KOH Aqueous Electrolyte Research Articles

Sonochemical synthesis of nickel tungstate (NiWO4) nanoparticles for dye degradation and electrochemical sensing of lead ions in environmental samples

Here we have synthesised Nickel Tungstate (NiWO4) nanoparticles via sonochemical method. The structural and morphological studies were examined using XRD, FTIR, UV–Vis, SEM and TEM analysis. XRD pattern confirms the monoclinic wolframite structure of NiWO4 nanoparticles. FTIR spectrum reveals that strong absorption peaks at 450 cm−1 to 1000 cm−1 for stretching and bending vibrational frequencies of the Ni–W-O peaks in NiWO4. UV–Vis spectrum shows maximum intensity peak at ∼ 473 nm corresponding to the band gap of 3.0 eV. The SEM and TEM images show irregular shapes of nanoparticles. BET analysis shows a surface area 31.811 m2/g for NiWO4 nanomaterials. Methylene Blue (MB) and Rhodamine B (RhB) dyes were used as model pollutants for the analysis of photocatalytic activity under UV and visible light irradiations and it has proved as a fine photocatalyst. The electrochemical activity of the samples was studied by cyclic voltammetry (CV) and Electrochemical Impedance spectroscopy (EIS) in 1 M KOH aqueous electrolyte. EIS measurements showed a reduction in the charge transfer resistance in acidic electrolyte. Modified carbon paste electrode employing NiWO4 nanoparticles has sensed lead in alkaline electrolyte. The electrode displayed high sensitivity for lead detection under varying concentrations. These results confirm that the NiWO4 nanoparticles are promising electrode material for sensing lead with high electrode reversibility.

Walnut shell derived N, S co-doped activated carbon for solid-state symmetry supercapacitor device

The kernel of the walnut constitutes a nutrient-dense food source. However, the walnut shell is useless and was thrown away. Therefore, as a small initiative towards waste-to-wealth, herein we developed walnut shell-derived highly porous heteroatom (nitrogen and sulfur) doped activated carbon (NS-WAC) via KOH activation and post-processing treatment by thioacetamide (TAA). The NS-WAC exhibits a high specific surface area (SSA) and various particle size distribution (PSD) involving micropores, mesopores, and macropores, conferring substantial supercapacitor advantages. The NS-WAC possesses a significant proportion of mesopores, which can decrease the ion diffusion path length and improve ion transport efficiency. Hence, NS-WAC demonstrates promising electrochemical performance achieving a high gravimetric specific capacitance of 271.4 Fg−1 at 0.5 Ag−1 in 3 M KOH aqueous electrolyte. Furthermore, the solid-state symmetric supercapacitor (SSC) device exhibited a gravimetric specific capacitance of 52 Fg−1 and volumetric specific capacitance of 74.36F cm−3 at a current density of 0.5 Ag−1. This SSC device also exhibited a gravimetric energy density of 23.4 Wh Kg−1 at a power density of 250 W Kg−1 at a current density of 0.5 Ag−1. It showed superior cycle stability of 91.8% after 10,000 cycles at 5 Ag−1.

Synthesis and electrochemical evaluation of porous carbon derived from sanitary pad waste for high performance in symmetric supercapacitor application

In recent years, the renewable energy storage system has attracted considerable attention from both industry and academia to address the ongoing global climate change. The waste derived porous materials gained attention as excellent electrode materials due to large specific area, good electrical conductivity to enhance ion transport and charge transfer. In this study, waste sanitary pad biomass has been successfully converted into carbon material through one-step simultaneous carbonization and activation by KOH. The as-prepared activated carbon at various temperatures was characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray spectroscopy (XRD), scanning electron microscopy (SEM), Raman spectroscopy and Brunauer-Emmett-Teller (BET) techniques. The prepared biomass derived activated carbon (SWAC 800) electrode, with a large surface area of 396.1 m2g−1 delivered high specific capacitance of 306 Fg−1 at 1 Ag−1 with excellent cyclic stability in a 6 M KOH aqueous electrolyte. The electrochemical performance of the SWAC 800 electrode in a symmetric supercapacitor was evaluated in 6 M KOH and 1 M Na2SO4 electrolytes. The neutral Na2SO4 electrolyte assist SWAC 800 symmetric supercapacitor device produce excellent energy density of 32.7 Wh.kg−1 in 1.6 V operating potential window. Overall the SWAC from renewable biowaste is prospective candidate for high performance electrode material for supercapacitor application.

