Deposited Manganese Oxide Research Articles

Synthesis of chemical bath deposited Manganese oxide thin films for high performance supercapacitor

The present study addresses the growing need for high-performance supercapacitors, emphasizing the benefits of Manganese oxide (MnO2) thin film as a promising electrode material. Thin film deposition of MnO2 is achieved through Chemical Bath Deposition (CBD) method by varying the deposition time on the stainless steel substrate. In order to investigate impact of deposition time on various physico-chemical properties of MnO2 thin films, different characterizations were carried out like X-ray diffraction, Scanning electron microscopy, Energy dispersive X-ray analysis, X-ray photoelectron spectroscopy, cyclic voltammetry, Galvanostatic charge–discharge analysis. The deposited MnO2 thin films are subsequently studied for their electrochemical properties in a 1 M KOH electrolyte solution. Remarkably, the best specific capacitance is obtained about 296.5 F/g at current density of 0.5 A/g, with 86.42 % retention after 5000 cycles, highlighting the excellent electrochemical performance of the MnO2 thin films deposited at 6 hrs of reaction time. This work highlights valuable insights into the CBD deposited MnO2 thin films for supercapacitor applications, providing a foundation for the development of an efficient, low-cost, and scalable energy storage devices.

Development of transition metal oxide platforms for aptasensing of PSA in cell cultures.

In this study, a novel aptasensor based on a transition metal oxide-modified pencil graphite electrode (PGE) was developed for the diagnosis of early-stage prostate cancer (PCa) via monitoring the prostate-specific antigen (PSA), which is the main biomarker for PCa. Single-use PGEs modified with pulsed deposited manganese oxide (MnOx) film were used to attach the amino-terminated aptamer specific to the PSA via carbodiimide chemistry. The designed aptasensor was placed in an electrochemical cell containing ferri/ferrocyanide ions as a redox probe to measure the charge transfer resistances (Rct) of the electrode surface by electrochemical impedance spectroscopy (EIS) to follow the response of each modification step. The effect of the medium pH on the ionic structure of the aptamer molecule according to its pI value and, thus, the reversing of the direction of the response (ΔRct) by the pH change was also discussed. The level of PSA secreted from PCa cells was investigated using impedimetric transduction. The specificity of the aptasensor was validated through selectivity studies against non-specific tumor markers like VEGF and different cancer cell lines including breast cancer and androgen-insensitive prostate cancer. The developed system showcases a label-free, fast, specific, and cost-effective approach for PSA detection, highlighting the importance of medium pH and the electrostatic environment on the aptamer's response. Our work emphasizes the potential for such aptasensors in clinical diagnostics and paves the way for further exploration into using transition metal oxides in biosensing applications.

Deposition and removal of manganese oxide in zinc electrowinning

Zinc electrowinning in sulfate-based electrolytes produces zinc at the cathode and oxygen gas at the anode. Lead anodes are commonly used despite its low activity towards oxygen evolution and potential environmental hazards. Recent advances in materials for oxygen evolution in acidic electrolytes offers a wide variety of alternative anode catalysts with much higher performance than lead. However, significant formation of manganese oxide alongside oxygen evolution at the anode prevents introduction of new and more active catalytic coatings. In this work, we investigate manganese oxide deposition at IrO2Ta2O5 coated Ti electrodes using chronoamperometry, linear sweep voltammetry and rotating disc electrode. The morphologies of the electrode and deposited manganese oxide are also examined. Oxygen evolution is observed to primarily occur at the electrode and not on the growing manganese oxide deposit. We provide experimental evidence that deposition of manganese oxide gradually becomes limited by diffusion of Mn2＋ within the growing manganese oxide deposit itself. We interpret this to be due to formation of a poorly conducting outer part of the deposit. An electrochemical sequence for removal of deposited manganese oxide is developed and validated in synthetic electrolyte (2molL-1 H2SO4 + 0.15molL-1 Mn2+) and industrial electrolyte. Most importantly the sequence includes formation of a prelayer of manganese oxide at a low electrode potential (1000s at 1.45V or 7Am−2) as we show this to reduce more easily. Furthermore, a short reduction step (100s at 0.4V or −35Am−2) is then sufficient to diminish the adhesion of remaining manganese oxide and allow for easy mechanical removal. Implementing this method can make it possible to replace the currently used anodes in zinc electrowinning with more energy efficient and environmentally friendly anodes.

