Mn-doped Co3O4 Research Articles

Light-weight flexible symmetric supercapacitors based on magnesium-zinc codoped MnO2 nanostructures on carbon cloth as enhanced-performance binder-free electrodes

Developing advanced flexible supercapacitors with high energy and power density is a critical research goal. One promising approach involves combining manganese dioxide (MnO2) with a three-dimensional carbon substrate. This strategy leads to the creation of supercapacitor electrode materials that exhibit high specific capacitance, stability, and environmental friendliness. However, the challenge lies in addressing the low electrical conductivity of MnO2, which limits the rate of electron transfer. The incorporation of metal ions enhances the conductivity of manganese oxide, resulting in a significant increase in lattice defects. These defects create abundant active sites for energy storage. In this study, we developed flexible electrodes based on magnesium-doped MnO2, zinc-doped MnO2, and magnesium-zinc codoped MnO2 nanostructures deposited on carbon cloth (CC) via a one-step hydrothermal method. The supercapacitive behavior of these electrodes was investigated using CV and GCD measurements. The as-prepared electrodes exhibit good electrical conductivity, and their interconnected network structure, composed of sponge-shaped nanostructure layers, results in a large specific surface area. This network also facilitates efficient pathways for effective electron transport. The optimized Mg-Zn codoped MnO2@CC sample exhibits a high capacitance of 79.9 mF/cm² at 0.7 mA/cm² and good rate performance, reaching around 46.59 mF/cm² up to 1.5 mA/cm² in the three-electrode system. Notably, the areal capacitance values calculated from the CV curves for all Mg-Zn codoped MnO2@CC electrodes surpass those of Mg-doped MnO2@CC and Zn-doped MnO2@CC. A flexible symmetric supercapacitor assembled using the best Mg-Zn codoped MnO2@CC as both positive and negative electrodes and PVA-Na2SO4 gel electrolyte delivers a desirable energy density of 0.196 mWh/cm2 at 2.38 mW/cm2. Furthermore, this fabricated supercapacitor demonstrates a broad voltage window of 2.25 V and remarkable cycling stability, retaining 83 % of its initial performance after 4000 charge-discharge cycles.

Co-doped MnO2 nanorods with oxygen vacancies as anode for Li-ion battery

Co-doped MnO2 nanorods with oxygen vacancies as anode for Li-ion battery

Enhanced pseudocapacitive properties of cobalt-doped manganese oxide electrode utilizing magnesium sulfate electrolyte for supercapacitors

This paper investigates the enhanced pseudocapacitive properties of cobalt-doped manganese oxide (Co-doped MnO2) electrode in magnesium sulfate (MgSO4) electrolyte for supercapacitor applications. Co-doped MnO2 was synthesized on nickel foam through a controlled hydrothermal process and specific heat treatment parameters. This resulted in the transformation into α-MnO2 with a 2 × 2 tunnel structure. Morphological investigation illustrates the presence of a hierarchical micro-flower structure with a substantial surface area and mesoporous distribution. The specific surface area of the Co-doped MnO2 electrode significantly increased to 158 m2 g−1, compared to the pristine (bare MnO2) electrode (80 m2 g−1). Electrochemical analyses revealed a specific capacitance of 527 F g−1 at 1 A g−1 in MgSO4 (1 M), showcasing a 1.6 times improvement over Na2SO4 (1 M). The unique structure of the Co-doped MnO2, combined with magnesium ions as efficient electron donors, contributes to superior charge-storage, making it a promising candidate for high-performance supercapacitors. Comprehensive characterizations, such as XRD, XPS, BET, SEM, GCD, and EIS, confirm the advantageous electrochemical performance and durability of the Co-doped MnO2 electrode in MgSO4 electrolyte.

