GCD Tests Research Articles

Microwave-assisted hydrothermal synthesis of αβ-Ni(OH)2 nanoflowers on nickel foam for ultra-stable electrodes of supercapacitors

Transition metal hydroxides (TMHs) are considered promising materials for supercapacitors because of their high theoretical capacitance and tunable morphology. Among TMHs, nickel hydroxide stands out for its multiple oxidation states, facilitating charge storage. This paper reports on a novel microwave-assisted hydrothermal technique employed to synthesize mixed-phase nickel hydroxide nanoflowers directly at the surface of nickel foam substrates with improved electrochemical stability compared to pure phases of nickel hydroxide. The analysis of nickel hydroxide in different phases alpha, beta and mixed-phase materials using physiochemical techniques like XRD, SEM, EDX, RAMAN, FT-IR and TGA is explained. The areal capacitance calculated from GCD tests for α-Ni(OH)2, β-Ni(OH)2 and αβ-Ni(OH)2 is estimated 7.35 F/cm2, 2.66 F/cm2 and 5.12 F/cm2 at a current density of 10 mAcm−2. The mass-specific capacitance calculated from GCD tests for α-Ni(OH)2, β-Ni(OH)2 and αβ-Ni(OH)2 is estimated 2311 Fg−1, 688 Fg−1 and 1511 Fg−1 at a current density of 10 mAcm−2. The cyclic stability test revealed the superior cycling performance of nickel hydroxide in mixed-phase as the cathode of an ultralong supercapacitor with nearly 100 % capacitance retention after 5000 cycles at 50 mAcm−2. The proposed synthesis technique advances the efficiency and control of nanostructure geometry, providing insights into the design for electrodes of extreme-performance supercapacitors. However, conventional synthesis methods are time-consuming and energy-intensive. These findings underscore the potential of mixed-phase nickel hydroxide as an outstanding electrode material with extended cyclic performance for supercapacitors, contributing to the improvement of energy storage technologies in the renewable energy landscape.

Advanced supercapacitor electrodes: Synthesis and electrochemical characterization of graphene oxide-bismuth metal-organic framework composites for superior performance

The primary requirements for a viable supercapacitor electrode material are increased energy density, high specific capacitance, and excellent cycle stability. The desired outcome may be attained by combining diverse active materials. In this research, two Bi-MOFs with 1,4-benzenetdicarboxylic (H2BDC) and 1,3,5-benzenetricarboxylic (H3BTC) organic linkers were synthesized by facile solvothermal method and bonded on the surface of graphene oxide to produce FGO-Bi(BTC) and FGO-Bi(BDC) composites. The electrochemical characteristics of the two electroactive compounds were evaluated by GCD, CV, and EIS tests in a three-electrode setup. Comparative electrochemical analyses demonstrated that the composites exhibit remarkable performance with reduced charge transfer resistance. In the three-electrode configuration, FGO-Bi(BDC) and FGO-Bi(BTC) exhibited specific capacitances of 559 and 422 F g-1 at 1 A g-1, respectively. After conducting 10,000 cycles of charge and discharge at 8 A g-1, the FGO-Bi(BDC) and FGO-Bi(BTC) electrodes exhibited impressive retention rates of 97.6% and 95.64% for their initial specific capacitance (Cs). Notably, the three-electrode system's results indicated superior electrochemical performance of the FGO-Bi(BDC) electrode over the FGO-Bi(BTC) electrode. This superiority is attributed to the FGO-Bi(BDC)'s larger specific surface area (SSA) and reduced oxygen concentration. For a more practical assessment, the FGO-Bi(BDC) composite was selected for evaluation in the two-electrode system. The FGO-Bi(BDC)//FGO-Bi(BDC) two-electrode system demonstrated a cyclic stability of 94.2% over 10,000 cycles, attaining a substantial Cs of 295 F g-1 at 1 A g-1. Moreover, it accomplished a power density of 750 W kg-1 and an energy density of 34.61 Wh kg-1, emphasizing the exceptional electrochemical attributes that position the FGO-Bi(BDC) composite as a promising electrode material for supercapacitors.

