As-synthesized MnO2 Research Articles

Advanced three-dimensional hierarchical porous α-MnO2 nanowires network toward enhanced supercapacitive performance

Hierarchical α-MnO2 nanowires with oxygen vacancies grown on carbon fiber have been synthesized by a simple hydrothermal method with the assistance of Ti4+ ions. Ti4+ ions play an important role in controlling the morphology and crystalline structure of MnO2. The morphology and structure of the as-synthesized MnO2 could be tuned from δ-MnO2 nanosheets to hierarchical α-MnO2 nanowires with the help of Ti4+ ions. Based on its fascinating properties, such as many oxygen vacancies, high specific surface area and the interconnected porous structure, the α-MnO2 electrode delivers a high specific capacitance of 472 F g−1 at a current density of 1 A g−1 and the rate capability of 57.6% (from 1 to 16 A g−1). The assembled symmetric supercapacitor based on α-MnO2 electrode exhibits remarkable performance with a high energy density of 44.5 Wh kg−1 at a power density of 2.0 kW kg−1 and good cyclic stability (92.6% after 10 000 cycles). This work will provide a reference for exploring and designing high-performance MnO2 materials.

Facile synthesis of nanourchin like manganese oxide electrode material for high performance symmetric supercapacitor

Herein, Manganese dioxide (MnO2) electrode material with a unique morphology was synthesized using low cost, one-step hydrothermal method on flexible carbon cloth substrate. For detail understanding the influence of deposition parameters on the electrochemical performance of MnO2 electrode material, we have synthesized MnO2 at different deposition parameters like deposition time and concentration of precursor solution. The structural, morphological, and surface area properties of the as-synthesized MnO2 nanostructures electrodes deposited at different deposition time as well as different precursor concentration have been systematically characterized by using different physical and electrochemical characterization techniques. The SEM micrographs show different morphologies like nanothorn, nanourchins and naoflowers at concerning deposition time and precursor concentration. Among all the electrodes nanourchin-like MnO2 nanostructures deposited using 0.005 M precursor concentration for 8 h at 160°C shows the highest specific capacitance value of 470.46 F/g at a scan rate of 5 mV/s and good cycling stability after 5000 cycles. For practical application purpose, a symmetric prototype supercapacitor device has been fabricated by using solid-state gel polymer electrolyte. The symmetric device shows good electrochemical performance. Overall results show that nanourchin-like MnO2 grown on carbon cloth substrate is potential electrode material for practical application for energy storage.

Eco-friendly synthesis of MnO2 nanoparticles using Saraca asoca leaf extract and evaluation of in vitro anticancer activity

Manganese oxide nanoparticles (MnO2 NPs) were synthesized through a simple one-pot green synthesis method using Saraca asoca leaves extract (SA-MnO2 NPs), and their physicochemical properties were characterized using various analytical techniques, including electron microscopy (FESEM and TEM), X-ray diffraction (XRD), and electron diffracted X-ray spectroscopy (EDAX). The as-synthesized MnO2 NPs had a highly crystalline structure with a calculated crystalline size of approximately 18 nm and a d-spacing value of 0.216 nm. The morphology of the SA-MnO2 NPs was like stacked cubes with high elemental purity, as confirmed by the EDAX spectrum. Further, confirming the as-obtained crystalline size and d-spacing value from the XRD analysis, the samples were subjected to anti-cancer activities to evaluate their reactance against cancer cell lines. The in vitro anti-cancer activity of the synthesized material was assessed against two breast cancer cell lines, namely MCF7 and MDA-MB-231. The results showed that SA-MnO2 NPs exhibited significantly lower levels of cytotoxicity against these cell lines, indicating their potential as an effective anticancer agent. Further, the IC50 value of SA-MnO2 NPs at 24 h was greater than 20 μg/mL. Therefore, the synthesized SA-MnO2 NPs could be a promising candidate for developing novel breast cancer treatment therapies.