Facile synthesis of oxygen vacancies mediated Co3O4 by Mn doping for high-performance ethanol sensing

The detection of volatile organic compounds (VOCs) at extremely low concentrations holds significant importance in industry and daily life. In this study, Mn-doped Co3O4 materials with a mesoporous structure and oxygen vacancies were synthesized through manual grinding and calcination treatment. The structural characterization measurements showed that Mn doping restrained the crystal growth of the cobaltous oxides which was beneficial for the mesoporous structure, and appropriate oxygen vacancies. The 0.2Mn–Co3O4 sensor operated at the optimum operating temperature of 260 °C, showed a higher response (32.0) to 30 ppm ethanol, which was about 5.81 times as much as that of the pure Co3O4 (5.5). Additionally, to ethanol the 0.2Mn–Co3O4 sensor manifested ultra-low detection limit (11.6 ppb), fast response/recovery time (25/15 s) and superior stability. These exceptional performances may be attributed to the synergistic effect of mesoporous structure formation and appropriate oxygen vacancy concentration. Consequently, the Mn-doped Co3O4 sensor has great potential for detecting low-concentration ethanol in practical applications.

Designing high-performance microwave absorption materials through co-doping strategy: Experimental and theoretical insights

The essence of designing ideal absorption materials is to control the electromagnetic parameters. In this work, doping strategy was adopted to regulate electromagnetic parameters. According to the experimental results and density functional theory calculations, the introduction of Co can make the charge redistribute, distortion increase, bonds length decrease, and bonds energy enhance, which can lead to the reducing of dielectric storage and raising of dielectric loss. Meanwhile, the superfine long nanowires of Co-doped MnO2 can bring abundant surface and interfaces, which improve the polarization relaxations. These changes result in the enhancement of attenuation and improvement of impedance matching feature at the same time. Therefore, the Co-doped MnO2 exhibits excellent microwave absorption performance, the minimal reflection loss is -51.03 dB and effective absorbing bandwidth can reach 7.04 GHz. This work offers an effective approach for the design of high-performance microwave absorption materials, which has been validated through experimental and theoretical evidence.

(Invited) Metal Oxide Nanoparticles for Stable Alkaline Oxygen Evolution Reaction in an Anion Exchange Membrane Electrolyser Cell

One of the key challenges to develop efficient water electrolysis system is to find effective and robust electrocatalysts for the oxygen evolution reaction (OER). Mixed transition metal oxides provide immense possibilities for such purpose.1 , 2 Abundant catalytically active sites could be generated via engineering the defects and oxygen vacancies within the transition metal oxides.3 The catalyst stability could also be improved by incorporating self-healing component into the catalysts .4 In this work, we adopt cobalt oxides as substrate materials to prepare mixed transition metal oxides. The catalysts are synthesized via a combined approach of hydrothermal and annealing processes. The final products are characterized thoroughly by a broad range of characterization techniques, including XRD, TEM, SEM, EDX, and XPS. The OER activities are initially evaluated in a three-electrode system. The results show that the as-prepared catalysts demonstrate high current density at a relatively low overpotential. Moreover, the catalysts exhibit excellent robustness for an 8-hours stability test in a three-electrode testing system. The stability and activity of the catalysts is further assessed in a lab-scale anion exchange membrane (AEM) electrolyser cell setup. Only a small degradation is observed for the best performing catalyst in 12 hours period. The details of the catalyst characterization and electrochemical measurements will be discussed. Acknowledgements This work was funded by European Union’s Horizon 2020 projects FlowPhotoChem (Grant agreement number 862453) and European Innovation Council Pathfinder ANEMEL (Grant agreement number 101071111). References Mohammed-ibrahim, J. & Moussab, H. Tuning the electronic structure of the earth-abundant electrocatalysts for oxygen evolution reaction (OER) to achieve efficient alkaline water splitting – A review. J. Energy Chem. 56, 299–342 (2021).Plevová, M., Hnát, J. & Bouzek, K. Electrocatalysts for the oxygen evolution reaction in alkaline and neutral media. A comparative review. J. Power Sources 507, (2021).Zhang, R. et al. Tracking the Role of Defect Types in Co3O4 Structural Evolution and Active Motifs during Oxygen Evolution Reaction. J. Am. Chem. Soc. (2023) doi:10.1021/JACS.2C10515.Silva, A. L. et al. Mn-doped Co3O4 for acid, neutral and alkaline electrocatalytic oxygen evolution reaction. RSC Adv. 12, 26846–26858 (2022).