Electrochemical Behaviour of Ultrasonic Probe Assisted Nickel Pyrophosphate (Ni2P2O7) Nanosheets for Supercapacitor Applications

New materials and synthesis strategies are needed to achieve better electrochemical performance. In this context, we developed a Ni2P2O7 Nanosheets (NNS) as a new classical-type active electrode using a simple and low-cost method. Crystal phase, chemical structure, and morphology of the sample were inspected by X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), and Field Emission Scanning Electron Microscopy (FESEM) - Energy Dispersive Spectroscopy (EDS) analysis, respectively. As prepared electrode material was confirmed with monoclinic phase and nanosheet morphology identified from XRD and FESEM analysis, respectively. Various types of electrochemical approaches, such as CV, GCD, Cycling stability, and EIS applied in 2 M KOH electrolytes to investigate supercapacitive behaviour. As fabricated electrode material portrays satisfied specific capacitance (Cs) of 514.7F/g at a scan rate of 1 mV/s along with the excellent cyclic ability of 80 % retention upon 3000 continuous CV cycles, good rate capability in the extended potential window of 1 V. The GCD tests revealed remarkable specific capacity (462C/g) and exceptional energy density (64 Wh/Kg). Moreover, electrode material displayed impressive columbic efficiency as to be 77 % and 51 % at lower and higher current densities, respectively. These notable merits suggest that our designed Nanosheets (NNS) sample is the best opportunity for the development of sustainable supercapacitor devices.

Fabrication of a novel porous nanostructure based on NiCuFe2O4@MCM-48, embedded with graphene oxide/poly (p-phenylenediamine) to construct an efficient supercapacitor

In this study, a new nanocomposite was created by combining copper-doped nickel ferrite (NiCuFe2O4) nanoparticles with MCM-48 (Mobil Composition of Matter No. 48) on a graphene oxide (GO) substrate functionalized with poly(ρ-phenylenediamine) abbreviated as (PρPD). This nanocomposite was developed to investigate its potential for enhancing the function of a supercapacitor in energy storage. Following NiCuFe2O4@MCM-48 preparation, Hummer’s technique GO was applied. In-situ polymerization of NiCuFe2O4@MCM-48/GO nanoparticles with ρ-phenylenediamine (ρPD) in the presence of ammonium persulfate (APS) produced PρPD, a conductive polymer. Structural characterization of the nanocomposite includes FTIR, XRD, VSM, TGA-DTG, EDX, and FE-SEM. Results from BET indicate a pore size increase of up to 5 nm. Fast ion penetration and higher storage in capacitor material are explained by this. Additionally, the nanocomposite’s electrochemical performance was evaluated using GCD and CV tests. The NiCuFe2O4@MCM-48/GO/PρPD nanocomposite has a specific capacitance of 203.57 F g−1 (1 A g−1). Furthermore, cyclical stability is essential for energy storage applications. The nanocomposite retains 92.5% of its original capacitance after 3000 cycles, indicating outstanding electrochemical stability.

Hierarchical three-dimensional nanoflower-like CuCo2O4@CuCo2S4@Co(OH)2 core-shell composites as supercapacitor electrode materials with ultrahigh specific capacitances

Here, we prepare three-dimensional nanoflower-shaped CuCo2O4@CuCo2S4@Co(OH)2 core–shell materials on nickel foam (NF). CuCo2O4 (CuC) nanowire arrays and CuCo2S4 (CuS) nanosheets are grown directly on NF as the core through routine hydrothermal and high-temperature calcination methods and Co(OH)2 (CH) small nanosheets deposited on CuC@CuS nanoflowers via the potentiostatic deposition for 15 mins. Due to its distinctive structure and the synergistic effect between multiple components of CuCo2O4@CuCo2S4@Co(OH)2, the electrode has a fantastic specific capacitance (Cs, 4075F/g) under the current density of 1 A/g and satisfying cyclic stability (88.4 % capacitance retention and 84.6 % coulomb efficiency after 10,000 cycles). Additionally, an asymmetric supercapacitor (ASC) device equipped with CuC@CuS@CH-15/NF as a positive and active carbon (AC) electrode as a negative electrode can work steadily at 0–1.6 V. The ASC device can offer an excellent energy density (E, Wh kg−1) of 232.02 Wh kg−1 at a high-power density of 2879.8 W kg−1 (P, W kg−1) and an unexpected cycle stability (84.2 % of the original Cs and 81.7 % of coulombic efficiency after 10,000 repeated GCD tests), which far surpasses other ASCs of the same type. These results guide to enhancement of the electrochemical properties of cobalt-based oxides/sulfides@Co(OH)2 as the positive electrode for supercapacitors.

