Electrodeposited Manganese Oxide Research Articles

Electrodeposited Manganese Oxide on Nickel Foam–Supported Carbon Nanotubes for Electrode of Supercapacitors

Manganese oxide (MnOx) has been electrodeposited on the nickel foam–supported carbon nanotubes (CNTs) and fabricated as the supercapacitor electrode. The three-dimensional (3D) hierarchically porous microstructure of the as-fabricated MnOx/CNT/Ni-foam electrode is beneficial to electrolyte penetration and ions exchange, whereas CNTs provide improved electronic conductivity. The MnOx/CNT/Ni-foam electrode with MnOx loading mass of 100 μg shows a high specific capacitance (SC) of 462 F g−1 with good long cycle stability at a current density of 5 A g−1, suggesting that it is a promising candidate for supercapacitor electrode.

Morphology evolution in anodically electrodeposited manganese oxide nanostructures for electrochemical supercapacitor applications—Effect of supersaturation ratio

An in-depth study of morphology-controlled growth of manganese oxide nanostructures from acetate-containing aqueous solutions was carried out. By varying the deposition parameters, including solution composition, pH value, deposition temperature and current density, a series of manganese oxide nanostructures, including continuous coatings with equiaxed and fibrous features, petal- and flower-like morphologies, discrete oxide clusters, columnar structures and interconnected nanosheets, were anodically deposited on Au-coated glass. Detailed results on the morphology, chemistry and crystal structure of the as-deposited manganese oxide nanostructures suggest that the rich morphology of manganese oxide obtained is primarily determined by the influence of supersaturation ratio on reaction kinetics in the aqueous solutions. The electrochemical properties (specific capacitance, rate capacity and electrochemical impedance response) of manganese oxide nanostructures are carefully examined. The experimental results show that manganese oxide electrodes with oriented nanostructures, such as a columnar structure and an interconnected nanosheet architecture, exhibit enhanced electrochemcial performance by improving manganese oxide utilization.

펄스 전착법을 이용한 전기분해용 망간 산화물 전극의 제조 및 특성

망간 산화물이 전착된 전기분해용 전극의 전기화학적 특성을 조사하기 위해 펄스 전위차 방법을 이용하여 티타늄 망 표면에 망간 산화물을 전착하였다. 전착된 망간 산화물을 확인하기 위해 EDX 분석과 SEM 분석을 실시하였다. 또한 제조된 전극의 EIS 측정을 실시하여 전기화학적 특성을 관찰하였다. 티타늄 망에 펄스 1cycle의 인가 시간이 증가함에 따라 티타늄 망 표면에 형성되는 망간 입자 크기는 증가 하였으며, 10 ms의 펄스 인가 시간에서 응집이 발생하여 약 100 nm 크기의 망간 산화물 불균일 상이 형성되는 것을 SEM으로 관찰하였다. 다양한 조건으로 제조한 전극들은 EIS 측정을 통해 과전위 부근에서 나타나는 전자이동저항(<TEX>$R_{ct}$</TEX>, Charge transfer resistance)을 평가하였고, Tafel plot을 이용하여 제조된 전극이 갖는 과전위를 계산하여 전기분해용 전극으로서의 가능성을 모색하였다. In order to investigate the electrochemical propertied of titanium electrode for electrolysis, manganese oxide was electrodeposited on surface of mesh titanium by pulse voltammetry. The morphological changes and impedance results of manganese oxide electrodeposited electrode were analyzed by SEM and EDX. The size of electrodeposited manganese oxide on mesh titanium was increased with first cycle pulse time increase, and approximately 100 non-uniform manganese oxide was grown at 10 ms pulse polarization time. Charge transfer resistance(<TEX>$R_{ct}$</TEX>) of near the overpotential was analyzed by EIS measurement and the feasibility of prepared electrode was evaluated by the overpotential calculated from Tafel plots.

전기화학적으로 석출된 망간 산화물이 산소 환원 반응에 미치는 영향

This study is concerned the electrocatalytic generation of oxygen gas at electrochem- ically deposited manganese oxide electrode in KOH solution. Manganese oxide nanoparticles electrodeposited onto relatively substrate, e.g glassy carbon, Au, Ti electrode. MnOx is electrode- posited in nanorod structure which cover the overall surface of the substrate. The γ-MnOOH that is kind of manganese oxide species plays a significant role as a catalytic mediator, which promote 4-electron reduction process. Modified electrodes with electrodeposited manganese oxide structures resulted in significant decrease in the anodic polarization compared with the unmodified electrodes in alkaline media.