Fabrication of a Flexible Aqueous Textile Zinc-Ion Battery in a Single Fabric Layer

Zinc-ion batteries (ZIB), with various manganese oxide-based cathodes, provide a promising solution for textile-based flexible energy storage devices. This paper demonstrates, for the first time, a flexible aqueous ZIB with manganese-based cathode fabricated in a single woven polyester cotton textile. The textile was functionalized with a flexible polymer membrane layer that fills the gaps between textile yarns, enabling fine control over the depth of penetration of the spray deposited manganese oxide cathode and zinc anode. This leaves an uncoated region in the textile-polymer network that acts as the battery’s separator. The textile battery cell was vacuum impregnated with the aqueous electrolyte, achieving good wettability of the electrodes with the electrolyte. Additionally, the choice of cathodic material and its influence over the electrochemical performance of the zinc ion battery was investigated with commercially available Manganese (IV) oxide and Manganese (II, III) oxide. The textile ZIB with Manganese (II, III) oxide cathode (10.9 mAh g−1 or 35.6 µA h.cm−2) achieved better performance than the textile ZIB with Manganese (IV) oxide (8.95 mAh g−1 or 24.2 µAh cm−2) at 1 mA cm−2 (0.3 A g−1). This work presents a novel all-textile battery architecture and demonstrates the capability of using manganese oxides as cathodes for a full textile-based flexible aqueous ZIB.

Phase tuning of nebulized spray deposited manganese oxide thin films by the effect of annealing temperature and their linear and non-linear optical parameters

In this work, the annealing temperature induced effect on the formation of various forms of manganese oxide (Mn3O4, Mn3O4:Mn2O3 and Mn2O3) thin films were deposited on glass and quartz substrates by nebulized spray pyrolysis technique. The X-ray diffraction patterns confirm that the film exhibited a phase transition from tetragonal-Mn3O4 to cubic-Mn2O3 structure. From the micro-Raman spectra, the A1g, T2g and Eg modes of Mn3O4 and Mn-O stretching vibration of Mn2O3 are identified. The surface morphological study showed the formation of granular particles and nanorods on the surface. The observed peaks corresponding to Mn2+ and Mn3+ ions in the XPS study are confirmed the formation of Mn3O4 in the as-deposited film. The continuous reduction in optical transmittance of the prepared films was observed as a function of annealing temperature. The in-depth optical parameters like optical energy band gap, dielectric constant, skin depth, Urbach energy, steepness parameter and optical conductivity of the films were extracted from the optical data as a function of annealing temperature. The as-deposited Mn3O4 film has an excellent surface quality due to the lower extinction coefficient value. The Mn2O3 film is highly active in the near-infrared region, because of higher optical conductivity compared to the Mn3O4 films. The obtained optical parameters were further analyzed to determine the non-linear refractive index, linear and third order non-linear optical susceptibility of the films.

Nano-Structural Characteristics and Optical and Electrical Properties of Obliquely Deposited Manganese Oxide Thin Films

Nano-Structural Characteristics and Optical and Electrical Properties of Obliquely Deposited Manganese Oxide Thin Films

An efficient strategy for transferring carbon nanowalls film to flexible substrate for supercapacitor application

The success to transfer graphene films and its engineering architecture, such as carbon nanowalls (CNWs), from the growth substrate to target substrate with large surface area and minimum structural damage is crucial for the future of graphene-based devices. Herein, we purpose a facile and an efficient strategy for transferring CNWs film grown on SiO2/Si substrate to flexible Indium Tin Oxide-Polyethylene Naphthalate (ITO-PEN) substrate. The feasibility of the proposed transfer method is demonstrated by studying the morpho-structural features of the transferred carbon nanowalls (TCNWs) vs the as-grown CNWs using FE-SEM, TEM, EDX, and Raman spectroscopy characterisation techniques. The transfer method successfully provides non-wrinkle and crack-free TCNWs film that preserve mostly the features of as grown CNWs. The TCNWs films with and without anodically deposited Manganese Oxide (MnO2) nanoparticles are explored as possible electrodes for energy storage applications. The MnO2/TCNWs hybrid film ensures a high areal capacitance of 40.3 mFcm−2 and preserves 75% of its initial capacitance as the charging current density increased from 1.0 to 6.0 mA cm−2 and capacitance retention of 99.5% after 2000 cycles at 1.0 mA cm−2. The contribution of this paper resides in paving the way for creating new opportunities for flexible energy storage devices.