Effect of Electrolyte Type on Supercapbatteries Based on Silicon as Anode and Cassava Tuber Activated Carbon as Cathode

Supercapbatteries are energy storage devices to solve low power and energy density problems. In this study, using cassava tubers activated carbon on the cathode side and silicon on the anode side. The electrodes are arranged in a coin cell device using various electrolytes 6M KOH and 1M Et4NBF4. The substrate used as the electrode is nickel foam with a drop-by-drop deposition technique. Microstructural properties of cassava tuber activated carbon and silicon were characterized using XRD, SEM, and FTIR. XRD showed cassava tuber-activated carbon was in an amorphous phase and the diffraction peak was similar to that of commercial activated carbon. On the other hand, silicon exhibits a crystalline phase. Based on SEM, the particle size distribution of cassava tuber activated carbon is 8.87μm, the average pore size is 0.988μm, and the percentage of porosity is 69.49%, while the particle size distribution of silicon is 0.065μm. The FTIR results show the formation of a C=C functional group which characterizes the nature of activated carbon at a wavelength of 1592.04 cm-1. GCD tests show that the electrochemical performance of super batteries is better when using 6M KOH electrolyte, specific capacitance, power density, and energy density 27.6F/g, 282.7W/kg, and 7.4Wh/kg.

The influence of anionic surfactant (SDS) on the optical, magnetic and capacitive properties of NiO nanocrystals via gas-liquid diffusion synthesis

A facile gas–liquid diffusion route with magnetic stirring was used for the preparation of black fungus-like NiO nanostructure with the assistance of SDS surfactant. The NiO obtained without addition of surfactant was used in the control test. The structure, composition and morphology of NiO nanocrystals were characterized by various methods including XRD, Raman, SEM, HRTEM, BET and XPS techniques. The optical properties were analyzed with UV–Vis DRS. The contact angle measurement and vibrating sample magnetometer were used to investigate surface wettability and magnetic properties respectively. The electrochemical behavior of two NiO samples was studied by CV and GCD tests. The characterization and test results showed that compared with surfactant-free NiO sample, the prepared NiO sample using SDS surfactant as template agent exhibited specific morphology and higher surface area, better optical properties, magnetic susceptibility and electrochemical properties.

Multicolor electrochromic polymers based on butterfly-shaped monomers for the visualization of energy storage

Electrochromic supercapacitors (ECSCs) enable visual indication of their energy storage, thus effectively preventing them from being overcharged or insufficient energy. The current studies mainly focus on improving its specific capacitance and cycling stability. Herein, two butterfly-shaped triphenylamine-thiophene derivatives with twisted molecular structures were designed and synthesized featuring an EDOT unit as the central core. Then, two conjugated polymers pBTTPAE and pETPAE were prepared through electrochemical polymerization. Both polymers exhibit distinct multicolor display behavior, faster response time and excellent cycling stability. GCD tests show that pBTTPAE exhibited a higher volumetric specific capacitance (324.4 F·cm−3) and GCD stability due to its high specific area. The prototype device based on pBTTPAE is remarkable for its impressive energy density of 17.94 mWh·cm−3 and power density of 6.32 W·cm−3, which can be switched reversibly from yellow to yellow-green and blue when the potential changes from -0.4 V to 1.5 V. The high-performance electrochromic supercapacitor materials demonstrate their extensive utilizations for intelligent energy-storage devices.

Electrochemical aspects of Co3O4 nanorods supported on the cerium doped porous graphitic carbon nitride nanosheets as an efficient supercapacitor electrode and oxygen reduction reaction electrocatalyst

