MnO2 Hybrid Research Articles

Enhanced lithium battery cathode performance via mechanical grinding of CFx_MnO2 hybrid materials for space-grade applications: Unveiling synergistic effects

CFx_MnO2 hybrid cathode materials are prepared from a (C2F)n-type graphite fluoride (CFx) and industrial MnO2. Because of its physicochemical (insulating behavior, low content of CF2 and CF3 groups, no or a few remaining sp2 carbon atoms) and electrochemical properties (flat plateau on galvanostatic curve and theoretical capacity of 623 mAh/g, higher than other conventional cathodes for primary lithium battery), graphite fluoride of (C2F)n-type is selected to evidence synergetic effects with MnO2 that occur at the fluoride/oxide and electrolyte/ electrode interfaces. Both materials are mixed by mechanical ball-milling using different sets of parameters. The hybrid material presents very good electrochemical properties with a maximum energy density of about 1600 Wh per kg of active material. Notably, it shows a considerable improvement in voltage plateau and voltage delay compared to CFx. The parameters applied during ball-milling also shape the electrochemical performance of the new hybrid material. Ball milling increases the average discharge voltage plateau, and the power density of the battery, and avoids ohmic drop which may cause a battery to be eliminated as soon as it begins to discharge. More finely, electrochemical impedance spectroscopy shows that pushed grinding leads to more homogeneous but more polarized material-electrolyte interfaces so better diffusion and capacity but lower discharge potential.

MnO2 and CuBi2O4 hybrid microstructures for efficient nonenzymatic hydroxylamine detection

MnO2 and CuBi2O4 hybrid microstructures for efficient nonenzymatic hydroxylamine detection

Graphene intermediated synthesis of thin-packing stacking-free MnO2 nanoflakes for high power output at high mass loading

Numerous advanced pseudocapacitive MnO2 with much-improved power output have been reported in recent years. However, most of their performance is verified in thin film form, with a mass density of less than 3 mg cm−2, which falls short of the commercial electrode demand of 10 mg cm−2. This high mass loading will inevitably diminish its power output, the crucial superiority of capacitive materials, to a considerable extent. To address this issue, their kinetic analysis for seeking out the rate-determining step (RDS) is a prerequisite. Herein, a comprehensive kinetic analysis protocol has been developed combining the interpretation of capacitance fitting and impedance spectroscopy. The results have demonstrated the RDS is dependent on the mass loading status, and it switches to resistance-controlled under high mass loading due to the high resistance from both thick-packing and laminar-stacking of MnO2 flakes. To break such restriction, 3-D graphene foam intermediated MnO2 hybrid structures have been synthesized via a strategy of high-voltage graphite exfoliation paired with simultaneous Mn2+oxidation. More than constructing an efficient electron migration network, the underlying graphene skeleton also tunes the MnO2 nanostructure on its surface, leading to a thin-packing and stacking-free structure configuration. As a result, the optimized sample achieves an energy density of 8 mWh cm−2 at a power density of 3,012 mW cm−2 in a symmetrical capacitor, which is much higher than 0.1 mWh cm−2 at 1,700 mW cm−2 for the control sample. In summary, this study highlights the "mass effect" of energy storage kinetics for pseudocapacitive MnO2 and proposes a graphene-intermediated protocol to improve its power output at high mass loading, which could be valuable in guiding its commercialization.

Development of in-situ electrochemical heavy metal ion sensor using integrated 1D/0D/1D hybrid by MWCNT and CQDs supported MnO2 nanomaterial