High surface area of crystalline/amorphous ultrathin MnO2 nanosheets electrode for high-performance flexible micro-supercapacitors

Herein, ultrathin MnO 2 nanosheets consisting of crystalline/amorphous phases are prepared by a simple interfacial reaction of surfactant assistance in water-bath with high specific surface area of 317.56 m 2 g −1 , which can accelerate ionic transport and provide more active sites during electrochemical reaction . The as-synthesized MnO 2 nanosheets electrode exhibits remarkable specific capacitance of 163.3 F g −1 at 1 A g −1 in a three-electrode system using 1 M NaSO 4 as electrolyte, and long-term stability with a capacity retention of 89.3% at 3 A g −1 after 10,000 cycles, which can be ascribed to a structural transition from crystalline to amorphous phase during cycling. Meanwhile, the flexible all-solid-state MnO 2 symmetry micro-supercapacitors (MSCs) using sodium alginate bio-hydrogel as electrolyte, the voltage window of the MSCs can be extended to 1.4 V. The MSCs reveals a high areal capacitance of 129.29 mF cm −2 at a current density of 0.2 mA cm −2 . The capacity retention rate up to 94.5% after 4000 cycles, and higher energy density of 35.19 μWh cm −2 at 0.07 mW cm −2 , as well as there is no significant capacitance degradation under different bending states, exhibiting a remarkable electrochemical performance and mechanical flexibility. The crystalline/amorphous ultrathin MnO 2 sheets with high specific surface area were prepared through simple preparation process and found the mechanism of the transformation of MnO 2 from crystalline phase to amorphous phase during the cycle providing a new perspective for the design of high-performance MnO 2 electrodes. • Ultrathin MnO 2 nanosheets are prepared by a simple interfacial reaction of surfactant assistance in water-bath. • The phase structure of ultrathin MnO 2 nanosheets includes crystalline/amorphous states. • The ultrathin MnO 2 nanosheets reveal an ultrahigh specific surface area of 317.56 m 2 g −1 . • The structural transition of ultrathin MnO 2 nanosheets is gradually from crystalline to amorphous phase during cycling. • A flexible micro-supercapacitors based on the ultrathin MnO 2 nanosheets exhibits excellecnt electrochemical performance.

Novel electrochemical sensing platform for detection of hydrazine based on modified screen-printed graphite electrode

The current work aimed to fabricate a screen-printed graphite electrode (SPGE) modified by MnO2 nanorods (MnO2 NRs) for sensing hydrazine. Thus, a facile protocol was adopted to construct the MnO2 nanorods that were subsequently applied to modify the SPGE surface directly. As-synthesized MnO2 NRs/SPGE sensor exhibited a strong sensing behavior towards the hydrazine, with a large peak current and small oxidation potential. This electrochemical sensor in the optimized conditions to detect the hydrazine possessed a low detection limit (0.02 μM), a broad linear dynamic range (0.05–275.0 μM) and an admirable sensitivity (0.0625 μA μM-1). The sensor applicability was practically estimated in real water samples, which revealed successful recovery values.

Realization of high-purity 1T-MoS2 by hydrothermal synthesis through synergistic effect of nitric acid and ethanol for supercapacitors

Phase engineering of molybdenum disulfide (MoS2) can achieve phase transformation from the semiconducting phase (2H-MoS2) with poor conductivity to the metallic phase (1T-MoS2) with superior electrochemical properties. Therefore, it is desirable to prepare high concentration 1T-MoS2 by simple and facile methods. In this work, MoS2 with high concentration of 1T phase is successfully prepared by one-pot hydrothermal synthesis through the synergistic effect of HNO3 and CH3CH2OH, which is stable for more than half of a year. The as-synthesized MoS2 shows high capacitance of 392 F g−1 at 1 A g−1 as used for supercapacitors electrodes, and displays excellent capacitance retention (83% after 10,000 cycles). Asymmetric supercapacitors (ASCs) devices assembled by the as-synthesized MoS2 and MnO2 on carbon cloths, exhibit high energy and power densities (0.194 mWh cm−2 and 13.466 mW cm−2). These results shed a light to realize 1T phase MoS2 through the synergistic effect in hydrothermal processing.

Role of deposition temperature on physical and electrochemical performance of manganese oxide electrode material for supercapacitor application

In the present work, Manganese dioxide (MnO2) with a nanothorn surface architecture was synthesized with a simple, industry scalable, and chemical approach, namely a one-step hydrothermal method. The structural, morphological, and surface area properties of the as-synthesized MnO2 nanostructures electrodes deposited at different deposition temperatures have been systematically characterized by using different characterization The supercapacitive properties of MnO2 electrodes were studied by using cyclic voltammetry, galvonastic charge-discharge, long-term cyclic stability, and electrochemical impedance techniques in 1 M Na2SO4 as electrolyte. The SEM micrographs show different morphologies like nanoflakes, nanoflowers, and nanothorn at concerning deposition temperature. Among all the electrodes of MnO2 nanostructures prepared, nanothorn-like MnO2 nanostructures deposited at 160 °C for 6 h delivered the highest specific capacitance value of 432.52 F/g at a scan rate of 5 mV/s and good cycling stability after 2000 cycles. The excellent large surface area and optimized charge transfer pathway mark the MnO2 and make it potential electrode material for energy storage applications.

