Morphology Of MnO2 Research Articles

Performance study of bimetallic Mn-Zn porous flower-like nanosheets as supercapacitor positive electrode materials

As environmental and carbon emission issues become increasingly severe, electrochemical energy storage systems have gained attention. Compared to traditional supercapacitors, zinc-ion hybrid capacitors (ZIHCs) are not only environmentally friendly but also cost-effective. MnO2, with its low cost, eco-friendliness, high theoretical capacity, and stable crystal structure, is considered a promising positive electrode material. In this study, the morphology of MnO2 was optimized using electrodeposition. During cycling, zinc ions reversibly intercalate and extract from MnO2, forming a cactus-like nanoflower structure. This structure is loose and porous, providing ample reaction space for active materials. The assembled device exhibits excellent performance in both energy density (85.68 Wh kg−1) and stability (91.60 %).

The morphologic dependence of MnO2 electrodes in capacitive deionization process

Manganese dioxide (MnO2) materials are one of promising cathode candidates for capacitive deionization (CDI) applications, with their morphology significantly impacting the performance of the electrode material itself. Therefore, this study systematically investigates the structure-performance relationships and the micro-interface ion storage mechanisms of four morphologies of MnO2 (1D nanorods (NNMO), nanowires (NWMO), 3D microspheres (MMO), and hollow urchin-like spheres (HUMO)) in relation to their capacitive deionization performance with typical heavy metal ions (Cd2+) through experimental and theoretical calculations. In terms of pore morphology, capacitance significantly increases with increasing surface curvature of materials, demonstrating a clear pore structure-dependent characteristic. NNMO, with the smallest pore size, has much lower surface capacitance (∼0.15 μF cm−2) than other materials (∼0.33 μF cm−2). As pore size increases, the capacitance distribution difference driven by pore structure size gradually disappears. Regarding surface and interface characteristics, high-energy crystal facets facilitate electron transfer ({310}>{200}≈{211}>{100}) and increase the proportion of surface active sites (Osur), thus promoting CDI absorption kinetics. During the capacitive deionization process, the pore structure (∼77 %) and surface-interface characteristics (∼23 %) exhibit highly coupled features and the driving force for interfacial ion storage among the four materials is in the order of HUMO>MMO>NWMO>NNMO. This work elucidates the morphology-dependent capacitive processes of MnO2 nanomaterials, enhancing the understanding of structure- electrochemical process at the nanoscale but also providing effective guidance for the design and development of practical, high-performance CDI electrode materials.

Improved near-resonant two photon absorption of α-MnO2 nanowires surface functionalized reduced graphene oxide sheets

The versatile study of graphene derivatives has resurgence of interest on understanding its nonlinear optical response at different nanoscales. Nanostructured manganese dioxide: reduced graphene oxide (MnO2: rGO) hybrids were synthesized by reduction method by varying the content of rGO (5, 10, 15 & 20 wt%). X-ray Photoelectron Spectroscopy studies confirmed the surface functionalization of MnO2 on rGO. Field Emission Scanning Electron Microscopy (FESEM) and High-Resolution Tunnelling Electron Microscopy (HRTEM) witness that with respect to the content of rGO, the morphology of MnO2 varies radically from clusters to nanorods to nanowires over the surface of rGO sheets. Ground state absorption spectra of the hybrids have absorption edge at 268 nm corresponding to combined metal oxide charge transfer between rGO (π-π* transition of CC and n-π transition of C-O bonds) and MnO2 (d-d transition). Moreover, hierarchical MnO2 nanowire network resided on 2D rGO sheets involves broad absorption at the visible spectral domain due to polaron transition as well the localization of π- π* transited electrons that facilitates the probability of occurrence of excited state absorption. Intensity dependent open aperture Z-scan technique of the prepared hybrids using Q-switched Nd: YAG 532 nm nanopulsed laser reveals unusual transitions and enhanced nonlinear absorption. MnO2:(5 wt%) rGO shows saturable absorption (SA) at low intensity and changeover dynamically to reverse saturable absorption (RSA) at higher intensity. MnO2:(10 & 15 wt%) rGO exposes coupled nonlinear absorption (SA + RSA) owing to the combined effect of graphene (π-states) and MnO2 (σ-states). MnO2:(20 wt%) rGO exhibits a stronger RSA ascribed to sequential two photon absorption. The third-order nonlinear absorption coefficient and limiting threshold of MnO2: rGO (20 wt%) are 4.04 ×10-10 m/W and 0.84 ×1012 W/m2, which shows five-fold increase compared to bare rGO and MnO2. The obtained results propose that the optical nonlinearity of MnO2 nanowires surface functionalized rGO sheets can significantly be tuned to meet the requirements for fabricating laser safety devices.

