Manganese Doping Research Articles

Effects of boron and manganese doping on electrical poling and properties of 0.94(Bi0.5Na0.5)TiO3-0.06BaTiO3 piezoelectric ceramics

Undoped, 1 mol % B3+ doped (1B), and 1 mol% B3+ - 1 mol% Mn3+ co-doped (1B-1Mn) 0.94(Bi0.5Na0.5)TiO3-0.06BaTiO3 (BNT-6BT) lead-free piezoelectric ceramics were produced by solid-state reaction method. Samples were shaped into disc pellets using high-purity perovskite phase powders of all compositions and were sintered at 1150 °C for 12 h in air. After the structural characterizations of the produced materials by using X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and Archimedes method, electrical property measurements were peformed for the undoped and variously doped samples. As it is a critical step for the improved piezoelectric properties, poling conditions were systematically studied in the range of 5–20 min time duration, at temperatures from room temperature (RT) up to 80 °C, and electric fields between 3 and 5 kV/mm. Major electrical properties were determined in terms of dielectric constant (εr), dielectric loss (tanδ), piezoelectric coefficient (d33), maximum polarization (Pmax), remanent polarization (Pr), coercive field (EC), and maximum strain (Smax). The measured values were compared for undoped, 1B and 1B-1Mn ceramics. The highest εr, d33, Pmax, Pr, and Smax values were obtained for 1B composition after the poling process at RT. Although all other properties were greatly improved by B3+ doping, high values of EC (26.87 kV/cm) and tanδ (0.0314) are considered to be detrimental for many applications. It has been observed that 1B-1Mn composition exhibited significantly reduced EC (22.73 kV/cm) and tanδ (0,0170) values with only a slight drop in other properties. It was also noted that Mn3+ doping increased the poling electric field and temperature, while the influence of poling time on properties was found to be quite negligible for all compositions in this study. As a result, the doping-dependent optimized poling conditions were determined for 1B-1Mn co-doped BNT-6BT lead-free piezoelectric ceramics in this study.

Anticancer Activity of Green Synthesized Manganese Doped Cerium Oxide Nanoparticles Prepared by Using Acacia Concinna Fruit Extract

AbstractPure CeO2 and Ce1‐xMnxO2, where x = 0, 2, 4 and 6% w/w, were synthesized by sol‐gel method using Acacia Concinna fruit extract as a surfactant and stabilizing agent. The synthesized particles were subjected to various characterization techniques, including XRD, HRTEM, FESEM, FTIR, Raman and UV‐Visible spectroscopy. The XRD pattern of the samples demonstrated single phase of CeO2, with cubic fluorite type structure and crystallite size of 6–7 nm. The morphology of the nanoparticles (NPs) was analyzed by FESEM and HRTEM which illustrated an aggregate of irregular spherical nanoparticles and the average particle size is around 18 nm. Raman spectroscopy validated the phase purity and indicated about the structural defects caused by the dopants. The bandgap energy of CeO2 NPs is calculated to be 3.00 eV from the Tauc plot of UV‐Visible spectroscopy, which gradually decreased to 2.43 eV with increase in manganese doping. Cytotoxicity studies signified the role of Mn‐doped CeO2 NPs as a potential nanotherapeutic agent for cancer treatment. The cell viability assay showed that 200 µg/mL of 6% Mn‐doped CeO2 nanoparticles exhibited remarkable cytotoxic effect by inhibiting 50% of cancer cells both in breast and colon cancer cell lines without affecting the healthy cell lines.