Construction of modified screen-printed graphite electrode for the application in electrochemical detection of sunset yellow in food samples

The current work introduced a novel electrochemical sensor (screen-printed graphite electrode (SPGE) modified with MnO2 nanorods anchored graphene oxide nanocomposite (MnO2 NRs/GO) for sensitive determination of sunset yellow. The characterization of MnO2 NRs/GO nanocomposite synthesized through a simple hydrothermal approach was determined employing varied analytical equipment like Field emission-scanning electron microscopy (FE-SEM), Fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction (XRD). Chronoamperometric measurements, differential pulse voltammetry (DPV), cyclic voltammetry (CV) and linear sweep voltammetry (LSV) were recruited to recognize the electrochemical oxidation of sunset yellow on the MnO2 NRs/GO/SPGE. The results of CV proved that the as-synthesized MnO2 NRs/GO nanocomposite has a good electrocatalytic activity toward sunset yellow. The MnO2 NRs/GO/SPGE electrode under optimized conditions using the DPV possessed a linear response for different concentrations of sunset yellow (between 0.01 and 115.0μM) with a low limit of detection (LOD) (0.008μM). Finally, the impressive applicability of this sensor was confirmed via real sample analysis with excellent recoveries (between 97.3 and 104.6%).

Composition controllable green synthesis of manganese dioxide nanoparticles using an edible freshwater red alga and its photocatalytic activity towards water soluble toxic dyes

• MnO 2 nanoparticles have been synthesized using a facile and sustainable strategy. • An edible freshwater red alga, Lemanea manipurensis has been used. • The MnO 2 NPs showed enhanced photocatalytic activity. Composition controllable, facile and ambient temperature green synthesis of high purity manganese dioxide (α-MnO 2 ) nanoparticles has been accomplished via reduction of an aqueous KMnO 4 solution using aqueous extract of an edible freshwater red alga, Lemanea manipurensis . The UV–vis spectrum exhibited a broad band centered at 368 nm and the band gap value obtained from the Tauc plot is 2.44 eV. The TEM analysis confirmed the predominant spherical morphology with extensive nanotwinning of the nanoparticles in the size range 6–28 nm. The FE-SEM depicted as spherical agglomerated morphology. The average hydrodynamic diameter of the nanoparticles is found to be ∼115 nm from DLS study. The X-ray diffraction (XRD) spectrum showed sharp intense peaks which correspond to the crystallization of phase-pure α-MnO 2 nanoparticles in tetragonal crystal morphology. The infrared spectroscopy provided clear evidence of the presence of phytomolecules which are responsible for the stabilization of the nanoparticles. The as-synthesized MnO 2 NPs showed excellent photocatalytic activity for degradation of toxic dyes, rhodamine B (RhB), methyl orange (MO) and methylene blue (MB), the degradation rate being 0.06781, 0.04323 and 0.03831 min −1 , respectively. The photocatalyst is readily recoverable and showed excellent stability even after four cycles. The best photocatalytic performance was observed for RhB degradation under scattered sunlight and with 3 mg MnO 2 NPs exhibiting almost complete degradation (92%) within 30 min of exposure time. The photocatalytic degradation for all the dyes followed a pseudo-first order kinetics.

Efficient ozone decomposition over bifunctional Co3Mn-layered double hydroxide with strong electronic interaction

Ground-level ozone is one of the primary pollutants detrimental to human health and ecosystems. Catalytic ozone decomposition still suffers from low efficiency and unsatisfactory stability. In this work, we report a manganese-based layered double hydroxide catalyst (Co3Mn-LDH), which exhibited a superior ozone decomposition performance with the efficiency of 100% and stability over 7 h under a GHSV of 2,000,000 mL g−1h−1 and relative humidity of 15%. Even when the relative humidity increased to 50%, the ozone decomposition also reached 86%, which significantly exceeds as-synthesized MnO2 and commercial MnO2 in performance. The catalytic mechanism was studied by H2-TPR, FT-IR and XPS. The excellent performance of Co3Mn-LDH can be attributed to its abundant surface hydroxyl groups that ensured the preferentially surface enrichment of ozone, as well as the cyclic dynamic replenishment of electrons between multivalent Co2+/Co3+, Mn2+/Mn3+/Mn4+ and oxygen species that endowed the stable ozone decomposition. This work offers new insights into the design of efficient catalysts for ozone pollution control.

