T.M. Silva

Electrochemical characterisation of oxide films formed on Ti6A14V alloy implanted with Ir for bioengineering applications

Iridium oxide anodically grown on pure iridium is known to have excellent properties for use as neural stimulating electrodes. Its mechanical properties, however, make pure iridium difficult to fabricate into small electrodes. In this work, the commercial Ti-Al-4V alloy surface modified by ion implantation with iridium is tested for its electrochemical properties, aiming at its use as a stimulating electrode. The results show that an oxide film with good charge storage capacity is formed on the surface of the material. The properties of the electrode are compared with those of pure iridium. Characterisation was made by cyclic voltammetry, electrochemical impedance spectroscopy and XPS.

Hydrogen evolution on nanostructured Ni-Cu foams

Three-dimensional (3D) nickel–copper (Ni–Cu) nanostructured foams were prepared by galvanostatic electrodeposition, on stainless steel substrates, using the dynamic hydrogen bubble template. These foams were tested as electrodes for the hydrogen evolution reaction (HER) in 8 M KOH solutions. Polarisation curves were obtained for the Ni–Cu foams and for a solid Ni electrode, in the 25–85 °C temperature range, and the main kinetic parameters were determined. It was observed that the 3D foams have higher catalytic activity than pure Ni. HER activation energies for the Ni–Cu foams were lower (34–36 kJ mol−1) than those calculated for the Ni electrode (62 kJ mol−1). The foams also presented high stability for HER, which makes them potentially attractive cathode materials for application in industrial alkaline electrolysers.

One-step process to form a nickel-based/carbon nanofoam composite supercapacitor electrode using Na2SO4 as an eco-friendly electrolyte

In this work, NiOx is anodically electrodeposited onto carbon nanofoam (CNF) to form a composite electrode devoted to supercapacitor applications. The use of NiSO4 as precursor in electrodeposition results in the formation of NiO and NiOOH species, as confirmed by XPS analysis, by means of a one-step anodic process. The presence of both NiO and NiOOH suggests the existence of pseudocapacitance, as observed in MnO2 and RuO2 materials. By employing Na2SO4, an eco-friendly electrolyte, the resulting composite delivers a specific capacitance of 150 F g−1 at 1 A g−1 considering the total mass of the electrode (deposit plus substrate). In addition, this composite electrode can operate in a very broad potential window, as high as 2.2 V, suggesting its application in high energy density electrochemical supercapacitors.

Electrodeposition: a versatile, efficient, binder-free and room temperature one-step process to produce MnO2 electrochemical capacitor electrodes

The use of room temperature cathodic electrodeposition to produce MnO2 electrochemical capacitor electrodes is demonstrated. By employing a permanganate-based bath, birnessite-type MnO2 electrodes are directly obtained with no further heat treatment. Moreover, a crystalline/amorphous structural transition is observed as the applied current density is increased up to 50 mA cm−2.