Fe-doping induced textural and morphological evolution of MnO2 and its enhanced performance for o-xylene complete oxidation

Fe-MnO2 nanocomposite was prepared via a redox–precipitation method combined with a subsequent aging treatment at low-temperature. Various characterizations showed that Fe was incorporated into MnO2 lattice that changed the relative intensity of MnO2 crystal planes. Thus, the structural defect was formed and the anisotropic growth of the MnO2 crystallite phase was suppressed. As a result, the morphology of MnO2 was transformed from nanowires to nanoparticles. In addition, the catalytic property of Fe-MnO2 was significantly enhanced than that of pristine MnO2 for the complete oxidation of o-xylene. This work provides a simple and effective strategy for regulating MnO2 texture and activity.

Designing reduced graphene oxide decorated Ni doped δ-MnO2 nanocomposites for supercapacitor applications

Reduced Graphene Oxide (rGO) decorated δ-MnO2 and Ni-doped δ-MnO2 samples have been synthesized by a microwave-assisted co-precipitation technique which is low cost, simple and fast reaction method. The structural and morphological properties of synthesized samples have been characterized using x-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). XRD result indicates that all samples have monoclinic crystal structure with δ phase of MnO2. The morphologies of MnO2 transformed into perforated porous nanoflakes with Ni doping and rGO composition in MnO2. AFM images confirmed that surface roughness for 3 % Ni-doped MnO2 samples is higher due to the chemical adsorption of samples. Raman spectroscopy results show the presence of vibrational and Raman active modes of MnO2.X-ray photoelectronic spectroscopy revealed the presence of mixed valencies of Mn such as Mn2+, Mn3+, and Mn4+ in prepared nanocomposites while Ni shows 2+ valency. The specific capacitance (Cs) of pure δ -MnO2 samples were 68 Fg-1 and rGO decorated 3 % Ni-doped MnO2 composition 694 Fg-1 at 10 mVs−1 respectively. EIS data of the rGO decorated Ni-doped MnO2 composition samples confirm that the porous nanoflake-shaped rGO decorated 3 % Ni-doped MnO2 composite sample has a low resistance value among all samples. These results reveal that rGO-decorated 3 % Ni-doped MnO2 nanoflakes should be a promising material for designing and fabricating the electrode material for high-performance supercapacitors.

Morphological effect of MnO2 promoter on iron-based Fischer-Tropsch synthesis catalysts

In this work, flower-like spherical, sea urchin-like and tubular MnO2 are prepared via hydrothermal synthesis and used as promoters of iron-based Fischer-Tropsch synthesis (FTS) catalysts to investigate their morphological effects. It is found that the different morphology of MnO2 exhibits observably distinct promotion functions on iron-based FTS catalysts. Tubular MnO2 contains moderate amount of surface oxygen vacancies accompany with weak Fe-Mn electronical interaction, as a result, tubular MnO2 promotes the formation of long-chain hydrocarbon and olefins, and restrains the generation of CH4. Flower-like spherical MnO2 presents negative roles in the CO conversion and formation of long-chain hydrocarbon, due to its insufficient oxygen vacancies and moderate Fe-Mn electronical interaction. With the most abundance of oxygen vacancies and strongest Fe-Mn interaction, sea urchin-like MnO2 modified catalysts exhibits the highest initial CO conversion, but deactivates rapidly. Besides, the sea urchin-like MnO2 enhances the formation of long-chain paraffins. This work presents new insights of the promotion roles of Mn additive, which is beneficial for the rational design of efficient iron-based FTS catalysts.