Effect of calcination temperature on morphology and phase transformation of MnO2 nanoparticles: A step towards green synthesis for reactive dye adsorption

Green synthesis of manganese oxide nanoparticles (NPs) was carried out by sol-gel method using Acacia Concinna fruit extract for removal of reactive dye. The effect of calcination temperature on its morphology was investigated. α-MnO2 and Mn3O4 NPs were synthesized at 400 °C and 900 °C respectively and were characterized by PXRD, SEM, TEM, FTIR, BET, Raman and TGA. As-synthesized MnO2 NPs were investigated for the adsorption of Reactive Blue 21 (RB-21) dye. The effect of pH, adsorbent dose, agitation speed, initial dye concentration and temperature on dye removal was explored. pHpzc was calculated from zeta potential study showing positive surface charge below pH 3.18 resulting in electrostatic force of attraction between adsorbate and adsorbent. Both linear and non-linear regression approaches were utilised for the fitting of kinetic models and adsorption isotherms. Adsorption data follows a pseudo second order kinetics and fits well with the Freundlich isotherm model. Thermodynamic parameters such as ΔHo, ΔSo and ΔGo were determined. The dye removal efficiency, in case of MnO2 NPs at pH 3.0 was obtained to be 98% whereas for Mn3O4, no such dye adsorption was observed. The mechanism of adsorption was studied theoretically confirming π-π interaction and H-bonding between the MnO2 and RB dye molecules.

Isotherm, Kinetics and Thermodynamics of Cu(II) and Pb(II) Adsorption on Groundwater Treatment Sludge-Derived Manganese Dioxide for Wastewater Treatment Applications

The ubiquitous occurrence of heavy metals in the aquatic environment remains a serious environmental and health issue. The recovery of metals from wastes and their use for the abatement of toxic heavy metals from contaminated waters appear to be practical approaches. In this study, manganese was recovered from groundwater treatment sludge via reductive acid leaching and converted into spherical aggregates of high-purity MnO2. The as-synthesized MnO2 was used to adsorb Cu(II) and Pb(II) from single-component metal solutions. High metal uptake of 119.90 mg g−1 for Cu(II) and 177.89 mg g−1 for Pb(II) was attained at initial metal ion concentration, solution pH, and temperature of 200 mg L−1, 5.0, and 25 °C, respectively. The Langmuir isotherm model best described the equilibrium metal adsorption, indicating that a single layer of Cu(II) or Pb(II) was formed on the surface of the MnO2 adsorbent. The pseudo-second-order model adequately fit the Cu(II) and Pb(II) kinetic data confirming that chemisorption was the rate-limiting step. Thermodynamic studies revealed that Cu(II) or Pb(II) adsorption onto MnO2 was spontaneous, endothermic, and had increased randomness. Overall, the use of MnO2 prepared from groundwater treatment sludge is an effective, economical, and environmentally sustainable substitute to expensive reagents for toxic metal ion removal from water matrices.

Preparation of Anisotropic MnO2 Nanocatalysts for Selective Oxidation of Benzyl Alcohol and 5-Hydroxymethylfurfural

Anisotropic MnO2 nanostructures, including α-phase nanowire, α-phase nanorod, δ-phase nanosheet, α + δ-phase nanowire, and amorphous floccule, were synthesized by a simple hydrothermal method through adjusting the pH of the precursor solution and using different counterions. The catalytic properties of the as-synthesized MnO2 nanomaterials in the selective oxidation of benzyl alcohol (BA) and 5-hydroxymethylfurfural (HMF) were evaluated. The effects of micromorphology, phase structure, and redox state on the catalytic activity of MnO2 nanomaterials were investigated. The results showed that the intrinsic catalytic oxidation activity was mainly influenced by the unique anisotropic structure and surface chemical property of MnO2. With one-dimensional and 2D structures exposing highly active surfaces, unique crystal forms, and high oxidation state of Mn, the intrinsic activities for MnO2 catalysts synthesized in pH 1, 5, and 10 solutions (denoted as MnO2-pH1, MnO2-pH5, and MnO2-pH10, respectively) were twice higher than those of other MnO2 catalysts in oxidation of BA and HMF. With a moderate aspect ratio, the α + δ nanowire of MnO2-pH10 exhibited the highest average oxidation state, most abundant active sites, and the best catalytic oxidation activity.