An integrated 1D/0D/1D hybrid nanomaterial was prepared from MWCNT supported carbon quantum dots @ MnO2 nanomaterial for a sensitive and selective electrochemical heavy metal ion sensor by hydrothermal methods. The developed nanomaterials were characterized by various analytical methods such as FESEM, HRTEM, XRD, FTIR, EDX and elemental mapping study, and also its electrochemical properties of the prepared samples were investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) analysis. Differential pulse voltammetry (DPV) analysis has been used to investigate the quantitative detection of heavy metal ions such as cadmium and chromium on modified electrodes under optimal conditions. The in-situ electrochemical sensitivity and selectivity of the samples were determined by varying various parameters, such as the concentration of heavy metal ions, different electrolytes and electrolyte pH. The observed DPV results show that prepared MWCNT (0.05 wt%) and CQD (0.1 wt%) supported MnO2 nanoparticles show effective detection response for chromium (IV) metal ion. In particular, 0D CQD, 1D MWCNT, and MnO2 hybrid nanostructures produced a synergistic effect among them, resulting in strong electrochemical performance of the prepared samples against the target metal ions.

Facile assembly of effective carbon quantum dots and multiwall carbon nanotubes supported MnO2 hybrid nanoparticles for enhanced photocatalytic and anticancer activity

Facile assembly of effective carbon quantum dots and multiwall carbon nanotubes supported MnO2 hybrid nanoparticles for enhanced photocatalytic and anticancer activity

Stainless steel foil: A more appropriate current collector than titanium foil for the cathodes of aqueous zinc ion batteries

Benefiting from the advantages in safety, reliability, affordability, and energy/power densities, aqueous zinc-ion batteries (AZIBs) with mildly acidic electrolytes have triggered tremendous research interest. However, Ti foil, as the most widely used current collector for cathodes of AZIBs, is rather expensive. In this work, stainless steel (SS) foil, with a much lower price, is proposed to be a more appropriate current collector than Ti, Ni, Al, and Cu foils. Among them, Ti and SS foils are found to own superior wettability with related solvents, excellent anti-corrosion ability, and strong binding with cathode material. In contrast, Al and Cu foils suffer from severe corrosion in aqueous electrolytes even without external potential, and Ni foil is electrochemically unstable in aqueous electrolytes. Further studies show that only Ti and SS current collectors can enable Zn//MnO2 battery to work normally. And SS foil behaves slightly better than Ti foil in both Zn//MnO2 battery and hybrid supercapacitor in terms of specific capacity, rate capability, and cyclability. This work provides guidance for the selection of current collectors for AZIBs and related energy storage devices.

Sequential electrodeposition fabrication of graphene/polyaniline/MnO2 ternary supercapacitor electrodes with high rate capability and cyclic stability

The incorporation of various capacitive materials to fabricate multi-component electrodes has emerged as a feasible methodology toward high-performance supercapacitors. In this paper, a facile two-step electrodeposition method is proposed to construct polyaniline (PANI)/MnO2 hybrid nanostructure on reduced graphene oxide (RGO) matrix for the ternary supercapacitor electrodes. By the sequential potentiostatic methods, PANI is first electropolymerized on RGO hydrogel films before MnO2 granules are electrodeposited on the RGO/PANI conductive substrates to obtain the free-standing composite films. The resulting RGO/PANI/MnO2 ternary composite electrodes present significantly promoted capacitive properties compared with the binary RGO/PANI electrodes. Particularly, the optimized electrode and corresponding all-solid-state device could achieve the high specific capacitances of 942.6 and 205.0 F g–1 at 1 A g–1 with superb capacitance retention of 86.4% and 80.3% at 30 A g–1, respectively. The device delivers a maximum energy density of 41.0 Wh kg–1 and demonstrates outstanding capacitance holdings of 96.1% after 10,000 cycles at 30 A g−1, 87.8% after 5000 cycles at 10 A g−1, and 82.5% after 3000 cycles at 5 A g−1, respectively. The prominent electrochemical performances of the ternary composite can be ascribed to the fact that graphene supplies the conductive matrix to immobilize the active pseudocapacitive constituents, while PANI and MnO2 can compensate each other to surmount the disadvantages of inferior conductivity or stability.

