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Search Results: 1 - 10 of 512039 matches for " Diogo M. F. Santos "
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Hydrogen production
Sequeira,César A. C.; Santos,Diogo M. F.;
Ciência & Tecnologia dos Materiais , 2010,
Abstract: possible means of producing hydrogen are discussed. emphasis is given on the electrolytic hydrogen production from water electrolysis, at large scale, via the use of renewable electricity (solar, wind, tidal, etc.). its storage, transport and possible end-uses are also considered.
Potentiometric monitoring of sodium borohydride in aqueous solutions
Santos,Diogo M. F.; Sequeira,César A. C.;
Ciência & Tecnologia dos Materiais , 2008,
Abstract: platinum, palladium, gold, cadmium, nickel and niobium immersed in sodium borohydride alkaline solutions are characterised by electrode responses that allow monitoring the borohydride present in aqueous media. a simple and relatively precise potentiometric titration technique is described and applied for the analysis of borohydride solutions.
Hydrogen production
César A. C. Sequeira,Diogo M. F. Santos
Ciência & Tecnologia dos Materiais , 2010,
Abstract: Possible means of producing hydrogen are discussed. Emphasis is given on the electrolytic hydrogen production from water electrolysis, at large scale, via the use of renewable electricity (solar, wind, tidal, etc.). Its storage, transport and possible end-uses are also considered. Discutem-se processos de obten o de hidrogénio. Em particular, considera-se a produ o electrolítica de hidrogénio em meio aquoso, à escala industrial, e à custa de energia eléctrica renovável (solar, vento, marés, etc.). Fazem-se ainda algumas previs es acerca do armazenamento, transporte e possíveis aplica es do hidrogénio electrolítico.
Potentiometric monitoring of sodium borohydride in aqueous solutions
Diogo M. F. Santos,César A. C. Sequeira
Ciência & Tecnologia dos Materiais , 2008,
Abstract: Platinum, palladium, gold, cadmium, nickel and niobium immersed in sodium borohydride alkaline solutions are characterised by electrode responses that allow monitoring the borohydride present in aqueous media. A simple and relatively precise potentiometric titration technique is described and applied for the analysis of borohydride solutions. Platina, paládio, ouro, cádmio, níquel e nióbio imersos em solu es alcalinas de borohidreto de sódio s o caracterizados por respostas de eléctrodo que permitem monitorizar o conteúdo em borohidreto presente num dado meio aquoso. Descreve-se uma técnica de titula o potenciométrica relativamente simples e precisa que pode ser aplicada para a análise de solu es de borohidreto.
Molecular Beam-Thermal Desorption Spectrometry (MB-TDS) Monitoring of Hydrogen Desorbed from Storage Fuel Cell Anodes
Rui F. M. Lobo,Diogo M. F. Santos,Cesar A. C. Sequeira,Jorge H. F. Ribeiro
Materials , 2012, DOI: 10.3390/ma5020248
Abstract: Different types of experimental studies are performed using the hydrogen storage alloy (HSA) MlNi 3.6Co 0.85Al 0.3Mn 0.3 (Ml: La-rich mischmetal), chemically surface treated, as the anode active material for application in a proton exchange membrane fuel cell (PEMFC). The recently developed molecular beam—thermal desorption spectrometry (MB-TDS) technique is here reported for detecting the electrochemical hydrogen uptake and release by the treated HSA. The MB-TDS allows an accurate determination of the hydrogen mass absorbed into the hydrogen storage alloy (HSA), and has significant advantages in comparison with the conventional TDS method. Experimental data has revealed that the membrane electrode assembly (MEA) using such chemically treated alloy presents an enhanced surface capability for hydrogen adsorption.
Studies of Modified Hydrogen Storage Intermetallic Compounds Used as Fuel Cell Anodes
Yun Chen,Diogo M. F. Santos,César A. C. Sequeira,Rui F. M. Lobo
Crystals , 2012, DOI: 10.3390/cryst2010022
Abstract: The possibility of substituting Pt/C with the hydrogen storage alloy MlNi 3.6Co 0.85Al 0.3Mn 0.3 as the anode active material of a proton exchange membrane fuel cell system has been analyzed. The electrochemical properties indicate that a much more electrochemically active anode is obtained by impregnating the active material loaded anode in a Nafion proton conducting polymer. Such performance improvement might result from the increase of three-phase boundary sites or length in the gas diffusion electrode where the electrochemical reaction occurs. The experimental data revealed that the membrane electrode assembly (MEA) shows better results when the anode active material, MlNi 3.6Co 0.85Al 0.3Mn 0.3, is treated with a hot alkaline KBH 4 solution, and then chemically coated with 3 wt.% Pd. The MEA with the aforesaid modification presents an enhanced surface capability for hydrogen adsorption, and has been studied by molecular beam-thermal desorption spectrometry.