Solar light driven photocatalytic degradation of methylene blue dye over Cu doped α-MnO2 nanoparticles

Cu-α-MnO2 nanoparticles were synthesized by hydrothermal method and their potential application in the aqueous-based degradation of organic contaminants was examined under solar light. Cu doping increases the particle size and affects the morphology of MnO2. The Cu-doped α-MnO2 XRD pattern showed a tetragonal crystalline structure with a crystal size of ∼30nm. When compared to α-MnO2, which has a band gap energy of 1.58eV, the 6% Cu-doped α-MnO2 photocatalyst has a lower band gap energy (1.23eV). As a result, the light absorption was increased towards the visible spectrum. The considerable change in PL intensity of MnO2 observed after Cu doping. The findings show that a 6% Cu- α-MnO2 sample degrades methylene blue dye completely within 2 h. The improvement of the photocatalytic activity of the Cu-α-MnO2 nanoparticles was significantly influenced by the expanded light absorption range and effective charge separation. A variety of scavengers were employed to identify the active species by capturing the radicals and holes generated upon the photocatalytic degradation process.

Hydrothermal Synthesis of MnO2 Microspheres and Their Degradation of Toluene.

Various urchin-like MnO2 materials were obtained with a facile hydrothermal method through controlling the Mn precursor, reaction time, and reaction temperature. The property of MnO2 materials was characterized by scanning electron microscopy, X-ray diffraction, and H2 temperature-programmed reduction. The results showed that the Mn precursor could significantly impact the morphology of as-prepared MnO2. When the precursor was Mn(CH3COO)2·4H2O, the MnO2 morphology consisted of tennis-like microspheres assembled by nanorods. While the precursor was MnCl2·4H2O, the sample morphology was a chestnut shell, and the samples were sea urchin microspheres, as the precursor was MnSO4·H2O. At the same time, the morphology of MnO2 was affected by hydrothermal time and temperature. The nanoneedles on the microsphere surface gradually lengthened with increasing hydrothermal time and hydrothermal temperature, until nanowires were formed. MnO2 crystallinity was also influenced by hydrothermal temperature. It was γ-MnO2 as the temperature was 50 and 80 °C while evolved to be α-MnO2 and β-MnO2 when the temperature increased to 140 °C. As MnO2 (MnO2-1 h, MnO2-2 h, MnO2-4 h, and MnO2-6 h) was prepared to degrade toluene, all the samples could completely catalyze toluene at the temperature of 225 °C. However, the MnO2-4 h showed the best catalytic effect at a lower temperature.

Effect of MnO2 Morphology on Kinetics and Stability in Zinc-Ion Batteries.

Research on zinc-ion batteries (ZIBs) with manganese-based cathodes has been severely hindered by their poor cycle stability. This study explores the fundamental parameters that affect the cycle stability of battery systems from a structural stability perspective. MnO2 electrodes with different classical morphologies and sizes were synthesized via a temperature-controlled coprecipitation strategy. The effects of the morphology and size of the MnO2 on the overall electrical properties and kinetics of ZIBs were analyzed and compared. The one-dimensional nanofibrous α-MnO2 produced using this method exhibited the most stable nanostructure with a favorable aspect ratio, which resulted in faster chemical kinetics. A more uniform particle distribution and better aspect ratios not only enabled a faster ion migration rate but also affected the remolding of the anode morphology. After 2000 cycles at a high current density of 1 A g-1, the material maintained an excellent discharge-specific capacity, highlighting it as a promising electrode material for ZIBs. The construction of nanoenergy materials with controllable morphologies and sizes will significantly advance battery applications.

