Graphite–Metal Oxide Composites as Potential Anodic Catalysts for Microbial Fuel Cells

In this study, graphite–metal oxide (Gr–MO) composites were produced and explored as potential anodic catalysts for microbial fuel cells. Fe2O3, Fe3O4, or Mn3O4 were used as a catalyst precursor. The morphology and structure of the fabricated materials were analyzed by scanning electron microscopy and X-ray diffraction, respectively, and their corrosion resistance was examined by linear voltammetry. The manufactured Gr–MO electrodes were tested at applied constant potential +0.2 V (vs. Ag/AgCl) in the presence of pure culture Pseudomonas putida 1046 used as a model biocatalyst. The obtained data showed that the applied poising resulted in a generation of anodic currents, which gradually increased during the long-term experiments, indicating a formation of electroactive biofilms on the electrode surfaces. All composite electrodes exhibited higher electrocatalytic activity compared to the non-modified graphite. The highest current density (ca. 100 mA.m−2), exceeding over eight-fold that with graphite, was achieved with Gr–Mn3O4. The additional analyses performed by cyclic voltammetry and electrochemical impedance spectroscopy supported the changes in the electrochemical activity and revealed substantial differences in the mechanism of current generation processes with the use of different catalysts.

Synthesis of N-doped carbon based on the waste of Brosimum alicastrum from a pilot plant and evaluation of its electrocatalytic activity for the oxygen reduction reaction

This work reports the synthesis and characterization of metal-free electrocatalysts made from Brosimum alicastrum waste as the carbon source. The residues were washed and grounded to a fine powder. The thermogravimetric analysis carried out on the raw sample showed that the optimal synthesis temperature is 700 °C. Thus, the raw sample was pyrolyzed at 700 °C and activated with potassium hydroxide (KOH) in a 2:1 ratio (KOH/fine power) to improve its properties. Afterwards, hydrazine was used as the nitrogen source for doping. The physicochemical characteristics of pyrolyzed, activated, and doped carbons were studied and their electrochemical properties were determined using cyclic and linear voltammetry techniques. The electrochemical measurements indicate that the sample doped at 140 °C has an acceptable onset potential (0.854 V vs. RHE), while the one doped at 160 °C shows the highest current density among the synthesized electrocatalysts (2.61 mA cm-2). Although the catalyst performance is lower compared to commercial 20% Pt/C, this biomass precursor favors the oxygen reduction reaction in alkaline media.

INVESTIGAÇÃO DOS PARÂMETROS FOTOELETROCATALÍTICOS DO m-BiVO4 NA OXIDAÇÃO DE GLICOSE

This work aims to evaluate the behavior of the FTO/m-BiVO4 photoanode in different electrolytes, pH, anions and cations, in order to investigate the influence of these parameters on their photoelectrochemical activity. The m-BiVO4semiconductor was developed by combustion synthesis in solution (SCS) and deposited by dip-coating technique on fluorinated doped tin oxide (FTO) coated glass substrate. The evaluation of the photosensitive behavior of the film was made by linear voltammetry and chronoamperometry in the presence of pulsed visible light. After photoelectrochemical parameters optimization, the study of photoelectrocatalysis in glucose degradation was performed. Thus, it was possible to evaluate the efficiency of the film in the photoelectrocatalytic processes, presenting itself as a potential material for such applications.

Electrochemical oxidation of aspirin on PbO2 electrode

The PbO2-based electrode was obtained by electrodeposition on the titanium plate surface. The structure and morphology of PbO2-based electrode samples obtained by deposition on the titanium plate surface using scanning electron microscopy and X-ray diffraction analysis were investigated. The surface of the titanium plate is covered with a continuous layer of lead dioxide. The study of the electrochemical oxidation of aspirin on a Ti/PbO2 electrode was carried out using cyclic and linear voltammetry. The oxidation of aspirin molecules on Ti/PbO2 electrode occurs at high potentials with the maximum current at 2.0 V. It has been shown that the concentration has practically no effect to the rate of the process of electrochemical oxidation aspirin. The effect of the current density top the efficiency of electrochemical oxidation of aspirin on is studied. The maximum degree of aqueous aspirin solutions purification is observed at a current density of 0.3 A/cm2. With an increase in the current density from 0.01 to 0.3 A/cm2, the degree of aspirin solution purification increases almost in a straight line, from 81 to 98%. The characterization of aspirin solutions before and after electrolysis was carried out using the UV-Vis absorption spectrometry. After electrolysis for two hours, the aspirin in solution is absent, which is expressed by a decrease in absorption on spectra at the 330 nm. During electrolysis within 2 hours, the absorption peak disappears almost completely, which is associated with the complete oxidation of aspirin molecules.

Voltammetric method for the quantification of cadmium using non-commercial electrodes and minimal instrumentation

A voltammetric method for the cadmium quantification was developed using minimal instrumentation. A manual homemade potentiostat for linear voltammetry was used. An Ag reference electrode and auxiliary and working electrodes of writing graphite were employed for the electroanalysis. The electrolytic conditions for the quantification were stablished. Linearity, detection and quantification limits, precision and accuracy were evaluated. The conditions for the quantification were 1 mol/L of KCl as supporting electrolyte, pH 5 and 10 s for the current sampling. The range of quantification was from 10-3 to 1.5∙10-2 mol/L. The linear correlation (r), determination (R2) and adjusted (R2adj.) coefficients were 0.9986, 0.9972 and 0.9970. The detection and quantification limits were 3∙10-4 mol/L and 10-3 mol/L. Results showed an acceptable repeatability, with coefficients of variation from 1.5 to 5.8 % depending of the concentration. Uncertainty associated with the cadmium concentration was in the range of 1.2∙10-4 to 7∙10-5 mol/L, diminishing with the increasing of the concentration. A good accuracy was observed, with recoveries between 86.84 and 109.64 %.

