Porous MnO2 Research Articles

Development of Polymer Composite Membrane Electrolytes in Alkaline Zn/MnO2, Al/MnO2, Zinc/Air, and Al/Air Electrochemical Cells.

This paper reports on the novel composite membrane electrolytes used in Zn/MnO2, Al/MnO2, Al/air, and zinc/air electrochemical devices. The composite membranes were made using poly(vinyl alcohol), poly(acrylic acid), and a sulfonated polypropylene/polyethylene separator to enhance the electrochemical characteristics and dimensional stability of the solid electrolyte membranes. The ionic conductivity was improved significantly by the amount of acrylic acid incorporated into the polymer systems. In general, the ionic conductivity was also enhanced gradually as the testing temperature increased from 20 to 80 °C. Porous zinc gel electrodes and pure aluminum plates were used as the anodes, while porous carbon air electrodes or porous MnO2 electrodes were used as the cathodes. The cyclic voltammetry properties and electrochemical impedance characteristics were investigated to evaluate the cell behavior and electrochemical properties of these prototype cells. The results showed that these prototype cells had a low bulk resistance, a high cell power density, and a unique device stability. The Al/MnO2 cell achieved a density of 110 mW cm-2 at the designated current density for the discharge tests, while the other cells also exhibited good values in the range of 70-100 mW cm-2. Furthermore, the Zn/air cell consisting of the PVA/PAA = 10:5 composite membrane revealed an excellent discharge capacity of 1507 mAh. This represented a very high anode utilization of 95.7% at the C/10 rate.

Fully superhydrophobic porous medium with super durability

BackgroundSuperhydrophobicity being a widely-used characteristic in functional materials that has attracted much interests in academic and industrial applications, such as self-cleaning, anti-corrosion, anti-drag, and anti-icing. Until now, the durability of superhydrophobicity is still a big challenge to limit its extensive applications. Method: Here, we develop a fully superhydrophobic strategy with super durability in a porous medium. The porous medium is achieved as a fully superhydrophobic bulk by treating with the 1 H,1 H,2 H,2 H-PerfluorodecyltriMethoxysilane (FAS-17) at 95 °C. Due to the capillary effect, the FAS-17 liquid readily flows to the whole of the porous medium to modify all surface for superhydrophobicity. Significant Findings: Evaluated via various treatments, including sanding 30 times, repeated exposure at −20 °C to 350 °C 100 times, and immersing in solutions of pH from 3 to 12, the superhydrophobic surface maintains a stabilized contact angle with a slight change. Additionally, this strategy would be a general method which is applicable to many porous media, including Co3O4, CeO2, Fe2O3, MnO2, CuO, and MgO. This work shows the great potential of the fully superhydrophobic porous medium to provide a simple way to design superhydrophobic materials with super durability and facilitates valid avenues for functional surface designing.

Preparation and Electrochromic Properties of MnO2/PPy Composite Films with Coral-like Structures.

MnO2/polypyrrole (PPy) composite films were deposited on fluorine-doped tin oxide (FTO) conductive glasses by a two-step wet-chemical method, including electrochemical deposition and chemical bath deposition (CBD). The porous MnO2 films were first grown on FTO glasses by an electrodeposition method. Second, polypyrrole nanoparticles were polymerized by the oxidation-reduction reaction between MnO2 and pyrrole, using the presynthesized MnO2 as the skeleton. Then, MnO2/PPy composite films with coral-like structures were obtained. The electrochemical and electrochromic (EC) properties of the prepared films were investigated. The results show that, compared to the single MnO2 or PPy film, the MnO2/PPy composite film has a larger optical modulation (67.3% at a wavelength of 900 nm), faster response times (4 s for coloration and 3 s for bleaching), and a higher coloration efficiency (218.16 cm2·C-1). The high coloration efficiency attests to the exceptional performance of the composite film in converting electrical signals into vivid color changes. The electrochemical stability test results show that the composite film maintains a stable EC performance after 200 coloration/bleaching cycles. The coral-like structures of the composite film are responsible for the better EC properties.