Effect of annealing temperature on charge storage kinetics of an electrospun deposited manganese oxide supercapacitor

Nanofibers (NFs) Mn2O3 thin films are prepared by facial and cost effective single-nozzle electrospinning method. The effect of annealing temperature on structural, morphological and surface analysis of NFs coated thin films are investigated. XRD measurement reveals, the formation of cubic crystalline Mn2O3 above 400 °C annealing temperature. Vibration bonds at 515 and 624 cm−1 confirms the presence of Mn2O3 from Fourier transform infrared spectroscopy studies. Field emission scanning electron spectroscopy analysis shows the NFs like morphology of Mn2O3 are observed after heat treatment. The synthesized NFs have high specific surface area with pore size, which is beneficial for charge storage application. Electrochemical performance of electrospunn Mn2O3 NFs are evaluated by using cyclic voltammetry (CV), galvanostatic charge–discharge (GCD) and electrochemical impedance spectroscopy (EIS) techniques. The sample annealed at 300 °C shows maximum specific capacitance of 526 F g−1 at 0.5 mA cm−2 in 1 M aq. Na2SO4 electrolyte. In addition, the NFs sample shows 96% retention in specific capacitance measured up to 1000 CV cycles. The storage of charge due to diffusion and capacitive controlled process are analysed in detail with their percentage contribution. It confirms that, the amorphous Mn2O3 NFs structure have high specific surface area and excellent capacitive performance as compared to crystalline Mn2O3.

Electrocrystallization process of manganese oxide in graphene hydrogel

Electrodepositing manganese oxide in a three-dimensional graphene architecture has barely been explored, and therefore an exploratory but systematic investigation was conducted. A series of manganese oxide/graphene hydrogel electrodes were prepared by galvanostatic technique. The effects of electrodeposition condition, including current density, deposition time, Mn2+concentration and bath temperature, on the morphology and capacitive performance of the deposits were investigated. Nucleation and growth processes of the deposited manganese oxide were then deduced. An optimal capacitance of 452.5 F g−1 was got. This study could provide insight into the crystallization mechanism for electrochemical preparation of MnOx/graphene electrode for advanced energy storage/conversion devices.

Performant Non-Precious Metal-Oxide Electrocatalysts for Oxygen Evolution Reaction in Alkaline Media: From Electrochemical Treatments of Ni Substrates to Surfactant-Assisted Electrodeposition of Perovskites