Fabrication of porous Cu2S nanosheets for high performance hybrid supercapacitor

Cu2S powders are synthesized by a facile combustion method using copper nitrate as oxidant and a mixture of thiourea and glycine as fuel. The structural, microstructural, and electrochemical properties are analyzed by X-ray diffractometry, scanning and transmission electron microscopy, cyclic voltammetry, and galvanic charge/discharge tests. The Cu2S powders are crystallized in cubic phase. The combusted powders are composed of sheetlike Cu2S particles with some micropores (∼1–2 nm). The electron diffraction patterns show that the Cu2S nanosheets are single crystal nature with 002 crystal facets, leading to the high specific capacitance of 677 F g − 1 at the current density of 1 A g − 1. Furthermore, the Cu2S//MnO2 hybrid capacitor exhibit a high energy density of 42.3 Wh kg−1 at the current density of 1 A g − 1 and high cycling stability of 86% at 3 A g − 1 following 6500 cycles.

SWCNT-bridged laser-induced graphene fibers decorated with MnO2 nanoparticles for high-performance flexible micro-supercapacitors

Hybrid nanocomposites comprised of metal oxide nanoparticles and three-dimensional (3D) graphene possess the advantages of metal oxide and graphene, which have generated extensive attention. Here, we fabricate flexible micro-supercapacitors (MSCs) based on hybrid materials of single-walled carbon nanotubes (SWCNT)-bridged laser-induced graphene fibers (LIGF) decorated with manganese dioxide (MnO2) nanoparticles. SWCNT is deposited on the LIGF surface and the space between LIGF, which can bridge LIGF to form more conductive paths and provide more active areas to grow with MnO2 nanoparticles. Profiting from the synergistic effect between conductive SWCNT-bridged LIGF network and the MnO2 nanoparticles with high theoretical capacitance, the obtained flexible MSCs based on LIGF-C4/MnO2 hybrid electrodes deliver an outstanding areal capacitance of 156.94 mF cm−2, which is about 8 times higher than that of LIGF-MnO2 based MSC (20 mF cm−2). Additionally, the LIGF-C4/MnO2 MSCs also exhibit considerable areal energy density of 21.8 μWh cm−2, long-term cycling stability, remarkable modular integration capability, and exceptional mechanical flexibility (with 90.5% capacitance retention after 1200 bending cycles). Therefore, the design of hybrid electrode materials proposed in this work offers a facile and novel method to develop flexible energy storage devices with high performance, suggesting great prospects for applications in future various wearable electronics.

Bismuth nanoparticles@carbon composite as a stable and high capacity anode for high-voltage bismuth-manganese batteries

Bismuth (Bi) electrochemistry holds great potential for aqueous energy storage in terms of its highly-reversible redox capability in alkaline solution, low-cost, and safety. However, Bi-based batteries still suffer from limited performance of Bi anodes and unsatisfying output voltage. Herein, to address these issues, we develop an advanced Bi electrode consisting of oxygen-functionalized Bi nanoparticles embedded in porous carbon frameworks (Bi@C), which was paired with a high potential MnO2 cathode via an electrolyte-decoupling configuration to achieve a high voltage bismuth-based battery. The presence of the subtly-designed oxygen interface favors efficient adsorption of OH− ions while its unique 3D carbon matrix provides an interconnected pathway for electron charge transport. As a result, the Bi@C anode exhibits a remarkable capacity (347.2 mAh g−1 at 3 A g−1) close to its theoretical value, an excellent rate capability (60% capacity retention at a high current density of 20 A g−1) and outstanding long-term cyclability (96% capacity retention over 9500 cycles). Furthermore, this new Bi//MnO2 hybrid battery possesses merits of high energy density (213 Wh kg−1) and output voltage (1.62 V). This work is expected to shed some lights on properly elevating the energy density of aqueous Bi batteries via electrode design.

Self-assembly of hyaluronic acid-mediated tumor-targeting theranostic nanoparticles.

