One-pot sonochemical synthesis of hierarchical MnWO4 microflowers as effective electrodes in neutral electrolyte for high performance asymmetric supercapacitors

In this article, manganese tungstate (MnWO₄) microflowers as electrode materials for high performance supercapacitor applications are prepared by a one-pot sonochemical synthesis. The crystalline structure and morphology of MnWO₄ microflowers are characterized through X-ray diffraction, field emission scanning electron microscopy. The electrochemical properties of the MnWO₄ microflowers are investigated using cyclic voltammograms, galvanostatic charge/discharge and electrochemical impedance spectroscopy. The MnWO₄ microflowers as electrode materials possess a maximum specific capacitance of 324 F g⁻¹ at 1 mA cm⁻² in the potential window from 0 to +1 V and an excellent cycling stability of 93% after 8000 cycles at a current density of 3 mA cm⁻². An asymmetric supercapacitor device is fabricated using the MnWO₄ and iron oxide (Fe₃O₄)/multi-wall carbon nanotube as the positive and negative electrode materials, it can be cycled reversibly at a potential window at 1.8 V. The fabricated ASC device can deliver a high energy density of 34 Wh kg⁻¹ at a power density of 500 W kg⁻¹ with cycling stability of 84% capacitance retained after 3000 cycles. The above results demonstrate that MnWO₄ microflowers can be used as promising high capacity electrode materials in neutral electrolyte for high performance supercapacitors.     

Binder free and high performance of sputtered tungsten nitride thin film electrode for supercapacitor device

Here, we demonstrates the fabrication of binder free and very efficient supercapacitor electrode based on tungsten nitride (W₂N) thin film on stainless steel (SS) substrate using reactive sputtering technique. W₂N thin film as a working electrode exhibits high specific capacitance (163 F g⁻¹ at 0.5 mA cm⁻² in 1 M H₂SO₄) along with excellent cycling stability. The binder free symmetric supercapacitor (W₂N||W₂N) device delivers a high specific capacitance (80 Fg^-1) and long life span (90.46% capacitance retention after 10,000 cycles) along with high energy (12.92 Whkg⁻¹) and power (∼674 kWkg⁻¹ at 9.36 Whkg⁻¹) densities. These observed excellent electrochemical performances of the present W₂N thin film based supercapacitor device, recommend it as a potential candidate for energy storage applications.     

Fabrication of a ternary PANI@Fe3O4@CFs nanocomposite as a high performance electrode for solid-state supercapacitors

In this work, a solid-state high performance supercapacitor is fabricated based on a ternary polyaniline@Fe₃O₄@carbon fibers nanocomposite. To prepare the polyaniline@Fe₃O₄@carbon fibers electrodes, a two-step method including electrophoretic deposition of Fe₃O₄ nanoparticles on carbon fibres followed by an in situ polymerization process of polyaniline is utilized. The results show that the polyaniline@Fe₃O₄@carbon fibers nanocomposite with a layer by layer microstructure is successfully formed. The fabricated nanocomposite represents a specific surface area of 3.12 m² g⁻¹. The electrochemical measurements in a three-electrode configuration reveals a high specific capacitance of 245.5 F g⁻¹ at 0.5 A g⁻¹ and an excellent cycle stability (82.44% after 1000 cycle) of the polyaniline@Fe₃O₄@carbon fibers electrode. The as-fabricated solid-state supercapacitor based on the polyaniline@Fe₃O₄@carbon fiber nanocomposite cloth with a surface area of 25 cm² powers up a blue light-emitting diode for 4 min and delivers a high energy density of 78.6 Wh.kg⁻¹ at a power density of 1047.5 W kg⁻¹.     

