MOF-derived PPy/carbon-coated copper sulfide ceramic nanocomposite as high-performance electrode for supercapacitor

To obtain a battery-type ceramic electrode material for supercapacitors, we used a metal-organic framework (HKUST-1) as a template to prepare ceramic material Cu₉S₈@C. Firstly, we adopted the calcination–vulcanization method to synthesize Cu₉S₈@C. Then we deposited it onto a carbon fiber cloth and employed it. Moreover, polypyrrole PPy/Cu₉S₈@C-CC nanocomposite electrodes were prepared via electrochemical deposition. By means of high-temperature calcination and vulcanization, the copper atoms of HKUST-1 were successfully transformed into Cu₉S₈ nanoparticles, and the organic ligand was carbonized into amorphous carbon in Cu₉S₈@C. The results showed that the PPy/Cu₉S₈@C-CC electrode presented a specific capacitance of 270.72F/g at a scan speed of 10 mV/s in a 1 M KCL aqueous solution. This value was much higher than that of Cu₉S₈@C-CC and Cu₉S₈-CC electrodes, as confirmed by the results of electrochemical test. At a scan rate of 10 mV/s, the capacitance retention rate for PPy/Cu₉S₈@C-CC after 3000 cycles was 80.36%, indicating its superior cycle characteristics. Moreover, PPy/Cu₉S₈@C-CC exhibited good frequency response. These results indicate that PPy/Cu₉S₈@C is an ideal electrode material for energy storage and conversion applications.     

Power and energy management of grid/PEMFC/battery/supercapacitor hybrid power sources for UPS applications

This paper presents a hybrid power and energy source supplied by a proton exchange membrane fuel cell (PEMFC) as the main power source in an uninterruptible power supply (UPS) system. To prevent the PEMFC from fuel starvation and degradation and realize their seamless linking in the hybrid UPS system, the power and energy are balanced by the battery and/or supercapacitor (SC) as two alternative auxiliary power sources. Based on the modeling and sizing of hybrid power and energy components, the power and energy management strategies and efficiency measurements of four operating modes in UPS system are proposed. To evaluate the proposed strategies, an experimental setup is implemented by a data acquisition system, a PEMFC generating system, and a UPS system including AC/DC rectifier, DC/AC inverter, DC/DC converter, AC/DC recharger and its intelligent control unit. Experimental results with the characteristics of a 300 W self-humidified air-breathing of PEMFC, 3-cell 12 V/5 Ah of batteries, and two 16-cell 120 F/2.7 V of SCs in parallel corroborate the excellent management strategies in the four operating modes of UPS system, which provides the basis for the optimal design of the UPS system with hybrid PEMFC/battery/SC power sources.     

Rare earth nanostructures based on PrO_x/CNT composites as potential electrodes for an asymmetric pseudocapacitor cell

Rare earth metal oxides have been widely used as pseudocapacitor electrodes owing to their unique physical and electronic properties.The present paper reports the synthesis and pseudocapacitor applications of praseodymium oxides,owing to their unique physical properties.PrO_x/unzipped carbonnanotubes were synthesized following a hydrothermal approach.Detailed morphological as well as electrochemical analyses were performed to elucidate how the unique properties of PrO_x affect the charge storage ability.Special emphasis was given on the effect of anion intercalation due to the surface oxygen vacancies in PrO_x which would contribute towards the pseudocapacitive energy storage.Oxygen intercalation was exploited for the first time in fluorite crystals for fast energy storage and a specific capacitance value as high as 1099 F/g was obtained with the electrodes.An asymmetric supercapacitor prototype was also fabricated with a V_2 O_5/graphene counter electrode and the energy and power density values obtained are as high as 52.08 Wh/kg and 2.9 kW/kg,respectively.     

Hierarchical N-Doped Porous Carbons for Zn–Air Batteries and Supercapacitors

Nitrogen-doped carbon materials with a large specific surface area,high conductivity,and adjustable microstructures have many prospects for energy-related applications.This is especially true for N-doped nanocarbons used in the electrocatalytic oxygen reduction reaction(ORR)and supercapacitors.Here,we report a low-cost,environmentally friendly,large-scale mechanochemical method of preparing N-doped porous carbons(NPCs)with hierarchical micro-mesopores and a large surface area via ball-milling polymerization followed by pyrolysis.The optimized NPC prepared at 1000°C(NPC-1000)offers excellent ORR activity with an onset potential(Eonset)and half-wave potential(E1/2)of 0.9 and 0.82 V,respectively(vs.a reversible hydrogen electrode),which are only approximately 30 mV lower than that of Pt/C.The rechargeable Zn–air battery assembled using NPC-1000 and the NiFe-layered double hydroxide as bifunctional ORR and oxygen evolution reaction electrodes offered superior cycling stability and comparable discharge performance to RuO2 and Pt/C.Moreover,the supercapacitor electrode equipped with NPC prepared at 800℃ exhibited a high specific capacity(431 F g^−1 at 10 mV s^−1),outstanding rate,performance,and excellent cycling stability in an aqueous 6-M KOH solution.This work demonstrates the potential of the mechanochemical preparation method of porous carbons,which are important for energy conversion and storage.     