Theranostic nanoparticles (NPs) have emerged as promising candidates for cancer diagnosis and treatment. Manganese dioxide (MnO2)-based NPs are potential contrast agents with excellent paramagnetic property and biocompatibility, exhibiting satisfactory magnetic resonance imaging (MRI) effects and biological safety. Recently, hyaluronic acid (HA) has gained increasing interest due to its tumor-targeting ability, which can improve the tumor affinity of manganese dioxide (MnO2)-based NPs. In this study, HA-coated and albumin (BSA)-templated MnO2 and polydopamine hybrid nanoparticles (HMDNs) with tumor-targeting and superior imaging capability were fabricated via modifying the nanoparticles prepared by integrating dopamine polymerization and MnO2 biomineralization. The modification was found to enhance the cellular uptake of HMDNs by cancer cells. The prepared HMDN had high MRI contrasting capability with a longitudinal relaxivity of 22.2 mM-1 s-1 and strong photothermal therapy (PTT) effects with nearly complete tumor ablation under laser irradiation in vivo. HMDNs also showed effective clearance through kidneys, with no toxicity to important tissues. Therefore, HMDNs with superior imaging and PTT capability presented a new method to prepare tumor-targeting multifunctional nanotheranostics.

Injectable redox and light responsive MnO2 hybrid hydrogel for simultaneous melanoma therapy and multidrug-resistant bacteria-infected wound healing

The recurrence of cutaneous cancer and multidrug-resistant (MDR) bacteria infected-wound healing after surgical excision remains a great challenge for both clinic and research. In this study, we developed an injectable redox and light responsive bio-inspired MnO2 hybrid (BMH) hydrogel for effective melanoma photothermo-chemotherapy and MDR bacteria infected-wound healing. The BMH hydrogel was ingeniously fabricated via non-covalent self-assembly and MnO2 nanosheets mediated covalent oxidative polymerization of the catechol functionalized chitosan for the first time. The BMH hydrogel displayed excellent shear-thinning, injectable, adhesive, redox/light responsive and contact-active antibacterial capabilities. Remarkably, our rationally designed BMH hydrogel could alleviate the hypoxic tumor microenvironment (TME) by decomposing the endogenous H2O2 into O2, and simultaneously release anticancer drug DOX. Increasing the local availability of O2 enhanced the cytotoxicity of DOX against melanoma in a highly site-specific manner. By further combining with a spatiotemporal controllable photothermal hyperthermia, we demonstrated a near-complete tumor suppression both in vitro (98.6%) and large solid tumors in vivo (96.2%). Moreover, BMH hydrogel could significantly promote the MDR-infected wound healing in vivo by efficiently eradicating bacterial invasion and perpetually ameliorating the oxidative and inflammatory wound microenvironment. Collectively, BMH hydrogel indicated great therapeutic potentials for both cancer therapy and tissue engineering.

Flexible N-Doped reduced graphene oxide/carbon Nanotube-MnO2 film as a Multifunctional Material for High-Performance supercapacitors, catalysts and sensors

A flexible 3D N-doped reduced graphene oxide (N-RGO)/carbon nanotube (CNT)MnO2 hybrid film was constructed with outstanding supercapacitor, excellent oxygen reduction reaction (ORR) and good sensing performances. The resultant hybrid film possessed large specific capacitances of 418 F g−1 and 209 mF cm−2 in aqueous and solid electrolytes, and outstanding capacitance retentions of 95% and 94% were obtained for both electrolytes after experiencing 5000 cycles. A simple supercapacitor based on the resultant flexible hybrid film was further fabricated with a much smaller time constant τ0 (0.38 s) than that of typical activated-carbon supercapacitors, suggesting a quick response frequency. Moreover, the assembled supercapacitor device showed high energy densities of 45.72 and 92.13 Wh kg−1 and simultaneously sustained large power densities of 12,526 and 15873 W kg−1 under a scan rate of 50 mV s−1 in aqueous and solid electrolytes, respectively. Furthermore, the resultant flexible film showed excellent performance in the ORR and can also be used to assemble a strain sensor with an excellent sensing performance for bending strain.