Low temperature synthesis of MnO2 nanostructures for supercapacitor application

Herein, we are reporting a facile and novel TEA-ethoxylate assisted low temperature hydrothermal route for synthesis of stable nanostructured MnO2 and their application as an electrode material in supercapacitor. The synthesis was accomplished at two different reaction temperatures viz. 60 °C and 80 °C. The synthesized samples were characterized by various physicochemical characterization techniques viz. XRD, FESEM, FTIR and BET-BJH surface area analysis etc. The morphological study of the as-synthesized MnO2 samples revealed the mixed morphology consisting of nanorod and nanocrystals. The electrochemical studies revealed that the sample prepared at 80 °C exhibits superior electrochemical behavior in 1 mol L−1 Na2SO4 liquid electrolyte solution and demonstrated high specific capacitance of ~348.2 Fg−1 at a current density of 0.1 mAcm−2 and energy density of 43.3 WhKg−1. Further, this electrode showed high rate capability of 89% after 2000 cycles. The electrochemical impedance spectroscopic investigations revealed the low equivalent series resistance for MnO2 electrode. This work represents the promising performance of the nanostructured MnO2 electrode for high energy density supercapacitor application.

Rational design of mesoporous MnO2 microwave absorber with tunable microwave frequency response

To design a single-component absorber with optimizing reflections loss and tunable absorption frequency, the unique lightweight MnO 2 microspheres are successfully synthesized by a template-free method. The as-synthesized MnO 2 microspheres are of mesoporous in diverse specific surface area. By controlling the pH value of the reacting solution, the specific surface area of MnO 2 microspheres is adjustable. The maximum specific surface area of MnO 2 microspheres with mesoporous nature being 90.52 m 2 /g for specimens is obtained from solution of pH = 5. The complex permittivity and permeability of manganese dioxide are tailored to obtain proper impedance matching. Thus, the resultant MnO 2 microspheres exhibit remarkable microwave characteristic in a wax matrix. The minimum reflection loss reaches −31.79 dB at 14.60 GHz, with the effective absorbing bandwidth below −10 dB being 5.78 GHz with a 2 mm thickness. The effective absorption broadband also changes from 10.27 to 13.75 GHz to 12.56–18.00 GHz as the increasing pH value. Such an outstanding microwave absorption performance ascribes to the unique mesoporous structure with designable specific surface area, giving rise to the multiple scattering and reflecting, interfacial polarization, and dielectric relaxation from the abundant interfaces and curved surfaces and impedance matching. • Mesoporous MnO 2 microspheres are facilely synthesized instead of tedious process. • Diverse specific surface area is obtained through adjusting pH of reaction system. • Specific surface area controls property and tunable absorption frequency response. • Maximum specific surface area is 90.52 m 2 /g, pore size concentrates on 4.909 nm. • Minimum reflection loss reaches −31.79 dB with effective bandwidth 5.78 GHz at 2 mm.

Solution Plasma-Assisted Green Synthesis of MnO2Adsorbent and Removal of Cationic Pollutant

In this study, we proposed the solution plasma- (SP-) assisted green synthesis method using plants extracts, i.e., glucose, with the expectation of acting as a reducing agent and promotor for the formation of powder state of nanostructured MnO2. MnO2was simply and rapidly synthesized within 10 min by the SP-assisted method. The structural features and morphology of as-synthesized MnO2were characterized by XRD, Raman, FE-SEM, and TEM analyses. For potential application of as-synthesized MnO2, cationic dye, i.e., methylene blue (MB), removal performance was investigated by batch experiment at an initial concentration ofC0 = 100 mg L−1. The obtained MnO2exhibited effective dye removal ability given highC0, and simultaneously applied plasma discharging further enhanced removal efficiency. These contributions therefore open a new window not only on a powerful and environmentally benign synthesis route for efficient adsorbents but also on supporting multiple removal mechanism.