Controlled growth of hierarchical FeCo2O4 ultrathin nanosheets and Co3O4 nanowires on nickle foam for supercapacitors

In recent years, the tenable design and synthesis of the core/shell heterostructure as electrode for the supercapacitor, have attained a huge attention and concerns. In this article, the three-dimensional heterostructure consisting of FeCo₂O₄ ultrathin nanosheets grown on the space of vertical Co₃O₄ nanowires has been designed and synthesized onto nickel foam (NF) for pseudocapacitive electrode applications. According to previous research, the NF@ FeCo₂O₄ electrodes can only exhibit specific capacity of 1172 F g⁻¹ at a current density of 1 A g⁻¹. In addition, although the capacity of the NF@Co₃O₄ electrodes can reach to 1482 F g⁻¹ and it has the disadvantage of agglomeration, which restricts the diffusion of ions and has a negative effect on the progress of electrochemical reactions. Therefore, a core-shell nanostructure is fabricated by an improved two-step hydrothermal process, which improves the probability of ion reaction with more efficient charge transfer. Furthermore, in as-prepared unique core/shell heterostructure, the resultant electrode possesses the merits of large capacitance of 1680 F g⁻¹ at a current density of 1 A g⁻¹, an excellent rate capability of 70.1% at 20 A g⁻¹ and only 9.8% loss of initial capacitance at a high charge/discharge current density after 2000 cycles. These results demonstrate that this kind of distinct electrode has potential utilization for supercapacitor.     

Fabrication of electrochemically interconnected MoO3/GO/MWCNTs/graphite sheets for high performance all-solid-state symmetric supercapacitor

Binder-free MoO₃/GO/MWCNTs/graphite sheets were successfully fabricated via electrodeposition of graphene oxide and functionalized multi walled carbon nanotube onto graphite sheets followed by electrodeposition of molybdenum oxide. The capacitive behavior of the MoO₃/GO/MWCNTs/G sheet was found to be superior with respect to those of MoO₃/MWCNTs/graphite and MoO₃/GO/G sheets. The high wettability, interconnected structure and synergetic effects between MoO₃, GO and MWCNTs made the MoO₃/GO/MWCNTs/G sheet exhibited a high areal capacitance of 103 mF cm⁻² at current density of 0.7 mA cm⁻² in 1.0 M KCl. An all-solid-state symmetric supercapacitor device prepared by using the MoO₃/GO/MWCNTs/G sheet as both positive and negative electrodes showed high cell voltage of 2.5 V and remarkable cycle life of 86.8% retention after 2000 cycles, suggesting the possibility for practical applications in energy storage device.     

Ni–Co–S nanosheets supported by CuCo2O4 nanowires for ultra-high capacitance hybrid supercapacitor electrode

Recently, constructing core-shell arrays directly on conductive substrates is proved as a promising strategy for energy storage devices, due to the abundant active sites and fast electrons transport paths. In this work, we design core-shelled CuCo₂O₄@Ni–Co–S arrays directly on Ni foam substrate by the hydrothermal and electrodeposition processes. The core-shelled arrays can possess the large accessible surface area, fast charge transfer kinetics and the synergistic effect from both components, leading to better electrochemical performances. Consequently, core-shell CuCo₂O₄@Ni–Co–S arrays can deliver a high specific capacitance of 12.10 F cm⁻² (corresponding to 2897 F g⁻¹ mass specific capacitance), and good cycle stability with 82.5% capacitance retention after 8000 cycles of charging and discharging at 20 mA cm⁻². In addition, a battery-supercapacitor hybrid device made of CuCo₂O₄@Ni–Co–S and activated carbon displays a high energy density of 0.65 mWh cm⁻² at 32 mW cm⁻² power density, and the capacitance loss less than 20% (~83.6%) after 8000 cycles.     

A comparative study of various polyelectrolyte/nanocomposite electrode combinations in symmetric supercapacitors

A more practical, nontoxic and cheaper electrolyte, poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPS) was used to construct supercapacitors with different nanocomposite electrodes. The flexible devices were fabricated including active carbon (AC) electrode and nanocomposites electrodes of AC/nano-silica (nano-SiO₂) and AC/multiwalled carbon nanotubes (MWCNTs) at various weight percentages. The symmetrical cell made from AC electrodes generated a maximum specific capacitance (Cs) of 315 F g⁻¹ at 0.5 A g⁻¹. The energy density of this device was 55.5 Wh kg⁻¹ at a power density of 690 W kg⁻¹. Excellent performance was achieved after 5000 charge-discharge cycles where the supercapacitor maintains 92% of its activity. The energy storage capability of the supercapacitors was also investigated with the addition of nano-SiO₂ and MWCNTs. The Cs of the supercapacitors made with the electrodes AC/nano-SiO₂ (5%, 10%, 25% and 50%) were 172, 228, 247 and 55 F g⁻¹, respectively. Similarly, the capacity of the device including the electrodes of AC/MWCNTs (5%, 10%, 25% and 50%) varied as 191, 244, 93 and 20 F g⁻¹ at 0.5 A g⁻¹. The maximum energy density of the devices having nano-SiO₂ and MWCNT were 44.4 Wh kg⁻¹ and 43.8 Wh kg⁻¹, respectively at a power density of 520 W kg⁻¹. A supercapacitor with certain dimension successfully operated a light-emitting diode (LED).     