N-Containing Porous Carbon-Based MnO Composites as Anode with High Capacity and Stability for Lithium-Ion Batteries.

MnO has attracted much attention as the anode for Li-ion batteries (LIBs) owing to its high specific capacity. However, the low conductivity limited its large application. An effective solution to solve this problem is carbon coating. Biomass carbon materials have aroused much interest for being low-cost and rich in functional groups and hetero atoms. This work designs porous N-containing MnO composites based on the chemical-activated tremella using a self-templated method. The tremella, after activation, could offer more active sites for carbon to coordinate with the Mn ions. And the as-prepared composites could also inherit the special porous nanostructures of the tremella, which is beneficial for Li+ transfer. Moreover, the pyrrolic/pyridinic N from the tremella can further improve the conductivity and the electrolyte wettability of the composites. Finally, the composites show a high reversible specific capacity of 1000 mAh g-1 with 98% capacity retention after 200 cycles at 100 mA g-1. They also displayed excellent long-cycle performance with 99% capacity retention (relative to the capacity second cycle) after long 1000 cycles under high current density, which is higher than in most reported transition metal oxide anodes. Above all, this study put forward an efficient and convenient strategy based on the low-cost biomass to construct N-containing porous composite anodes with a fast Li+ diffusion rate, high electronic conductivity, and outstanding structure stability.

Lignosulfonate-Assisted Synthesis of Porous Carbon-Supported MnO2 Composites with Reinforced Interface Bonding for High-Performance Asymmetric Supercapacitors

Lignosulfonate-Assisted Synthesis of Porous Carbon-Supported MnO₂ Composites with Reinforced Interface Bonding for High-Performance Asymmetric Supercapacitors

In-Situ Spontaneous Electropolymerization Enables Robust Hydrogel Electrolyte Interfaces in Aqueous Batteries.

Hydrogels hold great promise as electrolytes for emerging aqueous batteries, for which establishing a robust electrode-hydrogel interface is crucial for mitigating side reactions. Conventional hydrogel electrolytes fabricated by ex situ polymerization through either thermal stimulation or photo exposure cannot ensure complete interfacial contact with electrodes. Herein, we introduce an in situ electropolymerization approach for constructing hydrogel electrolytes. The hydrogel is spontaneously generated during the initial cycling of the battery, eliminating the need of additional initiators for polymerization. The involvement of electrodes during the hydrogel synthesis yields well-bonded and deep infiltrated electrode-electrolyte interfaces. As a case study, we attest that, the in situ-formed polyanionic hydrogel in Zn-MnO2 battery substantially improves the stability and kinetics of both Zn anode and porous MnO2 cathode owing to the robust interfaces. This research provides insight to the function of hydrogel electrolyte interfaces and constitutes a critical advancement in designing highly durable aqueous batteries.

In‐Situ Spontaneous Electropolymerization Enables Robust Hydrogel Electrolyte Interfaces in Aqueous Batteries

AbstractHydrogels hold great promise as electrolytes for emerging aqueous batteries, for which establishing a robust electrode‐hydrogel interface is crucial for mitigating side reactions. Conventional hydrogel electrolytes fabricated by ex situ polymerization through either thermal stimulation or photo exposure cannot ensure complete interfacial contact with electrodes. Herein, we introduce an in situ electropolymerization approach for constructing hydrogel electrolytes. The hydrogel is spontaneously generated during the initial cycling of the battery, eliminating the need of additional initiators for polymerization. The involvement of electrodes during the hydrogel synthesis yields well‐bonded and deep infiltrated electrode‐electrolyte interfaces. As a case study, we attest that, the in situ‐formed polyanionic hydrogel in Zn‐MnO2 battery substantially improves the stability and kinetics of both Zn anode and porous MnO2 cathode owing to the robust interfaces. This research provides insight to the function of hydrogel electrolyte interfaces and constitutes a critical advancement in designing highly durable aqueous batteries.