Ionic-Liquid-Assisted Synthesis of Mixed-Phase Manganese Oxide Nanorods for a High-Performance Aqueous Zinc-Ion Battery

Aqueous zinc-ion batteries (ZIBs) provide a safer and cost-effective energy storage solution by utilizing nonflammable water-based electrolytes. Although many research efforts are focused on optimizing zinc anode materials, developing suitable cathode materials is still challenging. In this study, one-dimensional, mixed-phase MnO2 nanorods are synthesized using ionic liquid (IL). Here, the IL acts as a structure-directing agent that modifies MnO2 morphology and introduces mixed phases, as confirmed by morphological, structural, and X-ray photoelectron spectroscopy (XPS) studies. The MnO2 nanorods developed by this method are utilized as a cathode material for ZIB application in the coin-cell configuration. As expected, Zn//MnO2 nanorods show a significant increase in their capacity to 347 Wh kg-1 at 100 mA g-1, which is better than bare MnO2 nanowires (207.1 Wh kg-1) synthesized by the chemical precipitation method. The battery is highly rechargeable and maintains good retention of 86% of the initial capacity and 99% Coulombic efficiency after 800 cycles at 1000 mA g-1. The ex situ XPS, X-ray diffraction, and in-depth electrochemical analysis confirm that MnO6 octahedra experience insertion/extraction of Zn2+ with high reversibility. This study suggests the potential use of MnO2 nanorods to develop high-performance and durable battery electrode materials suitable for large-scale applications.

Utilization of high specific activity 99Mo for assessing the active manganese oxide as a potential material for 99Mo/99mTc generator

Abstract The hydrothermal preparation of active MnO2 via KMnO4 and MnSO4.H2O as inorganic forerunners is demonstrated, and it is evaluated as an adsorbent for the 99Mo produced by 235U fission. The structure and morphology of MnO2 were distinguished using various methods such as FTIR spectrum, FESEM, EDX, XRD, TGA. The 99Mo adsorption conduct on active manganese oxide was investigated, and the Mo uptake capacity was determined using static and dynamic techniques, and it was found to be 22.8 ± 1 and 6.72 ± 0.3 mg/g MnO2, respectively. This sorbent material was used in preliminary studies to prepare a 99Mo/99mTc generator. 99mTc eluted from the prepared generator was estimated to be 78–82 % with a low 99Mo breakthrough (0.002 %) and acceptable radiochemical, radionuclidic, and chemical purities.

Potential of MnO2‐based composite and numerous morphological for enhancing supercapacitors performance

AbstractThe development of materials and electrochemical energy storage (EES) technologies are currently taking the lead and showing excellent performance in the global effort to tackle the issues of sustainable energy supply. Supercapacitors have been widely studied among the EES technologies as they exhibit quick charging rates under high‐power conditions. Manganese dioxide (MnO2) has attracted renewed interest as a promising material due to its high theoretical capacitance and high energy density. However, the widespread application is immediately impacted by low conductivity. Hence, combining nanomaterials and various morphologies of MnO2 can improve the electrochemical performance of supercapacitors. This paper presents a review based on the composites of nanomaterials/MnO2 with various morphologies. Their mechanism and practical applications in supercapacitors are introduced in detail. Finally, the challenges and next steps in developing MnO2 electrode materials are proposed.

MnO2 nanoparticles/methylene blue-chitosan nanocomposite modified glassy carbon electrode (MnO2 NPs/MB–CS/GCE) as sensor for electrochemical determination of β-glucan in Morchella esculenta samples