Sol-gel synthesis of ternary conducting polymer hydrogel for application in all-solid-state flexible supercapacitor

In this contribution, we reported the preparation of a novel conducting polymer hydrogel (CPH) by a sol-gel method, which was subsequently employed to fabricate a flexible all-solid-state supercapacitor device. Taking advantage of the synergistic effects of the different components in the conducting polymer hydrogel and the merits of the proposed synthesis strategies, the prepared supercapacitor device with CPH as electrode exhibited high area-normalized capacitance (2.2 F cm⁻²), high gravimetric capacitance (1573.6 F g⁻¹) as well as high energy density of 0.18 mWh cm⁻² (or 128.7 Wh Kg⁻¹) at 0.08  mW cm⁻² (or 55.1 W kg⁻¹). This study did not only represent a novel all-solid-state, high performance, flexible supercapacitor with potential applications in flexible energy-related devices, but also developed a new method for enhancing capacitances and mechanical stability of all-solid-state flexible supercapacitor.     

Yuba-like porous carbon microrods derived from celosia cristata for high-performance supercapacitors and efficient oxygen reduction electrocatalysts

Here, a novel yuba-like porous carbon microrod is prepared via a simple and facile strategy by using the fluffy fibers of celosia cristata petals (FCCP) as the raw material. The optimized carbon microrod (FCCP-CM-900) possesses unique yuba-like structure, high specific surface area (1680 m² g⁻¹) and large pore volume (0.98 cm³ g⁻¹), and effective nitrogen (∼4.52 at.%) and oxygen (∼5.49 at.%) doping, which can enhance the wettability and conductivity (7.9 S cm⁻¹). As the electrode material for supercapacitor, FCCP-CM-900-based supercapacitor presents high specific capacitance (314.5 F g⁻¹ at 0.5 A g⁻¹) in 6.0 M KOH aqueous electrolyte. The FCCP-CM-900-based symmetrical supercapacitor displays high energy density (18.6 Wh kg⁻¹ at 233.4 W kg⁻¹) and outstanding cycling stability (98% capacitance retention after 10,000 cycles) in 1.0 M Na₂SO₄ electrolyte. In addition, served as oxygen reduction electrocatalyst, the FCCP-CM-900 also exhibits excellent catalytic activity, good durability, together with high methanol tolerance in alkaline electrolyte, which makes it a highly efficient air cathode material toward zinc–air cell.     

Easily-prepared bimetallic metal phosphides as high-performance electrode materials for asymmetric supercapacitor and hydrogen evolution reaction

Transition metal phosphides are very attractive because of the remarkable performance in energy storage and conversion. Herein, a series of bimetallic phosphides are synthesized through a one-step solid-state reaction. The obtained bimetallic phosphides show outstanding properties as supercapacitor electrode materials. Results show that the incorporation of secondary metal into phosphides tunes composition, electronic structure and then the electrochemical performance. And electrochemical properties are closely associated with the secondary metal content. Notably, the obtained NiCoP shows the best performance with 2011 F g⁻¹ at 1 A g⁻¹. And an asymmetric supercapacitor (ASC) based on NiCoP shows energy density of 47.6 W h kg⁻¹, along with 90.5% of capacitance maintained after 10000 cycles. In addition, the NiCoP also possesses great performance toward hydrogen evolution reaction (HER), which displays the lowest potential of 0.221 V vs. RHE and 0.173 V vs. RHE at 10 mA cm⁻² in 0.5 M H₂SO₄ as well as 1.0 M KOH, respectively. The excellent properties may result from the enhanced electrical conductivity, synergistic effects among metal elements and the increased local electrical dipole. The regulation of electronic structure through introduction of secondary metal atom sheds considerable light on realization and preparation of the bimetallic transition metal compounds as electrode materials.     

