Kinetic characterization of Prussian Blue-modified graphite electrodes for amperometric detection of hydrogen peroxide

Prussian Blue-modified graphite electrodes (G/PB) with electrocatalytic activity toward H₂O₂ reduction were obtained by PB potentiostatic electrodeposition from a mixture containing 2.5 mm FeCl₃ + 2.5 mm K₃[Fe(CN)₆] + 0.1 m KCl + 0.1 m HCl. From cyclic voltammetric measurements, performed in KCl aqueous solutions of different concentrations (5 × 10⁻²–1 m), the rate constant for the heterogeneous electron transfer (k _s) was estimated by using the Laviron treatment. The highest k_s value (10.7 s⁻¹) was found for 1 m KCl solution. The differences between the electrochemical parameters of the voltammetric response, as well as the shift of the formal potential, observed in the presence of Cl⁻ and NO₃⁻ compared to those observed in the presence of SO₄²⁻ ions, points to the involvement of anions in the redox reactions of PB. The G/PB electrodes showed a good electrochemical stability proved by a low deactivation rate constant (0.8 × 10⁻¹² mol cm² s⁻¹). The electrocatalytic efficiency, estimated as the ratio , was found to be 3.6 (at an applied potential of 0 mV vs. SCE; Γ = 5 × 10⁻⁸ mol cm⁻²) for a H₂O₂ concentration of 5 mm, thus indicating G/PB electrodes as possible H₂O₂ sensors.     

Performance characteristics of organic–inorganic composite electrodes in magnesium reserve batteries

Electrochemical characteristics of m-dinitrobenzene (m-DNB) based composite cathode materials involving compounds such as AgCl, TiO₂, HgO and CuCl have been investigated and (Mg AZ31 alloy anode) as an activated battery system using 2 M magnesium perchlorate aqueous electrolyte. The concentration of the composites has been optimized so as to obtain high electrochemical performance of Mg/m-DNB reserve batteries through constant current discharge studies. Mg/m-DNB cells containing 5-wt % of HgO when discharged at current density of 2.1 mA cm⁻² delivered 5.3 Ah capacity corresponds to a columbic efficiency of 97% as compared to the cells without composite.     

Cathodic electrosynthesis of iron oxide films for electrochemical supercapacitors

Cathodic electrosynthesis has been utilized for the fabrication of γ-Fe₂O₃ films, containing chitosan additive as a binder. The films were studied by X-ray diffraction analysis, X-ray photoelectron spectroscopy, scanning electron microscopy, differential thermal analysis, and thermogravimetric analysis. Cyclic voltammetry and chronopotentiometry data showed that the iron oxide films exhibit electrochemical capacitance in the voltage window of −0.9 to −0.1 V vs SCE in 0.25 m Na₂SO₄ and 0.25 m Na₂S₂O₃ aqueous solutions. The highest specific capacitance (SC) of 210 F g⁻¹ was achieved using 0.25 m Na₂S₂O₃ as electrolyte, at a scan rate of 2 mV s⁻¹. The SC decreased with increasing film thickness, scan rate and cycle number. Heat treatment of the films at 140 °C resulted in increasing SC.     

Models of Hypochlorite production in electrochemical reactors with plate and porous anodes

Pseudo two-dimensional finite element models were developed to predict the hypochlorite (chloric(I)) (HOCl + OCl⁻) production by electrolysis of near-neutral aqueous sodium chloride solution, in reactors with (a) an anode and cathode in the form of plates, and (b) a lead dioxide-coated graphite felt anode and titanium plate cathode. The model was used to investigate the feasibility of using a porous anode to achieve high single pass conversions in oxidising chloride ions. For the model reactor with planar anode, the effects of diffusion, migration and convection on the mass transport of the reacting species were considered, whereas with the porous anode, a supporting electrolyte (Na₂SO₄) was notionally present to eliminate the migrational contribution to reactant transport. For an electrolyte flow rate of 10⁻⁶ m³ s⁻¹ (Re = 10 for plate electrodes, Re _porous = 0.76 for porous anode), a cell voltage of 3.0 V and an inlet NaCl of 100 mol m⁻³, the single-pass conversion of Cl⁻ was predicted to increase from 0.45 for the reactor with a planar anode to 0.81 for the reactor with a porous anode. For the same operating conditions, the overall current efficiency was also predicted to increase from 0.71 to 0.77 by replacing the plate with the porous anode.     