The aim of this work was performed for design the electrochemical biosensor (βg-GOx/MnO2 NPs/MB-CS/GCE) determination of β-glucan in morel samples by modification of glassy carbon electrode (GCE) with electrodeposition of methylene blue-chitosan (MB-CS) nanocomposite and MnO2 nanoparticles (MnO2 NPs) and immobilization β-glucanase and glucose oxidase (βg-GOx), respectively. The study of the morphology of MnO2 NPs/MB–CS/GCE by FE-SEM indicated that the electrodeposited MnO2 NPs in the chitosan layer are wrapped by MB nanocubes. The electrochemical properties of β-glucan nonconductive enzyme film were successfully immobilized in β-glucan/MnO2 NPs/MB-CS/GCE, and the synergetic advantageous effect of MB-CS and MnO2 NPs enhanced the sensitivity and selectivity of the β-glucan biosensor. The linear range of 0– 10,400 ng/mL was obtained, and the sensitivity of 0.00441 µA/ng.mL−1 and the detection limit of 0.34 ng/mL were determined. The study on the applicability of the βg-GOx/MnO2 NPs/MB–CS/GCE as β-glucan sensor in morel samples revealed significant conformity between the results of amperometric and β-Glucan Assay Kit assays, and the obtained good recoveries between 90.00% and 97.50% with relative standard deviation less than 5.18% for amperometric analysis were acceptable, confirming the appropriate applicability of the βg-GOx/MnO2 NPs/MB–CS/GCE for determination of the β-glucan content in fungal samples.

The increased oxygen vacancy by morphology regulation of MnO2 for efficient removal of PAHs in aqueous solution

Manganese dioxide (MnO2) is considered to have a promising future in degrading polycyclic aromatic hydrocarbons (PAHs) in aqueous phase because of its low cost and environmental friendliness. In this study, various MnO2 morphologies were prepared, and their removal performance and mechanism were evaluated using benzo(a)pyrene (B[a]P) as model molecule. Results showed that nanoflower MnO2 with higher concentration of oxygen vacancies exhibited better oxidative and easier oxygen migration properties, and thus enhanced PAHs removal by 14.28%–43.21% compared with other MnO2 samples. Additionally, the transformation rate of PAHs is correlated with their ionization potential (IP) values. Further mechanism studies showed that the degradation of B[a]P by MnO2 process was first to form a combination and then oxidized by non-radical Mn species and superoxide radical (O2−•) to produce degradation product (B[a]P-6-one and B[a]P-6,12-quinone). The specific surface area was not the main factor affecting the removal of B[a]P by MnO2 and oxidation was the main removal mechanism of degrading B[a]P by MnO2. Mn3+ and absorbed oxygen (Oabs) played an important role in the process of removing PAHs by MnO2. Additionally, synergistic effects of oxygen vacancy and Mn3+could be benefit for transforming Oabs to O2−•, leading to the efficient degradation of PAHs.

A manganese dioxide-silver nanostructure-based SERS nanoplatform for ultrasensitive tricyclazole detection in rice samples: effects of semiconductor morphology on charge transfer efficiency and SERS analytical performance.

Taking advantage of metal-semiconductor junctions, functional nanocomposites have been designed and developed as active substrates for surface-enhanced Raman scattering (SERS) sensing systems. In this work, we prepared three types of nanocomposites based on manganese oxide (MnO2) nanostructures and electrochemically synthesized silver nanoparticles (e-AgNPs), which differed according to the morphologies of MnO2. The SERS performance of MnO2 nanosheet/e-Ag (MnO2-s/e-Ag), MnO2 nanorod/e-Ag (MnO2-r/e-Ag), and MnO2 nanowire/e-Ag (MnO2-w/e-Ag) was then evaluated using tricyclazole (TCZ), a commonly used pesticide, as an analyte. Compared to the others, MnO2-s/e-Ag exhibited the most remarkable SERS enhancement. Thanks to its large surface area and ability to accept/donate the electrons of the semiconductor, MnO2-s acted as a bridge to improve the charge transfer efficiency from e-Ag to TCZ. In addition, the MnO2 content of the nanocomposites was also considered to optimize the SERS sensing performance. With the optimal MnO2 content of 25 wt%, MnO2-s/e-Ag could achieve the best SERS performance, allowing the detection of TCZ at concentrations down to 6 × 10-12 M in standard solutions and 10-11 M in real rice samples.