Chicken nuggets-like core/shell nanosheet arrays as high performance flexible all-solid-state supercapacitor cathode and buckwheat shell as anode

The energy density of a flexible all-solid-state supercapacitor (ASC) requires new electrode material with special structure and morphology as a prerequisite for its secured improvement. In this paper, a new morphological exploration of chicken nuggets-like core/shell NiCo₂O₄/MnO₂ (NCM) nanosheet arrays on Ni foam was employed. The application of this special morphology aims to greatly improve the electrochemical performance of the cathode electrode. Additionally, Buckwheat Biochar (BBC) is utilized as the anode while the PVA/KOH thin film is prepared as the separator. The chicken nuggets-like core/shell NCM nanosheet arrays were obtained by a two-step hydrothermal method. A series of characterization methods were carried out to further support the core/shell's well-designed structure and precise composition. The tests exhibited excellent specific capacitance of 593.3 F g^?1 at 5 mA cm^?2 and outstanding cycling stability with a retention of 90% after 10000 cycles. Furthermore, the assembled NCM//BBC ASC device indicated a high specific capacitance (239 F g^?1 at the current density of 5 mA cm^?2), this is in due part of the unique architecture of NCM nanosheet arrays and interconnected special porous structure of the BBC and the thin film PVA/KOH. Hence, the assembled ASC device exhibited high energy density (an energy density of 58 Wh·kg^?1 at 3263 W kg^?1) and remarkable cycling stability.     

Manganese oxide(Ⅲ)/carbon hybrids with interesting morphologies as improved active materials for supercapacitors

Mn₂O₃/C hybrids with almond-like, peach-like and peanut-like morphologies are fabricated via hydrothermal method followed by annealing in air at ambient pressure. Their physical properties and morphologies are characterized by X-ray diffraction (XRD), Raman scattering spectroscopy (Raman), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET), scanning electron microscopy (SEM) and scanning transmission electron microscopy (STEM). Almond-like Mn₂O₃/C (Mn₂O₃/C-ALL) and peach-like Mn₂O₃/C (Mn₂O₃/C-PCL) hybrids are highly porous with large-sized mesopores. In contrast, peanut-like Mn₂O₃/C (Mn₂O₃/C-PNL) is composed of densely packed slender nanofibers. The results show Mn₂O₃ and carbon have homogeneous contact accounting for high conductivity. In 1.0 M Na₂SO₄ aqueous electrolyte, Mn₂O₃/C-PCL has the highest specific capacitance of 158.8 F g⁻¹ at 1.0 A g⁻¹, compared to Mn₂O₃/C-ALL (105.1 F g⁻¹) and Mn₂O₃/C-PNL (77.5 F g⁻¹). Furthermore, the capacitance retention of Mn₂O₃/C-PCL achieves 48.8% upon a 50-fold increase in current density. Finally, the Mn₂O₃/C-PCL displays an impressive long-term cycle stability of 90.6% specific capacitance retention after 10,000 cycles at 1.0 A g⁻¹. Therefore, this work highlights the importance of morphology in Mn₂O₃/C hybrids design to obtain high performance supercapacitor materials.     

Facile preparation of Ni,Co - Alloys supported on porous carbon spheres for supercapacitors and hydrogen evolution reaction application

Carbon nanomaterials that are electrochemically bifunctional and active in supercapacitor and hydrogen-evolution-reaction (HER) applications have attracted recent research attention. We have prepared porous carbon spheres - doped Ni, Co - alloys by using a hydrothermal method with melamine and pectin as precursors and with the addition of nickel nitrate and cobalt nitrate. The corresponding materials exhibit good electrochemical performance and excellent electrocatalytic activity for HER. The overpotential (OP) of the as-prepared materials can achieve 240 mV keeping a Tafel slope (TS) of 55 mV dec⁻¹ at 10 mA cm⁻² in an acid (0.5 M H₂SO₄) solution. The corresponding samples maintain stability after 24 h and 5000 cycles in the chronovoltage and cyclic voltammetry methods, respectively. When the as-prepared materials are oxidized by 30% H₂O₂ for 12 h, the corresponding as-prepared oxidation samples exhibit excellent electrochemical performance in a supercapacitor application. The specific capacitance (SC) of the as-obtained materials reaches 312 F g⁻¹ at 1 A g⁻¹ with decent rate capability and cyclic stability. This work provides new applications for bifunctional electrochemically active materials.     