Effects of Ho and Ti Doping on Structural and Electrical Properties of BiFeO3 Thin Films

Effects of Ho and Ti ions individual doping and co‐doping on the structural, electrical, and ferroelectric properties of the BiFeO₃ thin films are reported. Pure BiFeO₃, (Bi_0.9Ho_0.1)FeO₃, Bi(Fe_0.98Ti_0.02)O_3+δ, and (Bi_0.9Ho_0.1)(Fe_0.98Ti_0.02)O_3+δ thin films were prepared on Pt(111)/Ti/SiO₂/Si(100) substrates by using a chemical solution deposition method. All thin films were crystallized in distorted rhombohedral structure containing no secondary or impurity phases confirmed by using an X‐ray diffraction study. Changes in microstructural features, such as grain morphology and grain size distribution, for the doped samples were analyzed by a scanning electron microscopy. From the experimental results, a low electrical leakage (1.2 × 10^?5 A/cm² at 100 kV) and improved ferroelectric properties, such as a large remnant polarization (2P_r) of 52 μC/cm² and a low coercive field (2E_c) of 886 kV/cm, were observed for the (Bi_0.9Ho_0.1)(Fe_0.98Ti_0.02)O_3+δ thin film. Fast current relaxation and stabilization observed in the (Bi_0.9Ho_0.1)(Fe_0.98Ti_0.02)O_3+δ imply effective reduction and neutralization of charged free carriers.     

Recovery of platinum group metals from secondary materials. I. Palladium dissolution in iodide solutions

Thermodynamic predictions are reported for platinum and palladium in aqueous ammonia and iodide solutions, to define less aggressive conditions than used hitherto for leaching palladium and platinum from secondary materials. Cyclic voltammetry and amperometry of thin films of palladium, electrodeposited onto rotating vitreous carbon disc electrodes, indicated that partially oxidised adsorbed species passivated dissolution in aqueous ammonium sulfate. By contrast, dissolution rates in aqueous potassium iodide solutions were a significant fraction of that corresponding to the mass transport controlled rate of reduction of tri-iodide, which was demonstrated to be a suitable oxidant for the envisaged metal recovery process. However, iodide concentrations > 1 m were required to achieve adequate solubility of the oxidation products, assumed to be PdI₄²⁻ ions, thereby avoiding inhibition by PdI₂. The reduction of tri-iodide on palladium was very facile, with large exchange current densities and Tafel coefficients; two alternative mechanisms are proposed that fitted experimental results well. In addition, a kinetic model to predict dissolution rates of Pd in tri-iodide solutions gave good agreement with experimental data, provided an equilibrium constant of 10^−4.5 was used for the PdI₂/PdI₄²⁻ reaction, rather than the value of 10^−2.8 derived from thermodynamic data.     