Facile fabrication of binder-free reduced graphene oxide/MnO2/Ni foam hybrid electrode for high-performance supercapacitors

A novel three-dimensional reduced graphene oxide aerogel and MnO2 (rGO/MnO2) hybrid is prepared via a mild method and freeze-drying treatment, followed by an electrodeposition process. The characterization results reveal that the deposited MnO2 is homogeneously anchored on the graphene sheets, which is served as binder-free electrode material to fabricate high-performance supercapacitor. The specific capacitance of rGO/MnO2 on Ni foam reaches 288 F g−1 at 0.5 A g−1. The assembled symmetrical rGO/MnO2/Ni supercapacitor exhibits a maximum energy density of 26.82 Wh kg−1 and a maximum power density of 8.61 kW kg−1, whose capacitance retention maintains 94.7% over 1000 cycles. Moreover, it can successfully activate different LEDs after being charged. These appreciable performances are primarily put down to the cooperative effect of porous structure of rGO/MnO2 and pseudocapacitive property of MnO2, which provides adequate electroactive sites and facilitates the electron/ion transfer during the electrochemical processes.

MnO2-Disguised Upconversion Hybrid Nanocomposite: An Ideal Architecture for Tumor Microenvironment-Triggered UCL/MR Bioimaging and Enhanced Chemodynamic Therapy

Upconversion nanoparticles (UCNPs) and MnO2 hybrid theranostic nanoplatform (UCMn) is highly desired; however, the rational design of such UCMn hybrid nanomaterials is still a great challenge. Here...

Supercapacitive retention of electrochemically active phosphotungstic acid supported poly(diphenylamine)/MnO2 hybrid electrode

Electrochemical-deposition method was engaged to prepare Fluorine doped Tin oxide (FTO) modified Polydiphenylamine (PDPA)/Phosphotungstic acid (PTA)/Manganese dioxide (MnO2) nanohybrid (FTO/PDPA/PTA/MnO2-ME) Electrode. Nanocomposites structural analysis, morphology, and molecular vibrational studies were characterized through X-ray diffractometer (XRD), Scanning Electron Microscope (SEM) and Fourier Transform Infra read Spectroscopy (FTIR). Recorded XRD and FTIR pattern authenticates the existence of PDPA, PTA, and MnO2 structures. Cyclic voltammetry (CV) studies performed using electrochemical workstation shows very high specific capacitance value of 514.77 Fg−1 at 5 mVs−1 for the modified hybrid electrode system. The superior capacitive performance, cyclic stability of FTO/PDPA/PTA/MnO2 electrode was attributed due to the existence and fast reversible multi‐electron redox response of tungsten atoms in PTA along with PDPA-MnO2 synergistic interaction that augments the electron transfer processes.

Fabrication of oxidase-like polyaniline-MnO2 hybrid nanowires and their sensitive colorimetric detection of sulfite and ascorbic acid

Recently, nanomaterials-based oxidase-like artificial enzymes have attracted much attention due to their unique catalytic efficiency, high environmental stability and low-cost. In this study, we for the first time show the application of polyaniline (PANi)-MnO2 hybrid nanowires for oxidase mimicking. The PANi-MnO2 hybrid nanowires are prepared via a redox reaction between PANi nanowires and KMnO4. The as-prepared PANi-MnO2 hybrid nanowires exhibit an enhanced oxidase-like catalytic activity compared with individual PANi nanowires and MnO2 alone due to the synergistic catalytic effect between the two components. Based on the above findings, we construct PANi-MnO2 hybrid nanowires-based colorimetric assay for sensitive and selective detection of sulfite and ascorbic acid (AA). The detection limits of sulfite and AA are as low as 79 and 26 nM, respectively, which is much lower than many previous reported enzyme mimics-based colorimetric sensors. This work demonstrates a broad potential prospect of PANi-MnO2 hybrid nanowires in biotechnology, environmental science and food safety.

