An efficient α-MnO 2 nanorods forests electrode for electrochemical capacitors with neutral aqueous electrolytes

STING-activable immunomodulatory bio-glue for multiple postsurgical management

In addition to the robust adhesive properties, there is a pressing demand for ideal adhesives in tumor surgery that possess anti-tumor therapeutic effects. In this study, we introduce BSA-MnO2-GP@Ca-Y (BMGY) bio-glue by integrating bovine serum albumin (BSA)-MnO2, genipin (GP), and Ca-Y zeolite. Ca-Y zeolite exhibits the thrombin activity for hemostasis, while the cross-linking of BSA, GP, and skin tissue induces wound adherence upon laser irradiation for normalized skin structure within nine days. The heat generated during the "photothermal suture" process ablates residual tumor cells and produces antigen fragments, which are internalized by antigen presenting cells. The released Mn ions subsequently activate the cGAS-STING pathway, enhancing immunogenicity. Consequently, tumor-infiltrating p-TBK1 and interferon-β levels are significantly increased, ensuring robust anti-tumor immunity following BMGY treatment. Thus, BMGY bio-glue achieves hemostasis, wound bonding, ablation of residual tumor cells, and tumor recurrence inhibition, simultaneously. Beyond Ca-Y zeolite, BSA-MnO2-GP serves as a versatile platform for loading other drugs or active species to boost therapeutic efficacy. Therefore, we present a successful bio-glue paradigm with significant translational potential for various postsurgical management applications.

Hydrothermal synthesis of NiO nanoparticles decorated hierarchical MnO2 nanowire for supercapacitor electrode with improved electrochemical performance

In this work, MnO2/NiO nanocomposite electrode materials have been synthesized by a cost-effective hydrothermal method. The effect of the concentrations (0, 1, 3, 5, and 7 wt%) of NiO nanoparticles on the surface morphology, structural properties, and electrochemical performance of the nanocomposites was characterized by different characterization techniques. The scanning electron micrographs (SEM) reveal that the as-prepared NiO nanoparticles are well connected and stuck with the MnO2 nanowires. The transmission electron microscopy (TEM) analysis showed an increase in the interplanar spacing due to the incorporation of NiO nanoparticles. The different structural parameters of MnO2/NiO nanocomposites were also found to vary with the concentration of NiO. The MnO2/NiO nanocomposites provide an improved electrochemical performance together with a specific capacitance as high as 343 F/g at 1.25 A/g current density. The electrochemical spectroscopic analysis revealed a reduction in charge transfer resistance due to the introduction of NiO, indicating a rapid carrier transportation between the materials interface. The improved electrochemical performance of MnO2/NiO can be attributed to good interfacial interaction, a large interlayer distance, and low charge transfer resistance. The unique features of MnO2/NiO and the cost-effective hydrothermal method will open up a new route for the fabrication of a promising supercapacitor electrode.

Manganese oxide-loaded activated carbon for ammonium removal from wastewater: the roles of adsorption and oxidation

The urgent need to address the severe issue of nitrogen pollution has prompted the search for a functional and easy recycling material. In this study, manganese oxides (MnOx) were loaded on activated carbon (AC), resulting in a composite known as AC-MnOx, for efficient ammonium removal from aqueous solutions. The results indicated a remarkable 15.6-fold increase in ammonium removal efficiency and a fivefold enhancement in removal capacity for AC-MnOx (3.20 mg/g) compared to AC. Under specific conditions (initial NH4+-N concentration of 15 mg/L, adsorbent dose of 2.5 g, pH of 6.5, and temperature of 35 ℃), the highest achieved ammonium removal efficiency reached 94.6%. Furthermore, the study distinguishes the contributions of catalytic oxidation and adsorption in the removal process. The adsorption process was effectively modeled using pseudo-second-order kinetics and Langmuir isotherm models. Interestingly, the amount of oxidation conversion (Ntur) exhibited a linear relationship with the dosage when the initial ammonium concentration was sufficiently high, while the relationship between initial ammonium concentration and the ratio of Ntur to adsorption capacity (Nsur) followed a negative exponential trend. The removal mechanisms involved electrostatic interaction between ammonium and the negatively charged dehydrogenated hydroxyl groups (- OHsur) or cation tunnel in crystal structures of MnOx, ion exchange adsorption, and the oxidation impact of MnOx. This research provides valuable insights into the application of immobilized MnOx media for ammonium removal. Moreover, filling AC-MnOx into constructed wetlands (CW) proved to be an effective method for reducing ammonium pollution, demonstrating its potential in the field of engineering wastewater treatment.