To meet the global energy demand in a sustainable way, the development of reliable and efficient energy storage systems seems crucial. One of the attractive ways to store energy is through water electrolysis, producing hydrogen as an energy carrier (1). This process is limited by the sluggish kinetics of the oxygen evolution reaction (OER) occurring at the anode of an electrolyzer (eq. 1) (1). 4OH- → O2 + 2H2O + 4e- (Eo 298 = 0.401 VSHE) (1) In the alkaline media, a wide range of electrocatalyst materials including both precious and non-precious group metal compounds such as IrO2, RuO2, nickel oxides, manganese oxides, FeNiOx and perovskites have been intensively studied for OER electrocatalysis (2-8). Among these oxides, manganese oxides along with cobalt-based perovskites (e.g. LaCoOx) have shown promising electrocatalytic activity and long-term durability toward OER (2, 5, 7, 8). To alleviate the low electrical conductivity of such oxides, carbon-based materials are widely being used as catalyst supports and backing layers (5, 9, 10). However, typical carbonaceous materials suffer durability issues mainly caused by carbon corrosion at the high anodic potentials corresponding to the OER (11, 12). The Nickle-based electrodes have been employed in such applications in alkaline media to avoid the carbon corrosion showing high electrocatalytic activity and durability toward OER (13, 14). This study aims at investigating electrocatalytic activity and long-term stability of manganese oxides and perovskites deposited on Ni foams. Novel chemical and electrochemical treatments on the Ni foam substrates have been employed to enhance the durability of the deposited oxides. The deposited manganese oxide has provided the lowest initial OER overpotentials of between 210-230 mV at 10 mA cm-2, losing about 20 mV over 1 hr of testing (Fig. 1). The surfactant-assisted LaCoOx deposit has shown excellent durability over 1 hr of testing with an OER overpotential of about 260 mV at 10 mA cm-2. The electrochemical treatments of the Ni foam substrates have significantly decreased the OER overpotentials of the deposited oxides while increasing their long-term durability for OER through enhanced adhesion of the electrocatalysts to the treated Ni substrates. Figure 1. OER benchmarking study of the electrodeposited non-PGM electrocatalysts. The conditions are as follows: MnOx (T): MnOx electrodeposited in presence of Triton X-100. LaCoOx (T): LaCoOx electrodeposited in presence of Triton X-100. Acid-etched Ni: Mixed acid treatment on the Ni foam. CV Ni: Cyclic voltammetry treatment on the Ni foam for 10 cycles in 45 wt% KOH at 293 K. LSV5: Linear sweep voltammetry treatment on the Ni foam for 5 sweeps in 45 wt% KOH at 293 K. CA1: Chronoamperometry treatment on the Ni foam for 1 min in 45 wt% KOH at 293 K. Test conditions are: 10 mA cm-2. 45 wt% KOH. 400 rpm. 323 K.

(Invited) Fabrication and Operation Under the Same Conditions: Oxygen Reduction on Cathodically Deposited Manganese Oxide

We present the data on the oxygen reduction (ORR) and oxygen evolution (OER) in an alkaline solution for manganese oxide electrocatalysts fabricated by means of cathodic electrocrystallization. The catalysts are deposited from a permanganate alkaline bath, and later operate in the same 1 M NaOH medium. The effect of the deposition potential is addressed. The goal of the study is to obtain carbon-free oxide electrocatalysts with satisfactory activitiy and stability. A qualitative difference of the electrochemical behavior is observed for oxides deposited at low (potentials above ~0.75 V RHE, region 1) and at higher overvoltage (potentials below ~0.75 V (RHE) region 2). Current efficiency is close to 40% in region 1, and increases up to 60% in region 2. All the samples consist of delta-MnO2 (birnessite), but their microstructure is essentially different for electrodeposition from regions 1 and 2. For the deposits fabricated in region 2 the birnessite structure is slightly distorted, while for the deposits prepared in region 1 a complete disordering along the layer stacking direction is observed. The voltammograms of oxides in supporting electrolyte solution undergo fast evolution under potential cycling, accompanied by a decrease of the total charge. Stabilized voltammograms for the samples fabricated in region 2 are featureless and demonstrate a pronounced Ohmic contribution, while for the samples deposited in region 1 a reversible redox behavior is observed, with broad current peaks and formal potential of ~ 0.85 V RHE. The total charge is proportional to the oxide loading in the interval under study (~ 10 – 90 mkg/cm2). Both types of samples do not exhibit reductive degradation at potentials above 0.7 V (RHE). ORR activities are estimated from the rotating disc electrode data in an O2-saturated solution. For oxides fabricated in region 1 the kinetic currents at 0.85 V RHE approach 40-50 A/g (for intermediate loadings), making them promising binder-free ORR catalysts. The ORR activity of oxides electrodeposited at higher overvoltages is an order of magnitude lower corroborating the influence of structure on the electrocatalytic activity. Even though the OER activities of electrodeposited oxides at 1.63 V RHE do not exceed 3 A/g, their remarkable stabilities both in the ORR and in the OER potential interval allows one to hope that these materials may be of interest as a component of hybrid bi-functional catalytic compositions together with other oxides more active in the OER. The authors are grateful to Yu.A. Velikodnyi and A.Ye. Baranchikov for their help with structural characterization of the samples. The work is supported by EraNetRus program, project (#270 NANO-Morf).