The potential role and biological assessment of Cu doped manganese oxide nanoparticles

The potential role and biological assessment of Cu doped manganese oxide nanoparticles

Structural, optical, and dielectric properties of Mn-doped Ce1-xMnxO2 nanocrystals for frequency-dependent device applications

Cerium oxide (CeO2) is a significant oxide semiconductor known for its advantageous electrical, optical, and dielectric properties. This study investigates the effects of manganese (Mn) doping on the structural, optical, and dielectric characteristics of CeO2. Pure and Mn-doped Ce1-xMnxO2 nanocrystalline powders, with Mn concentrations of 0, 1, 3, 5, and 7 %, were synthesized using a co-precipitation method. Structural analysis confirmed the formation of a cubic crystal structure, while surface morphology revealed agglomerated spherical particles. Notably, the band gap of Ce1-xMnxO2 decreased from 2.80 eV to 2.30 eV with increasing Mn content, indicating enhanced electronic properties due to doping. The dielectric properties exhibited a pronounced frequency dependence, with significant variations in dielectric constant and loss, demonstrating the potential of Mn-doped CeO2 as a diluted magnetic semiconductor. These findings underscore the material's applicability in biosensors and optoelectronic devices, paving the way for advancements in frequency-related technologies.

Electron transfer mechanism mediated MOF-derived nanoflowers catalyst for promoting peroxymonosulfate activation and ciprofloxacin degradation

Three MOF-derived nanoparticles were synthesized by manganese doping and calcination of ZIF-67 precursor. The surface physicochemical properties of these materials were compared using SEM, TEM, XRD, FTIR and BET analyses. Among them, cobalt-manganese oxide nanoflowers (CoMn2O4-NFs) exhibited excellent catalytic performance in the degradation of ciprofloxacin (CIP) by activated peroxymonosulfate (PMS), achieving 100 % removal within 30 minutes with a rate constant (kobs) of 0.2960 min−1. The catalytic mechanism was elucidated by quenching experiments, EPR, electrochemical analysis and X-ray photoelectron spectroscopy (XPS). The results show that the non-radical oxidation process was initiated mainly by direct electron transfer and 1O2 (∼80 %), with a small contribution from the radical SO4·- (∼20 %). The nano-confined structure on the surface of CoMn2O4-NFs makes it easy to combine with PMS to form CoMn2O4-NFs/PMS* complexes, which directly capture electrons from CIP to complete the degradation process. The double redox cycle of cobalt-manganese ions and oxygen vacancies on CoMn2O4-NFs could accelerate the electron transfer process. CoMn2O4-NFs maintained high removal efficiency (>99 %) over a wide pH range (3−11), with minimal interference from most environmental anions, demonstrating strong stability and interference resistance. This study provides insights into using metal-based materials for oxidative degradation of organic pollutants via non-radical pathways.

Zn2-xGeO4-GeO2:(x)Mn2+ films with long persistence, intense brightness and high quantum efficiency, deposited by ultrasonic spray pyrolysis

This work shows the synthesis and characterization of the Zn2-xGeO4-GeO2:(x)Mn2+ (x = 0.10, 0.25, and 0.50 at.%) films using the Ultrasonic Spray Pyrolysis (USP) technique. These films were deposited at 500 °C and heat treated at 800 °C for 13 h. X-ray diffraction (XRD) measurements showed the rhombohedral and hexagonal phases of Zn2-xGeO4 (78.8 %) and GeO2 (21.2 %), respectively. SEM micrographs exhibited the surface morphology of these films. The STEM and HAADF show Ge, Zn, and O atomic layers. In addition, XPS was carried out to observe the oxidation states of Mn2+ (75.4 %) and Mn3+ (24.6 %) for the films doped with Mn ions (0.10 at.%). Incorporating manganese ions into the Zn2-xGeO4-GeO2 host lattice generated an extremely green emission, exciting at 250 nm. The photoluminescence and persistence luminescence properties were studied in accordance with the manganese doping concentration. For photoluminescence, it was found that the optimal doping percentage was 0.25 at.%, and for persistence luminescence, it was 0.10 at.% Mn with λex = 250 nm. Quantum efficiency measurements gave a result of 100 %. In addition, preliminary CL measurements were exhibited.