Research on Three-Dimensional Porous Composite Nano-Assembled α-MnO2/Reduced Graphene Oxides and Their Super-Capacitive Performance

A series of three-dimensional porous composite α-MnO₂/reduced graphene oxides (α-MnO₂/RGO) were prepared by nano-assembly in a hydrothermal environment at pH 9.0-13.0 using graphene oxide as the precursor, KMnO₄ and MnCl₂ as the manganese sources and F^- as the control agent of the α-MnO₂ crystal form. The α-MnO₂/RGO composites prepared at different hydrothermal pH levels presented porous network structures but there were significant differences in these structures. The special pore structure promoted the migration of ions in the electrolyte in the electrode material, and the larger specific surface area promoted the contact between the electrode material and the electrolyte ions. The introduction of graphene solved the problem of poor conductivity of MnO₂, facilitated the rapid transfer of electrons, and significantly improved the electrochemical performance of materials. When the pH was 12.0, the specific surface area of the 3D porous composite material αMGs-12.0 was 264 m²·g^-1, and it displayed the best super-capacitive performance; in Na₂SO₄ solution with 1.0 mol·L^-1 electrolyte, the specific capacitance was 504 F·g^-1 when the current density was 0.5 A·g^-1 and the specific capacitance retention rate after 5000 cycles was 88.27%, showing that the composite had excellent electrochemical performance.

Construction of α-MnO2 on Carbon Fibers Modified with Carbon Nanotubes for Ultrafast Flexible Supercapacitors in Ionic Liquid Electrolytes with Wide Voltage Windows

In this study, α-MnO₂ and Fe₂O₃ nanomaterials are prepared on a carbon fiber modified with carbon nanotubes to produce the nonbinder core–shell positive (α-MnO₂@CNTs/CC) and negative (Fe₂O₃@CNTs/CC) electrodes that can be operated in a wide voltage window in ultrafast asymmetrical flexible supercapacitors. MnO₂ and Fe₂O₃ have attracted wide research interests as electrode materials in energy storage applications because of the abundant natural resources, high theoretical specific capacities, environmental friendliness, and low cost. The electrochemical performance of each electrode is assessed in 1 M Na₂SO₄ and the energy storage properties of the supercapacitors consisting of the two composite electrodes are determined in Na₂SO₄ and EMImBF4 electrolytes in the 2 V and 4 V windows. The 2 V supercapacitor can withstand a large scanning rate of 5000 mV S⁻¹ without obvious changes in the cyclic voltammetry (CV) curves, besides showing a maximum energy density of 57.29 Wh kg⁻¹ at a power density of 833.35 W kg⁻¹. Furthermore, the supercapacitor retains 87.06% of the capacity after 20,000 galvanostatic charging and discharging (GCD) cycles. The 4 V flexible supercapacitor shows a discharging time of 1260 s and specific capacitance of 124.8 F g⁻¹ at a current of 0.5 mA and retains 87.77% of the initial specific capacitance after 5000 GCD cycles. The mechanical robustness and practicality are demonstrated by physical bending and the powering of LED arrays. In addition, the contributions of the active materials to the capacitive properties and the underlying mechanisms are explored and discussed

Composite Assembling of Oxide-Based Optically Transparent Electrodes for High-Performance Asymmetric Supercapacitors