Controlling the Interfacial Environment in the Electrosynthesis of MnOx Nanostructures for High-Performance Oxygen Reduction/Evolution Electrocatalysis.

High-performance, nonprecious metal bifunctional electrocatalysts for the oxygen reduction and evolution reactions (ORR and OER, respectively) are of great importance for rechargeable metal-air batteries and regenerative fuel cells. A comprehensive study based on statistical design of experiments is presented to investigate and optimize the surfactant-assisted structure and the resultant bifunctional ORR/OER activity of anodically deposited manganese oxide (MnOx) catalysts. Three classes of surfactants are studied: anionic (sodium dodecyl sulfate, SDS), non-ionic (t-octylphenoxypolyethoxyethanol, Triton X-100), and cationic (cetyltrimethylammonium bromide, CTAB). The adsorption of surfactants has two main effects: increased deposition current density due to higher Mn2+ and Mn3+ concentrations at the outer Helmholtz plane (Frumkin effect on the electrodeposition kinetics) and templating of the MnOx nanostructure. CTAB produces MnOx with nanoneedle (1D) morphology, whereas nanospherical- and nanopetal-like morphologies are obtained with SDS and Triton, respectively. The bifunctional performance is assessed based on three criteria: OER/ORR onset potential window (defined at 2 and -2 mA cm-2) and separately the ORR and OER mass activities. The best compromise among these three criteria is obtained either with Triton X-100 deposited catalyst composed of MnOOH and Mn3O4 or SDS deposited catalyst containing a combination of α- and β-MnO2, MnOOH, and Mn3O4.The interaction effects among the deposition variables (surfactant type and concentration, anode potential, Mn2+ concentration, and temperature) reveal the optimal strategy for high-activity bifunctional MnOx catalyst synthesis. Mass activities for OER and ORR up to 49 A g-1 (at 1556 mVRHE) and -1.36 A g-1 (at 656 mVRHE) are obtained, respectively.

Investigation of Structural, Optical and Topographical properties of Spray Deposited Manganese Oxide thin film for Acetaldehyde Vapor Sensor Application

Thin films of MnO2 are well suited for sensing application due to their structural, optical and topographical properties. MnO2 thin films (with various quantity of precursor solution) are prepared on glass substrate using a simple, low-cost and homemade chemical spray pyrolysis technique. The MnO2 films are characterized by X-ray diffraction (XRD). Transmittance activities of the samples are carried out by ultraviolet-visible (UV-VIS) optical spectroscopy and topography of the film is examined by atomic force microscopy (AFM). The XRD patterns reveal that MnO2 films possess cubic structure with poly crystalline nature. The AFM image implies that nanoparticles are present over the substrate. The vapor sensing characteristics of the MnO2 film(formed with 70 ml quantity of precursor solution) are investigated by chemiresistive method for various concentrations of acetaldehyde vapor at room temperature (∼ 30 °C). The sensing parameters like sensitivity, response and recovery times of the sensor are also studied and reported.

Carbon nanotubes as conducting support for potential Mn-oxide electrocatalysts: Influences of pre-treatment procedures

Different oxygen and nitrogen containing functional groups were created on the surface of the multi-walled carbon nanotubes. The multi-walled carbon nanotubes were treated in ultrasonic bath with sulfuric or nitric acid. Furthermore the surface texture was modified by increase of the roughness. In particular after treatment with the oxidizing nitric acid, in comparison to the H2SO4 or ultra-sonic treated samples, craters and edges are dominating the surface structures. Manganese oxide was deposited on the multi-walled carbon nanotubes by precipitation mechanism. Various manganese oxides are formed during the deposition process. The samples were characterized by elemental analysis, microscopy, thermal analysis, Raman spectroscopy, and by the zeta potential as well as X-ray diffraction measurements. It was shown that the deposited manganese oxides are stabilized rather by surface texture of the multi-walled carbon nanotubes than by created functional groups.