Characterization and electrochemical performance of Mn-doped Co3O4 nanoparticles for supercapacitor applications

Characterization and electrochemical performance of Mn-doped Co3O4 nanoparticles for supercapacitor applications

Enhancing pseudo-capacitive behavior in Mn-doped Co3O4 nanostructures for supercapacitor applications

The study focused on Mn-doped Co3O4 samples, which were synthesized successfully using the coprecipitation method and subsequently annealed at 600 °C. The X-ray diffraction (XRD) patterns displayed distinct peaks corresponding to the spinel-cubic structure of Co3O4. Notably, these patterns indicated a preference for (311) plane orientations, which shifted toward lower diffraction angles as the concentration of Mn increased. The analysis of crystallite sizes for the Mn-doped Co3O4 nanoparticles revealed values of 40 nm, 38 nm, and 38 nm for Co3O4:3%Mn, Co3O4:5%Mn, and Co3O4:7%Mn, respectively. Employing X-ray photoelectron spectroscopy (XPS), the study provided insights into the chemical constituents and valence states of the samples. It revealed the presence of both Co2+ and Co3+ ions, along with different oxygen states. The investigation into the electrochemical behavior of the Mn-doped Co3O4 nanostructures highlighted their pseudo-capacitive nature. The specific capacitance and cyclic stability of these structures were found to be contingent on the concentration of Mn doping. Electrochemical impedance spectroscopy (EIS) data unveiled low interfacial charge resistance and enhanced ion diffusion rates. Notably, the most striking results were observed with the 7 wt% Mn-doped Co3O4 nanomaterials. These materials exhibited an outstanding specific capacitance of 537 F/g at a current density of 1.5 A/g. Additionally, they demonstrated remarkable capacity retention of 94% over a span of 1500 cycles. In conclusion, the Mn-doped Co3O4 nanostructures showcased promising electrochemical performance, which could render them suitable for potential applications in supercapacitors.

Ammonium perchlorate catalyzed with novel porous Mn-doped Co3O4 microspheres: superior catalytic activity, advanced decomposition kinetics and mechanisms

Mn-doped Co3O4 nanoparticles of 15 nm were developed via solvothermal synthesis. Mn@Co3O4 microspheres were developed via controlled annealing treatment at 600 °C. Mn@Co3O4 microspheres demonstrated an average diameter of 5.5 µm, with specific area (BET) of 73.7 m2 g−1. The pore diameter was centered at 13.1 nm, and the mean pore size was 16 nm; porous structure could secure extensive interfacial surface area. Mn@Co3O4 microspheres were integrated into ammonium perchlorate (AP) matrix. The catalytic activity of Mn@Co3O4 on AP decomposition was assessed via DSC and TGA/DTG. Whereas Mn@Co3O4/AP nanocomposite demonstrated decomposition enthalpy of 1560 J g−1, pure AP demonstrated 836 J g−1. While Mn@Co3O4/AP nanocomposite demonstrated one decomposition temperature at 310 °C,pure AP exposed two decomposition stages at 298 °C, and 453 °C. Decomposition kinetics was investigated via isoconversional (model free) and model fitting. Kissinger, Kissinger–Akahira–Sunose (KAS), integral isoconversional method of Ozawa, Flyn and Wall (FWO), and differential isoconversional method of Friedman. Mn@Co3O4/AP demonstrated apparent activation energy of 149.7 ± 2.54 kJ mol−1 compared with 173.16 ± 1.95 kJ mol−1 for pure AP. While AP demonstrated sophisticated decomposition models starting with F3 followed by A2, Mn@Co3O4/AP nanocomposite demonstrated A3 decomposition model. Mn@Co3O4 can expose active surface sites; surface oxygen could act as electron donor to electron deficient perchlorate group. Furthermore, Mn@Co3O4/AP could act as adsorbent of released NH3 gas with efficient combustion. This study shaded the light on Mn@Co3O4 as potential catalyst for AP decomposition.