Synthesis of ε-MnO2 in deep eutectic solvent for visible-light-driven photocatalytic activity

ε-MnO2 were synthesized through Mn2+/MnO4−reaction using a deep eutectic solvent (DES) of choline chloride-urea. The prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and ultraviolet spectroscopy (UV). Moreover, the as-synthesized MnO2 were employed into the photocatalytic degradation of rhodamine B(RhB) dye solution in the presence of H2O2 under visible light irradiation. As a result, the sample synthesized at 25 °C exhibited much higher photocatalytic activity for degradation of RhB.

Preparation of MnO2/porous carbon material with core–shell structure and its application in supercapacitor

Tubular manganese dioxide (MnO2) is synthesized by hydrothermal method, and a silicon dioxide (SiO2) used as template is wrapped on the as-synthesized MnO2. Then poly(styrene-co-divinylbenzene) (PS) as heteropolymeric carbon precursor was wrapped on as-prepared MnO2/SiO2 to form intermediate product MnO2@SiO2@PS. The intermediate products were treated by carbon tetrachloride, stripped template and carbonized, thus the final product MnO2/porous carbon composite (MnO2@PC) with core–shell structure was obtained. The core–shell structural composite is used as an electrode of supercapacitors, which combines high conductivity and high surface specific area of porous carbon material and high electrochemical activity of MnO2. The resulting core–shell MnO2@PC exhibits a maximum specific capacitance of 196.2 F g−1 at a discharge density of 1 A g−1 with capacitance retention of 78.52% over 5000 discharge/charge cycles.

Synthesis of manganese oxide nanorods and its application for potassium ion sensing in water

Potassium is an important body mineral that control the cellular and electrical functions in the body. The potassium ion concentration change in human serum causes the risk of acute cardiac arrhythmia. Hence, it is important to monitor the potassium level in drinking water/food to control the intake and prevent its effect. This paper reports synthesis of manganese oxide (MnO2) nanorods using low-temperature sol-gel method for the fabrication of non-enzymatic potassium ion sensor. The detailed investigation of the as-synthesized MnO2 nanorods were carried out using field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The morphological and structural observations revealed that this method yield small nanorods with average length and diameters of about 210 ± 10 nm and 20 ± 3 nm, respectively. Further, as-synthesized α-MnO2 nanorods were used to fabricate non-enzymatic potassium ion sensor following the deposition of α-MnO2 nanorods on glassy carbon electrode (GCE) with the help of conductive binder. The electrochemical characterizations of fabricated non-enzymatic potassium sensor showed good sensing performance (i.e. sensitivity, selectivity, long term stability, and reproducibility). Moreover, applicability of the sensor to detect potassium ion in water samples were also demonstrated.

Influence of rare earth elements on porosity controlled synthesis of MnO2 nanostructures for supercapacitor applications

Nanostructured MnO2 was synthesized using a facile hydrothermal technique with potassium permanganate as a precursor. Rare earth elements, lanthanum and cerium, were used to control the porosity of the MnO2 nanostructures. Nanorod-, nanoflower-, nanoneedle-, and nanoneedles/nanopetal-shaped MnO2 nanostructures were synthesized by changing the concentration of the rare earth elements. The as-synthesized MnO2 nanorods, La – MnO2 nanoneedles, Ce – MnO2 nanoflowers, and La/Ce – MnO2 nanoneedles/nanopetals were examined using a range of physico chemical characterization techniques. Scanning electron microscopy and transmission electron microscopy – energy dispersive X-ray spectroscopy confirmed the morphology of the MnO2 nanostructures and the elemental distribution. The porous natures of the synthesized MnO2 nanostructures were analyzed by nitrogen adsorption technique. The electrochemical behavior of the MnO2 nanostructures was examined by cyclic voltammetry, charge – discharge and electrochemical impedance spectroscopy tests. The La/Ce – MnO2 nanoneedles/nanopetals electrode exhibited a high specific capacitance of 825 F g−1 at an applied current density of 10 A g−1. The La/Ce – MnO2 nanoneedles/nanopetals were also mixed with 5, 10, 15 and 20 wt% of rGO nanosheets to enhance the electrochemical behavior. The 20 rGO@La/Ce – MnO2 sample showed extraordinary electrochemical behavior; the calculated specific capacitance was 1165 F g−1 at an applied current density of 10 A g−1. A 20 rGO@La/Ce – MnO2 and activated carbon asymmetric supercapacitor coin cell device exhibited ∼93% capacitance retention after 1000 cycles. These results highlight the potential of 20 rGO@La/Ce – MnO2 as an electrode material for supercapacitor applications.