Facile fabrication of comb-like porous NiCo2O4 nanoneedles on Ni foam as an advanced electrode for high-performance supercapacitor

It is very desirable to develop the high-performance supercapacitors to meet the rapidly growing demands for energy-autonomous operation and miniaturization of devices. Herein, comb-like porous NiCo₂O₄ nanoneedles on the three-dimension (3D) nickel foam (NF) have been successfully synthesized through a facile pulsed laser ablation (PLA) approach without any post-treatments and surfactant (denoted as NiCo₂O₄-PLA). The influence of working solution during the fabricated process on the properties of NiCo₂O₄-PLA has been demonstrated in detail in terms of the crystalline structure, specific surface area, morphology, and electrochemical performance. Benefiting from the large specific surface (261.4 m² g⁻¹), abundant pores, and highly conductive scaffold, the NiCo₂O₄-PLA binder-free electrode exhibits an outstanding specific capacitance (1650 F g⁻¹ at a current density of 1 A g⁻¹) and eminent cycling performance (91.78% retention after a 12,000-cycle test at a current density of 10 A g⁻¹) compared with the control samples. The assembled asymmetric device (NiCo₂O₄-PLA//AC-ASCs) delivers the high specific capacitance of 126.9 F g⁻¹ at the current density of 1 A g⁻¹, the large energy density of 56.7 Wh kg⁻¹ at a power density of 756 W kg⁻¹, and the low internal resistance. The attractive results strongly prove that it is an ideal candidate for advanced supercapacitor application.     

Co-precipitation synthesis of nickel cobalt hexacyanoferrate for binder-free high-performance supercapacitor electrodes

Prussian blue analogue with a typical metal-organic framework has been widely used as an electrode material in supercapacitor. In this work, nickel cobalt hexacyanoferrate (Ni₂CoHCF) was grown on nickel foam directly using a simple co-precipitation method. The as-prepared Ni₂CoHCF was tested by transmission electron microscope, scanning electron microscope, X-ray diffraction and X-ray electron energy spectrum. The results showed that Ni₂CoHCF has a unique open face-centered cubic structure. The Ni₂CoHCF was used to set an asymmetric supercapacitor directly. A series of electrochemical tests showed that Ni₂CoHCF had an excellent electrochemical performance. The specific capacitance of the supercapacitor was 585 C g⁻¹ (1300.0 F g⁻¹, 162.5 mAh g⁻¹) at the current density of 0.5 A g⁻¹. After 2000 cycles, it still maintained 85.57% of its initial specific capacitance at the current density of 10 A g⁻¹. The energy density was 30.59 Wh kg⁻¹ at the power density of 378.7 W kg⁻¹. The results show that the supercapacitor constructed by Ni₂CoHCF as an electrode material has high-current charge-discharge capacity, high energy density and long cycle life.     

NiFe-LDH/MWCNTs/NF nanohybrids as a high-performance bifunctional electrocatalyst for overall urea electrolysis

It is crucial for the storage and conversion of hydrogen energy to substitute the low theoretical potential of urea oxidation reaction (UOR) for the high theoretical potential of anodic water electrolysis (oxygen evolution reaction (OER)). In this paper, it puts forward a brief and scalable strategy, so as to synthesize a novel bifunctional nickel-iron layered double hydroxide and multi-walled carbon nanotube composites supported on Ni foam, represented as NiFe-LDH/MWCNTs/NF. Electrochemical measurements demonstrate that NiFe-LDH/MWCNTs/NF is able to realize an efficient electrocatalysis for UOR. During this process, merely a potential of 1.335 V is needed at 10 mA cm⁻², which can be taken to replace OER, thus reducing overpotential in H₂-production as well as power consumption. In addition, NiFe-LDH/MWCNTs/NF also exhibits electro-defense electrocatalytic efficiency to achieve the reaction of hydrogen evolving process, which provides a low overpotential of 98 mV at 10 mA cm⁻². To further prove it, all-water-urea electrolysis measurement is carried out in 1 M KOH and 0.5 M Urea with NiFe-LDH/MWCNTs/NF as cathode and anode respectively. NiFe-LDH/MWCNTs/NF||NiFe-LDH/MWCNTs/NF electrode manages to provide 10 mA cm⁻² at a voltage of merely 1.507 V, 156 mV lower than that of water splitting, which proves its commercial viability in energy-saving hydrogen production.     