Simultaneously achieving a transparent and high-energy density supercapacitor is a major challenge because of the trade-off between energy storage capacity and optical transparency of active electrode materials. Herein, we demonstrate a novel approach to construct an optically transparent asymmetric supercapacitor (Trans-ASC) by assembling positive (ZnO-SnO2) and negative (TiO2-SnO2) composite thin-film electrodes on a conductive indium-doped tin oxide substrate via reactive DC magnetron cosputtering. The optical transmittance for both composite thin films is found to be 68% (ZnO-SnO2) and 64% (TiO2-SnO2). Furthermore, electrochemical kinematics of the primed transparent electrodes are scrutinized in 0.5 M KOH electrolyte without affecting the transparency of active electrodes. The structural reliability of the electrodes aids the superb electrochemical performance to construct a Trans-ASC, TiO2-SnO2//ZnO-SnO2, which works at a voltage of +1.2 V and attains a higher areal capacitance of 44.6 mF cm-2 at 2 mA cm-2. The assembled Trans-ASC delivers a maximum areal energy density of 8.75 μW h cm-2 with an optimal areal power density of 570 μW cm-2. Additionally, the capacitance retention of 81.6% and transparency of both electrodes remain almost the same (up to 60% for ZnO-SnO2 and 62% for TiO2-SnO2) even after 10,000 charging-discharging cycles. These remarkable electrochemical properties and outstanding cycling stability of the designed Trans-ASC device make it a potential candidate for storing energy and for further use in transparent electronic devices.

Triethanolamine–ethoxylate (TEA-EO) assisted hydrothermal synthesis of hierarchical β-MnO2 nanorods: effect of surface morphology on capacitive performance

In this study we are presenting the synthesis of MnO2 nanorods using hydrothermal method assisted by facile tri-ethanolamine-ethoxylate. Structural (x-ray diffraction, Rietveld refinement), functional (Fourier Transform Infrared spectroscopy and x-ray Photoelectron Spectroscopy) and morphological (Field emission scanning electron microscope, Transmission electron microscopy) characterization conform the β-MnO2 nanostructure with a rod-like morphology and uniform thickness. The morphological variations of the nanorod thickness can be easily controlled by simply monitoring the reaction temperature. Comparative investigations of β-MnO2 samples synthesized at two different reaction temperatures (viz. 100 °C and 120 °C) used as a supercapacitive electrode material have been performed with the aid of different electrochemical techniques. With different electrolytes (Li2SO4 and Na2SO4), supercapacitor device is tested using Cyclic voltammetry, impedance spectroscopy and galvanostatic charge discharge. Interestingly, the low temperature synthesized β-MnO2 nanorods sample exhibit superior electrochemical performance in 1 mol l−1 Li2SO4 electrolyte in terms of high specific capacitance (462 Fg−1 at10 mVs−1), energy density (9.72 WhKg−1), and outstanding cyclic stability (90.26% over 2000 cycles).

In situ polymerization of PEDOT:PSS films based on EMI-TFSI and the analysis of electrochromic performance

In this report, PEDOT composite films were prepared by in situ electrochemical polymerization. 1-Ethyl-3-methylimidazole bis(trifluoromethylsulfonyl)imide (EMI-TFSI) was used as an ionic liquid dopant for PEDOT:PSS films. Subsequently, these PEDOT:PSS/EMI-TFSI films were compared with PEDOT:PSS films based on their morphology, structure, electrochromic properties, and optical properties at different deposition voltages and deposition times. It was observed that the addition of EMI-TFSI enhanced all the aforementioned properties of the films. PEDOT:PSS/EMI-TFSI films were seen to have a larger ion diffusion coefficient (1.38 × 10−20 cm2·s−1), a wider color change range (43.48%), a shorter response time (coloring response time = 1.2 s; fade response time = 2 s), and a higher coloring efficiency (189.86 cm2·C−1) when compared with normal PEDOT:PSS films. The introduction of EMI-TFSI in the films ultimately resulted in superior electrochemical and optical properties along with higher stability.

Tuning Electrocatalytic Aptitude by Incorporating α-MnO2 Nanorods in Cu-MOF/rGO/CuO Hybrids: Electrochemical Sensing of Resorcinol for Practical Applications