Flexible films with three-dimensional ion transport channels: Carbon nanotubes@MnO2 as interlayer spacers in porous graphene electrodes for high-performance supercapacitors

Flexible supercapacitors have a high potential for application in wearable electronics and microdevices, but their commercial appeal is limited because of low energy density. To overcoming this challenge, this paper proposes a strategy to fabricate dense films with high specific capacitance. A composite film with rapid ion diffusion channels and a high density of 0.86 g cm–3 was synthesized by combining porous graphene nanosheets (PGNs), carbon nanotubes (CNTs), and MnO2 nanosheets. The incorporation of CNTs@MnO2 between graphene layers effectively mitigated aggregation and enhanced electrolyte ion diffusion within the dense graphene structure. PGNs and CNTs synergistically established a three-dimensional pathway for efficient ion transport while optimizing electron dynamics. In 1 mol L–1 Na2SO4 electrolyte, the material exhibited a gravimetric capacitance of up to 320 F g–1 at 1 A g–1 and a volumetric capacitance reached 275 F cm–3. Furthermore, the assembled asymmetric supercapacitors, PGNs-CNTs@MnO2//PGNs-CNTs, exhibited a gravimetric energy density of up to 26.4 Wh kg–1 and a volumetric energy density of up to 22.7 Wh L–1. These findings offer insights into advancing flexible supercapacitor technology for diverse applications.

One fell swoop strategized bipolar energy device for triboelectric energy harvesting and electrochemical energy storage

Bipolar energy devices are an essential feature due to the enlargement of intelligent and portable electronics in the present decade. In this work, we demonstrated a bipolar energy device using binder-free MnO2 deposited on carbon cloth (CC) by a one-step electrochemical deposition process (EDP), which was employed for solid-state supercapacitor device (SSCD) and another side of CC with Kapton (KP) as TENG device. The efficiency of the bare CC electrode was boosted by growing uniform porous MnO2 nanoballs on the surface of CC, the standalone CC electrode was aided as a positive tribo-layer, and the Kapton film as the negative tribo-layer in the TENG device. The constructed CC-KP TENG device generated a maximum peak power of 15.11 μW, whereas the MnO2 SSCD delivered energy/power density of 37.41 Wh kg−1/10000 W kg−1, respectively. Overall, the results conclude that these types of bipolar energy devices were splendid and could be used in miniatured low-power electronic devices.

PANI-grafted radially porous MnO2 for supercapacitor applications

PANI-grafted radially porous MnO2 for supercapacitor applications

Porous Mn2O3 nanorods-based electrode for high-performance electrochemical supercapacitor

In this research, we introduce an effective electrode material, i.e. porous manganese oxide (Mn2O3) nanorods (NRs) prepared by simple hydrothermal process, designed for use in electrochemical supercapacitors. XRD analysis unequivocally confirms that the Mn2O3 NRs possess a pure cubic crystalline structure with an Ia3 space group, indicating the high degree of crystallinity and phase purity. Morphological examinations confirmed that the Mn2O3 NRs display a distinct rod-like structure, featuring an average size of around 30 nm, underscoring their nanostructured characteristics. The electrochemical performance of the synthesized Mn2O3 NRs as electrodes for supercapacitors was thoroughly examined, resulting in an impressive specific capacitance of 483 F/g at a scan rate of 10 mV/s. Electrochemical impedance spectroscopy (EIS) analysis was carried out to assess the effective series resistance (ESR), revealing a minimal resistance value of 3.2 Ω, highlighting excellent charge transfer kinetics. Mn2O3 NRs electrode displayed exceptional capacitance retention even after undergoing 500 charge–discharge cycles at a high current density of 5 A/g, indicating their remarkable chemical stability as an electrode material. This study introduces a promising and scalable approach for the development of high-performance supercapacitors, with Mn2O3 NRs as a critical component, and offers valuable insights into the design and engineering of advanced energy storage devices.

Inducing preferential intercalation of Zn2+ in MnO2 with abundant oxygen defects for high-performance aqueous zinc-ion batteries.

