ni foam as the positive electrode and an active carbon electrode as the negative electrode with 3 M KOH as the electrolyte. The ASC displays a high-energy density of 41.8 Wh kg-1, an ultrahigh power output of 8 kW kg-1, as well as a long cycling life (91.4% capacity retention after 10 000 cycles). The excellent electrochemical performance makes the porous NiCoSe2 nanostructures a promising alternative in energy storage devices.

Improved performance of a CoTe//AC asymmetric supercapacitor using a redox additive aqueous electrolyte.

Cobalt telluride (CoTe) nanosheets as supercapacitor electrode materials are grown on carbon fiber paper (CFP) by a facile hydrothermal process. The CoTe electrode exhibits significant pseudo-capacitive properties with a highest C m of 622.8 F g-1 at 1 A g-1 and remarkable cycle stability. A new asymmetric supercapacitor (ASC) is assembled based on CoTe (positive electrode) and activated carbon (negative electrode), which can expand the operating voltage to as high as 1.6 V, and has a specific capacitance of 67.3 F g-1 with an energy density of 23.5 W h kg-1 at 1 A g-1. The performance of the ASC can be improved by introducing redox additive K4Fe(CN)6 into alkaline electrolyte (KOH). The results indicate that the ASC with K4Fe(CN)6 exhibits an ultrahigh specific capacitance of 192.1 F g-1 and an energy density of 67.0 W h kg-1, which is nearly a threefold increase over the ASC with pristine electrolyte.