Three-Dimensional MoS2 Nanodot-Impregnated Nickel Foam Electrodes for High-Performance Supercapacitor Applications

An economical and binder-free electrode was fabricated by impregnation of sub-5 nm MoS₂ nanodots (MoS₂ NDs) onto a three-dimensional (3D) nickel substrate using the facile dip-coating method. The MoS₂ NDs were successfully synthesized by controlled bath sonication of highly crystalline MoS₂ nanosheets. The as-fabricated high-surface area electrode demonstrated promising electrochemical properties. It was observed that the as-synthesized NDs outperformed the layered MoS₂ peers as the electrode for supercapacitors. MoS₂ NDs exhibited an excellent specific capacitance (C _sp) of 395 F/g at a current load of 1.5 A/g in a three-electrode configuration. In addition, the fabricated symmetric supercapacitor demonstrated a C _sp value of 122 F/g at 1 A/g and a cyclic performance of 86% over 1000 cycles with a gravimetric power and energy density of 10,000 W/kg and 22 W h/kg, respectively. Owing to its simple and efficient fabrication and high surface area, such 3D electrodes show high promise for various energy storage devices.

Electrochemical Energy Storage Properties of Ni-Mn-Oxide Electrodes for Advance Asymmetric Supercapacitor Application

In this work, we report a facile one-spot synthesis process and the influence of compositional variation on the electrochemical performance of Ni-Mn-oxides (Ni:Mn = 1:1, 1:2, 1:3, and 1:4) for high-performance advanced energy storage applications. The crystalline structure and the morphology of these synthesized nanocomposites have been demonstrated using X-ray diffraction, field emission scanning electron microscopy, and transmission electron Microscopy. Among these materials, Ni-Mn-oxide with Ni:Mn = 1:3 possesses a large Brunauer?Emmett?Teller specific surface area (127 m² g^?1) with pore size 8.2 nm and exhibits the highest specific capacitance of 1215.5 F g^?1 at a scan rate 2 mV s^?1 with an excellent long-term cycling stability (?87.2% capacitance retention at 10 A g^?1 over 5000 cycles). This work also gives a comparison and explains the influence of different compositional ratios on the electrochemical properties of Ni-Mn-oxides. To demonstrate the possibility of commercial application, an asymmetric supercapacitor device has been constructed by using Ni-Mn-oxide (Ni:Mn = 1:3) as a positive electrode and activated carbon (AC) as a negative electrode. This battery-like device achieves a maximum energy density of 132.3 W h kg^?1 at a power density of 1651 W kg^?1 and excellent coulombic efficiency of 97% over 3000 cycles at 10 A g^?1.

Hierarchical whisker-on-sheet NiCoP with adjustable surface structure for efficient hydrogen evolution reaction

We have reported the synthesis of hierarchical whisker-on-sheet (HWS) NiCoP anchored on Ni foam with adjustable surface structure for efficient hydrogen evolution reaction (HER). The HWS NiCoP was obtained by controllable phosphidation of HWS Ni-Co-carbonates hydroxide precursor grown on Ni foam (NF). The experimental parameters were optimally tuned to understand the formation process of the precursor and to regulate the microstructure of the materials. The test results indicated that the HWS NiCoP/NF can produce a current density of 10 mA cm-2 (η10) at a low overpotential of 59 mV and a current density of 100 mA cm-2 (η100) at an overpotential of 220 mV for HER. Notably, upon surface activation with KOH, the HER performance of HWS NiCoP/NF could be dramatically enhanced with η10 and η100 values of 42 mV and 141 mV, respectively. The HWS NiCoP/NF showed a superior performance to NiCoP displaying other morphologies (sheets and wires etc.) The good performance of HWS NiCoP/NF should be attributed to their special whisker-on-sheet structures that are favourable for effective contact with the electrolyte. Also, hydrated metals can be formed on surface after the alkali treatment step, which is beneficial to moderate the bonding to hydrogen and thus, improve the HER activity. The present study will be indicative toward the construction of highly-efficient HER catalysts by regulating the structure of the materials.

Metal Phosphides and Phosphates-based Electrodes for Electrochemical Supercapacitors

Phosphorus compounds, such as metal phosphides and phosphates have shown excellent performances and great potential in electrochemical energy storage, which are demonstrated by research works published in recent years. Some of these metal phosphides and phosphates and their hybrids compare favorably with transition metal oxides/hydroxides, which have been studied extensively as a class of electrode materials for supercapacitor applications, where they have limitations in terms of electrical and ion conductivity and device stability. To be specific, metal phosphides have both metalloid characteristics and good electric conductivity. For metal phosphates, the open-framework structures with large channels and cavities endow them with good ion conductivity and charge storage capacity. In this review, we present the recent progress on metal phosphides and phosphates, by focusing on their advantages/disadvantages and potential applications as a new class of electrode materials in supercapacitors. The synthesis methods to prepare these metal phosphides/phosphates are looked into, together with the scientific insights involved, as they strongly affect the electrochemical energy storage performance. Particular attentions are paid to those hybrid-type materials, where strong synergistic effects exist. In the summary, the future perspectives and challenges for the metal phosphides, phosphates and hybrid-types are proposed and discussed.

Electrodeposition: a versatile, efficient, binder-free and room temperature one-step process to produce MnO2 electrochemical capacitor electrodes

The use of room temperature cathodic electrodeposition to produce MnO₂ electrochemical capacitor electrodes is demonstrated.