In this study, Cu-MOF/rGO/CuO/α-MnO₂ nanocomposites have been fabricated by a one-step hydrothermal method and used in the voltammetric detection of resorcinol (RS). The poor conductivity of MOFs in the field of electrochemical sensing is still a major challenge. A series of Cu-MOF/rGO/CuO/α-MnO₂ nanocomposites have been synthesized with varying fractions of rGO and with a fixed amount of α-MnO₂ via a facile method. These nanocomposites are well characterized using some sophisticated characterization techniques. The as-prepared nanohybrids have strongly promoted the redox reactions at the electrode surface due to their synergistic effects of improved conductivity, high electrocatalytic activity, an enlarged specific surface area, and a plethora of nanoscale level interfacial collaborations. The electrode modified with Cu-MOF/rGO/CuO/α-MnO₂ has revealed superior electrochemical properties demonstrating linear differential pulse voltammetry (DPV) responses from a 0.2 to 22 μM RS concentration range (R² = 0.999). The overall results of this sensing podium have shown excellent stability, good recovery, and a low detection limit of 0.2 μM. With excellent sensing performance achieved, the practicability of the sensor has been evaluated to detect RS in commercial hair color samples as well as in tap water and river water samples. Therefore, we envision that our hybrid nanostructures synthesized by the structural integration strategy will open new horizons in material synthesis and biosensing platforms.

Enhanced electrochemical performance of hierarchical porous carbon/polyaniline composite for supercapacitor applications

In this work, activated carbon/polyaniline (AC/PANi) composites were synthesized by low temperature in situ polymerization and their electrochemical performance was investigated. Microstructure and morphology examination of the samples confirmed a uniform coating of polyaniline on AC surfaces without any change in the structure. The electrochemical studies of the samples confirmed the improvement in the electrochemical performance of AC/PANi composites. Despite a decrease in the specific surface area a substantial increase in electrochemical performance is recorded for the AC/PANi composites due to the synergistic effect between the pseudocapacitance and double layer capacitance. The highest specific capacitance of 1021 F g−1 was calculated for the APA-29.4 composite in neutral aqueous electrolyte (1 M Na2SO4) which is many times greater than the specific capacitance values for AC (253 F g−1) and PANi (389 F g−1). The enhancement in the electrochemical performance of AC after polymerization with PANi in composites favours its use as a favourable electrode material for the energy storage devices.

Molten salt strategy and plasma technology induced MnO2 with oxygen vacancy for high performance Zn-ion batteries

The oxygen vacancy-rich MnO2 was synthesized by the molten salt method and the plasma etching strategy. The amorphous layer increased the active sites and the oxygen vacancies on the surface of MnO2 that promoted the rapid transfer of charges.

Activation of percarbonate by water treatment sludge-derived biochar for the remediation of PAH-contaminated sediments

Sludge from a groundwater treatment plant was used to prepare biochar by pyrolysis. The Fe-Mn rich biochar was used to activate percarbonate for the remediation of polycyclic aromatic hydrocarbons (PAHs) contaminated aquatic sediments. Results showed that the sludge-derived biochar (SBC) produced at a pyrolysis temperature of 700 °C was the most effective in activating percarbonate, which exhibited significant oxidative removal of PAHs. PAHs degradation took place via a Fenton-like oxidation manners, contributed from the Fe³⁺/Fe²⁺ and Mn³⁺/Mn²⁺ redox pairs, and achieved the highest degradation efficiency of 87% at pH₀ 6.0. Reactions between oxygenated functional groups of biochar and H₂O₂ generated of O₂^•- and HO• radicals in abundance under neutral and alkaline pH was responsible for the catalytic degradation of PAHs. Our results provided new insights into the environmental applications of SBC for the green sustainable remediation of organics-contaminated sediments and aided in reduction of associated environmental and health risk.

Gold nanoparticles-functionalized three-dimensional flower-like manganese dioxide: A high-sensitivity thermal analysis immunochromatographic sensor

A sensitive photothermal immunochromatographic test strip (PITS) for the detection of deoxynivalenol (DON) was developed using flower-like gold nanoparticle-deposited manganese dioxide nanocarrier (FMD-G NC) labeled antibodies (Abs) as the photothermal-sensing probe. FMD was used as a template to deposit small gold nanoparticles (GNPs) to synthesize FMD-G NC with large specific surface area and significant photothermal conversion property. The FMD-G-Ab probe was competitively captured by DON target and antigen coated on test line (T-line), forming colorimetric signals under naked eyes and photothermal signals under an 808 nm laser. Under optimal conditions, the PITS exhibited sensitive and specific detection of DON from 0.19 ng mL^-1 to 12 ng mL^-1 with detection limits of 0.013 ng mL^-1, which were over 15-fold and 58-fold more sensitive than visual FMD-G-ITS and traditional GNPs-ITS. In addition, the novel FMD-G-PITS possessed a universal applicability, which could be well applied in green bean, corn, and millet.