Cyclic voltammetric study on the catalysis of electrodeposited manganese oxide on the electrochemical oxygen reduction reaction (ORR) in room temperature ionic liquids (RTILs) of 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIBF4) on glassy carbon clectrode

For the first time, the electrochemical oxygen reduction reaction (ORR), was investigated using cyclic voltammetry (CV) on the electrodeposited manganese oxide (MnOx)-modified glassy carbon (MnOx-GC) electrode in the room temperature ionic liquids (RTILs) of EMIBF4, i.e. 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIBF4). The results demonstrated that, after being modified by MnOx on a GC electrode, the reduction peak current of oxygen was increased to some extent, while the oxidation peak current, corresponding to the oxidation of superoxide anion, i.e., O2− was attenuated in some degree, suggesting that MnOx could catalyze ORR in RTILs of EMIBF4, which is consistent with the results obtained in aqueous solution. To accelerate the electron transfer rate, multi-walled carbon nanotubes (MWCNTs) was modified the GC electrode, and then MnOx was electrodeposited onto the MWCNTs-modified GC electrode to give rise to a MnOx/MWCNTs-modified GC electrode, consequently, the improved standard rate constant, ks, originated from the modified MWCNTs, along with the modification of electrodeposited MnOx, showed us a satisfactory electrocatalysis for ORR in RTILs of EMIBF4.

Non-platinum electrocatalysts: Manganese oxide nanoparticle-cobaltporphyrin binary catalysts for oxygen reduction

This study is concerned with the development of non-platinum electrocatalysts for the efficient 4-electron reduction of molecular oxygen to water in acidic media. A binary catalyst composed of electrodeposited manganese oxide nanoparticles (nano-MnO x ) and cobalt porphyrin macro complex (CoP) has been proposed in. The modification of glassy carbon (GC) electrode with CoP alone resulted in a significant positive shift of the oxygen reduction reaction (ORR) compared to the unmodified GC electrode while maintining a 2-electron reduction. That is a positive shift of the onset potential of the ORR of ca. 450 mV was achieved at the former electrode. The modification of the GC electrode with nano-MnO x alone did not affect the ORR peak potential, but caused a remarkable increase in the reduction peak current due to the catalytic disproportionation of the electrogenerated hydrogen peroxide into water and oxygen. The modification of a GC electrode with CoP and nano-MnO x (utilizing the advantages of the individual catalysts) resulted in the occurrence of the ORR at a significantly positive potential with almost double peak current compared to the unmodified GC electrode, suggesting a promising procedure for developing electrocatalysts for oxygen reduction in replacement of costly Pt. XPS and SEM techniques were employed to probe the structural and morphological characterization of the proposed binary catalysts.

Electrosynthesis of Single-Crystalline MnOOH Nanorods onto Pt Electrodes: Electrocatalytic Activity toward Reduction of Oxygen

This study concerns the synthesis and fabrication of manganese oxide nanostructures via electrodeposition onto Pt electrodes from aqueous solution of containing . The structural and morphological characterization of the electrodeposited manganese oxide was performed with scanning electron microscopy and high-resolution transmission electron microscopy. These techniques revealed the formation of intersected nanorods of single-crystalline (manganite phase), in agreement with the results of the X-ray diffraction data. Furthermore, a significant enhancement of the electrocatalytic activity of Pt toward the oxygen reduction reaction (ORR) has been observed in -saturated KOH upon the electrodeposition of nanorods. A surface coverage of MnOOH of ca. 0.3 caused a positive shift of the peak potential of the ORR by about compared to that obtained at bare Pt electrode. Similar Tafel slopes were obtained at the bare and the modified Pt electrodes, indicating that the ORR proceeds via the same rate-determining step at the aforementioned electrodes.

