Morphology controlling of manganese-cobalt-sulfide nanoflake arrays using polyvinylpyrrolidone capping agent to enhance the performance of hybrid supercapacitors.

Transition metal sulfide-based electrode materials are promising candidates for energy storage applications owing to their richer redox-active sites and higher electrical conductivity than their oxide counterparts. Manganese-cobalt-sulfide (MCS) nanoflakes were synthesized on nickel foam in the presence of polyvinylpyrrolidone (PVP) as a capping agent using a one-step hydrothermal method. The variation in the amount of PVP in the reaction solution had a prominent impact on the MCS electrode morphology. PVP altered the morphology of the MCS nanoflakes. Different shapes of interconnecting-nanoflake arrays were formed with different amounts of PVP. The MCS electrode prepared using 0.2 g of PVP (MCS-P2) showed the best efficiency with a specific capacity of 1312 C g-1 (3215 F g-1) at 1 A g-1 and still retained a remarkable capacity of 1000 C g-1 (2480 F g-1) at 20 A g-1. Moreover, the hybrid supercapacitor (HS) device consisting of MCS-P2//reduced graphene oxide (rGO) revealed a high energy density of 48.7 Wh kg-1 at a corresponding power density of 386 W kg-1. Even at a higher power density of 10.8 kW kg-1, a notable energy density of 25.5 Wh kg-1 was retained. These remarkable results highlight the potential applications of the MCS-P2 electrode material in energy storage.

A Comparative Study of the Influence of Nitrogen Content and Structural Characteristics of NiS/Nitrogen-Doped Carbon Nanocomposites on Capacitive Performances in Alkaline Medium.

Supercapacitors (SCs) have been regarded as alternative electrochemical energy storage devices; however, optimizing the electrode materials to further enhance their specific energy and retain their rate capability is highly essential. Herein, the influence of nitrogen content and structural characteristics (i.e., porous and non-porous) of the NiS/nitrogen-doped carbon nanocomposites on their electrochemical performances in an alkaline electrolyte is explored. Due to their distinctive surface and the structural features of the porous carbon (A-PVP-NC), the as-synthesized NiS/A-PVP-NC nanocomposites not only reveal a high wettability with 6 M KOH electrolyte and less polarization but also exhibit remarkable rate capability (101 C/g at 1 A/g and 74 C/g at 10 A/g). Although non-porous carbon (PI-NC) possesses more nitrogen content than the A-PVP-NC, the specific capacity output from the latter at 10 A/g is 3.7 times higher than that of the NiS/PI-NC. Consequently, our findings suggest that the surface nature and porous architectures that exist in carbon materials would be significant factors affecting the electrochemical behavior of electrode materials compared to nitrogen content.

A 3D walking palm-like core-shell CoMoO4@NiCo2S4@nickel foam composite for high-performance supercapacitors.

Supercapacitors are one of the most promising renewable-energy storage systems. In this study, a three-dimensional walking palm-like core-shell CoMoO4@NiCo2S4@nickel foam (NF) nanostructure was synthesized using a two-step hydrothermal method for high electrochemical performance. The as-prepared composite exhibited a high areal capacitance of 17.0 F cm-2 (2433 F g-1) at a current density of 5 mA cm-2 in a three-electrode system. The results revealed outstanding cycling stability of 114% after 10 000 charge-discharge cycles. An aqueous asymmetric supercapacitor device assembled with CoMoO4@NiCo2S4@NF and activated carbon (AC)@NF as the positive and negative electrodes, respectively, showed a high capacitance of 4.19 F cm-2 (182 F g-1) and delivered a high energy density of 60.2 W h kg-1 at a power density of 188 W kg-1 and a high power density of 1.5 kW kg-1 at an energy density 29.2 W h kg-1, lighting 22 parallel-connected red light emitting diodes for over 60 s. The synergistic effects of the core-shell CoMoO4@NiCo2S4@NF electrode material highlight the potential of this composite as an effective active material for supercapacitor applications.

One-step synthesis of hollow C-NiCo2S4 nanostructures for high-performance supercapacitor electrodes.