Solvent‐free synthesis of ZIF‐67 thin films as the catalyst for the direct growth of carbon nanotubes for the fabrication of electrical double‐layer capacitors

AbstractObjectiveThis work is focused on the direct growth of vertically aligned carbon nanotubes (CNTs) onto the flexible stainless‐steel mesh (SM) substrate using ZIF‐67 as the catalytic layer.Materials & MethodsThe CNTs/SM electrode is prepared by two‐step chemical vapor deposition (CVD) method using ZIF‐67 thin films as the catalytic layers. The time duration for the deposition of ZIF‐67 thin films by an atmospheric CVD process is controlled for direct, vertically aligned, dense and uniform growth of CNTs by a low‐pressure CVD process at a low temperature of 450 °C.Results & DiscussionThe electrochemical performance of CNTs/SM electrode is studied by cyclic voltammetry and galvanostatic charge/discharge measurements using KOH aqueous electrolyte which showed their better EDLC features and outstanding rate capability. The binder‐free directly grown CNTs/SM electrode displayed a low interfacial resistance between CNTs and SM substrate which comes from their synergistic effect of lower charge loss and better charge collection. Moreover, vertically aligned one‐dimensional CNTs could be rendered as the charge highway in the axial direction, which can promote the rapid charge transportation.ConclusionsThe directly grown CNTs on the commercial SM substrate using the ZIF‐67 catalytic layer fabricated via the solvent free technology can be regarded as a promising EDLC electrode for flexible super capacitors.

Fabrication of carbon quantum dots modulated/polyindole(PIn/CDs) thin film by electrospray deposition for high-performance next-generation solid-state supercapacitor

A binder-free polyindole/carbon quantum dots (PIn/CDs) thin-film/layer electrode is synthesized by a hybrid-electrospray method. The synthesized CDs and PIn/CDs samples are used for furthercharacterization. Owing to the synergistic consequence of PIn and CDs, PIn/CDs display outstanding electrochemicalassets and cyclability, whichare deserved from the presence of robust interactions amongst polymeric chains and CDs. Further, CDs offer an electron allocation pathway owing to their extraordinary electricconductivity and high specific surface area. In a 3 M KOH aqueous-electrolyte, the Qs of PCDs-2is394 C/g at 6 A/g, which is higher than other comparative electrodes. The PCDs-2 film shows excellent cyclicretention of 75% at 20 Ag−1 up to 3000 cycles. The fabricated PIn/CDs-2//rGO asymmetric device shows the highest specific capacity of 54.5 C/g at 1 A/g with theenergy and power density of 15.9 Wh/kg and 955.6 W/kg. Theseresults demonstrate that PIn/CDs thin-film could be used as an efficient electrode for supercapacitor application.

Experimental and theoretical insights of binder-free magnesium nickel cobalt selenide star-like nanostructure as electrode

In recent progress of electrode development, transition metal selenides have drawn great attention in supercapacitors. Their admirable properties have been exhibited through superior electrochemical performance, lower cost, and environmental friendliness. For the first time, we successfully demonstrate the structural orientation of ternary Mg-Ni-Co selenide (MNCSe) by fine-tuning of solvothermal reaction temperature. Self-alignment MNCSe nanoflakes facilitates the electrochemical performance by providing porous channels and large specific area. The self-aligned star-like MNCSe-180 nanoflakes can deliver a high specific capacity of 299.16 mAh g−1 (1 A g−1) in an aqueous KOH electrolyte. Moreover, a hybrid supercapacitor device provides a high energy density of 46.56 Wh kg−1 and a maximum power density of 5.9 kW kg−1. Hence, the presented electrode design holds great promise in material synthesis and this work also provides a deep understanding of the charge-storage process of novel materials capable of capacitive properties for next-generation energy storage devices.