Cation intercalated one-dimensional manganese hydroxide nanorods and hierarchical mesoporous activated carbon nanosheets with ultrahigh capacitance retention asymmetric supercapacitors

We have reported the electrochemical performance of K⁺ ion doped Mn(OH)₄ and MnO₂ nanorods as a positive electrode and a highly porous activated carbon nanosheet (AC) made from Prosopis Juliflora as negative electrode asymmetric supercapacitor (ASC) with high rate capability and capacity retention. The cation K⁺ doped Mn(OH)₄ and MnO₂ nanorods with large tunnel sizes allow the electrolyte to penetrate through a well-defined pathway and hence benefits from the intercalation pseudocapacitance and surface redox reactions. As a result, they exhibit good electrochemical performance in neutral aqueous electrolytes. More specifically, the K⁺-Mn(OH)₄ nanorods exhibit higher capacitance values than K⁺-MnO₂ nanorods due to the homogenous distribution of 1D nanorods and optimum amount of OH bonds. The fabricated K⁺-Mn(OH)₄ symmetric electrochemical Pseudocapacitor shows very high energy density of 10.11 Wh/kg and high-power density of 51.04 W/kg over the range of 1.0 V in aqueous electrolyte. The energy density of AC||K⁺-Mn(OH)₄ ASC is improved significantly compared to those of symmetric supercapacitors. The fabricated ASC exhibits a wide working voltage window (1.6 V), high power (143.37 W/kg) and energy densities (41.38 Wh/kg) at 0.2 A g^-1, and excellent cycling behavior with 107.3% capacitance retention after 6000 cycles at 2 A g^-1 indicating the promising practical applications in electrochemical supercapacitors.

Electrochemical study of TiO2 in aqueous AlCl3 electrolyte via vacuum impregnation for superior high-rate electrode performance

This communication elucidates the charge storage mechanism of a TiO2 electrode in 1 mol dm− 3 AlCl3 for use in aqueous-ion batteries. Cyclic voltammetry studies suggest a surface contribution to charge storage and that cycle life can be improved by limiting the potential ≥ − 1.0 V vs SCE. In order to enhance this surface contribution, a simple vacuum impregnation technique was employed to improve electrode-electrolyte contact. This resulted in a significant improvement in the high rate performance of TiO2, where a capacity of 15 mA h g− 1 was maintained at the very high specific current of 40 A g− 1, a decrease of only 25% from when the electrode was cycled at 1 A g− 1. The vacuum impregnation process was also applied to copper-hexacyanoferrate, envisaged as a possible positive electrode, again resulting in significant improvements to high-rate performance. This demonstrates the potential for using this simple technique for improving electrode performance in other aqueous electrolyte battery systems.

Electro-activation of O2 on MnO2/graphite felt for efficient oxidation of water contaminants under room condition

The activation of oxygen (O₂) under room condition is highly desirable for oxidative removal of organic pollutants in water. Herein, we report a graphite felt (GF)-supported α-MnO₂ catalyst which is active for activating O₂ with assistance of an anodic electric field. The electro-assisted catalytic wet air oxidation (ECWAO) process on MnO₂/GF is able to rapidly degrade a variety of dyes, pharmaceutics and personal care products (PPCPs) under room condition. The congo red, basic fuchsin, neutral red and methylene blue are completely mineralized in 160 min, and the bisphenol A, triclosan and ciprofloxacin are mineralized by 89.9%, 81.5% and 65.4%, respectively, in 300 min. Mechanistic study indicates a surface-catalyzed non-free radical pathway for the oxidation of organic pollutants by O₂ in the ECWAO process. The oxygen vacancies on MnO₂ are identified as the catalytically active sites, at which oxygen atom is transferred from O₂ to organic molecule through chemisorbed oxygen species. The anodic electric field assists such an oxygen transfer pathway by activating the complex of chemisorbed oxygen species and organic molecule through electro-oxidation reaction. The ECWAO process on MnO₂/GF electrode exhibits a great potential for practical wastewater treatment under room condition.