Crystal symmetry and magnetism in Ti substituted Bi0.8Ba0.2FeO3 ceramic

The effect of Ti⁴⁺ substitution on the crystal structure and magnetic properties of the Bi_0.8Ba_0.2FeO₃ ceramic nanoparticles was investigated. Bi_0.8Ba_0.2Fe_1−xTi_xO₃ (x=0, 0.05, 0.10, 0.15 and 0.20) ceramics have been prepared by tartaric acid modified sol-gel method. Rietveld refinement of the XRD profile pattern of Bi_0.8Ba_0.2FeO₃ ceramic revealed the formation of pseudo-cubic (Pm3m) phase and confirms structural distortion on incorporation of Ti⁴⁺ ions, which consequently transform pseudo-cubic (Pm3m) structure to tetragonal (P4mm) structure. The saturation magnetization increases appreciably on Ti⁴⁺ ions substitution in Bi_0.8Ba_0.2FeO₃ and is found to be 0.57 emu/g for Bi_0.8Ba_0.2Fe_0.95Ti_0.05O₃ ceramic. The increase in the magnetization by the substitution of non-magnetic Ti⁴⁺ ions has been ascribed to crystal structure modification made by the Ti⁴⁺ ions. However, a sudden decrease in the magnetization has been observed for Bi_0.8Ba_0.2Fe_0.8Ti_0.2O₃ ceramic nanoparticles. The prominent Ti (3d) – O (2p) hybridization would stabilize the ferroelectric distortion and consequently reduce the magnetization. Scanning Electron Microscope (SEM) image of Bi_0.8Ba_0.2Fe_0.8Ti_0.2O₃ ceramic sample revealed the formation of dense microstructure with uniform grains size.     

Electrochemical studies of titanium in fluoride-chloride molten salts

The interaction between titanium and Ti⁴⁺ ions (K₂TiF₆), the electroreduction reaction of Ti⁴⁺ ions and the anodic reaction of Ti in KCl–NaCl–KF melts with K₂TiF₆ at 973 K were studied by means of electrochemical and physical measurements. It was found that the fluoride ions played a very important role in these reactionsIn KCl–NaCl-3 wt % K₂TiF₆ molten salts with less than 3 wt % KF, the interaction reaction was considered to proceed as Ti⁴⁺+Ti=2Ti²⁺. If the bath contained more than 10 wt% KF, the reaction 3Ti⁴⁺+Ti=4Ti³⁺ occurred.The electrochemical reduction of Ti⁴⁺ (K₂TiF₆) ions in the molten salts with less fluoride ions was observed to proceed according to three reaction steps, i.e. Ti⁴⁺+e=Ti³⁺, Ti³⁺+e=Ti²⁺, Ti²⁺+2e=Ti. In the case of the fluoride ion concentration being higher, two reduction steps, i.e. Ti⁴⁺+e=Ti³⁺, Ti³⁺+3e=Ti were suggested.     

Synthesis,optical, and magnetic properties of six-layered Aurivillius bismuth ferrititanate

This work reports on the preparation, structure, photochemical, and magnetic properties of six-layered Aurivillius bismuth ferrititanates, that is, Bi₇Ti₃Fe₃O₂₁, Bi₇(Ti₂Nb)Fe₃O_21+δ, and Bi₇(Ti₂Mg)Fe₃O_21−δ nanoparticles. The samples were prepared through the modified citrate complexation and precursor film process. The XRD Rietveld refinements were conducted to study the phase formations and crystal structure. The morphological and chemical component characteristics were investigated using SEM, TEM, and EDX analyses. Bi₇Ti₃Fe₃O₂₁, Bi₇(Ti₂Nb)Fe₃O_21+δ, and Bi₇(Ti₂Mg)Fe₃O_21−δ nanoparticles present an indirect allowed transitions with band energies of 2.04, 2.03, and 2.02 eV, respectively. The hybridized (O2p+Fet_2g+Bi6s) formed the valence band (VB) and electronic components of (Ti–3d+Fe–e_g) formed the conduction band (CB) of this six-layered Aurivillius bismuth ferrititanate. The three samples showed efficient photocatalytic degradation of Rhodamine B (RhB) dyes with the excitation wavelength λ > 420 nm. The optical absorption, photodegradation, and magnetic abilities were improved through microstructural modification on “B” site via partial substitution of Mg²⁺ and Nb⁵⁺ for Ti⁴⁺. The photocatalytic results were discussed based on the layer structure and multivalent Fe ions. Fe^3+/2+ in the perovskite slabs (Bi₅Fe₃Ti₃O₁₉)²⁻ could act as the catalytic mediators in the photocatalysis process. As a photocatalyst, Aurivillius Bi₇(Ti₂Mg)Fe₃O_21−δ nanoparticle is advantageous due to its photocatalytic and magnetically recoverable abilities.     