Carbon-containing NiCo2S4 hollow-nanoflake structures were fabricated by a one-step solvothermal method using CS2 as a single source for sulfidation and carbonization. The reaction mechanism for the hollow structure with carbon residues was explored based on the formation of a bis(dithiocarbamate)-metal complex and the Kirkendall effect during solvothermal synthesis. The NiCo2S4 nanoflake electrode exhibited a high specific capacitance of 1722 F g-1 (specific capacity 688.8 C g-1) at a current density of 1 A g-1 and an excellent cycling stability (capacity retention of 98.8% after 10 000 cycles). The as-fabricated asymmetric supercapacitor based on NiCo2S4 nanoflakes and activated carbon electrodes revealed a high energy density of 38.3 W h kg-1 and a high power density of 8.0 kW kg-1 with a capacitance retention of 91.5% and a coulombic efficiency of 95.6% after 5000 cycles, highlighting its great potential for practical supercapacitor applications.

Acyclic and cyclic imines and their metal complexes: recent progress in biomaterials and corrosion applications.

This review describes the contemporary development applications on scientific areas of acyclic and cyclic Schiff bases and their complexes with an emphasis on the author's contribution to the field. After a short historical introduction, this manuscript is divided into two main parts. In the first section, Schiff bases are reviewed for their biological activities including antibacterial, antifungal, antioxidant, cytotoxic, and enzymatic activities as well as their interaction with single-stranded-DNA which have shown remarkable activities in each region of research. The second part deals with the corrosion of metal and its alloys in corrosive environments and their organic inhibitors. The main section of this part is to investigate the different chemical structures for Schiff bases used in such aggressive solution to protect metals. Knowing the maximum corrosion efficiency or bioactivity of a specific chemical structure in a specific application environment is helpful for choosing the most appropriate compound.

Ternary Spinel MCo2O4 (M = Mn, Fe, Ni, and Zn) Porous Nanorods as Bifunctional Cathode Materials for Lithium-O2 Batteries.

The development of Li-O2 battery electrocatalysts has been extensively explored recently. The Co3O4 oxide has attracted much attention because of its bifunctional activity and high abundance. In the present study, toxic Co(2+) has been replaced through the substitution on the tetrahedral spinel A site ions with environmental friendly metals (Mn(2+), Fe(2+), Ni(2+), and Zn(2+)), and porous nanorod structure are formed. Among these spinel MCo2O4 cathodes, the FeCo2O4 surface has the highest Co(3+) ratio. Thus, oxygen can be easily adsorbed onto the active sites. In addition, Fe(2+) in the tetrahedral site can easily release electrons to reduce oxygen and oxidize to half electron filled Fe(3+). The FeCo2O4 cathode exhibits the highest discharging plateau and lowest charging plateau as shown by the charge-discharge profile. Moreover, the porous FeCo2O4 nanorods can also facilitate achieving high capacity and good cycling performance, which are beneficial for O2 diffusion channels and Li2O2 formation/decomposition pathways.

High-performance lithium-ion battery and symmetric supercapacitors based on FeCo2O4 nanoflakes electrodes.

A successive preparation of FeCo2O4 nanoflakes arrays on nickel foam substrates is achieved by a simple hydrothermal synthesis method. After 170 cycles, a high capacity of 905 mAh g(-1) at 200 mA g(-1) current density and very good rate capabilities are obtained for lithium-ion battery because of the 2D porous structures of the nanoflakes arrays. The distinctive structural features provide the battery with excellent electrochemical performance. The symmetric supercapacitor on nonaqueous electrolyte demonstrates high specific capacitance of 433 F g(-1) at 0.1 A g(-1) and 16.7 F g(-1) at high scan rate of 5 V s(-1) and excellent cyclic performance of 2500 cycles of charge-discharge cycling at 2 A g(-1) current density, revealing excellent long-term cyclability of the electrode even under rapid charge-discharge conditions.

Mesoporous ZnCo2O4 nanoflakes with bifunctional electrocatalytic activities toward efficiencies of rechargeable lithium-oxygen batteries in aprotic media.

This study reports the successful synthesis of ternary spinel-based ZnCo2O4 nanoflakes (NFs) with mesoporous architectures via the combination of a urea-assisted hydrothermal reaction with calcination in an air atmosphere. Owing to their favorable mesostructures and desirable bifunctional oxygen reduction and evolution activities, the resulting mesoporous ZnCo2O4 NFs yielded stable cyclability at a cut-off capacity of 500 mA h gcarbon(-1) in the case of aprotic Li-O2 batteries.