Unfavorable proton intercalation leading to the generation and shedding of side reaction products is still a major challenge for the performance of manganese-based aqueous zinc-ion batteries (AZIBs). In this study, we present a porous oxygen-deficient MnO2 (Od-MnO2) synthesized through n-butyllithium reduction treatment to induce preferential Zn2+ intercalation, thereby effectively mitigating the adverse consequences of proton intercalation for high-performance AZIBs. Remarkably, Od-MnO2 as a cathode material for AZIBs exhibits a specific capacity of 341 mA h g-1 at 0.1 A g-1 and 139 mA h g-1 at 5 A g-1, and outstanding long-term stability with a capacity retention of 85.4% for over 1200 cycles at 1 A g-1. Moreover, the Zn/Od-MnO2 pouch cell displays decent durability with a capacity retention of ∼90% for over 200 cycles at 1C. Our study opens new opportunities for the rational design of high-performance cathode materials by regulating the electronic structure and optimizing the energy storage process for rechargeable AZIBs.

Porous MnO nanoplate–graphene hybrid as a high-capacity anode material for lithium ion batteries and its safety characteristics

Robust reduced graphene oxide (rGO) protected porous MnO nanoplates were constructed to relieve the pulverization and gradual aggregation during the conversion process.

Porous MnO/pitch carbon composite as an anode material for low-cost and high-performance lithium-ion battery

With the development of lithium-ion batteries, the demand for low-cost and high-performance anode materials is urgent. In this work, an inexpensive porous MnO and pitch carbon composite was synthesized, through a simple solvent-thermal reaction and carbothermal reduction treatment. As an anode material for lithium-ion batteries, the composite exhibits excellent initial capacity (597 mA h g−1) and remarkable reversible capacity (419 mA h g−1 at 0.1 A g−1 after 150 cycles), which is higher than that of pitch carbon. It also shows outstanding rate performance and long cycling stability. The porous structure is conducive to the diffusion of the electrolyte and activation of the active material. The addition of pitch carbon can improve the conductivity of the composite and alleviate the bulk expansion of MnO, thereby achieving stable electrochemical properties. The proposed simple synthesis strategy is expected to promote the development of low-cost anode materials for lithium-ion batteries.

Sustainable production of Fe-doped MnO2 nanoparticles for accelerated tetracycline antibiotic detoxification

Manganese dioxide (MnO2) has been recognized as one of the natural systems' most active mineral oxidants. However, when it comes to catalytic oxidation of antibiotic applications, pure MnO2 falls short in delivering satisfactory performance. Hence, a set of Fe3+-doped porous MnO2 (0.02Fe–MnO2, 0.1Fe–MnO2, and 0.14Fe–MnO2) nanoparticles were synthesized here via a convenient and energy-efficient one-step reaction method. A series of experiments revealed that Fe-doping strategy enhances the properties of MnO2 host by suppressing the crystalline structure, increasing the amount of surface oxygen defects, and modifying the Mn3+/Mn4+ ratio. Specifically, the tetracycline (TC) removal efficiency of 0.14Fe–MnO2 reaches 92% without the need for any additional co-oxidant, representing a 20% improvement over pristine MnO2 nanoparticles. Moreover, this process shows a fast dynamic (achieving 70% of TC removal in just 5 min) and demonstrates pH-resistance, maintaining high TC removal efficiency (≥90%) over a wide pH range of 3.0–9.0. Mechanical studies reveal that the degradation of TC can be attributed to the oxidation by reactive oxygen radicals and Mn3+, with 1O2 being the primary radical involved in the reaction, accounting for 55% of TC removal. Importantly, cytotoxicity testing indicates that the biotoxicity of TC toward organisms can be effectively mitigated using 0.14Fe–MnO2 nanomaterial. This study presents a readily applicable candidate for economically and conveniently eliminating of environmental TC pollution, thereby reducing the threat posed by TC pollution to the ecosystem.