The compatibility of transition metal oxide/carbon composite anode and ionic liquid electrolyte for the lithium-ion battery

Three types of transition metal oxide/carbon composites including Fe₂O₃/C, NiO/C and CuO/Cu₂O/C synthesized via spray pyrolysis were used as anode for lithium ion battery application in conjunction with two types of ionic liquid: 1 M LiN(SO₂CF₃)₂ (LiTFSI) in 1-ethyl-3-methyl-imidazolium bis(fluorosulfonlyl)imide (EMI-FSI) or 1-methyl-1-propylpyrrolidinium bis(fluorosulfonyl)imide (Py13-FSI). From the electrochemical measurements, the composite electrodes using Py13-FSI as electrolyte show much better electrochemical performance than those using EMI-FSI as electrolyte in terms of reversibility. The Fe₂O₃/C composite shows the highest specific capacity and the best capacity retention (425 mAh g⁻¹) under a current density of 50 mA g⁻¹ for up to 50 cycles, as compared with the NiO/C and CuO/Cu₂O/C composites. The present research demonstrates that Py13-FSI could be used as an electrolyte for transition metal oxides in lithium-ion batteries.     

Microstructural and multiferroic properties in layered perovskite-related Sm6Ti4Fe2O20

Layered perovskite-related Sm₆Ti₄Fe₂O₂₀ compound was successfully synthesized through the intercalation of bilayer SmFeO₃ into the Sm₂Ti₂O₇ with pyrochlore structure by means of floating-zone melting technique. The microstructural properties were characterized using aberration-corrected scanning transmission electron microscopy and X-ray diffraction. Electron energy-loss spectroscopy investigation reveals that the Fe³⁺ ions prefer to occupy the inner sites within the perovskite-like layers. This compound exhibits clearly the spin glass-like behavior as demonstrated by the magnetic properties measurement. Such complex magnetic behavior could be attributed to the partial chemical order of Ti/Fe over the B sites and the interactions between magnetic ions including Sm³⁺ and Fe³⁺. In addition, the multiferroic behavior with the coexistence of the ferroelectricity and ferromagnetism was well established by magnetic and piezoresponse measurements.     

Hydrogen evolution on RuxTi1−xO2 in 0.5 M H2SO4

Hydrogen evolution from 0.5 M H₂SO₄ on Ti electrodes coated with a Ru_xTi_1−xO₂ (x=0.04-0.5) layer has been studied by potentiostatic polarisation, cyclic voltammetry and ac-impedance spectroscopy. The results indicate that after a certain activation period the performance of such an electrode coating is comparable to platinum. The addition of small amounts of sodium molybdate increased the capacitance of the electrode and a reduction of the performance was observed. Increasing the temperature of the pure electrolyte from 20 to 75 °C caused an increase in the rate of the hydrogen evolution and in addition an increase of the electrode capacitance. The electrodes have been found to be rather tolerant to chloride and Fe²⁺ ions, and could hence be promising candidates as catalyst materials for solid polymer water electrolysis systems. From steady state measurements the Tafel slopes were found to change from −105 mV/decade for pure titanium to about −40 mV/decade for the (RuTi)O₂ coated electrodes. The exchange current densities were calculated from the steady state curves, as well as from impedance data, to be about 10⁻⁴ A cm⁻² after activation.     