Synergistic improvement of the sulfur redox reaction by MOF-driven dual-defect polyhedral Mn-doped Co1-xS embedded in an N-doped carbon composite host for practical lithium-sulfur batteries

In the quest for practical sulfur hosts for lithium-sulfur batteries, a novel approach has been delineated. By meticulously adjusting the Mn:Co (1:5/1:9/1:1) ratio and the sulfidation temperature, a series of nitrogen-doped carbon nanopolyhedron composites have been synthesized, denoted as 1:9 Mn-Co1-xS-NC@NC, 1:5 Mn-Co1-xS-NC@NC, 1:1 Mn-Co1-xS-NC@NC, and Co1-xS-NC@NC. These materials, inheriting the polyhedral shape and a novel cavity structure from their precursors, exhibit enhanced lithium polysulfide adsorption and catalytic activity due to the introduction of Mn heteroatoms and cobalt vacancies. The resultant S@1:9 Mn-Co1-xS-NC@NC cathode excels in electrochemical performance, delivering an initial discharge capacity of 999.37 mA h g−1 at 1 C, and sustaining 715.65 mA h g−1 over 100 cycles. Notably, at an elevated sulfur loading of 3.05 mg cm−2 (E/S, 14.5 uL g−1), the cathode retains an areal capacity of 3.24 cmmA h cm−2 (corresponding specific capacity of 1067.59 mA h g−1) after 61 cycles at 0.2 C. The synergistic effect of manganese dopants and cobalt vacancies confers superior adsorptive and catalytic properties, presenting a promising avenue for the development of sulfur host materials with tailored morphologies and defect-rich structures.

Interplay of luminescence and magnetic phenomena in Mn-doped ZnS zinc blende nanocrystals: Influence of magnetic doping

This research comprehensively investigates the interplay between luminescence and magnetic phenomena in the zinc blende phase of manganese-doped and undoped zinc sulfide. The study involves the synthesis of zinc sulfide nanocrystals through a soft chemical method, followed by an in-depth experimental characterization. Theoretical studies were conducted using a 2 × 2 × 2 supercell model with 64 atoms to explore the impact of native defects and manganese doping on zinc sulfide's the electronic, magnetic, and optical properties. The research findings offer a detailed physical description of magnetic and optic phenomena observed, underpinned by a strong correlation between theoretical predictions and experimental results. An essential contribution of this work is developing a depiction that elucidates the relationship between optical transitions and spin-exchange in the context of these phenomena.

Manganese doping in zinc based hybrid metal halides to realize highly stable efficient green emission and flexible radiation detection

Extensive studies have been conducted on hybrid metal halides due to their application in radiation detection, solid-state lighting, and solar cells. Here, we present an environmentally friendly zero-dimensional halide, (C9H15N3)ZnBr4, which crystallizes in the P21/c space group. This compound is highly thermally stable, and doping Mn2+ results in a bright green light emission, with an impressive internal quantum efficiency of 52.9 % and an external quantum efficiency of 45.9 % for (C9H15N3)Mn0.3Zn0.7Br4. Combining spectroscopic analysis with first-principles density functional theory (DFT), it is concluded that the high external quantum efficiency arises from efficient energy transfer from the organic component to the [MnBr4]2-. Notably, the (C9H15N3)Mn0.3Zn0.7Br4 luminescence intensity maintains 50 % of its room temperature level even at 400 K. Moreover, these doped powders display exceptional scintillation performance, higher than Bi4Ge3O12. Finally, the radioluminescence intensity of (C9H15N3)Mn0.3Zn0.7Br4@polydimethylsiloxane flexible films is about three times that of Bi4Ge3O12. These features position Mn:(C9H15N3)ZnBr4 as an ideal material for X-ray detection and an efficient green photoluminescent material.

Vacancy-engineered Mn-doped iron oxide nano-crystals for enhanced sonodynamic therapy through self-supplied oxygen