Cyclic Voltammetric Investigation on the Catalysis of Electrodeposited Manganese Oxide on the Electrochemical Reduction of Oxygen (ORR) in Room Temperature Ionic Liquids (RTILs) of 1-Ethyl-3-Methylimidazolium Tetrafluorobroate (EMIBF4) on Glass Carbon (GC) Electrode

In this preliminary work, for the first time, the electrochemical oxygen reduction reaction (ORR) was investigated using cyclic voltammetry (CV) on the electrodeposited manganese oxide (MnO x)-modified glass carbon electrode (MnO x-GC) at room temperature ionic liquids (RTILs) of EMIBF 4, i.e., 1-ethyl-3-methylimidazolium tetrafluorobroate (EMIBF 4). The results demonstrated that, after being modified by MnO x on GC, the reduction peak current of oxygen was increased to some extent, while the oxidation peak current, corresponding to the oxidation of superoxide anion, O 2 - , was attenuated in some degree, suggesting that MnO x catalyzed ORR in RTILs of EMIBF 4, which is consistent with the results obtained in aqueous solution. To accelerate the electron transfer rate, multi-walled carbon nanotubes (MWCNTs) were modified on GC, and then MnO x was electrodeposited onto the MWCNTs-modified GC electrode to give rise to the MnO x /MWCNTs–modified GC electrode; consequently, the improved standard rate constant, 9s, originated from the modified MWCNTs, along with the modification of electrodeposited MnO x, showed us a satisfactory electrocatalysis for ORR in RTILs of EMIBF 4. In addition, not only for the MnO x-modified GC but also for the MnO x/ MWCNTs-modified GC, there is a novel small oxidation peak appearing at – 0.2 V vs . solid Ag/AgCl, implying that the catalysis of MnOx for ORR in EMIBF 4 is somewhat different from that observed in aqueous solution, though the exact interpretation is not achieved in this preliminary work. Initiating the catalysis of MnO x on ORR in RTILs is the main contribution of this work. Further discussions are in progress.

Poly(3-methylthiophene)/MnO 2 composite electrodes as electrochemical capacitors

Composite electrodes prepared by electrodeposition of manganese oxide on titanium substrates modified with poly(3-methylthiophene) (PMeT) were investigated and compared with Ti/MnO 2 electrodes. The polymer films were prepared by galvanostatic deposition at 2 mA cm −2 with different deposition charges (250 and 1500 mC cm −2). The electrodes were characterized by cyclic voltammetry in 1 mol L −1 Na 2SO 4 and by scanning electron microscopy. The results show a very significant improvement in the specific capacitance of the oxide due the presence of the polymer coating. For Ti/MnO 2 the specific capacitance was of 122 F g −1, while Ti/PMeT 250/MnO 2 and Ti/PMeT 1500/MnO 2 displayed values of 218 and 66 F g −1, respectively. If only oxide mass is considered, the capacitances of the composite electrode increases to 381 and 153 F g −1, respectively. The micrographs of samples show that the polymer coating leads to very significant changes in the morphology of the oxide deposit, which in consequence, generate the improvement observed in the charge storage property.

An electrochemical impedance spectroscopy study of electrodeposited manganese oxide films in borate buffers

The reduction-oxidation processes and conducting properties of manganese dioxide films prepared by electrochemical deposition on Pt substrate were studied in borate/boric acid solutions using electrochemical impedance spectroscopy (EIS). The characteristic parameters of the film can be determined as a function of the manganese oxide deposition routine as well as film thickness by application of transfer function analysis using non-linear fit routines. A model developed for thin layer intercalation electrodes, which is based on the insertion of protons and electrons, was used and the diffusion coefficients of protons were calculated for different manganese oxide thicknesses. The reversible behaviour of the manganese oxides during discharge-charge processes as a function of deposition routines was analyzed. Data obtained under a wide variety of experimental conditions show that the film generated on Pt substrate behaves as a n-type semiconductor.

A study of the discharge process of manganese oxide in borate solution using in situ techniques

The change of electrodeposited manganese oxide on gold during the reduction process was investigated in borate solution at pH 9.2, using in situ optical techniques. Raman spectroscopy (RS) showed five bands of manganese dioxide at 410, 480, 520, 580 and 640 cm −1, which decreased and disappeared during the cathodic discharge process. These changes occurred reversibly during the reduction-oxidation cycle. The band at 580cm −1 can be assigned to the MnO stretching because of the correlation found between the XPS analyses and the Raman spectroscopy. In situ Raman spectra of thermal manganese oxide were also performed, and showed the same five Raman bands at 415, 485, 515, 585 and 635cm −1. Electrochemically modulated infrared spectroscopy (EMIRS) is associated with the appearance of a OH stretching band. The changes of RS, EMIRS and XPS reveal the proton—electron injection for the reduction reaction of electrolytic MnO 2.