Optimized Ni, Co, Mn Oxides Anchored on Graphite Plates for Highly Efficient Overall Water Splitting

Nickel, cobalt, and manganese oxides are easily obtainable non-noble metal catalysts for water splitting. However, the relationship between composition and catalysts’ performance still needs systematic studies. Herein, guided by theoretical calculations, a low overpotential, easily prepared Mn-doped Co3O4 was deposited on graphite plates for water splitting. The 30% Mn-doped Co3O4 (Co2.1Mn0.9O4) required the lowest overpotential for oxygen evolution reaction (OER), in which the Co2.1Mn0.9O4 reached 20, 30, and 50 mA cm−2 in the overpotentials of 425, 451, and 487 mV, respectively, with 90% IR compensation. Under overall water-splitting conditions, the current density reached 30 mA cm−2 at an overpotential of 0.78 V without IR compensation. Charge density difference analysis illustrates that doped Mn provides electrons for O atoms, and that Mn doping also promotes the electron fluctuation of Co atoms. XPS analysis reveals that Mn-doping increases the chemical valence of the Co atom, and that the doped Mn atom also exhibits higher chemical valence than the Mn of Mn3O4, which is advantageous to boost the form of based-OOH* radical, then decrease the overpotential. Considering the particular simplicity of growing the Co2.1Mn0.9O4 on graphite plates, this work is expected to provide a feasible way to develop the high-performance Co-Mn bimetallic oxide for water splitting.

Enhancing electrochemical performance in aqueous rechargeable Zn-ion batteries through bimetallic oxides of manganese and cobalt as electrode

The capacity of Co3O4//Zn batteries is decreased by the volume change of Co3O4 cathode in practical application, so its advantages are not fully utilized. To improve the capacity of Co3O4//Zn battery, a cathode of Mn-doped Co3O4 based on carbon cloth in aqueous zinc-ion battery was successfully prepared by one-step hydrothermal. Compared to existing preparation processes, greatly reducing preparation time and cost, and the Mn-doped Co3O4 cathode had a unique mesoporous microsphere structure. The battery in aqueous electrolyte had a high charge/discharge voltage of 2.2 V, a high specific capacity of 279.3 mAh/g at 1 A/g, outstanding rate capability, a high energy density of 863.15 Wh/kg, a high power of 1327.9W/Kg and superior cycle stability of 97% capacity retention over 1000 cycles at 5 A/g. The improvement in electrode material provided a new idea for preparing new mesoporous Co3O4 nanocomposites.

Sn and Mn co-doping synergistically promotes the sensing properties of Co3O4 sensor for high-sensitive CO detection

In the realm of gas sensors, p-type metal oxide semiconductor (MOS) usually exhibits inherently low sensitivity toward target gases caused by the hole accumulation layer configuration, which seriously hinders its practical application. Diatomics co-doping is an efficient tactic for adjusting the characteristics of MOS related to gas-sensing due to their synergistic effect. In this work, we controllably synthesized bare Co3O4, Sn-doped Co3O4, Mn-doped Co3O4 and Sn/Mn co-doped Co3O4 nanosheets. The experimental results reveal that Sn/Mn co-doped Co3O4 sample presents porous nanosheets structure. 1 mol% Sn/Mn co-doped Co3O4 sensor presents enhanced response [(Rg-Ra)/Ra = 330 %∼40 ppm at 150 °C] toward CO compared with the bare Co3O4, 1 mol% Sn-doped Co3O4, and 1 mol% Mn-doped Co3O4 nanosheets. Besides, 1 mol% Sn/Mn co-doped Co3O4 nanosheets show a low limit of detection (500 ppb/experimental value), good stability and selectivity. We infer that the good CO-sensing properties may be ascribed to the oxygen vacancies defects generated by Sn4+ and Mn2+/Mn3+ co-doping, high Co3+ ratio, and high specific surface area. This study affords an effective co-doping strategy for enhancing the gas-sensing performances of p-type MOS.