Sonodynamic therapy (SDT) is a minimally invasive therapeutic approach, that uses ultrasound activating sonosensitizers to generate reactive oxygen species (ROS) for inducing the tumor cell death. However, the SDT is always limited by the dissatisfactory performance of sonosensitizers and hypoxic tumor microenvironment (TME). Nano iron oxide is a narrow bandgap semiconductor material with good biocompatibility. The doping of manganese into iron oxide (Mn-doped iron oxide nano-crystals named Mn-Fe2O3 NCs) not only reduced the band gap of iron oxide and altered the valence band position of iron oxide, but also introduced more oxygen vacancies and inhibited the complexation of electrons (e-) and holes (h+), significantly enhancing the ability to generate ROS. The Mn-Fe2O3 NCs improved the hypoxic TME by self-generating oxygen and consuming endogenous glutathione (GSH), which amplified oxidative stress and further enhanced the SDT. The therapeutic results showed that the prepared Mn-Fe2O3 NCs could efficiently inhibit the triple-negative breast cancer (TNBC) cells by SDT (80.49 % inhibition ratio in vivo). Overall, we propose a simple method to design inorganic sonosensitizers for enhancing efficient sonodynamic therapy.

Perovskite manganese oxide-based superposed multilayer film with high emittance tunability for smart radiation devices

Smart radiation devices (SRDs) with the ability to switch emittance according to the radiator surface’s temperature are significant for spacecraft thermal control on exploration missions with drastic changes in thermal environments. However, it is quite urgent to improve the performance of the intelligent thermal control films in SRDs due to the limitations such as low emittance tunability and inappropriate phase transition temperature. Consequently, a film with self-adaptive infrared emittance based on anti-reflective design is proposed in this paper. The main structure is a superposed multilayer film based on a doped perovskite manganese oxide La0.825Sr0.175MnO3 (LSMO) and BaF2 stacks. The emittances of the designed multilayer film are 0.18 and 0.83 at the temperatures of 100 K and 295 K, and therefore the emittance tunability achieves 0.65. Compared with single-layer LSMO, the emittance tunability has increased 25 % approximately. The enhancement in emittance tunability can be explained by the fact that multilayer films with staggered low and high refractive index dielectric layers may cause destructive interference and suppress the Fresnel reflections at high temperatures. In addition, the thickness of dielectric part is carefully designed to avoid the formation of high emissivity Fabry-Perot (FP) resonance when LSMO switches to metallic state at low temperatures. This perovskite manganese oxide-based multilayer film exhibits remarkable intelligent thermal control properties. It provides a significant opportunity to improve the performance of SRDs and a promising potential for maintaining the optimal operating temperature of the spacecraft.

Self‐healable Mn‐doped PVA‐borax hydrogel electrodes for supercapacitor applications

AbstractThis study aims to investigate the effect of Mn doping on the performance of polyvinyl alcohol/borax‐structured (PMB) supercapacitor electrodes for high‐capacity, flexible, and self‐healing supercapacitor electrodes. The PMB electrodes were characterized by x‐ray diffraction (XRD), Raman spectroscopy, and scanning electron microscopy (SEM). Electrochemical characterization was conducted using cyclic voltammetry (CV), which revealed that redox reactions, which are evident at low scan rates, enhance capacitive performance. However, high scan rates introduce limitations owing to the increased vibrations of the PVA chains and incomplete electrolyte polarization. The PMB electrodes exhibited remarkable electrochemical properties and capacitive performances, which were significantly affected by the MnO₂ structure. The electrodes exhibited self‐healing properties and demonstrated flexibility to stretch by up to 40%. In addition, the results indicate that the electrode capacity of the PVA/borax system increased by 2.03 times after 1000 cycles with manganese doping. The solid electrolyte interface (SEI) layer formed on the electrode surface plays a critical role in stabilizing the capacity loss during prolonged charge–discharge cycles. The study concluded that PMB supercapacitors offer higher capacitance in 0‐2 V applications compared to other PVA/borax combination hydrogels. Moreover, the incorporation of metal‐based additives, particularly manganese, enhanced the capacitive performance, and operating voltage levels.