Electrochemical treatment of bisphenol-A using response surface methodology

The decomposition of bisphenol-A (BPA) in synthetic solution and in municipal effluent was investigated using an electro-oxidation process. Electrolysis was conducted using a cylindrical electrolytic cell containing two circular anodes (expanded metal) and two circular cathodes (stainless steel) alternated in the electrode pack. Different anode materials (Ti/SnO₂, Ti/IrO₂ and Ti/PbO₂) were tested, and Ti/PbO₂ was found to be the most effective electrode for BPA degradation. An experimental design methodology (2³ Box–Behnken design) was applied to determine the optimal experimental conditions in terms of cost effectiveness. The BPA concentration (C ₀ = 1.0 mg l⁻¹) could be optimally diminished by up to 90% by applying a current intensity of 2.0 A for a 100-min reaction period in the presence of 250 mg Na₂SO₄ l⁻¹ (used as a supporting electrolyte). Then, the optimal conditions were applied on a municipal wastewater effluent (sampled after secondary treatment) artificially contaminated with 1 mg BPA l⁻¹ without the addition of a supporting electrolyte. The treatment was more effective with the municipal effluent due to the presence of a high concentration of chloride ions that could easily be transformed into active chlorine. BPA could be oxidized by both direct anodic electrochemical oxidation (by means of OH·) and indirect electrochemical oxidation via mediators, such as hypochlorous acid generated by chloride oxidation. Both actions (direct and indirect effects) lead to the formation of powerful oxidizing agents capable of rapidly oxidizing BPA.     

Electrodeposition of zinc–iron alloy from an alkaline bath in the presence of sorbitol

The chronopotentiometric technique was used to analyze the electrodeposition of Fe–Zn film on a Pt electrode. Three different Fe³⁺/Zn²⁺ molar ratios, Fe26.8 wt.%–Zn73.2 wt.%, Fe46 wt.%–Zn54 wt.% and Fe66.6 wt.%–Zn33.4 wt.%, were used in a solution containing sorbitol as the Fe³⁺-complexing agent, with a total concentration of the two cations of 0.20 M. Coloration of Fe–Zn films were light gray, dull dark gray and bright graphite, depending on the Fe³⁺/Zn²⁺ ratios in the deposition bath. The highest stripping to deposition charge density ratio was 47.5%, at 15 mA cm⁻² in the Fe26.8 wt.%–Zn73.2 wt.% bath. Energy dispersive spectroscopy indicated that the codeposition type of Fe and Zn in the Fe26.8 wt.%–Zn73.2 wt.% and Fe46 wt.%–Zn54 wt.% baths was normal at all j_d tested, while in the Fe66.6 wt.%–Zn33.4 wt.% bath there was a transitional current density from normal to equilibrium codeposition at 50 mA cm⁻². Scanning electron microscopy showed that Fe–Zn films of high quality were obtained from the Fe66.6 wt.%–Zn33.4 wt.% and Fe26.8 wt.%–Zn73.2 wt.% baths, since the films were smooth. X-ray analysis of the Zn–Fe films obtained at 15, 25 and 50 mA cm⁻², in the Fe26.8 wt.%–Zn73.2 wt.%, Fe46 wt.%–Zn54 wt.% and Fe66.6 wt.%–Zn33.4 wt.% plating baths, suggested the occurrence, in general, of a mixture of Fe₁₁Zn₄₀, Fe₄Zn₉, βFe, αFe, Fe₂O₃, Zn and PtZn alloys in the deposit.     

Reaction between Hydrosulfide and Iron/cerium (hydr)oxide: Hydrosulfide Oxidation and Iron Dissolution Kinetics