Dramatically improved energy conversion and storage efficiencies by simultaneously enhancing charge transfer and creating active sites in MnOx/TiO2 nanotube composite electrodes

We report a general approach to achieve greatly boosted efficiency of electrochemical process in the photoelectrochemical (PEC) water splitting reaction and supercapacitive process by simultaneously enhancing charge transfer and creating active sites in TiO2 nanotube arrays (TNAs) electrodes. Shallow donor defects self-doping and MnOx deposition are adopted to fulfill the two desired roles, respectively. Our results clearly demonstrated that the enhanced charge transfer resulted from vacuum induced defect self-doping could dramatically improve the water splitting performance and areal capacitance of the pristine TNAs, whilst the deposited manganese oxide species, serving as electrochemically active sites, can further substantially boost their energy conversion and storage efficiencies. As a result, the MnOx/TNAs anode exhibited a photoconversion efficiency of 0.56% in neutral Na2SO4, which is the highest value of TiO2 anode in the same electrolyte under AM 1.5G illumination. Also, the composite electrode presented an areal capacitance of 12.51mFcm−2 at 5mVs−1, nearly three orders of magnitude lager than that of the pristine TNAs counter electrode. Moreover, a specific capacitance of 1117Fg−1 (at 5mVs−1) was achieved based on the mass of deposited MnO2, which also ranks in the top performance level of MnO2 based supercapacitor devices. It is hoped that the present work may shed new light on achieving enhanced performance in energy conversion and storage devices.

Cathodic electrodeposition and electrochemical response of manganese oxide pseudocapacitor electrodes

In this work, we reported the cathodic electrodeposition of manganese oxide films, from nitrate based electrolytes, for pseudocapacitors working in alkaline media. The correlation of the post–thermal treatment, the deposition potential, the electrolyte concentration and the applied charge on surface morphology and electrochemical response of the electrodeposited films were studied. Morphological characteristics and electrochemical response varied depending on the deposition parameter. Via the optimized deposition process, hierarchical nanoparticles/nanoflakes Mn3O4 films were obtained, exhibiting a high specific capacitance value of 416 F g−1 at an applied current density of 1 A g−1 in 1 M NaOH electrolyte. The films exhibited specific capacitance retention of 64% when increasing the current density from 1 A g−1 to 10 A g−1. The films showed the specific capacitance value 196 F g−1 after continuous charge–discharge at 1 A g−1 for 1000 cycles, thus pointing out the possibility of using cathodically deposited manganese oxide films as electrodes for pseudocapacitors.

Metal Doped Manganese Oxide Thin Films for Supercapacitor Application

Co and Fe doped manganese oxide thin films were prepared by anodic deposition at current density of 50 mA cm(-2) using the electrolyte containing manganese sulfate and either cobalt sulfate or ferrous sulfate. Surface morphology and crystal structure of oxides were studied by scanning electron microscope (SEM) and X-ray diffraction (XRD). Chemical composition of materials was analyzed by X-ray energy dispersive spectroscope (EDS), iodometric titration method and complexometric titration method, respectively. Supercapacitive behavior of Co and Fe doped manganese oxide films were characterized by cyclic voltammetry (CV) and impedance spectroscopy (EIS). The results show that the doped manganese oxides are composed of nano fiber-like structure with radius of 5-20 nm and remain amorphous structure after heat treatment at 100 degrees C for 2 hours. The average valence of manganese increases from +3.808 to +3.867 after doping Co and from +3.808 to +3.846 after doping Fe. The doped manganese oxide film electrodes exhibited preferably ideal pseudo-capacitive behavior. The specific capacitance value of deposited manganese oxide reaches a maximum of 175.3 F/g for doping Co and 244.6 F/g for doping Fe. The thin films retained about 84% of the initial capacity even after 500 cycles of charge-discharge test. Doping Co and Fe decreases diffusion and charge transfer resistance of the films. The electric double layer capacitance and capacitor response frequency are increased after doping.