Achieving high acousto-optic properties and low thermal expansion anisotropy in TeO2 single crystals via Mn-doping

TeO2 single crystals have been widely used in military and civilian fields as an excellent acousto-optic (AO) material. However, due to its significant thermal expansion anisotropy and poor mechanical properties, there is a considerable risk of cracking, which hinders further applications in the AO field. Here we successfully grew a TeO2 single crystal doped with 2 % Mn4+ ions (TeO2:0.02Mn4+). This single crystal demonstrates excellent characteristics, including lower acoustic attenuation (α) and larger refractive index values. In addition, it also possesses a higher AO figure of merit (M2) of 832 × 10−15 s3/kg than TeO2 single crystal (∼793 × 10−15 s3/kg). More importantly, the TeO2:0.02Mn4+ single crystal demonstrates low thermal expansion anisotropy within a temperature range of up to 450 °C, indicating a greater practical value. The high AO performance may be attributed to manganese ion doping. The doping of Mn increased the refractive indices by enhancing the electronic polarizability and achieved lower acoustic attenuation by improving mechanical properties. Combining the results of elastic modulus and Raman spectroscopy analysis, it is observed that manganese doping optimizes crystal structure disorder, thus improving the issue of thermal expansion anisotropy. These results indicate that this TeO2:0.02Mn4+ single crystal has significant potential in designing and manufacturing AO devices.

A manganese doping deficient cerium base metal organic framework as radical scavenger for highly-durable proton exchange membrane water electrolysis

Eliminating hydrogen peroxide and free radicals from electrochemical reactions is crucial for mitigating chemical degradation and improving the durability of proton exchange membranes (PEMs). Herein, we prepare a metal–organic framework containing manganese and cerium ions that possesses oxygen vacancy defects and amino functional groups. The prepared Ce4MnBDC-NH2 acts as a catalyst for H2O2 decomposition and as a free radical scavenger, and it is incorporated into a perfluorosulfonic acid (PFSA) ionomer matrix. Featuring large pore volume, high porosity, and abundant amino groups, the Ce4MnBDC-NH2 is locked in a PEM. The obtained Ce4Mn-NH2BDC@PFSA composite membrane exhibits high dimensional stability, excellent proton conductivity and low high-frequency impedance, yielding a proton conductivity of up to 137 mS cm–1 and superior water electrolysis performance of up to 1.83 V at 3.0 A cm–2. Moreover, the obtained Ce4Mn-NH2BDC@PFSA membrane experiences lower weight loss during the Fenton reaction, a low fluoride-ion release rate, and excellent stability in high current density durability testing: its decay rate is only 5.2 μV h–1, which is lower than that of CeO2@PFSA and Nafion 117 membranes. This work provides a promising method to prepare efficient free radical scavengers for steady-state PEM water electrolysis.

Size Uniformity of CsPbBr3 Perovskite Quantum Dots via Manganese-Doping.

The achievement of size uniformity and monodispersity in perovskite quantum dots (QDs) requires the implementation of precise temperature control and the establishment of optimal reaction conditions. Nevertheless, the accurate control of a range of reaction variables represents a considerable challenge. This study addresses the aforementioned challenge by employing manganese (Mn) doping to achieve size uniformity in CsPbBr3 perovskite QDs without the necessity for the precise control of the reaction conditions. By optimizing the Mn:Pb ratio, it is possible to successfully dope CsPbBr3 QDs with the appropriate concentrations of Mn²⁺ and achieve a uniform size distribution. The spectroscopic measurements on single QDs indicate that the appropriate Mn²⁺ concentrations can result in a narrower spectral linewidth, a longer photoluminescence (PL) lifetime, and a reduced biexciton Auger recombination rate, thus positively affecting the PL properties. This study not only simplifies the size control of perovskite QDs but also demonstrates the potential of Mn-doped CsPbBr3 QDs for narrow-linewidth light-emitting diode applications.