NiCoLDH nanosheets grown on MOF-derived Co_3O_4 triangle nanosheet arrays for high-performance supercapacitor

Hierarchical Co₃O₄@NiCoLDH nanosheets(NSs)were prepared on carbon cloth through a multistep method,containing Metal-organic frameworks(MOF)-templated thermal annealing and electrodeposition.The triangle-shaped Co₃O_(4 NSs)were firstly obtained by thermal treatment of MOF templates in air.Then,ultrathin NiCoLDH_NSswere in-situ electrodeposited on the surface of Co₃O_4NSs,constructing a core-shell structure.Benefiting the unique hierarchical structure,high conductivity of Co₃O_(4 NSs)core and large surface area of NiCoLDHNSs shell,the Co₃O₄@NiCoLDH_NSsarray served as supercapacitor electrode exhibits excellent electrochemical properties,such as high specific capacitance of 1708 F g^-1(850 C g^-1)at a current density of 1 A g^-1,good rate capability,and excellent cycling stability.Further,the asymmetric supercapacitor assembled by Co₃O₄@NiCoLDH_NSsand activated carbon,also displays superior electrochemical perfo rmance with high energy density and power density.Remarkably,the strategy of constructing core-shell structure based on MOF templates could be extended to other electrochemical fields.     

Manufacturing of polypyrrole-FeOOH supercapacitors

The low capacitance of charge storage materials for negative electrodes of supercapacitors (SCap) is a bottleneck in the manufacturing of asymmetric SCap with high operation voltage and high power. Polypyrrole (PPR)-FeOOH-carbon nanotube (NT) electrodes with high electrochemically active material mass (AM) of 32 mg cm^?2 are manufactured for operation in a negative potential range. The manufacturing method involves the use of copolymer of styrenesulfonic and maleic acids (PSAMA) as a new poly-charged dopant for PPR and pyrocatechol violet (PCV) as a co-dispersant for NT and FeOOH. PPR-FeOOH-NT electrodes show enhanced properties in the negative potential range, compared to PPR-NT electrodes. A capacitance (C_S) of 3.8 F cm^?2 is obtained for PPR-FeOOH-NT electrodes with PPR:FeOOH mass ratio of 7:2. The electrodes offer advantages of low resistance and high ratio of AM to conductive support mass. The C_S of negative PPR-FeOOH-NT electrodes matches the C_S of positive MnO₂-NT electrodes of the same AM. Asymmetric SCap is fabricated, which shows high capacitance in a voltage range of 0–1.6 V and low resistance, high power, and energy, which make it important for industrial SCap applications.     

A facile preparation of graphene/reduced graphene oxide/Ni(OH)2 two dimension nanocomposites for high performance supercapacitors

A Ni(OH)₂ composite with good electrochemical performances was prepared by a facile method. Ni(OH)₂ was homogeneously grown on the hydrophilic graphene/graphene oxide (G/GO) nanosheets, which can be prepared in large scale in my lab. Then G/GO/Ni(OH)₂ was reduced by L-Ascorbic acid to obtain G/RGO/Ni(OH)₂. Caused by the synergy effects among the components, the G/RGO/Ni(OH)₂ electrode showed good electrochemical properties. The G/RGO/Ni(OH)₂ electrode possessed a specific capacitance as high as 1510 F g⁻¹ at 2 A g⁻¹ and even 890 F g⁻¹ at 40 A g⁻¹. An asymmetric supercapacitor device consisting of G/RGO/Ni(OH)₂ and reduced graphene oxide (RGO) was installed and displayed a high energy density of 44.9 W h kg⁻¹ at the power energy density of 400.1 W kg⁻¹. It was verified that the G/GO nanosheets are ideal supporting material in supercapacitor.     

Interfacial synthesis of porous MnO2 and its application in electrochemical capacitor

In this paper, the porous manganese dioxide (MnO₂₎ was prepared by an interfacial reaction of potassium permanganate in water/ferrocene in chloroform. The surface area and pore distribution of MnO₂ can be controlled by simply adjusting the reaction time and the content of surfactant in the aqueous phase. The electrochemical performance of the prepared MnO₂ was evaluated as an electrode material for supercapacitors by the means of cyclic voltammetry and galvanostatic charge-discharge tests. Electrochemical tests results indicated that the pore size plays an important role at high charge-discharge rate, the sample with a large pore size shows a better rate capability, while the sample with a small pore size but large surface area delivers a large capacitance at low current rate.     

Synthesis and characterization of aerogel-like mesoporous nickel oxide for electrochemical supercapacitors

Highly porous NiO was prepared via a combination of sol-gel process with supercritical drying method in this paper. The as-synthesized NiO samples exhibit 80–90% porosity and high surface area, ie, 180.5–325.6 m²g⁻¹. Cyclic voltammetric and chronopotentiometric measurements indicated the aerogel-like NiO in 1 mol.L⁻¹ KOH solution to behave capacitive well due to its uniform mesoporous microstructure. It was also observed that post-heating temperature plays a critical role in the mesoporous nature of the aerogel-like materials. An optimal heating temperature of 300^∘C was found to favor the formation of mesopores, which account for the large specific capacitance of as high as 125 F.g⁻¹. The average specific capacitance of the aerogel-like NiO was observed to be about 75–125 F.g⁻¹ between a potential window of 0–0.35 V vs. SCE.     

Microwave assisted synthesis of rGO/ZnO composites for non-enzymatic glucose sensing and supercapacitor applications

Zinc oxide (ZnO) and Graphene Oxide (GO) are known to show good electrochemical properties. In this paper, rGO/ZnO nanocomposites have been synthesised using a simple microwave assisted method. The nanocomposites are characterized using XRD, Raman, SEM and TEM. XRD reveals the wurtzite structure of ZnO and TEM shows the heterogeneous nucleation of ZnO nanocrystals anchored onto graphene sheets. The electrochemical properties of the rGO/ZnO nanocomposite enhanced significantly for applications in glucose sensors and supercapacitors. The non-enzymatic glucose sensor of this nanocomposite tested using cyclic voltammetry (CV) and chronoamperometry, exhibits high sensitivity (39.78 mA cm⁻² mM⁻¹) and a lower detection limit of 0.2 nM. The supercapacitor electrode of rGO/ZnO nanocomposite exhibits a significant increase in specific capacitance.