Hydrosulfide oxidation and iron dissolution kinetics were studied at normal pressure, under inert (N₂) atmosphere, in a liquid–solid mechanically-stirred slurry reactor. The kinetic variables undergoing variations were: hydrosulfide initial concentration (0.90–3.30 mmol/L), oxide initial surface area (16–143 m²/L) and pH (8.0–11.0). The hydrosulfide consumption and products (thiosulfate and polysulfide) formation were quantified by means of capillary electrophoresis, while iron dissolution was monitored through atomic absorption spectroscopy. Most of Fe(II) produced at pH = 9.5 remained associated with the oxide surface in the time-scale of the experiments. The hydrosulfide oxidation by the iron/cerium (hydr)oxide was found to be surface-controlled, with rates (R_i) of both sulfide oxidation and Fe(II) dissolution expressed in terms of an empirical rate equation: R_i = k_i[HS⁻]_t=0^−0.5[A]_t=0[H⁺]_t=0^−0.5 , where k_i represents the apparent rate constants for the oxidation of HS⁻ (k_HS) or the dissolution of Fe(II) (k_Fe), [HS⁻]_{t = 0} is the initial hydrosulfide concentration, [A]_{t = 0} is the initial Fe/Ce (hydr)oxide surface area and [H⁺]_{t = 0} is the initial proton concentration. The rate constant, k_HS, for the oxidation of hydrosulfide at pH = 9.5 was (3.4219 ± 0.65) × 10⁻⁴ mol² L⁻¹ m⁻² min⁻¹, with the rate of hydrosulfide oxidation being ca. 10 times faster than the rate of Fe(II) dissolution (assuming a 1:2 stoichiometric ratio between HS⁻ oxidized and Fe(II) produced; k_Fe = (3.9116 ± 0.41) × 10⁻⁵ mol² L⁻¹ m⁻² min⁻¹).     

Effects of lanthanum strontium cobalt ferrite (LSCF) cathode properties on hollow fibre micro-tubular SOFC performances

Single layer La_0.6Sr_0.4Co_0.2Fe_0.8O₃ hollow fibre (HF) precursors (<1 mm ID) produced by phase inversion (PI) were sintered at 1,200, 1,350 and 1,400 °C. The increase in sintering temperature resulted in microstructural changes in the LSCF fibres, reflected in their electrical conductivities. LSCF-based cathodes with different designs were brushed onto co-extruded nickel–gadolinium-doped ceria (CGO) anode/CGO electrolyte dual-layer HFs (<1 mm ID) fabricated by PI. The effect of cathode layers on the overall performance of the fuel cells (FCs) was assessed using nearly identical anode and electrolyte compositions, thicknesses, and microstructures. Cathode microstructure design caused cells to perform differently producing peak power densities of 0.35–0.7 W cm⁻² at 600 °C. Impedance spectroscopy analysis at 600 °C on the FCs produced 0.12–0.24 Ω cm² confirming the cathode’s structural effect on the overall area-specific resistance of the FCs. The best performing FC with a brush-deposited cathode was compared to a similar FC where cathode was deposited by dip coating; at 600 °C the first produced 0.6 W cm⁻² while the second cell 0.7 W cm⁻². Co-extruding anodes and electrolytes by using PI and combining dip coating for cathode deposition could lead to the fabrication of FCs with enhanced microstructures and improved performances.     

Reduction of 1-nitroso-2-naphthol at a Ti/ceramic TiO2 cathode in different media

The cyclic voltammetric behaviour of a Ti/ceramic TiO₂ cathode has been studied in 50% (v/v) ethanolic 1 m H₂SO₄, 0.1 m Na₂SO₄ and 1 m NaOH solutions, both in the absence and presence of various concentrations of added 1-nitroso-2-naphthol (NN). Catalytic reduction of NN at the Ti/ceramic TiO₂ cathode occurs by the electrogenerated Ti³⁺ species. Galvanostatic electrolytic reduction of NN at a Ti/ceramic TiO₂ cathode carried out in these media gave 1-amino-2-naphthol in high yield with a high current efficiency. The cyclic voltammetric and galvanostatic studies on the reduction of NN in these media have also been carried out at a glassy carbon electrode (GCE) for comparison.     