Preparation of Manganese Doped Bismuth Oxide for the photocatalytic Degradation of Methylene Blue

The current study describes a unique method for degrading methylene blue dye utilizing Mn-doped Bi2O3 nanoparticles (NPs) exposed to UV light. Bi2O3 nanoparticles (NPs) doped with Mn were produced using a hydrothermal process. Scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and were use to characterize the prepared nanoparticles. It was discovered that the band gaps of Mn/ Bi2O3 NPs are 2%, 3%, and 4%, respectively, and are 4.13 eV, 3.92 eV, and 3.77 eV. Functional group identification using Fourier transforms infrared spectroscopy (FT-IR). Mn-doped Bi2O3 nanoparticles were captured in SEM pictures at various magnifications, and the photos clearly display the particles' dual morphologies, cubic and cylindrical. The Mn-doped Bi2O3 particles were found to be crystalline, with mean diameters of 20 nm, according to the XRD data. The photodegradation efficiency of Mn/Bi2O3 at experimental dye concentrations of 2%, 3%, and 4% was determined to be 90.29, 91.6, and 93.16 percent, respectively, over a 150 minute time interval. At the ideal catalyst dosage of 0.2 g and concentration of 40 ppm, a high percentage of dye degradation was observed. Numerous metals have been doped into zinc oxides, although no work has documented doping of Bi2O3 with Mn. Additionally, it was utilized for the first time to look at the deterioration of Methylene Blue dye.

Colossal Zero-Field-Cooled Exchange Bias via Tuning Compensated Ferrimagnetic in Kagome Metals.

Exchange bias (EB) is a crucial property with widespread applications but particularly occurs by complex interfacial magnetic interactions after field cooling. To date, intrinsic zero-field-cooled EB (ZEB) has only emerged in a few bulk frustrated systems and their magnitudes remain small yet. Here, enabled by high temperature synthesis, we uncover a colossal ZEB field of 4.95 kOe via tuning compensated ferrimagnetism in a family of kagome metals, which is almost twice the magnitude of known materials. Atomic-scale structure, spin dynamics, and magnetic theory revealed that these compensated ferrimagnets originate from significant antiferromagnetic exchange interactions embedded in the holmium-iron ferrimagnetic matrix due to supersaturated preferential manganese doping. A random antiferromagnetic order of manganese sublattice sandwiched between ferromagnetic iron kagome bilayers accounts for such unconventional pinning. The outcome of the present study outlines disorder-induced giant bulk ZEB and coercivity in layered frustrated systems.

Elemental doping tailoring photocatalytic hydrogen evolution of InP/ZnSeS/ZnS quantum dots

Photocatalytic water splitting for hydrogen production has garnered considerable attention as an effective method to alleviate energy shortages. In comparison to cadmium-based quantum dots (QDs) photocatalysts, InP QDs possess a smaller bandgap, larger exciton radius, broader absorption range, and are environmentally friendly. Although InP/ZnS core/shell QDs exhibit immense potential in photocatalysis, they suffer from rapid electron-hole recombination owing to interface defects and lattice mismatch. To address these issues, this study introduces an intermediate ZnSeS shell to reduce defects and tailor QD redox properties through transition metals (manganese and copper) doping. The characterization of QDs was performed from various perspectives, including morphology, element distribution, band structure, and charge transport efficiency. Notably, the photoelectrochemical properties of doped QDs were superior to those of the undoped QDs, while Mn-doped QDs showed inferior catalytic performance compared to the undoped ones. The mechanism of different photoelectrochemical and photocatalytic performances has been studied more intensely. The Mn-doped QDs undergo a process where Mn4+ is converted to Mn2+, consuming electrons in competition with the photocatalytic hydrogen evolution process. Conversely, InP/ZnSeS:Cu/ZnS QDs introduced an additional energy level into the original band structure, capturing some holes and slowing down the electron-hole recombination, thereby providing positive feedback for photocatalytic hydrogen production. Profiting from both the synergies of energy level structure and doping metal state, effective electron-hole separation, and rapid electron transfer to the surface of Cu-doped QDs accomplish the efficient hydrogen generation. The present study offers more possibilities for exploiting the required photocatalytic performance of QD catalysts via elemental doping.

