Angel R. Pierna

Bio: Angel R. Pierna is an academic researcher from University of the Basque Country. The author has contributed to research in topics: Amorphous solid & Amorphous metal. The author has an hindex of 13, co-authored 54 publications receiving 471 citations.

Effect of irreversible structural relaxation on the electrochemical behavior of Fe78−xSi13B9Cr(x=3,4,7) amorphous alloys

Abstract: In the present work, the effect of irreversible structural relaxation on the electrochemical behavior of Fe78−xSi13B9Cr(x=3,4,7) amorphous alloys is studied. These studies were based on enthalpy and Curie temperature changes, derived from temperature-modulated differential scanning calorimetry measurements (MDSC). We have observed that the Curie temperature of the amorphous phase increases upon relaxation without change in the crystallization enthalpy. The shift of the Curie transition affects the electrochemical behavior of the heat-treated samples. The effect is a shift of the corrosion potential of the relaxed samples toward higher durability.

On the enhancement of methanol and CO electro-oxidation by amorphous (NiNb)PtSnRu alloys versus bifunctional PtRu and PtSn alloys

Abstract: It has been observed in this work and previous works [J. Barranco, A.R. Pierna, J. Non-Cryst. Solids 35 (2007) 851; J. Barranco, A.R. Pierna, J. Power Sources 169 (2007) 71 [1,2] ] that (NiNb) 99 (PtSn) 1 alloys surfaces are very effective catalyst for CO electro-oxidation, but not for methanol electro-oxidation. On the contrary, (NiNb) 99 (PtRu) 1 alloys seem to be a very effective catalyst for methanol, but not for CO, electro-oxidation. Since CO ads is postulated to be a by-product in methanol electro-oxidation on Pt alloy surfaces, the lack of inactivity of (NiNb) 99 (PtSn) 1 amorphous alloys appears paradoxical. In this work we present the behaviour of a tricatalytic amorphous alloy, in methanol and CO ads electro-oxidation in an attend to enhance the methanol and CO oxidation mechanisms of the Sn and Ru containing alloys, respectively. It has been observed that the specific activity for (NiNb) 99 (PtSnRu) 1 for methanol electro-oxidation, is enhanced around 50–80% with respect the bicatalytic PtSn alloys, at low methanol concentration, whereas PtRu catalysts seems to be more effective. At high methanol concentrations, (NiNb) 99 (PtSnRu) 1 catalysts seems to be more effective. The enhanced in the CO ads , is observed by the lower rate of poisoning of such alloy compare with the bicatalytic ones. The onset of CO ads oxidation, appear to shift 0.25 V towards negative values of potentials, with respect (NiNb) 99 (PtRu) 1 electrodes.

Amorphous Ni59Nb40Pt(1−x)Yx (Y = Sn, Ru; x = 0%, 0.4%) modified carbon paste electrodes and their role in the electrochemical methanol deprotonation and CO oxidation process

Abstract: This work presents the electrochemical response to methanol deprotonation and CO oxidation in acid media (HClO 4 ) of different compositional amorphous alloys obtained by ball milling technique. These powders with compositions Ni 59 Nb 40 Pt (1− x ) Y x ( x = 0%, 0.4% atm, Y = Sn, Ru ) are used as modified carbon paste electrodes (MCPEs), and mainly as anodes. Concerning the reactivity towards methanol electro-oxidation, the current density is drastically decreased with the presence of tin, susceptible to the potential range, followed by the Ni 59 Nb 40 Pt 1 and Ni 59 Nb 40 Pt 0.6 Ru 0.4 alloys, however DEMS studies demonstrates that the electrodes of compositions Ni 59 Nb 40 Pt 0.6 Ru 0.4 and Ni 59 Nb 40 Pt 0.6 Ru 0.2 Sn 0.2 show the best tolerance to CO produced by methanol deprotonation, giving rise to more negative onset potential values for the CO 2 production, although the voltammograms for the stripping of a CO monolayer clearly show that, the electrode that possesses a better tolerance to CO adsorbed on the surface of the electrode is Ni 59 Nb 40 Pt 0.6 Sn 0.4 , decreasing the onset potential values 281 mV and 158 mV with respect to the Ni 59 Nb 40 Pt 1 and Ni 59 Nb 40 Pt 0.6 Ru 0.4 , respectively. The catalytic activity of the former electrode might be attributed to an adsorbed state of CO unique in this alloy.

Review of 5-V electrodes for Li-ion batteries: status and trends

Abstract: Lithium-ion batteries have dominated the battery industry for the past several years in portable electronic devices due to their high volumetric and gravimetric energy densities. The success of these batteries in small-scale applications translates to large-scale applications, with an important impact in the future of the environment by improving energy efficiency and reduction of pollution. We present the progress that allows several lithium-intercalation compounds to become the active cathode element of a new generation of Li-ion batteries, namely the 5-V cathodes, which are promising to improve the technology of energy storage and electric transportation, and address the replacement of gasoline engine by meeting the increasing demand for green energy power sources. The compounds considered here include spinel LiNi0.5Mn1.5O4 and its related doped-structures, olivine LiCoPO4, inverse spinel LiNiVO4 and fluorophosphate Li2CoPO4F. LiNi0.5Mn1.5O4 thin films, nanoscale prepared materials and surface-modified cathode particles are also considered. Emphasis is placed on the quality control that is needed to guarantee the reliability and the optimum electrochemical performance of these materials as the active cathode element of Li-ion batteries. The route to increase the performance of Li-ion batteries with the other members of the family is also discussed.