Effect of In-doping on electrochromic behavior of NiO thin films

Undoped and Indium doped Nickel Oxide (NiO) thin layers with different doping content (2, 4, 6 at.%) were successfully deposited on glass and Indium-doped Tin Oxide (ITO) substrates using spray pyrolysis (SP) technique. The effect of indium on the microstructural, morphological, optical, and electrochromic behaviors of NiO films was investigated by X-ray diffraction (XRD), Raman spectroscopy, Scanning Electron Microscopy coupled with Energy Dispersive X-ray Spectroscopy, UV–Vis-NIR spectrophotometry. XRD examination shows that all NiO layers have a polycrystalline cubic phase with a preferred orientation along the (111) plane. Raman spectroscopy proves the XRD result. SEM images show nanograins formation in all the sprayed films. The EDS analysis and the elemental mapping reveal the homogeneous distribution of the elements. The optical analysis reveals an average transmission of about 72% in the visible light region and an optical band gap energy of 3.54 eV for the undoped sample. These values decreased with increasing Indium content to reach 65% and 3.46 eV, respectively for the 6 at.% In-doped sample. The electrochromic behavior of NiO films deposited on ITO substrates was measured by cyclic voltammetry in a 2 M KOH aqueous electrolyte. The results show that a specific capacitance of 66 F. g − 1 at 5 mV.s − 1, an optical density variation of 43%, and a coloration efficiency of 93.74 cm2/C were obtained for 2 at.% In doped NiO. These values are considerably higher than those obtained for the undoped films, indicating that the In doping improved the electrochromic performance of nickel oxide films.

Metal-organic framework-mediated construction of confined ultrafine nickel phosphide immobilized in reduced graphene oxide with excellent cycle stability for asymmetric supercapacitors

Transition metal phosphides (TMPs) with unique metalloid features have been promised great application potential in developing high-efficiency electrode materials for electrochemical energy storage. Nevertheless, sluggish ion transportation and poor cycling stability are the critical hurdles limiting their application prospects. Herein, we presented the metal-organic framework-mediated construction of ultrafine Ni2P immobilized in reduced graphene oxide (rGO). Nano-porous two-dimensional (2D) Ni-metal-organic framework (Ni-MOF) was grown on holey graphene oxide (Ni(BDC)-HGO), followed by MOF-mediated tandem pyrolysis (carbonization and phosphidation; Ni(BDC)-HGO-X-P, X denoted carbonization temperature and P represented phosphidation). Structural analysis revealed that the open-framework structure in Ni(BDC)-HGO-X-Ps had endowed them with excellent ion conductivity. The Ni2P wrapped by carbon shells and the PO bonds linking between Ni2P and rGO ensured the better structural stability of Ni(BDC)-HGO-X-Ps. The resulting Ni(BDC)-HGO-400-P delivered a capacitance of 2333.3 F g−1 at 1 A g−1 in a 6 M KOH aqueous electrolyte. More importantly, Ni(BDC)-HGO-400-P//activated carbon, the assembled asymmetric supercapacitor with an energy density of 64.5 Wh kg−1 and a power density of 31.7 kW kg−1, almost maintained its initial capacitance after 10,000 cycles. Furthermore, in situ electrochemical-Raman measurements were exploited to demonstrate the electrochemical changes of Ni(BDC)-HGO-400-P throughout the charging and discharging processes. This study has further shed light on the design rationality of TMPs for optimizing supercapacitor performance.

Secondary utilization of jujube shell bio-waste into biomass carbon for supercapacitor electrode materials study

Currently, the final destination of waste jujube shells from the deep processing of jujubes is usually burnt or simply thrown away, which has a significant impact on the natural environment. In this work, we established a strategy for the secondary use of waste jujube shells to solve the problems above. The jujube shell biomass carbon materials were prepared by using waste jujube shell residue after extraction of essential oils as carbon source, ZnCl2 as activator, boric acid and urea as dopants. In the three-electrode system, the specific capacitance of the boron-nitrogen co-doped carbon supercapacitor is 535F/g at the current density of 1 A/g, and the capacitance retention rate is 62.8%, Moreover, the assembled symmetrical two-electrode supercapacitor in an aqueous KOH electrolyte presented considerable synergetic energy–power output properties with an energy density of 13.97 Wh/kg at a power density of 250.0 W/kg, and 5.58 Wh/kg at 2.5 kW/kg.