Using Biophysics Tools to Probe Permeability of Ions in Porous Manganese Oxide

Measurements of ion current and reversal potential at different salts have been used to get information on the effective opening, surface characteristics and ionic selectivity of biological channels and solid-state nanopores. For example a non-zero transmembrane potential recorded when a pore is in contact with an electrolyte concentration gradient is a quantitative measure of the pore's preference to an ion of a given charge and/or size. We applied these tools to study ionic properties of nano-voids present in manganese oxide. Mangenese oxide is used in many applications, e.g. batteries, however ionic transport through this material is not well-understood. Single polymer pores with opening diameters of ∼100 nm were used as a template to electrochemically deposit wires of manganese oxide. The material assumes the shape of the pore thus the recorded ion current probes properties of the deposited manganese oxide and not the polymer template itself. Measurements of current-voltage curves at different electrolyte configurations revealed a negative surface charge of the manganese oxide nanovoids and sub<5 nm diameter of the voids' opening. The average opening diameter of the voids were found based on observation of ion current saturation at low salt concentrations, and a calculation of the Debye length. Conductance of the manganese oxide nanovoids in lithium, sodium and potassium salts does not follow the behavior of bulk solutions, which indicates that the voids are sufficiently narrow to differentiate between different monovalant ions.

Electrochemically Prepared Manganese Oxide as a Cathode Material for a Microbial Fuel Cell

This work describes the construction of a mediatorless microbial fuel cell (MFC) using the microorganism Acetobacter aceti as the biocatalyst in the anode compartment with glucose as a fuel. The periplasmic membrane bound pyrroloquinoline quinone (PQQ) containing enzymes of these genera provide fast and highly efficient oxidation of a wide variety of substrates and helps in the direct routing of electrons to the anode. We describe our preliminary findings with regard to the use of electrochemically deposited manganese oxide films on carbon substrates as cathode materials in MFCs. Manganese oxide was electrochemically deposited on carbon paper in the presence and in the absence of the surfactant, sodium lauryl sulfate (SLS). Electrochemical characterizations of the electrodeposited films are carried out by cyclic voltammetry and impedance spectroscopy. Structural characterization of the film is carried out by XRD, XPS, and SEM. The XPS studies reveal that the presence of Mn4+ (as MnO2) in the absence of SLS and Mn3+/2+ (as Mn3O4or Mn2O3 or MnOOH) ion in the presence of SLS. The power output obtained from MnO2 cathode was 666 ± 9 mW m−3 and it is the highest value reported for MFCs with cubical configuration with the same cathode.

The Electrochemical Characterization of Electrochemically Synthesized MnO&lt;sub&gt;2&lt;/sub&gt;-Based Mixed Oxides for Supercapacitor Applications

Nanostructured elements, including: manganese-molybdenum (Mn-Mo) oxide, manganese-molybdenum-tungsten (Mn-Mo-W) oxide, manganese-molybdenum-iron (Mn-Mo-Fe) oxide, manganese-molybdenum-cobalt (Mn-Mo-Co) oxide, manganese-vanadium-tungsten (Mn-V-W) oxide, manganese-vanadium-iron (Mn-V-Fe) oxide and manganese-iron (Mn-Fe) oxide, have been anodically deposited onto titanium substrates by employing an iridium dioxide interlayer (Ti/IrO2 anode). The electrochemical characteristics of the resultant oxide deposits have been investigated by cyclic voltammetry (CV) in an aqueous 0.1 M Na2SO4 solution. The voltammetric behaviors of the oxide deposits observed are significantly influenced by the doped elements. Molybdenum doping is found to be advantageous at improving the capacitance characteristics of anodically deposited manganese oxide. Comparatively, iron and vanadium doping are found to be unfavorable. The structure and crystallinity of these deposits have been identified by X-ray diffraction (XRD). The surface morphologies of these oxides were acquired from field emission scanning electron microscopes (FESEM). The high values of electrical parameters for the doped deposits are attributed to the net-like and sponge-like nanostructure, and low crystallinity of the doped manganese oxides. The deposit of Mn-Mo oxides exhibits an excellent capacitive-like behavior, possessing the maximum specific capacitance of 810 F g-1 at a CV scan rate of 5 mV s-1 in aqueous 0.1 M Na2SO4 solution.