Interlacing Rod and Sphere Morphology of MnO2 in RGO/NiO/MnO2 Ternary Nanocomposites for Supercapacitive Applications

Supercapacitors are promising energy storage devices. Herein a comparative study was carried out between two samples of reduced graphene oxide-infused binary metal oxides, in which the morphology of one of the metal oxides (Manganese oxide) is altered. MnO2 was synthesized in two morphologies namely nanorods and nanospheres. The two morphologies (rod and spheres) were separately composited with the as-synthesized cone-structured nickel oxide and sheets of reduced graphene oxide (rGO) and were subjected to various structural, functional, morphological, electrochemical characterizations etc. The morphologies and structures of the as prepared samples were characterised by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy and X-ray photoelectron spectrometer (XPS). The functional properties were determined using Fourier Transform Infra-Red (FTIR) Spectroscopy. The electrochemical performance of both the samples were analysed using Cyclic Voltammetry (CV), Galvanostatic Charge/Discharge (GCD) measurements and Electrochemical Impedance Spectroscopy (EIS) under electrolytes with different pH namely 1M Na2SO4(pH = 7) and 1M Na2CO3(pH = 11). The CV was analysed with different scan rates and GCD was taken under 1–5 Ag−1 current densities. The cycling stability of the materials were testified for 5000 cycles of CV and GCD. The results are discussed. The main advantage of this work is that the best suited morphology with better ion transfer rate having commendable electrochemical ability and long-standing cycle rate for a promising supercapacitor is identified which will serve as the reference for the future supercapacitor electrodes.

Synchronously modulated the morphology and crystal defects of α-MnO2 for high-performance mono-component electromagnetic wave absorber

Developing mono-component electromagnetic wave (EMW) absorbing materials is desirable owing to their simple preparation methods; thus, it is crucial to investigate EMW absorbing mechanisms. However, owing to the requirements of excellent impedance matching and attenuation capability, EMW material design is considerably challenging. To address these challenges, this study reports an Ag+-doped α-MnO2 with a hierarchical structure for EMW absorption. The microscopic morphology and crystal defects are synchronously modulated, resulting in considerable improvement in EMW absorption performance; an optimal reflection loss of −68.6 dB and an effective absorption bandwidth (EAB) of 4.2 GHz are achieved at a thin thickness of 1.43 mm. Thus, thin thickness, enhanced absorption intensity, and widened absorption bandwidth are simultaneously achieved. The regulating effect of Ag+ doping on the morphology of MnO2 and the corresponding EMW absorption mechanism are also discussed. The findings of this study provide new insights for designing mono-component EMW absorbing materials with higher absorption performance.

MnO2 modified perovskite oxide SrCo0.875Nb0.125O3 as supercapacitor electrode material

Cobalt-based perovskite SrCo0.875Nb0.125O3 is an advantageous electrode material for supercapacitors. However, the particle form of SrCo0.875Nb0.125O3 is not conducive to the electrochemical behavior. Based on this, surface MnO2 modified SrCo0.875Nb0.125O3 on carbon cloth (MnO2@SrCo0.875Nb0.125O3@CC) has been prepared as supercapacitor electrode. The dandelion-like morphology of MnO2 significantly increases the specific surface area and inhibits the grain agglomeration of SrCo0.875Nb0.125O3, thus promoting the ion diffusion during the electrochemical process. As a result, the electrochemical performance of the composite is significantly optimized due to the synergistic effect of SrCo0.875Nb0.125O3 and MnO2. The MnO2@SrCo0.875Nb0.125O3@CC electrode yields an ultra-high specific capacitance of 2066.0 mF cm−2 at 2 mA cm−2 current density. Compared with SrCo0.875Nb0.125O3@CC electrode and MnO2@CC electrode, this work provides a much improved performance. Besides, an asymmetric supercapacitor composed of MnO2@ SrCo0.875Nb0.125O3@CC as positive electrode and CuS@CC as negative electrode exhibits a voltage window of 1.8 V and a specific capacitance of 114.6 mF cm−2 when the current density is 3 mA cm−2. A high energy density of 51.57 μ Wh cm−2 is achieved at a power density of 4.86 mW cm−2 for the device.