Preparation of tank-like resin-derived porous carbon sphere for supercapacitor: The influence of KOH activator and activation temperature on structure and performance

The resorcinol-melamine-formaldehyde (RMF) resin as a promising carbon precursor has aroused wide public concern due to its low cost, high nitrogen content, and ease of industrial production. In this work, the tank-like resorcinol–melamine-formaldehyde (RMF) resin spheres are synthesized via the hydrothermal method with the F127 assisting, and tank-like porous carbon spheres (TPCSs) are further prepared by pre‑carbonization and KOH treatment. The F127 is crucial in the formation of tank-like resin spheres and the influence of KOH dosage and activation temperature on morphology, particle size and structure-activity relationships for resin-based carbon spheres are explored in detail. The particle size of RMF resin and TPCSs-X-Y mainly locate at 1.75–2.75 μm and 1–1.8 μm, respectively. TPCSs-2-600 possesses a specific surface area of 1338 m2 g−1 and a high N content of 11.49 %. The specific surface area of resin-based carbon materials initially increases and then decreases with increasing KOH activator, which affects the specific capacitance in a similar trend. The rate performance of resin-based porous carbon materials gets better with increasing KOH dosage due to enhanced ion transport ability resulting from pore size getting larger. Increasing activation temperature enhances the specific surface area and pore size of the carbon electrode, but the specific capacitance reduces gradually in three-electrode system. The cycle stability of TPCSs-2-600 can be 87.8 % after 10,000 times charge-discharge cycles at 10 A g−1 in two-electrode system, and the symmetric supercapacitor assembled with TPCSs-2-700 electrode shows a good energy density of 6.68 Wh kg−1 with a power density of 484 W kg−1 in 6 M KOH aqueous electrolyte.

Bimetallic nickel-cobalt nanospheres electrodeposited on nickel foam as a battery-type electrode material for fabrication of asymmetric supercapacitors

The development of electrode materials with nanostructures is of great importance in the field of supercapacitors. In the present research, the direct simultaneous deposition of Ni-Co nanosphere (Ni-Co NS) on nickel foam as a substrate has been performed by facile one-step electrodeposition method without any template to provide excellent electrical conductivity and efficiency of electrode materials. The SEM images of Ni-Co NS electrode showed a nanosphere shape. The electrochemical performance of the electrodeposited nanosphere has been investigated by cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy in 3 M KOH aqueous electrolyte. The Ni-Co NS electrode showed a good specific capacity of 564.6 C g−1 at 2 A g−1 with rate capability of 70% in the current density range of 2–20 A g−1, reasonable cyclic stability of 86% after 5000 cycles at the scan rate of 70 mV s−1, low internal resistance, and high surface area of the nanospheres. Interestingly, an asymmetric supercapacitor fabricated using Ni-Co NS and activated carbon as the positive and negative electrodes, respectively, operating at the potential window of 1.5 V delivered high energy and power densities of 34.5 Wh kg−1 and 683 W kg−1, respectively.

High-performance asymmetric supercapacitors utilizing manganese oxide nanoparticles grafted graphitic carbon nitride nanosheets as the cathode and hypercross-linked polymer derived activated carbon as the anode

Herein, we demonstrated the inexpensive construction of a high-performance asymmetric supercapacitor (ASC) that was combined with manganese oxide nanoparticles grafted graphitic carbon nitride nanosheets (Mn3O4@GCN-NS) as the cathode and nitrogen doped hypercross-linked polymer derived activated carbon (NHCP-AC) as the anode with 6.0 M aqueous KOH electrolyte. In the beginning, Mn3O4@GCN-NS was successfully prepared via a single-step pyrolysis assisted method and the NHCP-AC was synthesized via Friedel-Crafts reaction. The as-synthesized nanocomposites exhibited higher specific capacitance of 436.2 at 0.5 A g−1 in three-electrode cell configuration. Furthermore, the ASC device was fabricated by integrating Mn3O4@GCN-NS with NHCP-AC, which demonstrated considerable energy density of 22.2 Wh/kg at 400 W/kg power density together with remarkable cyclability (93.5 % capacitive retention even after 5000 cycles of charge and discharge). The light emitting diode (5 mm dia.) was powered for about 15 min using two ASC devices coupled in series, demonstrating the effectiveness of its power source. Thus, the results demonstrated that the ASC devices have enormous potential for investigating cutting-edge applications in the field of advanced energy storage.

