Examinando por Autor "Zamora, Hector"

Mostrando 1 - 6 de 6

Composite Titanium Silicon Carbide as a Promising Catalyst Support for High-Temperature Proton-Exchange Membrane Fuel Cell Electrodes
(Wiley, 2016-01-20) Lobato, Justo; Zamora, Hector; Plaza, Jorge; Rodrigo, Manuel Andrés
This manuscript focuses on the assessment of a composite titanium silicon carbide (SiCTiC) as a catalyst support for high-temperature proton-exchange membrane fuel cells (HT-PEMFCs). The support showed very high thermal and electrochemical resistances under harsh conditions (phosphoric acid). Pt nanoparticles were successfully deposited on the new SiCTiC support and it demonstrated a higher stability (lower agglomeration of the nanoparticles) than the more conventional Vulcan carbon-based catalyst, both in a commercial formulation and as prepared in the lab, with the same procedure as that used for the novel carbide material under very harsh conditions.
Enhancement of high temperature PEMFC stability using catalysts based on Pt supported on SiC based materials
(Elsevier, 2016-12-05) Zamora, Hector; Plaza, Jorge; Cañizares, Pablo; Lobato, Justo; Rodrigo, Manuel Andrés
With the aim of overcome the carbon supports of high temperature Proton Exchange Membrane Fuel cells (HT-PEMFC) electrodes, two novel non-carbonaceous support based on SiC have been assessed, SiC and SiCTiC. 40% wt. Pt was successfully deposited on them and they were physicochemical and electrochemically characterized. Both catalysts on SiC based materials showed a very high electrochemical stability in the half cell experiments in comparison with Pt on carbon support, showing a lower degradation rate of the electrochemical surface area (ECSA). Membrane Electrode Assemblies (MEAs) were prepared with the different catalysts and tested in a single cell (25 cm2) operated at 160 °C. The Pt/SiCTiC showed a good performance and the highest stability in the fuel cell tests carried under the same operation conditions. © 2016 Elsevier B.V.
High Stability Electrodes for High Temperature Proton Exchange Membrane Fuel Cell by Using Advanced Nanocarbonaceous Materials
(Wiley, 2017-09-18) Zamora, Hector; Plaza, Jorge; Cañizares, Pablo; Rodrigo, Manuel Andrés; Lobato, Justo
This work studies the stability and performance of a cathodic electrode for high-temperature proton exchange membrane (HT-PEMFC) systems prepared with a carbon nanosphere (CNS) based microporous layer and carbon nanofibers (CNFp) used as a catalyst support. The obtained results are compared with a standard Vulcan carbon XC72 based electrode. With this purpose, two membrane−electrode assemblies (MEAs) were prepared using the cathodic electrodes and tested in a 25 cm2 HT-PEMFC system. Preliminary short-life tests around 330 h were carried out with both MEAs. During the tests, different characterization procedures, consisting of polarization curves, spectroscopy impedance analysis, cyclic voltammetry and linear sweep voltammetry were performed in order to evaluate the evolution of the main stability and performance parameters of the MEAs. Results showed that the application of these new materials increases positively the stability of the MEA in comparison with the standard Vulcan carbon XC72 material, with a negligible decrease in the performance of the advanced MEA during all tests, making these results very promising to overcome the service lifetime limitations of these systems.
Improved Electrodes for High Temperature Proton Exchange Membrane Fuel Cells using Carbon Nanospheres
(Wiley, 2016-04-14) Zamora, Hector; Plaza, Jorge; Cañizares, Pablo; Lobato, Justo; Rodrigo, Manuel Andrés
This work evaluates the use of carbon nanospheres (CNS) in microporous layers (MPL) of high temperature proton exchange membrane fuel cell (HT-PEMFC) electrodes and compares the characteristics and performance with those obtained using conventional MPL based on carbon black. XRD, hydrophobicity, Brunauer–Emmett–Teller theory, and gas permeability of MPL prepared with CNS were the parameters evaluated. In addition, a short life test in a fuel cell was carried out to evaluate performance under accelerated stress conditions. The results demonstrate that CNS is a promising alternative to traditional carbonaceous materials because of its high electrochemical stability and good electrical conductivity, suitable to be used in this technology.
Microporous layer based on SiC for high temperature proton exchange membrane fuel cells
(Elsevier, 2015-08-15) Lobato, Justo; Zamora, Hector; Cañizares, Pablo; Plaza, Jorge; Rodrigo, Manuel Andrés
This work reports the evaluation of Silicon Carbide (SiC) for its application in microporous layers (MPL) of HT-PEMFC electrodes and compares results with those obtained using conventional MPL based on Vulcan XC72. Influence of the support load on the MPL prepared with SiC was evaluated, and the MPL were characterized by XRD, Hg porosimetry and cyclic voltammetries. In addition, a short lifetest was carried out to evaluate performance in accelerated stress conditions. Results demonstrate that SiC is a promising alternative to carbonaceous materials because of its higher electrochemical and thermal stability and the positive effect on mass transfer associated to its different pore size distribution. Ohmic resistance is the most significant challenge to be overcome in further studies. © 2015 Elsevier B.V.
SiCTiC as catalyst support for HT-PEMFCs. Influence of Ti content
(Elsevier, 2017-06-15) Zamora, Hector; Plaza, Jorge; Velhac, P.; Cañizares, Pablo; Rodrigo, Manuel Andrés
This manuscript studies the influence of the titanium content on the main physicochemical properties of a binary silicon carbide- titanium carbide raw material (SiCTiC), to be used as catalyst support in High Temperature PEM fuel cells (HT-PEMFCs). Three SiCTiC samples with 10, 20 and 30% TiC molar content were studied, analysing the most relevant parameters to be used as catalyst support. First, BET surface area, electrical conductivity, thermal resistance in hot acidic media, and electrochemical resistance were the parameters studied. Results achieved show a decreasing of the BET surface area with the increasing of TiC content, but also an enhancement of the electrical conductivity. All materials studied demonstrated high thermal and electrochemical resistance. After the preliminary physicochemical characterization, Pt-based catalysts with a 40% wt. metal content were synthesized using different carbides studied. Platinum particle and crystallite size, real platinum content and distribution, and electrochemical surface area (ECSA) were the parameters studied. SiCTiC with 30% Pt content exhibited a poor Pt dispersion and ECSA value, achieving better results with catalysts prepared using SiCTiC supports with lower Ti content, resulting on good candidates to be used in this kind of technology.