The Influence of Zr on Microstructure, Mechanical Properties and Corrosion Resistance in Mg-Y-Zr Biodegradable Alloys

The latest magnesium alloys are widely used in the medical field, especially for biodegradable implants. Magnesium alloys are very attractive for applications in different structures in the automotive, aerospace, printing and even medical fields [1]. It should be noted that some magnesium alloys have excellent damping properties as well as good mechanical properties, making them promising to respond to high damping needs for vibration control [1,2]. Although widely used, magnesium has a low corrosion resistance. To improve this resistance, different types of magnesium based on aluminum, such as Ca, Mn, Zn, Zr, Si and rare rare (Y, Gd ..), can be developed. The main purpose of this paper is to investigate the properties of a primary alloy based on the Mg-1Y-0,5Zr system with different concentrations of Zr (0.5,1,2) used in the development of alloys based on the biodegradability of Mg. Surface morphology was characterized by electronic scanning microscopy (SEM), X-ray diffraction (XRD) and optical microscopy. After XRD analysis, it was observed that certain specific compounds were made up of Mg2Ca, MgZr, Mg2Y, Mg24Y5 having the main Mg formed in the hexagonal structure, but Mg24Y5 are the cubic crystalline structure. Also, the microhardness of the alloy is higher than pure Mg and the scratch mark is smaller than that of pure Mg. The corrosion resistance was developed using linear voltammetry in specific medium and corrosion showed that it had significantly decreased for masteralloy. As a final conclusion, the structural properties of this model are recommended for use as medical implants.

The New Anode Environmentally Friendly for Water Electrolysis Based on 430 Stainless Steel Coated with Recycled Cobalt from Spent Lithium–Ion Batteries

In this paper, a new anode environmentally friendly for hydrogen production was developed based on 430 stainless steel with an electrodeposited cobalt layer. The novelty of this work is the cobalt source once the electrodeposition bath was obtained from recycling of spent Li-ion batteries cathode with composition LiCoO2. The electrodeposited cobalt behaves as supercapacitor in KOH 1M. In the linear voltammetry in KOH 1M, when the overpotential reaches 370 mV, the anodic density current for 430 SS/Co is 19 mA cm−2. Thus, the anode developed in this paper achieves the double of density current with half of production cost if compared with 316SS. Moreover the anode construction described in this paper is an excellent option for Li- ion battery recycling.

Visible Light Driven Photoanodes for Water Oxidation Based on Novel r-GO/β-Cu2V2O7/TiO2 Nanorods Composites

This paper describes the preparation and the photoelectrochemical performances of visible light driven photoanodes based on novel r-GO/β-Cu2V2O7/TiO2 nanorods/composites. β-Cu2V2O7 was deposited on both fluorine doped tin oxide (FTO) and TiO2 nanorods (NRs)/FTO by a fast and convenient Aerosol Assisted Spray Pyrolysis (AASP) procedure. Ethylenediamine (EN), ammonia and citric acid (CA) were tested as ligands for Cu2+ ions in the aerosol precursors solution. The best-performing deposits, in terms of photocurrent density, were obtained when NH3 was used as ligand. When β-Cu2V2O7 was deposited on the TiO2 NRs a good improvement in the durability of the photoanode was obtained, compared with pure β-Cu2V2O7 on FTO. A further remarkable improvement in durability and photocurrent density was obtained upon addition, by electrophoretic deposition, of reduced graphene oxide (r-GO) flakes on the β-Cu2V2O7/TiO2 composite material. The samples were characterized by X-ray Photoelectron Spectroscopy (XPS), Raman, High Resolution Transmission Electron Microscopy (HR-TEM), Scanning Electron Microscopy (SEM), Wide Angle X-ray Diffraction (WAXD) and UV-Vis spectroscopies. The photoelectrochemical (PEC) performances of β-Cu2V2O7 on FTO, β-Cu2V2O7/TiO2 and r-GO/β-Cu2V2O7/TiO2 were tested in visible light by linear voltammetry and Electrochemical Impedance Spectroscopy (EIS) measurements.

Enhancement of the cerium oxide primer layers deposited on AA2024-T3 aircraft alloy by preliminary Enhancement of the cerium oxide primer layers deposited on AA2024-T3 aircraft alloy by preliminary anodization

<p class="PaperAbstract"><span lang="EN-US">The possibility for combination between Anodized Aluminum Oxide (AAO) and Cerium Oxide Primer Layer (CeOPL) for elaboration of efficient protective coatings for AA2024-T3 aircraft alloy is proposed in the present research. The combined AAO/CeOPL coating characterizations include Electrochemical Impedance Spectroscopy (EIS) combined with Linear Voltammetry (LVA), for extended times (until 2520 hours) to a model corrosive medium (3.5% NaCl). Topographical and cross-sectional (SEM and EDX) observations were performed in order to determine the AAO/CeOPL film thickness and composition. The AAO/CeOPL layer durability tests were confirmed by standard Neutral Salt Spray (NSS). The data analysis from all the used measurement methods has undoubtedly shown that the presence of AAO film significantly improves the cerium oxide primer layer (CeOPL) protective properties and performance. </span></p>