Enriched electrochemical performance of copper vanadate loaded reduced graphene oxide for supercapacitor applications

In this work, the electrochemical performance of copper vanadate (Cu3V2O8) nanoparticles (NPs) and Cu3V2O8 NPs loaded reduced graphene oxide (Cu3V2O8@rGO) nanocomposites (NCs) were reported. Cu3V2O8 NPs and Cu3V2O8@rGO (0.02 M Cu3V2O8 and 0.01 g of rGO) NCs were prepared by a simple reflux technique, and the prepared NCs were analytically investigated. The monoclinic crystalline structure of the prepared Cu3V2O8 NPs was revealed by the XRD analysis. Presence of plate-like structured Cu3V2O8 NPs and layer-structured rGO in the prepared NCs were observed through HR-TEM images. The electrochemical performance of the prepared NCs was investigated through the fabrication of Cu3V2O8 NPs, and Cu3V2O8@rGO NCs modified working electrode and supercapacitor under 1 M aqueous KOH electrolyte. The cyclic voltammetry result suggested that the pure Cu3V2O8 NPs modified working electrode possessed the specific capacitance value of 538 Fg-1 (at 5 mVs-1), and this value was further enhanced to 1341 Fg-1 by the addition of rGO. The maximum specific capacitance values calculated from GCD analysis were found to be 13.2 Fg-1 (at 0.1 Ag-1) for Cu3V2O8 NPs and 1305 Fg-1 (at 1.5 Ag-1) for Cu3V2O8@rGO NCs, based electrodes. The energy and power density values of the fabricated device using Cu3V2O8 NPs were found to be 2.067 W h kg1 and 403.8 W kg-1, respectively. Whereas, Cu3V2O8@rGO NCs-based device possessed 7.642 W h kg-1 and 90 W kg-1 of superior energy and power densities, respectively. The cyclic test result confirmed that the Cu3V2O8@rGO NCs-based device possessed the superior specific capacitance retention of 74% at the end of 2000 cycles, whereas, Cu3V2O8 NPs-based device exhibited only 69.5% of cyclic retention. The electrochemical results suggested that the inclusion of rGO in prepared copper vanadate nanoparticles induced the battery-like behavior. The proposed NCs can be utilized as the supercapacitor and/or battery electrodes.

Structural and electrochemical properties of Cu doped NiCo2O4 prepared by microwave hydrothermal method

A series of NiCuxCo2-xO4 with x = 0, 0.02, 0.04, 0.06, 0.08 and 0.10 samples were synthesized using microwave hydrothermal method (MH). The structural, microstructural, and spectroscopic characterizations were carried out using X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). All the samples are in Cubic phase with space group Fd3m. The samples x ≥ 0.08 shows some impurity phases. The average grain size for all the samples is in the range of 30–55 nm. The specific capacitance (Csp) 250.66 Fg−1, energy density (E) 22.22 Whkg−1 and power density (P) 757.80 Wkg−1 was observed for x = 0.06 with a mass loading of 7 mgcm−2 and in 2 M aqueous KOH electrolyte solution at a current density of 1 Ag−1. Therefore, the Cu doping with x = 0.06 shows good redox activities and hence can be used in electric batteries and supercapacitors.

Unveiling Superior Capacitive Behaviors of One-Pot Molten Salt-Engineered B, N Co-Doped Porous Carbon Sheets.