Electrochemical performance of activated carbons prepared from rice husk in different types of non-aqueous electrolytes

Activated carbons (ACs) prepared from rice husk (RH), an agricultural byproduct, have mesoporosity that is obtainable from leaching of the mineral component of silica. To verify the suitability of RH-derived ACs for the use of electrode materials of electrical double-layer capacitors, we evaluated the electrochemical performance of three RH-derived ACs (two micro- and mesoporous ACs and one mesoporous AC). Evaluation was done by using the non-aqueous ionic electrolyte solutions 1 mol dm⁻³ triethylmethyl ammonium tetrafluoroborate/propylene carbonate (PC) solution, 1.5 mol dm⁻³ spiro-(1,1′)-bipyrrolidinium tetrafluoroborate/PC (SBP·BF₄/PC) solution, and the ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIm·BF₄). Under low voltage scan rate (1 mV s⁻¹) and low current density (<1 mA cm⁻²), mesoporous AC, which had the highest specific surface area, showed the highest specific capacitance (120 F g⁻¹) in EMIm·BF₄. However, its specific capacitance considerably decreased because of the increase in scan rate and current density. Under high scan rate (10 and 100 mV s⁻¹) and high current density (>10 mA cm⁻²), micro- and mesoporous AC in 1.5 mol dm⁻³ SBP·BF₄/PC showed the highest specific capacitance and highest retention of specific capacitance, even though its specific surface area was not the highest. Mesoporous AC showed voltage-dependent specific capacitance, indicating that ionic transport in the mesoporous structure was sensitive to electric field. It was finally shown that micro- and mesoporosity developed by utilizing natural structure and composition of RH was useful for the electrode materials of advanced electrical double-layer capacitors requiring more viscous non-aqueous electrolytes.     

CoFe2O4@methyl cellulose core-shell nanostructure and their hybrids with functionalized graphene aerogel for high performance asymmetric supercapacitor

Recently, the use of asymmetric supercapacitors (ASC) has attracted much attention due to their optimum storage of energy and a high range of voltage. Here, we have indicated the design and fabrication of a unique ASC based on metal-spinel core-shell nanocomposite (CoFe₂O₄@MC) as a positive electrode and a p-phenylenediamine (PPDA)-graphene aerogel composite (AP) as a negative electrode in aqueous KOH electrolyte solution. The CoFe₂O₄@MC nanocomposite was prepared by the chemical deposition method. The AP was also effortlessly organized using the hydrothermal method. Considering the incorporation of methylcellulose carbohydrate polymer (MC) into the CoFe₂O₄ nanomaterial and consequently having a porous structure, a specific capacitance of 433.3 F g^?1 was obtained at the current density of 1 A g^?1 with the configuration of three electrodes. The CoFe₂O₄@MC//AP-ASC operates in the voltage range up to 2.3 V and provides a specific capacitance of 99 in 1 A g^?1. It presents an impressive energy density and power density of ~73 W h Kg^?1 and 1056 W kg^?1, respectively which prove its quality. The most important feature seems to be good cycling stability and capacity retention of 89% after 2000 cycles. These splendid outcomes show that CoFe₂O₄@MC nanocomposite possibly seems to be a satisfying choice for the next generation of devices with the capability of energy storage.     

Fabrication and electrochemical characterization of two-dimensional ordered nanoporous manganese oxide for supercapacitor applications

A nanoporous manganese oxide (MnO₂) film was fabricated via a polystyrene templated electrodeposition in the solution containing MnSO₄. The nanoporous MnO₂ film obtained has been characterized by field emission scanning electron microscopy, cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charge/discharge methods. The specific capacitance of 1018 F g⁻¹ was observed at a low current density of 500 mA g⁻¹. When the current density increased to 30.0 A g⁻¹, the specific capacitance of 277 F g⁻¹ remained. The high capacitance retention at high rates makes the prepared MnO₂ a promising candidate for supercapacitor applications.     

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.