Metal-organic frameworks and composites on their basis: structure, synthesis methods, electrochemical properties and application prospects (a review)

Various types of metal-organic frameworks (MOF) and their structural parameters have been reviewed and their classification has been presented. Most widely used synthesis methods and approaches for MOF and composites on their basis have been discussed. MOF structure is a regular 3D lattice formed by organic linkers and metallic clusters. It has been shown for an example of literary data on MOF synthesis and structural studies that the types of bonds and metals can strongly affect the spatial structure and dimensions of MOF crystals: they can have nano-, micro- and meso-dimensions, be dense or porous, bulk or layered. This variety of structural parameters determines the wide range of their properties and potential applications. Prospects and methods of controlling the shapes of the crystals, their size and spatial bonds between organic components and metal ions have been reviewed. Major attention has been paid to zeolite-like frameworks (ZIF) as the most promising ones from the viewpoint of structure, synthesis and electrochemical current source applications. Discussion has touched on possible modifications and methods of controlling the properties of those MOFs and composites on their basis and introduction of impurities, including those having magnetic properties. Possible synthesis options of complex composites through controlled MOF pyrolysis have been presented, for either small-batch or scalable processes. The effect of heat treatment conditions on the final properties and electrochemical applications of those materials has been demonstrated. ZIF-67 structured MOF doping with one more metal has been presented as variant of modifying the properties of MOF and composites on their basis. For example, the Authors have implemented cobalt MOF synthesis wherein cobalt is partially substituted for manganese at the synthesis stage. Furthermore, a simple water solution co-deposition synthesis technique has been modified with ultrasonication thus reducing the time consumption of the process. Electrochemical studies have shown that the unit electrochemical capacity of pyrolyzed MOF electrodes with partial cobalt substitution for manganese is appreciably higher as compared to the manganese-free materials. The unit capacity and energy density increase with manganese content in the MOF. MOF manganese doping delivers a considerable improvement in the electrochemical parameters of the electrode materials for hybrid supercapacitors on their basis (from 100 to 298 F/g at 0.25 A/g current density). The results suggest that cobalt substitution for manganese is an effective method of improving the electrochemical parameters of MOFs. It has been demonstrated that the development of new approaches to the design of MOF based composite materials and the study of the physicochemical regularities of their interaction with various carriers is an important task.

Enhanced electrochemical performance of MgFeO4 spinel as anode materials for Lithium-ion batteries through manganese doping

Existing graphite anode materials are reaching their limits, and iron-based AB2O4 spinel materials are considered as potential anodes for Li-ion batteries owing to their significant theoretical capacities. In this work, novel nanocrystalline MgFe2-xMnxO4 (x = 0, 0.1, 0.2, and 0.3) spinel ferrites were evaluated as anode materials for high-capacity Li-ion batteries. The Mn-doped MgFe2-xMnxO4 (x = 0, 0.1, 0.2, and 0.3) spinel ferrites were synthesized through a facile sol-gel synthesis method coupled with an annealing process. Their crystal structure, morphology, and purity were examined via X-ray diffraction (XRD), Raman spectroscopy, and scanning electron microscopy (SEM). The X-ray diffraction analyses with Rietveld refinement of the synthesized ferrites reveal pure cubic structure with a characteristic Fd3̅m space group for all prepared samples. This was confirmed by Raman spectroscopy by revealing five spinel Raman active modes. The SEM images showed interconnected nanosized particles for all compositions, which led to a porous morphology. Their electrochemical proprieties as anode materials for Li-ion batteries were examined by cyclic voltammetry and galvanostatic charge-discharge tests. For all compositions, the cyclic voltammetry plots demonstrate the conversion type for the Li-ion storage mechanism. At an applied current density of 150 mA g−1, the compositions x = 0, 0.1, 0.2, and 0.3 show initial discharge/charge capacities of 1235/712, 1187/680, 1542/938, and 1239/768 mAh g−1, respectively. After 100 operational cycles, their galvanostatic charge/discharge capacities remain 529/534, 612/606, 642/663, and 700/700 mAh g−1. However, the compositions x = 0.2 and 0.3 exhibit excellent cycling stability during 100 cycles, even at higher rates. As a result, the Mn doping led to enhanced specific capacity and cycling stability of the MgFe2O4 spinel. The optimized compositions with x = 0.2 and 0.3 are, thus, proposed as promising anodes materials compositions for Li-ion batteries.