Effect of MnO2 morphology on the thermal properties and combustion behavior of nano-Al/MnO2 thermite

Al/granular MnO2 and Al/rod MnO2 thermite samples were prepared to investigate the effects of different morphologies of MnO2 on the thermal properties and combustion behavior of nano-Al/MnO2 thermite. The morphology and thermal properties of the thermite were characterized by field emission scanning electron microscopy (FE-SEM), x-ray diffractometry (XRD), and differential scanning calorimetry (DSC). DSC results show that the Al/rod MnO2 releases 1274.39 J·mol−1 heat, which is 292.58 J·mol−1 more than the Al/granular MnO2. The initial reaction temperature of Al/rod MnO2 is 567.39 °C, which is delayed by 17.39 °C versus 550 °C of Al/granular MnO2. Non-isothermal thermodynamic analysis was used to measure the activation energy of Al/rod MnO2 to be 234.36 kJ·mol−1, which is 46.53 kJ·mol−1 higher than that of Al/granular MnO2. This corresponds to an increase in the ignition temperature in the DSC curve and indicating a higher safety profile. In the open burning experiment, the burning time of Al/granular MnO2 was longer and sparks sputtered around the flame. The Al/rod MnO2 has a large combustion flame and a fast combustion rate. The light intensity peaks of the two groups of samples are close in the light intensity test. The light intensity existence time of Al/rod MnO2 is 0.0146 s, which is 0.094 s shorter than Al/granular MnO2. This shows that the combustion rate of Al/rod MnO2 is much faster than that of Al/granular MnO2. The closed-tube combustion experiment shows that the combustion wave velocity of Al/rod MnO2 increases first and then decreases; the maximum wave velocity reaches 339.6 m·s−1, and Al/granular MnO2 cannot self-propagate combustion in the microporous environment. In the constant volume combustion experiment, the peak combustion pressure of Al/rod MnO2 is 0.938 Mpa, and the peak value of Al/granular MnO2 combustion pressure is 0.581 Mpa; the difference is obvious. This shows that the rod MnO2 gas production performance is better. According to the duration of the pressure peak, the burning speed of Al/rod MnO2 in the light intensity test is confirmed again to be much faster than that of Al/granular MnO2. The Al/rod MnO2 is better than Al/granular MnO2 in thermal and combustion performance and is also safer. This provides a basis for future performance and safety research on aluminothermic materials.

Ethylene carbonate as an organic electrolyte additive for high-performance aqueous rechargeable zinc-ion batteries

Rechargeable zinc-ion batteries (ZIBs) have recently received tremendous attention for large-scale electrochemical energy storage, but their poor cyclic stability and reversibility and low coulombic efficiency, which are mainly caused by dendrite issues and parasitic reactions of zinc (Zn) anode, prevent them from achieving their full potential. Herein, we investigated the use of ethylene carbonate (EC) as an electrolyte additive to improve the performance of ZIBs. The addition of 6% (w/v) EC substantially enhanced the first-cycle discharge capacity from 115 to 203 mAh g−1 at 0.1 A g−1, while retaining this high discharge capacity (102% retention of the initial capacity) after 200 cycles, and from 43 to 54 mAh g−1 at 1 A g−1 with 85% capacity retention after 1,000 cycles. The ex-situ characterizations and electrochemical impedance spectroscopy analysis before and after Zn–MnO2 and Zn–Zn battery cycling suggested that the addition of EC could effectively suppress dendrite formation and parasitic reactions on the Zn anode, possibly via electrolyte/Zn anode interface film formation in the presence of EC. Moreover, the presence of EC made the MnO2 morphology more open and accessible. These led to substantial improvements in the rate performance and cyclability compared to the additive-free electrolyte.