Herein, the electrochemical performance of Ce-PGCN,NS/Co3O4 as a metal-free ORR electrocatalyst and supercapacitor electrode was investigated. FESEM, TEM, BET, FTIR, XRD, EDX, FTIR, and Raman tests were used to characterize the synthesized electrocatalysts. For ORR measurements, voltammetry (CV, LSV, Choronoamperometry) and EIS tests were used to investigate the electrocatalytic activity of the electrocatalysts. And for supercapacitor measurements, the CV and GCD tests were conducted to examine the electrode's capacitance. The results of the voltammetry tests show that Ce-PGCN,NS/Co3O4 with an onset potential of −0.027 V, selecting four-electron pathway (n = 3.86), Tafel slope of 137 mV/dec, charge transfer of 570 Ω, and high durability in alkaline media (0.1 M KOH) show an excellent electrochemical performance as an ORR electrocatalyst and can be introduced as a promising substitution for commercial Pt/C catalysts. On the other hand, the results of CV in supercapacitor mode and GCD reveal that Ce-PGCN,NS/Co3O4 electrode with the specific capacitance of 789 F g−1 at the current density of 1 A g−1 and high stability in alkaline media (2 M KOH), have superior performance as a supercapacitor electrode than other electrode based on the g-C3N4. Also, it is observed that converting bulk g-C3N4 to PGCN,NS, doping Cerium atoms on the structure of the PGCN,NS, and adding Co3O4 nanorods impact the electrocatalytic activity of g-C3N4 positively.

CuO induced effects on the electrochemical properties of (In2O3)1-xCuOx nanocomposites for supercapacitor flexible electrode materials

• Novel (In 2 O 3 ) 1-x CuO x heterostructure nanocomposites with different concentration was fabricated through the surfactant-assisted co-precipitation method. • The electrochemical performance and electrochemical cycle stability of all the prepared samples were assessed over the carbon cloth (CC) electrode. • The (In 2 O 3 ) 0.5 (CuO) 0.5 was demonstrated higher capacitance 883 F/g at 1A/g than all other samples. • Approximately 83.5% capacity retention after 6000 GCG tests was measured for (In 2 O 3 ) 0.5 (CuO) 0.5 . Recent research on electrochemical energy storage devices has shown that their specific capacities, cyclic-lives, as well as rate performances, are chiefly controlled by their electrodes. Therefore, a key challenge for 21st-century material researchers is to seek out novel electrode materials with improved crystal structures, excellent specific capacities and better electronic conductivities, in order to fabricate a highly efficient energy storage system. To address this concern (In 2 O 3 ) 1-x CuO x (where x = 0, 0.1, 0.3, 0.5, 0.7, 1) heterostructure nanocomposites have been prepared through the surfactant-assisted co-precipitation strategy. The nature of the atomic and molecular interactions, chemical compositions, textures and shapes of the synthesized nanocomposites have been investigated in detail. In this study, the novel composite materials have been supported over carbon cloth (CC) to produce flexible working electrodes. It has been found that the electrode with a particular composition of (In 2 O 3 ) 0.5 (CuO) 0.5 -over-CC has demonstrated superior capacitance (883 F/g at 1 A/g), improved electrochemical and cycle stability (83.5 % after 6000 GCD tests) and a higher rate capability (708 F/g at 5 A/g) than all other fabricated nanocomposite-based flexible electrodes. The electrode's improved electrochemical activity is attributed to its flexible design, higher electronic conduction, non-resistive current collector behaviour and unique nanoarchitecture. These versatile and simple-to-prepare nanocomposites are potential candidates as electrodes for high-performance pseudocapacitors nanodevices.

In situ grown of thulium/samarium mixed metal–organic frameworks onto Ni foam as outstanding binder-free battery type high-performance electrode for supercapacitors

In this paper, a sphere-like thulium/samarium mixed-metal MOF with 1-imidazole-carboxylate (IMC) as the organic linker (i.e. Tm,Sm-IMC-MOF) was grown onto Ni-foam (NF) porous support by one-step cathodic deposition procedure. The synthesized Tm,Sm-IMC-MOF material was characterized through XRD, FT-IR, TGA/DSC and FE-SEM/EDS techniques. The charge storage performance of the fabricated Tm,Sm-IMC-MOF/NF electrode was analyzed through CV and GCD tests, where a battery-like supercapacitive ability with a highest capacity of 645 C/g at 1 A/g was observed. The assembled Tm,Sm-IMC-MOF/NF//RGO/NF ASC device showed specific capacity of 239 C/g, areal capacity of 2.11 C cm−2 at 4 A/g and ~63 % capacity retention after increasing the applied current load from 1 to 20 A/g. The assembled ASC device exhibited 85.4 % and 91.5 % cycling retentions after 5000 cycles at 4 and 8 A/g, respectively. These results demonstrated that the fabricated Tm,Sm-IMC-MOF/NF electrode could be a promising candidate as active electrode material for electrochemical supercapacitors.