Preparation of Mn-Doped Co3O4 Catalysts by an Eco-Friendly Solid-State Method for Catalytic Combustion of Low-Concentration Methane

Coalbed methane is a significant source of methane in the atmosphere, which is a potent greenhouse gas with a considerable contribution to global warming, thus it is of great importance to remove methane in coalbed gas before the emission. Exploring the economical non-noble metal catalysts for catalytic methane combustion (CMC) has been a wide concern to mitigate the greenhouse effect caused by the emitted low-concentration methane. Herein, a series of Mn-doped Co3O4 catalysts have been synthesized by the environmentally friendly solid-state method. As a result, the Mn0.05Co1 catalyst performed the best CMC activity (T90 = 370 °C) and good moisture tolerance (3 vol% steam). The introduction of an appropriate amount of manganese conduced Co3O4 lattice distortion and transformed Co3+ to Co2+, thus producing more active oxygen vacancies. Mn0.05Co1 exhibited better reducibility and oxygen mobility. In situ studies revealed that methane was adsorbed and oxidized much easier on Mn0.05Co1, which is the crucial reason for its superior catalytic performance.

Ni/Fe Bimetallic Ions Co-Doped Manganese Dioxide Cathode Materials for Aqueous Zinc-Ion Batteries

The slow diffusion dynamics hinder aqueous MnO2/Zn batteries’ further development. Here, a Ni/Fe bimetallic co-doped MnO2 (NFMO) cathode material was studied by density functional theory (DFT) calculation and experimental characterization techniques, such as cyclic voltammetry (CV), galvanostatic intermittent titration technique (GITT) and electrochemical impedance spectra (EIS). The results indicated that the energy band structure and electronic state of MnO2 were effectively optimized due to the simultaneous incorporation of strongly electronegative Ni and Fe ions. Consequently, the NFMO cathode material exhibited a faster charge transfer and ion diffusion dynamics than MnO2 (MO), thus, the assembled NFMO/Zn batteries delivered excellent rate performance (181 mA h g−1 at 3 A g−1). The bimetallic ions co-doping strategy provides new directions for the development of oxide cathode materials towards high-performance aqueous zinc-ion batteries.

Theoretical investigation of quantum capacitance of Co-doped α-MnO2 for supercapacitor applications using density functional theory.

The rapid depletion of fossil fuels and ever-growing energy demand have led to a search for renewable clean energy sources. The storage of renewable energy calls for immediate attention to the fabrication of efficient energy storage devices like supercapacitors (SCs). As an electrode material for SCs, MnO2 has gained wide research interest because of its high theoretical capacitance, variable oxidation state, vast abundance, and low cost. However, the low electric conductivity of MnO2 limits its practical application. The conductivity of MnO2 can be enhanced by tuning the electronic states through substitution doping with cobalt. In the present work, first principles analysis based on density functional theory (DFT) has been used to examine the quantum capacitance (CQC) and surface charge (Q) of Co-doped MnO2. Doping enhanced the structural stability, electrical conductivity, potential window, and quantum capacitance of α-MnO2. The shortened band gap and localized states near the Fermi level improve the CQC of α-MnO2. For the narrow potential range (-0.4 to 0.4 V), the CQC is observed to increase with doping concentration. The highest CQC value at +0.4 V is observed to be 2412.59 μF cm-2 for Mn6Co2O16 (25% doping), five times higher than that of pristine MnO2 (471.18 μF cm-2). Mn6Co2O16 also exhibits better CQC and 'Q' at higher positive bias. Hence, it can be used as an anode material for asymmetric supercapacitors. All these results suggest better capacitive performance of Co-doped α-MnO2 for aqueous SCs and as an anode material for asymmetric supercapacitors.

Self-assembly of Co-doped MnO2 nanorod networks with abundant oxygen vacancy-modified separators for high-performance Li–S batteries

A novel separator of Co-doped MnO2 with abundant oxygen vacancies exhibits a high reversible capacity of 902.0 mA h g−1 at 0.5 C after 200 cycles for Li–S batteries.