Fabrication of a Robust and Porous MnO2 Electrode as the Cathode for High‐Performance Aqueous Zinc‐Ion Batteries

Due to their excellent qualities (cheaper raw materials, convenient fabrication method, and high level of safety) of aqueous Zn–MnO2 batteries, they have aroused interest as potential replacements for lithium‐ion batteries. However, the sluggish electron/ion‐transfer rate of MnO2 cathodes hinders their further application as energy‐storage devices. Hence, a simple preparation method is proposed for MnO2 cathodes with porous structures that can effectively reduce the difficulty of electron/ion migration inside an electrode. In addition, the filamentous poly(1,1‐difluoroethylene) generated during the preparation process can act as a supporting structure in the cathode, which maintains the structural stability of the MnO2 cathode, even enduring long‐term charge/discharge cycles. Thus, this cathode has great Zn2+‐storage performance: a high specific capacity of 313 mAh g−1 at 0.1 A g−1 and an impressive rate capability of 106.4 mAh g−1 at an ultrahigh current density of 5 A g−1. In particular, the cathode exhibited superior cycling stability with 69.7% capacity retention after 800 cycles at 3 A g−1. In addition, this cathode presents excellent comprehensive performance of energy conservation. In this method, a versatile approach may be provided for producing cathodes with superior performance in aqueous zinc‐ion batteries systems.

A new multimodal magnetic nanozyme and a reusable peroxymonosulfate oxidation catalyst: Manganese oxide coated-monodisperse-porous and magnetic core-shell microspheres

Monodisperse-porous, polydopamine and manganese oxide coated, core-shell type, magnetic SiO2 (MagSiO2@PDA@MnO2) microspheres 6.4 μm in size were synthesized for the first time, using magnetic, monodisperse-porous SiO2 (MagSiO2) microspheres 6.2 μm in size as the starting material. MagSiO2 microspheres were obtained by a recently developed method namely “staged shape templated hydrolysis and condensation protocol”. In the synthesis, MagSiO2 microspheres were consecutively coated by polydopamine (PDA) and then by a MnO2 layer in the aqueous medium. The pore volume and the specific surface area of monodisperse-porous MagSiO2@PDA@MnO2 microspheres were measured as 0.59 cm3 g−1 and 154 m2 g−1, respectively. Their Mn and Fe contents were determined as 66 ± 1 mg g−1 and 165 ± 5 mg g−1 respectively. MagSiO2@PDA@MnO2 microspheres exhibited multimodal enzyme mimetic behavior with highly superior catalase-like, oxidase-like and peroxidase-like activities. The effective production of singlet oxygen (1O2) and superoxide anion (O2−*) radicals in MagSiO2@PDA@MnO2-peroxymonosulfate (PMS) system was demonstrated by ESR spectroscopy. By evaluating this property, MagSiO2@PDA@MnO2 microspheres were tried as a reusable catalyst for dye removal via peroxymonosulfate (PMS) activation in batch experiments for the first time. The degradation runs were made with, rhodamine B (Rh B), methyl orange (MO) and methylene blue (MB) as the pollutant. The core-shell type design allowing the deposition of porous MnO2 layer onto a large surface area provided very fast, instant removals with all dyes, via both physical adsorption and degradation via PMS activation. In the reusability experiments, the removal yields of MO and Rh B decreased 1.8% and 8.9% over five consecutive runs in batch fashion. MagSiO2@PDA@MnO2 microspheres exhibited very good functional and structural stability in consecutive dye degradations. No significant change was observed in Fe content of microspheres while Mn content exhibited a decrease of 7.4% w/w over 5 consecutive degradation runs.

