Vol 55, No 2 (2019)

Pt free methanol electro oxidation catalysts with stable response are of interest to reduce the overall cost of the direct methanol fuel cell (DMFC). Here, nickel based bi and tri metallic catalysts have been prepared on multiwall carbon nanotube (MWCNT) support by incipient wetness impregnation method. Methanol oxidation performance was investigated in 1 M KOH by cyclic-voltammetry (CV) and chronoamperometry (CA). The results of electrochemical tests showed that among all the catalysts tested, catalyst sample, CAT-3 exhibited the highest current density of 125.5 mA/cm² and have stable electrochemical response, which is very promising. These catalysts have been characterized by field emission scanning electron microscopy (FESEM) coupled with energy dispersive X-ray-(EDX), transmission electron microscopy (TEM), X-ray diffraction XRD and X-ray photoelectron spectroscopy (XPS) to study the structural and morphological properties. Characterization results revealed small and uniform particle size distribution and better homogeneity in CAT-3. It was also observed that addition of ‘Fe’ in tri metallic catalyst lowers the Cu contents in the catalysts and in the contrary lowers the electro-catalytic performance. All the catalyst found to be quite stable and CAT-3 gave the highest oxidative current response, which is attributed to higher Cu contents.

New strategies are proposed for modification of the anode of a Microbial Fuel Cell (MFC). Immobilization of yeast cells as electrogenic microorganism in MFC was reported using alginate. Yeast cells entrapment within alginate matrices was done through films deposited at the surface of a carbon felt electrode and the resulting anodes were characterized by chronoamperometry. Yeast entrapped within alginate films on carbon felt oxidized glucose and generates a current by direct and mediated electrons transfer from yeast cells to the carbon electrode. The result substantiated that immobilization of yeast for MFC could be a promising method to product green electricity.

Vanadium pentoxide (V₂O₅) based electrodes for energy storage devices have captured sizeable attention in the past decade owing to their attractive physiochemical features. In the present work, flaky structured V₂O₅ was prepared using a single step hydrothermal route. The results from analytical investigations hold up well with the formation scheme proposed. The flaky morphology of V₂O₅ facilitates additional pathways for electron transport and effective ion access. When employed as a supercapacitor electrode in a neutral electrolyte, this flaky V₂O₅ electrode demonstrates a specific capacitance of 472 F g⁻¹. Besides, it retains maximum capacitance at higher current density confirming its good rate performance. An asymmetric type supercapacitor using flaky V₂O₅ as positive electrode and activated carbon as negative electrode exhibits specific capacitance of 69 F g⁻¹. This device shows energy density of 10 W h kg⁻¹ within the operational window of 1 V.

The efficiency of films prepared in aqueous solutions of organic inhibitors on the surface of low-carbon steel preliminarily modified in solutions of zinc complexes with 1-hydroxyethane-1,1-diphosphonic (Zn-HEDP) or aminotrimethylenephosphonic acids (Zn-AMP) is studied by electrochemical and corrosion methods. It is shown that modifying considerably increases the efficiency of passivation and that Zn-AMP is much more efficient in this respect than Zn-HEDP

Porous platinum electrodes on ZrO₂ + 10 mol % Y₂O₃ solid electrolyte (YSZ) are activated by Tb_{1 − x}Ce_xO_{2 − α} (x = 0; 0.15; 0.33; 0.5; 1.0) mixed oxides by impregnation, and their polarization characteristics are studied. The activation is carried out under the conditions that an oxide activator nanofilm forms on the electrolyte surface as a result of heat treatment of the electrode. The activation is performed by impregnating the electrodes with low-concentrated alcohol solution of terbium and cerium nitrates (1.5% as recalculated to the oxides) and subsequent slow heating (≤50°C/h) to 850°C. An average thickness of the film on the electrolyte after a single activation (≈0.1 mg oxides/cm²) is estimated at 10–20 nm. The electrodes of Pt|YSZ|Pt cell activated by Tb_{1 − x}Ce_xO_{2 − α} films are studied by the impedance method in the oxidative and reductive atmospheres in the range of 700 to 500°C. The polarization conductivities of the activated electrodes increase by 2–3 orders of magnitude. The studied electrodes are discussed within the model of compact oxide electrodes, where platinum plays the role of collector. The advantage of these electrodes is that they can work both in the oxidative and reductive conditions. According to the aggregate of the properties, Tb_{1 − x}Ce_xO_{2 − α} compounds at x = 0.3–0.5 are recommended for activation.