Facile Electrodeposition of Poly(3,4-ethylenedioxythiophene) on Poly(vinyl alcohol) Nanofibers as the Positive Electrode for High-Performance Asymmetric Supercapacitor

Poly(vinyl alcohol)/poly(3,4-ethylenedioxythiophene) (PVA/PEDOT) nanofibers were synthesized as a positive electrode for high-performance asymmetric supercapacitor (ASC). PVA/PEDOT nanofibers were prepared through electrospinning and electrodeposition meanwhile reduced graphene oxide (rGO) was obtained by electrochemical reduction. The PVA/PEDOT nanofibers demonstrated cauliflower-like morphology showing that PEDOT was uniformly coated on the smooth cross-linking structure of PVA nanofibers. In addition, the ASC showed a remarkable energy output efficiency by delivering specific energy of 21.45 Wh·kg−1 at a specific power of 335.50 W·kg−1 with good cyclability performance (83% capacitance retained) after 5000 CV cycles. The outstanding supercapacitive performance is contributed from the synergistic effects of both PVA/PEDOT//rGO, which gives promising materials for designing high-performance supercapacitor applications.

Multi-functional MnO2 nanomaterials for photo-activated applications by a plasma-assisted fabrication route

Supported MnO2-based nanomaterials were fabricated on fluorine-doped tin oxide substrates using plasma enhanced-chemical vapor deposition (PE-CVD) between 100 °C and 400 °C, starting from a fluorinated Mn(ii) diamine diketonate precursor. Growth experiments yielded β-MnO2 with a hierarchical morphology tuneable from dendritic structures to quasi-1D nanosystems as a function of growth temperature, whose variation also enabled a concomitant tailoring of the system fluorine content, and of the optical absorption and band gap. Preliminary photocatalytic tests were aimed at the investigation of photoinduced hydrophilic (PH) and solid phase photocatalytic (PC) performances of the present nanomaterials, as well as at the photodegradation of Plasmocorinth B azo-dye aqueous solutions. The obtained findings highlighted an attractive system photoactivity even under visible light, finely tailored by fluorine content, morphological organization and optical properties of the prepared nanostructures. The results indicate that the synthesized MnO2 nanosystems have potential applications as advanced smart materials for anti-fogging/self-cleaning end uses and water purification.

A free-standing, flexible PEDOT:PSS film and its nanocomposites with graphene nanoplatelets as electrodes for quasi-solid-state supercapacitors

Research and development on all-solid-state, flexible supercapacitors is the prime concern of the scientific community these days due to their various advantages including their easy transportability, miniaturization, and compactness in different appliances. We report the novel configuration of all-solid symmetrical supercapacitors employing free-standing, flexible films of poly(3,4-ethylenedioxythiophene) poly(styrene sulfonate) (PEDOT:PSS) and its nanocomposite electrodes with graphene nanoplatelets (GNPs), separated by ionic liquid (IL) (1-ethyl 3-methylimidazolium trifluoromethanesulfonate (EMITf))-based gel polymer electrolyte (GPE) films. The free-standing and flexible form of PEDOT:PSS/GNP nanocomposite films have been prepared via simple mixing of the two counterparts. Scanning electron microscopy, x-ray diffraction, Raman analysis, and thermal and mechanical characterizations have been performed to ascertain the suitability of pristine and nanocomposite PEDOT:PSS films as potential supercapacitor electrodes. The GPE film, comprising of a solution of NH₄CF₃SO₃ (NH₄-triflate or NH₄Tf) in IL, entrapped in poly(vinylidine fluoride-co-hexafluoropropylene) (PVdF-HFP), is a promising electrolyte due to its high ionic conductivity and sufficient electrochemical stability window. The supercapacitor with a PEDOT:PSS nanocomposite containing ∼3.8 wt.% of GNP has been found to give an optimum specific capacitance of ∼106 F g^-1 (evaluated from electrochemical impedance spectroscopy), and specific energy and power of ∼6.95 Wh kg^-1 and 2.58 kW kg^-1, respectively (evaluated from galvanostatic charge-discharge). More importantly, the capacitors demonstrate stable performance for more than 2000 charge-discharge cycles, with only ∼10% initial fading in capacitance. Interestingly, the PEDOT:PSS/GNP nanocomposite-based solid-state supercapacitors with the IL-incorporated GPE have shown comparable (even better) performance than other reported PEDOT:PSS-based supercapacitors.