Bipolar Al/02 battery with planar electrodes in alkaline and acidic electrolytes

A filter-press-type Al/O₂ battery with bipolar assembly of the electrodes was developed. The current-voltage curves and power output of monopolar and of bipolar batteries containing one to four cells were measured in alkaline (4 m NaOH and 7.5 M KOH) and acidic (3 m H₂SO₄ + 0.041 m HCl) electrolytes. The unit cell had an open circuit voltage of 1.85 V in alkaline media and 1.3 V in acidic media. The single bipolar unit delivered a maximum power of about 7.5 W (75 mW cm^–2) at 0.7 V. The stack (four cells) had a maximum power of 30 W in 4 m NaOH and 35 W in 3 m H₂S0₄ + 0.04 m HCl. The power output of the bipolar stack determined experimentally for different external loads could be described using the model of an electric equivalent circuit.     

Interfacial tension between aluminum and cryolite melts during electrolysis of the systems Na3AlF6–AlF3 (NaF)–Al2O3

The interfacial tension between aluminum and cryolite melts containing different salt additions has been measured by the capillary depression method. The technique is based on the measurement of the capillary depression occurring when the capillary, which is moved vertically down through the molten salt layer, passes through the salt/metal interface. The depression is measured by simultaneous video recording of the immersion height of the alumina capillary. The interfacial tension was found to be strongly dependent on the n(NaF)/n(AlF₃) ratio (cryolite ratio, CR). At the cryolite ratio 2.28 (80 wt.% Na₃AlF₆ + 10 wt.% AlF₃ + 10 wt.% Al₂O₃ // Al, t = 1000 °C) the interfacial tension was 546 mN m⁻¹, while it was 450 mN m⁻¹ at the cryolite ratio 4.43 (80 wt.% Na₃AlF₆ + 10 wt.% NaF + 10 wt.% Al₂O₃ // Al, t = 1000 °C). Experiments under current flow conditions were also performed. During the electrolysis the interfacial tension at n(NaF)/n(AlF₃) ratio 2.28 decreased from 546 mN m⁻¹ at zero current to 518 mN m⁻¹ at 0.112 A cm⁻². The same trend was observed in the system with a cryolite ratio 4.43. The interfacial tension decreased from 450 mN m⁻¹ at zero current to 400 mN m⁻¹ at 0.112 A cm⁻². The consequent increase in interfacial tension of these systems caused by interruption of electrolysis was observed. Electrolysis of the system 25 wt.% NaF + 75 wt.% NaCl (eutectic mixture)/Al indicated no influence of applied current on the interfacial tension at 850 °C.     

Manganese oxide nanocomposites with improved surface area prepared by one-pot surfactant route for electro catalytic and biosensor applications

Braunite phase manganese oxide is naturally available in manganese–silicate rocks with minor amount of silicate content. New synthetic route is attempted to prepare the manganese oxide nanoparticle and silica incorporated manganese oxide nanocomposite in the present study. XRD patterns reveal the braunite phase formation for as synthesized manganese oxide nanocomposite and silica incorporated MnO₂ nanocomposite materials. Improved BET surface area values are achieved by one step surfactant assisted method (i.e., 82 and 151 m²/g) compared to conventional route prepared manganese oxide nanomaterial. Flaky pastry type morphology was observed for as synthesized Si–MnO₂ nanocomposites. Cyclic voltammetry studies predict the electrocatalytic activity of manganese oxide nanoparticle and Si–MnO₂ nanocomposite in presence of electroactive redox couple. Si–MnO₂ nanocomposite modified glassy carbon (GC) electrode shows the effective electroactive response in presence of Fe²⁺/Fe³⁺ redox couple at 0.69 V with current density of 0.343 × 10⁻⁵ A/cm² compared to manganese oxide nanoparticle modified GC electrode. The biosensor responses for ascorbic acid have been tested in the present study and manganese oxide nanoparticle modified GC electrode shows effective response at low concentration of (1 × 10⁻⁵ M) ascorbic acid in phosphate buffer solution. Manganese oxide nanoparticle modified electrode shows the better response with current density value of 0.115 × 10⁻⁵ A/cm² compared to Si–MnO₂ nanocomposite.