Spontaneously dissolved MnO: A better cathode material for rechargeable aqueous zinc-manganese batteries

Manganese-based oxides (MnOx) cathodes, with profuse crystal structures and valence states, have raised extensive research interstate for aqueous zinc-manganese batteries. However, the lack of a clear reaction mechanism and source of capacity presents significant challenges for the design and development of advanced manganese-based oxide cathodes. Herein, by exploring the electrochemical activation processes and reaction mechanisms of MnOx (including MnO2, Mn2O3, Mn3O4 and MnO), MnO is proved to hold superior potential for zinc-ion batteries cathode application compared to other MnOx owing to its exceptional spontaneous dissolution activation activity and the largest proportion of Mn. Further, to ulteriorly enhance the dissolution activation and poor electronic conductivity of MnO, a porous carbon matrix-encapsulated MnO nanocomposite (MnO@PC) is successfully synthesized. Moreover, the porous carbon matrix could facilitate electrolyte infiltration and promote adsorption towards Mn2+ and Zn2+ cations, leading to more Zn4SO4·(OH)6·xH2O (ZSH) deposition and greater stability of the reversible ZSH-assisted deposition/dissolution reaction. Therefore, MnO@PC can display improved capacity of 269 mAh g-1 (0.1 A g-1) with an exceptional capacity retention of 93% after 120 cycles in pure ZnSO4 electrolyte. And at 2.0 A g-1, the capacity could reach 75 mAh g-1 and be well maintained in 2000 cycles.

Mass Loading-Independent Lithium Storage of Transitional Metal Compounds Achieved by Multi-Dimensional Synergistic Nanoarchitecture.

Nanostructured transitional metal compounds (TMCs) have demonstrated extraordinary promise for high-efficient and rapid lithium storage. However, good performance is usually limited to electrodes with low mass loading (≤1.0 mg cm-2 ) and is difficult to realize at higher mass loading due to increased electrons/ions transport limitations in the thicker electrode. Herein, the multi-dimensional synergistic nanoarchitecture design of graphene-wrapped MnO@carbon microcapsules (capsule-like MnO@C-G) is reported, which demonstrates impressive mass loading-independent lithium storage properties. Highly porous MnO nanoclusters assembled by 0D nanocrystals facilitate sufficient electrolyte infiltration and shorten the solid-state ions transport path. 1D carbon shell, 2D graphene, and 3D continuous network with tight interconnection accelerate electrons transport inside the thick electrode. The capsule-like MnO@C-G delivers ultrahigh gravimetric capacity retention of 91.0% as the mass loading increases 4.3 times, while the areal capacities increase linearly with the mass loading at various current densities. Specifically, the capsule-like MnO@C electrode delivers a remarkable areal capacity of 2.0 mAh cm-2 at a mass loading of 3.0 mg cm-2 . Moreover, the capsule-like MnO@C also demonstrates excellent performance in full battery applications. This study demonstrates the effectiveness of multi-dimensional synergistic nanoarchitecture in achieving mass loading-independent performance, which can be extended to other TMCs for electrochemical energy storage.

Combination of porous structure and MnO2 modification for improving capacitance of planar BDD electrode

Wearable electronic devices have become a preferred choice for health monitoring, but suffer from low capacitance of planar electrodes. This work aims to improve the capacitive performance through the combination of porous boron-doped diamond (BDD) and MnO2 modification. BDD film was deposited on the substrate of titanium foam using hot-filament chemical vapor deposition (HFCVD). Constant-voltage deposition was then employed to deposit MnO2 on the BDD, and the deposition time was adjusted to evaluate the influence of MnO2 modification on the electrode capacitance. Porous structure formed by titanium foam enables BDD electrode to exhibit larger specific surface area, and reach a capacitance of 67.9 mF/cm2. Porous BDD/MnO2 film (MnO2 deposited for 1500 s) shows pea-like morphology and has optimal capacitive performance. BDD/MnO2-1500 s electrode displays a maximum capacitance of 1383.6 mF/cm2 at a current density of 2 mA/cm2, which is about 195 times that of the planar BDD electrode (7.1 mF/cm2 at a current density of 2 mA/cm2) along with a minimum Rct value of 2 Ω. This allows us to see the fact that improvement mechanism of combining porous structure and MnO2 modification may result from common effect of three following aspects: (1) Porous structure gives BDD superior specific surface area and favorable ion transport channels than planar electrode; (2) Pseudocapacitance effect of MnO2 increases the capacitance density; (3) Pea structure of MnO2 may markedly increase the specific surface area of the film and shorten ion/electronic diffusion distances.