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A dynamic two phase flow model for a pilot scale sodium borohydride hydrogen ge...
Sousa, T.; Rangel, C. M.A two-dimensional, non-isothermal and dynamic model was developed to describe a sodium borohydride/hydrogen reactor for stationary use. All relevant transport phenomena were treated in detail and the kinetic model developed previously by the authors was introduced into the algorithm. In this paper the reactive solution was modelled as a two phase flow; with this approach the impact of the hydrogen production on...
Stability of LaNiO3 gas diffusion oxygen electrodes
Silva, R. A.; Soares, C. O.; Carvalho, M. D.; Rangel, C. M.; Pereira, M. I. da SilvaIn this work LaNiO3 perovskite-type oxide, prepared by a self-combustion method, was optimized for activity and stability as an anode material for water electrolysis. A full electrochemical study was conducted in order to kinetically characterize electrodes prepared using carbon paper as a base for porous gas-diffusion electrodes in alkaline media, regarding water oxidation and oxygen reduction reactions at roo...
Modelling and identification of the dominant phenomena in hydrogen fuel-cells b...
Lopes, Vitor V.; Rangel, C. M.; Novais, Augusto Q.This paper proposes the use of the distribution of relaxation times (DRT) for the analysis of the dynamic behavior of hydrogen fuel-cells. With this aim it presents a new method to compute the DRT directly from electrochemical impedance spectroscopy (EIS) data. The method is formulated as a nonconvex complex domain optimization problem where each EIS spectra is approximated by a general fractional-order Legen...
Dielectric properties of Al-Nb amorphous mixed oxides
Di Franco, F.; Santamaria, M.; Di Quarto, F.; La Mantia, F.; Sá, A. I. Correia de; Rangel, C. M.An impedance study of amorphous thin oxide films grown on sputtered Al-Nb alloys is presented. The characterization of the electronic properties of mixed amorphous oxide on the basis of the theory of amorphous semiconductor Schottky barrier has been carried out for anodic film on Al-92at.%Nb in a very detailed manner. The semiconductor to insulator transition of formed oxides as a function of the alloy composit...
Enhanced bifunctional activity of LaNiO3-based gas diffusion electrodes for reg...
Silva, R. A.; Soares, C. O.; Carvalho, M. D.; Rangel, C. M.; Pereira, M. I. da SilvaPerovskites are of great interest when searching replacements for precious metals as catalyst for bifunctional oxygen electrodes involving the oxygen evolution(OER) and oxygen reduction reaction (ORR) as is the case of regenerative fuel cells. In this work a full electrochemical study on the electrochemical properties of gas diffusion electrodes (GDEs) using LaNiO3-based catalysts, conducted in alkaline media, ...
Electrocatalitic activity of platinum deposited on carbon functionalized with s...
Capelo, Anabela; Esteves, M. Alexandra; Sá, A. I. Correia de; Rangel, C. M.Results are presented for Pt deposited on 4-aminobenzenesulphonic acid-functionalized carbon, Pt/C_ABSA. Vulcan XC-72R was functionalized in order to influence catalyst dispersion and decrease the resistance of three phase boundary, by introducing sulphonic groups and lessening the amount of Nafion® added to the catalyst layers. Electrochemical characterization of the supported catalyst was done in a 0.5 M H2SO...
Assessing cell polarity reversal degradation phenomena in PEM fuel cells by ele...
Travassos, Maria Antónia; Lopes, Vitor V.; Silva, R. A.; Novais, Augusto Q.; Rangel, C. M.Electrochemical impedance spectroscopy (EIS) is identified as one of the most promising in-situ diagnostics tools available for assessing fuel cell ageing and degradation. In this work, the degradation phenomena caused by cell polarity reversal due to fuel starvation of an open cathode 16 membrane electrode assembly (MEA) – low power (PEM) fuel cell (15 W nominal power) – is reported using EIS as a base techni...
Synthesis and characterization of new benzimidazole phosphonates for hybrid mat...
Teixeira, Fátima C.; Rangel, C. M.Fuel cells are electrochemical devices that convert the chemical energy stored in a fuel, directly and efficiently into electrical energy and are a promising and clean alternative to traditional energy fuels [1]. The roton-exchange membrane fuel cells (PEMFCs) are considered a promising type of electrochemical device for power generation. The proton exchange membrane (PEM) is a key part for the operation of PEM...
Influence of the electrolyte on the electrochemical performance of a polyimide ...
Furtado, Olívia; Paiva, T. I.; Rangel, C. M.The charge storage on organic polymers has led to increasing application of these new materials such as active electrodes in rechargeable batteries [1, 2]. Taking advantage of the redox properties of aromatic polyimide imide group [3], which allows it to be electrochemically oxidized and reduced reversibly, we will present the advances made on the electrochemical studies carried out with a polyimide derivative ...
Structural features of electrodeposited copper electrodes for CO2 conversion
Machado, A. S. Reis; Fernandes, T. R. C.; Pardal, T.; Rangel, C. M.Direct electrochemical reduction of CO2 is a process that could contribute to the reduction of the emission of greenhouse gases by using CO2 as a raw material for fuel production. This paper focuses on voltammetric studies of functionalized electrodes for the electrochemical conversion of CO2 and reports on its use as a tool for electrode screening and optimization. Nickel substrates modified with copper and ru...
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