Enhancing extracellular electron transfer efficiency and bioelectricity production by vapor polymerization Poly (3,4-ethylenedioxythiophene)/MnO2 hybrid anode

Electron transfer efficiency in electroactive biofilm is the limiting factor for bioelectricity output of bioelectrochemical system. Here, carbon felt (CF) is coated with manganese dioxide (MnO2) which acts as electron mediator in electroactive biofilm. A wrapping layer of conducting Poly 3,4-ethylenedioxythiophene is developed to protect the MnO2 and enhance electron transfer efficiency of MnO2 mediator. The hybrid bioanode (PEDOT/MnO2/CF bioanode) delivered the highest electron transfer efficiency (6.3 × 10−9 mol cm−2 s−1/2) and the highest capacitance of 4.78 F, much higher than bare CF bioanode (1.50 ± 0.04 × 10−9 mol cm−2 s−1/2 and 0.42 F). As a result, microbial fuel cells could produce a maximum power density of 1534 ± 13 mW m−2, approximately 57.7% higher than that with the bare carbon felt anode (972 ± 21 mW m−2). Possible mechanisms are proposed to help understanding the different function of the PEDOT and MnO2 on the anodic layer. This study introduces an effective method for the fabrication of high performance anode.

Three-Dimensional Graphene/MnO2 Nanowalls Hybrid for High-Efficiency Electrochemical Supercapacitors

In this paper, a facile method is designed to fabricate three-dimensional (3D) graphene (GR)/manganese dioxide (MnO2) nanowall electrode material. The 3D GR/MnO2 hybrid is prepared by a combination of electrochemical deposition (ELD) and electrophoresis deposition (EPD), followed by thermal reduction (TR). Firstly, the 3D graphene oxide (GO)/MnO2 hybrid is obtained by the ELD–EPD method. Secondly, the 3D GR/MnO2 hybrid is obtained through hydrogen reduction at a certain temperature. The as-fabricated hybrid has been characterized by scanning electron microscope (SEM), transmission electron microscope (TEM) and Raman spectroscopy. The electrochemical properties have been also measured by cyclic voltammetry. The results showed that the 3D GR/MnO2 nanowalls hybrid has a high specific capacitance of 266.75[Formula: see text]Fg[Formula: see text] and a high energy density of 25.36[Formula: see text]Whkg[Formula: see text]. Moreover, a high specific capacitance (240.15[Formula: see text]Fg[Formula: see text]) at a high scan rate of 200[Formula: see text]mVs[Formula: see text] (90% capacity retention) has been also obtained. Additionally, the hybrid can serve directly as the electrodes of supercapacitor without adding binder. This work provides a novel road to fabricate a binder-free 3D GR-based hybrid for high-performance energy storage devices.

Self-Propagated Flaming Synthesis of Highly Active Layered CuO-δ-MnO2 Hybrid Composites for Catalytic Total Oxidation of Toluene Pollutant.

A new self-propagated flaming (SPF) technique was applied to the synthesis of highly active layered CuO-δ-MnO2 hybrid composites, for the de-polluting catalytic total oxidation of gaseous toluene vapor. Other transition metal oxide-doped MnO2 hybrid composites were also successfully prepared and investigated, ensuring a feasible strategy for the fabrication of various layered MOx-δ-MnO2 (M═Co, Ni, or Zn) hybrids. By changing the molar ratio of the precursors (KMnO4 and acetate salt) and the type of transition metal oxide introduced, it is possible to control the crystal structure and reducibility of the sheetlike hybrid composites as well as the catalytic activity for the total oxidation of toluene. The catalyst sample (CuO-δ-MnO2) with a Mn/Cu molar ratio of 10:1 exhibited the highest catalytic performance, with a lower reaction temperature of 300 °C for complete toluene removal, which was comparable to the reaction temperature for total toluene conversion by the Pt-based catalyst. The SPF technique provides an approach for developing highly efficient catalysts for the complete removal of volatile organic compounds, by allowing the facile and energy-saving fabrication of large quantities of layered CuO-δ-MnO2 hybrids.