Redox-active anomalous electrochemical performance of mesoporous nickel manganese sulfide nanomaterial as an anode material for supercapattery devices

In this work, we are reporting nickel manganese sulfide hierarchical redox-active nanostructured material synthesized using a facile one-step hydrothermal technique to investigate its potential for supercapattery devices. The surface morphology, crystallinity, elemental analysis/composition surface area, porosity, and homogeneity were investigated through X-ray diffraction (XRD), Energy dispersive X-ray (EDX) spectra, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and Brunauer–Emmett–Teller (BET). The electrochemical characterizations were performed in a three-electrode standard cell whereas the electrolyte used was 1 M potassium hydroxide. These characterizations predict that sample S-0.4 is exhibiting superior performance over all other electrodes and therefore it was paired with activated carbon for the assembling of supercapattery (Ni–Mn–S//AC). This supercapattery was probed electrochemically with CV, GCD, EIS, and stability tests which reveals superb performance by delivering a high value of capacity (420.10 C/g) with a maximum energy density of 75.96 Wh/kg. The device was able to deliver the power density of 2865 W/kg, along with an outstanding cyclic life by sustaining 85% of capacity even after 5000 GCD cycles. Our analysis for this electrode material suggests that our synthesized material can be applied for future high-performance supercapattery devices.

Fabrication of nanostructured iron-cobalt layered double hydroxide: An innovative approach for the facile synthesis

Studying semiconductive materials-based supercapacitors is significant for developing next-generation energy storage devices. However, the fabrication of a novel semiconductive material-based electrode with self-supporting design, flexible support, and nanoarchitecture is a challenge for the material researcher of 21st century. We present a facile method to fabricate three-dimensional (3D), porous, conductive electrodes based on semiconductive materials with high electrochemical performance. We fabricate the FeCo-LDH sample via hydrothermal route and decorate it on the flexible carbon cloth (CC) to get a flexible and self-supporting electrode. Textural, morphological, elemental, thermal, and functional group studies of the hydrothermally generated powder were performed using XRD, SEM, EDX, TGA, and FTIR methods. Well-known EIS, GCD, and CV tests were used to evaluate the electrochemical possessions of the FeCo-LDH/CC electrode. The performed electrochemical experiments indicated that our manufactured FeCo-LDH/CC electrode has an excellent specific capacity of 1041F/g at 0.5 A/g. Our self-supporting and flexible electrode has excellent cycle stability (it loses only 7.3 percent of its capacity after 5000 GCD cycles). It retains 79.2 percent of its capacitance when the current density increases from 0.5 A/g to 9 A/g. The superior electrochemical activity observed is attributed to the electrode's novel structure and logical design. According to the electrochemical experiment findings, our manufactured FeCo-LDH/CC electrode has great promise for practical applications in next-generation electrochemical capacitors.

Enhanced photocatalytic, antibacterial, and electrochemical properties of CdO-based nanostructures by transition metals co-doping

In the present work, single Ni-doped and Co, Cr, Cu co-doped CdO nanostructures via sol-gel approach were fabricated. The XRD diffractograms have confirmed the successful doping and co-doping in CdO lattice without any impurity phase generation. FTIR and Raman spectra have further confirmed the metal-oxygen bonding vibration and optical phonon modes related to CdO. FE-SEM images exhibited nanobelt type morphology varied with the type of dopant and EDX evident the presence of dopants along with Cd, and O. PL and IV results exhibited that the charge carrier recombination hinders and electrical conductivity has improved by co-doping. UV–vis absorbance spectra have shown redshift in energy bandgap by co-doping. The CV, EIS, and GCD tests suggested the superior electrochemical capacitive characteristic of co-doped CdO and can serve as efficient electrode materials. The photocatalytic activity results exhibited increased photodegradation performance by co-doping, and the highest was achieved for Ni/Cr co-doped samples. The antimicrobial activity results have shown a higher zone of inhibition against Escherichia coli and Staphylococcus aureus bacterial strains. The narrow energy bandgap, lower recombination, and low charge transfer resistance are responsible for boosting the properties of CdO by co-doping and making it a prospective candidate as effective photocatalysts, antibiotic-resistant agents, and supercapacitor electrode materials.