Kinetic measurements during transient film growth on zinc
Chen, Yun;Lobo, Rui F. M.;Santos, Diogo M. F.;Sequeira, César A. C.;
Química Nova , 2009, DOI: 10.1590/S0100-40422009000200022
Abstract: the electrochemical behaviour of zinc has been extensively studied in alkaline and acid media, but only a few studies have been reported in neutral solutions, particularly in deaerated media. zinc passivation in neutral medium and the effect of the clo4- ion on the nucleation and growth of the passive layer is studied in this paper by a transient technique at different electrolyte concentrations and applied potentials. zno growth rate was shown to decrease with increasing electrolyte concentration. moreover, passive layer growth occurred followed by pitting nucleation and growth. film growth and pit nucleation are explained by means of the macdonald and engell-stolica models.
Anion- or Cation-Exchange Membranes for NaBH4/H2O2 Fuel Cells?
Biljana ?ljuki?,Ana L. Morais,Diogo M. F. Santos,César A. C. Sequeira
Membranes , 2012, DOI: 10.3390/membranes2030478
Abstract: Direct borohydride fuel cells (DBFC), which operate on sodium borohydride (NaBH 4) as the fuel, and hydrogen peroxide (H 2O 2) as the oxidant, are receiving increasing attention. This is due to their promising use as power sources for space and underwater applications, where air is not available and gas storage poses obvious problems. One key factor to improve the performance of DBFCs concerns the type of separator used. Both anion- and cation-exchange membranes may be considered as potential separators for DBFC. In the present paper, the effect of the membrane type on the performance of laboratory NaBH 4/H 2O 2 fuel cells using Pt electrodes is studied at room temperature. Two?commercial ion-exchange membranes from Membranes International Inc., an anion-exchange membrane (AMI-7001S) and a cation-exchange membrane (CMI-7000S), are tested as ionic separators for the DBFC. The membranes are compared directly by the observation and analysis of the corresponding DBFC’s performance. Cell polarization, power density, stability, and durability tests are used in the membranes’ evaluation. Energy densities and specific capacities are estimated. Most tests conducted, clearly indicate a superior performance of the cation-exchange membranes over the anion-exchange membrane. The two membranes are also compared with several other previously tested commercial membranes. For long term cell operation, these membranes seem to outperform the stability of the benchmark Nafion membranes but further studies are still required to improve their instantaneous power load.
Oxygen reduction at a manganate electrocatalyst in KOH solutions
Sequeira, César A. C.;Santos, Diogo M. F.;Baptista, Walmar;
Journal of the Brazilian Chemical Society , 2006, DOI: 10.1590/S0103-50532006000500014
Abstract: the electrocatalysis of the oxygen reduction reaction by lanthanum calcium manganate, (la0.5ca0.5mno3) (lcm) has been studied by cyclic voltammetry using the rotating ring-disc electrode technique (rrde) in alkaline medium. from the ring-disc data and other kinetic parameters it has been assumed that the oxygen reduction occurs by dissociative chemisorption at low overpotentials. at higher overpotentials, the formation of hydrogen peroxide (ho2- in this case) has been observed on this electrocatalyst. the apparent exchange current density value for oxygen reduction on lcm has been found to be 5 ′ 10-8 a cm-2, while the corresponding tafel slope is 0.115 v per decade. the possible reaction mechanism for electroreduction of oxygen on this oxide catalyst has been discussed.
Synthesis and characterization of new amino acyl-4-thiazolidones
Leite, Ana Cristina Lima;Santos, Luciene Maria F.;Moreira, Diogo Rodrigo de M.;Brondani, Dalci José;
Química Nova , 2007, DOI: 10.1590/S0100-40422007000200008
Abstract: a series of heterocyclic compounds with a 4-thiazolidone nucleus and amino acyl moiety were synthesized by protection reaction of thiosemicarbazide using the symmetrical anhydride (boc)2o and cyclization with chloroacetic acid under mild conditions. trifluoroacetic acid was used to obtain 4-thiazolidone and the a-amino acid condensation reactions were carried out using strategies for peptide synthesis. the characterization of this new class of compounds was performed using ir and 1h-nmr spectroscopy.
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