Heteroatom-doped porous carbon materials with distinctive surface properties and capacitive behavior have been accepted as promising candidates for supercapacitor electrodes. Currently, the researches mainly focus on developing facile synthetic method and unveiling the structure-activity relationship to further elevate their capacitive performance. Here, the B, N co-doped porous carbon sheet (BN-PCS) is constructed by one-pot pyrolysis of agar in KCl/KHCO3 molten salt system. In this process, the urea acts as directing agent to guide the formation of 2D sheet morphology, and the decomposition of KHCO3 and boric acid creates rich micro- and mesopores in the carbon framework. The specific capacitance of optimized BN-PCS reaches 361.1 F g-1 at a current density of 0.5 A g-1 in an aqueous KOH electrolyte. Impressively, the fabricated symmetrical supercapacitor affords a maximum energy density of 43.5Wh kg-1 at the power density of 375.0W kg-1 in 1.0mol L-1 TEABF4 /AN electrolyte. It also achieves excellent long-term stability with capacitance retention of 91.1% and Columbic efficiency of 100% over 10000 cycles. This study indicates one-pot molten salt method is effective in engineering advanced carbon materials for high-performance energy storage devices.

In-situ growth of binder-free Cr/NiO thin film electrodes via co-sputtering for asymmetric supercapacitors

Recently, metal oxides (MOs) have received tremendous interest for flexible energy storage systems: in particular, supercapacitors (SCs). SC electrodes are commonly fabricated via the coating of MOs particles, conductive carbon and binders. However, such electrodes, can weaken the performance of SCs. In this work, binder-free nanocluster Cr-doped NiO thin films are grown on flexible stainless-steel (SS) foils using a one-step co-sputtering technique. The distinctive nanocluster structure of Cr-incorporated NiO thin film electrodes (TFEs) has the benefit of reduced ion diffusion length and good charge transport, and can increase the accessibility of ions onto the active surface area. The developed TFEs are examined in 2 M KOH aqueous electrolyte, demonstrating highest areal capacitance of 429 mF cm−2 (251 mC cm−2). Subsequently, an asymmetric coin cell (ACC) SC is assembled. Even after 5,000 cycles, the developed ACC SC demonstrates exceptional cycling stability. Thereafter, the aging test is conducted after 720 h and reveals good electrochemical performance with minimal capacitance fading. Results reveal that Cr-doped NiO TFEs show excellent electrochemical performance with higher areal capacitance and stability compared to NiO and other metal oxide-based TFEs reported previously. The grown Cr-doped NiO binder-free TFEs are good candidates for high-performance and flexible energy storage systems.

Yolk‐Shell Structured Zinc‐Cobalt‐Ruthenium Alloy Oxide Assembled with Ultra‐Small Nanoparticles: A Superior Cascade Catalyst toward Oxygen Evolution Reaction

AbstractStructure engineering has proven to be an effective strategy for improving the catalytic performance and reducing the cost of ruthenium oxide‐based catalysts toward oxygen evolution reactions (OER). Herein, a polyhedron‐shaped yolk‐shell structure composed of zinc‐cobalt‐ruthenium ternary metal alloy oxide (ZnCo‐RuO2/C) is prepared, by taking advantage of the Kirkendall effect. The yolk‐shell frame and the ensembled metal oxide nanoparticles are 116.9 ± 25.9 nm and 3.1 ± 0.7 nm in diameter, respectively. The porous yolk‐shell structure of ZnCo‐RuO2/C exposes abundant active sites and facilitates mass transfer for OER. Theoretical calculations indicate that ZnCo‐RuO2 may break the linear scaling relationship for the OER intermediates and dramatically reduces the energy barrier of the potential determining step, which may be one of the factors that are responsible for the enhanced OER performance of ZnCo‐RuO2/C. In 1 m KOH aqueous electrolyte, ZnCo‐RuO2/C delivers an overpotential of only 180 mV at 10 mA cm−2 and a Tafel slope of 63 mV dec−1, superior to that of single metal‐doped, pristine and commercial RuO2. As an anode catalyst of zinc‐air batteries, ZnCo‐RuO2/C exhibits improved power density and durability relative to commercial RuO2, very promising for practical application.