Nanostructured V2O5 and its nanohybrid with MXene as an efficient electrode material for electrochemical capacitor applications

Vanadium pentoxide (V 2 O 5 ) is an excellent electrode material for electrochemical capacitor (ECCs) applications, but its lower electrical conductivity is the primary obstacle that restricts its practical applications. This obstacle can be eliminated by forming its nanohybrid (NCs) with a highly capacitive and conductive matrix such as MXene. MXene is a new two-dimensional (2D) material with good electronic conductivity and a larger specific surface area, making it a very suitable substrate for composite formation. Unfortunately, the two-dimensional MXene sheets stacked quickly, limiting their specific surface area and charge/mass transport properties. Here we used the hydrothermal approach to fabricate V 2 O 5 nanowires (NWs) and form their nanohybrid with MXene via the ultrasound route. To assess electrochemical suitability, the fabricated samples were loaded onto a carbon cloth (CC) and used as a working electrode in the half-cell configuration. The nanohybrid (V 2 O 5 /MXene) sample showed a good specific capacity (C sp ) of 768 F/g (at 1 A/g) because of its greater surface area, hybrid composition, excellent electrical conductivity, and passive nanostructure. It also showed superior cyclic, electrochemical and mechanical capability and maintained a specific capacity of 93.3%, even after completion of 6000 GCD tests. In addition, the nanohybrid sample electrode also exhibits superb rate performance and lost only 14.4% of its initial specific capacity on increasing the applied current density from 1 to 5 A/g. There is no doubt that V 2 O 5 NWs inter-stack between MXene nanosheets to develop effective interface interaction and suppress their stacking.

A new rapid synthesis of hexagonal prism Zn-MOF as a precursor at room temperature for energy storage through pre-ionization strategy

In this paper, a new hexagonal prismatic Zn-MOF is rapidly synthesized at room temperature through a one-step precipitation method as precursor for the preparation of porous carbon. The SEM and GCD tests indicate that the pre-ionization process of BTC greatly accelerates the reaction speed between BTC and Zn ions, and only 0.5 h is required for the preparation of Zn-MOF with orderly morphology at room temperature, far less than 3–24 h of the existing hydrothermal synthesis. The derived porous carbon (BTCC) is provided with a considerable specific surface area of 1,464 m2 g−1 and suitable pores of 3.9 nm in size. Its richly porous structure offers a superior supercapacitor performance. The BTCC electrode offered a high specific capacitance and an excellent cycle stability. Furthermore, the assembled two symmetrical supercapacitors, C|1 M Na2SO4|C and C|6 M KOH|C, provide high energy density of 22.4 Wh kg−1 and 13.7 Wh kg−1, respectively. Their energy retention rates were 80.0% and 89.4%, respectively after 10,000 cycles at 20 A g−1. The proposed pre-ionization strategy is a facile, convenient and easy-to-industrial method for the preparation of new MOFs, thereby significantly reducing the manufacturing cost of porous carbon for energy storage.

MnO2 cathode materials with the improved stability via nitrogen doping for aqueous zinc-ion batteries

The research and exploration of manganese-based aqueous zinc-ion batteries have been controversial of cycle stability and mechanism investigation, thus improving the stability and exploring storage mechanism are still the most main issue. Defect engineering has become an effective method to improve cycle stability. Herein, a nitrogen-doped ε-MnO2 (MnO2@N) has been prepared using electrochemical deposition and heat treatment under nitrogen atmosphere. As the cathode for zinc-ion batteries, the capacity retention rate of MnO2@N cathode is close to 100% after 500 cycles at 0.5 A g−1, while the capacity retention rate for the initial MnO2 cathode is 62%. At 5 A g−1, the capacity retention rate of MnO2@N cathode is 83% after 1000 cycles, which is much higher than the 27% capacity retention rate for the original MnO2 cathode. And it can be found that the oxygen vacancies increase after nitrogen doping, which can improve the conductivity of the MnO2@N cathode. Also, there is Mn-N bond in MnO2@N, which can enhance the electrochemical stability of MnO2@N cathode. In addition, the electrochemical mechanism of MnO2@N cathode has been explored by the CV, GCD and GITT tests. It is found that nitrogen doping promotes the intercalation of H+ and the corresponding capacity contribution. Compared with the original MnO2 cathode, the diffusion coefficient of H+ and Zn2+in MnO2@N cathode increases. Also, the reactions during the charging and discharging process are explored through the ex-situ XRD test. And this work may provide some new ideas for improving the stability of manganese-based zinc-ion batteries.