Mn2+ Doped Cobalt Oxide and Its Composite with Carbon Nanotubes for Adsorption-Assisted Photocatalytic Applications

In this study, cobalt oxide (Co3O4), Mn-doped Co3O4 (MDCO), and Mn-doped Co3O4-functionalized carbon nanotube (MDCO-CNTs) were synthesized via the co-precipitation method using cobalt nitrate and manganese nitrate as a cobalt and manganese precursor, respectively. Synthesized materials were assessed using different characterization techniques like scanning electron microscopy, X-ray diffraction, and UV-visible spectroscopy. Congo red in an aqueous solution was adopted as the model dye to estimate the adsorption-assisted photocatalytic efficiency of the synthesized materials. The samples studied for adsorpsstion-assisted photocatalysis were found to be highly effective and among all the samples, the best removal performance (80%) was obtained by treating the MDCO-CNTs composite for 50 min at 50 °C. Mathematical modeling shows that all of the samples followed a pseudo-second-order kinetic model and data best fitted to a Langmuir isotherm, implying that the process involved in the removal of Congo red dye is chemisorption.

Ni/Ce co-doping δ-MnO2 nanosheets with oxygen vacancy for enhanced electrocatalytic oxygen evolution reaction

The design and manufacture of strongly engaged, low-cost, and resilient oxygen evolution reaction (OER) electrocatalysts is the most challenging task in electrochemical hydrolysis. Herein, Ce and Ni co-doped MnO2 (NiCe/MnO2) nanosheets (NSs) with oxygen vacancy (VO) and abundant active sites have been prepared in one step employing a defect strategy. The co-doping of Ce/Ni on the one hand reduced the catalyst particle size and increased the specific surface area, which promoted the exposure of more active sites. On the other hand, heteroatom doping altered the species the crystalline surface, stimulating the formation of Vo and thus activating the catalyst performance simultaneously. The OER performance of NiCe/MnO2 NSs was significantly enhanced over the pure δ-MnO2, with an overpotential of 170 mV (10 mA cm−2), which was verified by density functional theory. This work shows a straightforward and practical method for making non-precious metal electrocatalysts with high electrochemical hydrolysis performance.

Manganese-doped cobalt spinel oxide as bifunctional oxygen electrocatalyst toward high-stable rechargeable Zn-air battery

High-performance and low-cost bifunctional electrocatalysts for ORR and OER are urgently required for rechargeable Zn-air batteries. Herein, a series of Mn-doped Co3O4 nanoparticles grown on carbon nanotubes (Mn-Co3O4@CNTs) bifunctional electrocatalysts are designed. Owing to the moderate doped Mn atoms, the Mn-Co3O4 heightens ORR activity via the synergistic effect between Co and Mn atoms, and more Co3+ active sites are exposed on the surface of Mn-Co3O4 to enhance the OER rate. As a result, the 40% Mn-doped Mn-Co3O4@CNTs electrocatalyst exhibits higher ORR (E1/2 = 0.84 V) and OER (η10 = 356 mV at 10 mA cm−2) performance. More significantly, the Mn-Co3O4@CNTs equipped with rechargeable ZAB displays a high power density of 116 mW cm−2, a low charge-discharge voltage gap of 0.94 V at 10 mA cm−2, and superior cycling stability of over 425 h and 1200 cycles, being much more outperforming than Pt- and Ru-based ZABs.

The physical properties of spinel cubic Co3O4 thin films prepared by a PSM

Undoped and Mn-doped Co3O4 films were deposited on heated glasses substrates (TS = 400°C) using a homemade pneumatic spray method (PSM). The solution concentration and deposition time are 0.1 M and 4 min respectively. The effect of manganese doping concentration on structural, optical and electrical properties of cobalt oxide were investigated. The elaborated films were characterized by X-ray diffraction, UV-Vis spectroscopy, atomic force microscopy (AFM) the three-dimensional (3D), energy dispersive spectroscopy (EDS), and four points probe measurements. The XRD study showed that all films were polycrystalline consisting with spinel cubic phase orientated along to (111) plane. The lattice strain and crystallite size were estimated by Williamson-Hall method. The morphology of Mn-doped Co3O4 thin films shows a homogeneous surface with straight acicular nanorods (SANRs). EDS analysis showed the presence of peaks associated with Co, O and Mn elements which confirm the composition of the thin films. The optical band gaps varies from 1.42±0.07 to 1.47±0.07 eV of Egop1and Egop2 varies from 1.87±0.10 to 2.11±0.11 eV. In addition, the electrical measurement show a maximum electrical conductivity (σ= 15.54±0.78 (Ω.cm)-1) at 6% wt of Mn.