Employment of ultrasonic irradiation for production of poly(vinyl pyrrolidone)/modified alpha manganese dioxide nanocomposites: Morphology, thermal and optical characterization

This work explains the production, morphology, and features of novel nanocomposite (NC) established on poly(vinyl pyrrolidone) (PVP) as polymer background and modified alpha manganese dioxide (α-MnO₂) nanorod (NR) asan efficient filler. At first, one-dimensional α-MnO₂ nanorods (NRs) were produced by a hydrothermal technique and then they were amended with stearic acid (SA) by a solvothermal process. In following, the NCs were made by adding different volumes of α-MnO₂-SA NR (1, 3 and 5wt%) in the PVP matrix through ultrasonic irradiation as a green, low-cost, fast, and useful technique. Structural and morphological descriptions confirm crystallinity of α-MnO₂-SA NRs and showed that NRs have been separately dispersed in PVP matrix with rod-like morphology and diameter of about 40-60nm. The use of modifier and ultrasonic waves is accountable for good homogeneities of NRs. Thermogravimetric analysis revealed that thermal permanency of the obtained NCs has grown with increasing the α-MnO₂-SA content. Also, the UV-vis absorption of NCs was enhanced with the incorporation of the modified α-MnO₂ NR in PVP matrix. The substantial perfections in NCs properties are associated to compatible intermolecular relations between the surface modifying groups of the α-MnO₂-SA and PVP chain.

Activated Carbon Fibers with Hierarchical Nanostructure Derived from Waste Cotton Gloves as High-Performance Electrodes for Supercapacitors

One of the most challenging issues that restrict the biomass/waste-based nanocarbons in supercapacitor application is the poor structural inheritability during the activating process. Herein, we prepare a class of activated carbon fibers by carefully selecting waste cotton glove (CG) as the precursor, which mainly consists of cellulose fibers that can be transformed to carbon along with good inheritability of their fiber morphology upon activation. As prepared, the CG-based activated carbon fiber (CGACF) demonstrates a surface area of 1435 m2 g-1 contributed by micropores of 1.3 nm and small mesopores of 2.7 nm, while the fiber morphology can be well inherited from the CG with 3D interconnected frameworks created on the fiber surface. This hierarchically porous structure and well-retained fiber-like skeleton can simultaneously minimize the diffusion/transfer resistance of the electrolyte and electron, respectively, and maximize the surface area utilization for charge accumulation. Consequently, CGACF presents a higher specific capacitance of 218 F g-1 and an excellent high-rate performance as compared to commercial activated carbon.

Carbon Quantum Dot-Induced MnO2 Nanowire Formation and Construction of a Binder-Free Flexible Membrane with Excellent Superhydrophilicity and Enhanced Supercapacitor Performance

Manganese oxides (MnO₂) are regarded as typical and promising electrode materials for supercapacitors. However, the practical electrochemical performance of MnO₂ is far from its theoretical value. Nowadays, numerous efforts are being devoted to the design and preparation of nanostructured MnO₂ with the aim of improving its electrochemical properties. In this work, ultralong MnO₂ nanowires were fabricated in a process induced by carbon quantum dots (CQDs); subsequently, a binder-free flexible electrode membrane was easily obtained by vacuum filtration of the MnO₂ nanowires. The effects of the CQDs not only induced the formation of one-dimensional nanostructured MnO₂, but also significantly improved the wettability between electrode and electrolyte. In other words, the MnO₂ membrane demonstrated a superhydrophilic character in aqueous solution, indicating the sufficient and abundant contact probability between electrode and electrolyte. The binder-free flexible MnO₂ electrode exhibited a preeminent specific capacitance of 340 F g^-1 at 1 A g^-1; even when the current density reached 20 A g^-1, it still maintained 260 F g^-1 (76% retention rate compared to that at 1 A g^-1). Moreover, it also showed good cycling stability with 80.1% capacity retention over 10 000 cycles at 1 A g^-1. Furthermore, an asymmetric supercapacitor was constructed using the MnO₂ membrane and active carbon as the positive and negative electrodes, respectively, which exhibited a high energy density of 33.6 Wh kg^-1 at 1.0 kW kg^-1, and a high power density of 10 kW kg^-1 at 12.5 Wh kg^-1.