A novel Co-precipitation assisted Li1.05Ni0.5Mn1.40Ce0.10O4 spinel as an eloquent electrocatalyst for methanol oxidation

A novel Li1.05Ni0.5Mn1.40Ce0.10O4 compound has directly developed at 900˚C without requiring low-temperature or lowering gas treatments. TEM images illustrate a transparent increase in the surface area. A typical high-temperature calcination technique has a considerable effect on the crystal structure in terms of cation ordering degree and Mn3+ concentration. Interesting properties are displayed by the obtained Li1.05Ni0.5Mn1.40Ce0.10O4 has the best performance in oxygen vacancy defect-dependent activity. Methanol oxidation reaction using four electrons alkaline solution reaction chains work may open a simple route to designing the spinel Li1.05Ni0.5Mn1.40Ce0.10O4 with the tunable oxygen vacancies defect to speed up different electrochemical reactions in fuel cells and other applications. In a 1 M KOH aqueous electrolyte, Li1.05Ni0.5Mn1.40Ce0.10O4 showed current densities of 320 mAcm−2 at 5 mV overpotentials and a low Tafel slope of 108 mV dec−1. Considering this, the recently constructed Li1.05Ni0.5Mn1.40Ce0.10O4 spinel has unique electrocatalytic properties toward methanol oxidation with a high mass, specific activity, a large electrochemically active surface area, and better long-term stability.

Design and fabrication of nickel lanthanum telluride microfibers for redox additive electrolyte-based flexible solid-state hybrid supercapacitor

In this article, we describe the design of a flexible solid-state hybrid supercapacitor (FSSHSC) using mixed metal telluride NiLaTe microfibers (MFs) atop Ni foam (NF). The goal of the study is to examine the effect of counter metal ions Ni and La, in addition to Te, in the formation of longer one-dimensional (1-D) architecture. The NiTe MFs and La2Te3 microrods (MRs) were synthesized and compared with bimetallic telluride. La exhibit's slower reaction kinetics than Ni when reacting with Te due to the different crystal structural stability of La2Te3 (cubic phase) and Te (hexagonal phase). Three-electrode investigations incorporating aqueous potassium ferrocyanide (KFC) reveal that the electrochemical performance of NiLaTe MFs is doubled compared to the typical aqueous KOH electrolyte alone. The presence of the redox pair [Fe(CN)6]3−/[Fe(CN)6]4− allows for faster ion transport inside the active electrode surface, which improves electrochemical performance. The FSSHSC device was fabricated, comprising NiLaTe as the positive, activated carbon (AC) as the negative electrode, and PVA-KOH-KFC gel, which acts as an electrolyte and a separator. The device performance was compared to that of a liquid system as well as one without a redox additive gel system. The significance of polymer-based gel and KFC for device construction is briefly reviewed. The final built device NiLaTe//AC in gel + KFC system has a maximum areal capacity of 65.6 μAh cm−2 (60.0 mA h g−1) at a current density of 2 mA cm−2, a maximum energy density of 45.5 Wh Kg−1 (52.36 μWh cm−2), and a maximum power density of 5488.7 W Kg−1(6312.0 μW cm−2). Furthermore, the device outperforms the cyclic stability for 10,000 cycles with an 80.1 % capacity retention and exhibits excellent flexibility at different bending angles. The assembled FSSHSCs device successfully illuminates an LED bulb for 70 s.

High-frequency supercapacitors with phosphorus-doped Ketjen black

Compact supercapacitors (SCs) have attracted attention for their great potential to replace bulky aluminum electrolytic capacitors (AECs) in alternating current (AC) line filtering applications. Herein, the fabrication of a high-frequency SC is reported using Ketjen black (KB) nanoparticles doped with phosphorus (P) to achieve a high areal capacitance of up to 2.26 mF cm−2 along with a high-rate capability, with a phase angle of –80.2° at 120 Hz. The high performance of the phosphorus-doped KB (designated PKB) SC with a 6 M KOH aqueous electrolyte is associated with its increased surface wettability and additional capacitive sites provided by the P-doping. Density functional theory (DFT) calculations further indicate that the P-doping enhances the interactions between the electrolyte ions and the carbon surface, thus leading to an improved electrochemical performance. These results suggest that the P-doped carbon-based SC could be highly favored in replacing conventional AECs in various high-frequency electronic devices.