On-pot fabrication of binder-free composite of iron oxide grown onto porous N-doped graphene layers with outstanding charge storage performance for supercapacitors

An effective one-step electrochemical method was developed to synthesize three-dimensional N-doped porous graphene/magnetite nanoparticles hybrid onto Ni foam (Fe3O4@3D-NPG/NF electrode). In this method, 3D nitrogen-doped porous graphene layers are electrophoretically deposited onto Ni foam, accompanied by the simultaneous in situ electrochemical deposition (ECD) of magnetite particles onto 3D-NPG layers. For comparison, Fe3O4 particles and N-doped graphene were separately deposited onto Ni foam, and pristine Fe3O4/NF and 3D-NPG/NF electrodes were fabricated. The structure, composition and morphology of the fabricated electrode materials were systematically characterized by XRD, FT-IR, FE-SEM, Raman, TEM, BET, and TGA/DSC techniques. The formation mechanism of Fe3O4@3D-NPG hybrid through EPD/ECD was proposed and described in detail. The charge storage capabilities of the fabricated electrodes were analyzed as the supercapacitor electrode. The results GCD tests revealed that Fe3O4@3D-NPG electrode is able to deliver specific capacity value of 715 F g−1 at 2 A g−1 and cycle life of 94.3% after 5000 GCD cycles, where the pristine Fe3O4/NF electrode delivered only specific capacity of 219 F g−1 and 77.6% capacity retention. These findings implicated the positive synergistic effects between Fe3O4 and 3D-NPG in the hybrid electrode to exhibit higher supercapacitive performance. This simple strategy could find practical uses in the large-scale fabricating Fe3O4@3D-NPG electrode.

Folded graphene/copper oxide hybrid aerogels: folding, self-reinforcement, and electrochemical performance

In our previous work, the Origami and enhancement theory was introduced into the construction of graphene aerogels to achieve the self-enhancement effect of graphene aerogels through the folding process of graphene lamellae. Based on the above work, after the graphene lamination was folded by Cu ion, it was further converted to cupric oxide by in situ mode, thus participating in the enhancement of the electrochemical behavior of graphene aerogels, and the "folding—enhanced—electrochemical" multiple effects were obtained. The innovation of this article was to use copper ions to achieve the folding of graphene sheet, and convert copper ions into copper oxides to improve the electrochemical properties of graphene aerogels, thereby achieving self-enhancement and electrochemical applications of graphene aerogels.The molecular structure and elemental composition of fGA/CuO were studied by FTIR and XPS. The surface microstructure of fGA/CuO was studied by SEM and bet. The results showed that fGA/CuO was successfully prepared with small and round micropores on the surface.The mechanical and electrochemical properties of fGA/CuO were studied by mechanical properties test, CV, GCD, and EIS tests. The results show that fGA/CuO has good mechanical and electrochemical properties.

Synthesis and characterization of reduced graphene oxide/magnetite/polyaniline composites as electrode materials for supercapacitors

The ternary composites consisted of reduced graphene oxide, magnetite, and polyaniline (rGO/Fe3O4/PANI) were synthesized by a simple procedure. Fe3O4 nanoparticles were produced by chemical precipitation route and then hybridized with rGO through chemical reduction of GO. PANI chains were grown by in situ polymerization on the rGO/Fe3O4 to attain the ternary composite powders. The synthesized composites were characterized by XRD, UV–Vis, FTIR, Raman, FESEM, and EDS techniques. The results confirm the formation of PANI nanofibers beside rGO nanoplatelets decorated by crystallized Fe3O4 nanoparticles. The electrochemical behavior of the synthesized composites as electrode materials for supercapacitors was evaluated by CV, EIS, and GCD tests. The unique nanostructure of the synthesized composites and the synergic interaction among rGO nanoplatelets, Fe3O4 nanoparticles, and PANI chains result in the superior performance of the ternary composite in the charge storage. The rGO/Fe3O4/PANI electrode unveils a high specific capacitance of 610.4 F g−1 and excellent cyclic stability with a retention ratio of 87% after 1000 cycles at 1 A g−1. Although increasing the PANI content in the rGO/Fe3O4/PANI composite degrades the electrochemical performance of the electrode, but the specific capacitance of the ternary composite electrode is still higher than the sole PANI and Fe3O4 or the binary rGO/Fe3O4 composite.