Percorrer por autor "Capelo, Anabela"
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- Dielectric UV filters for protection of fire-resistant glass based on intumescent layersPublication . Silva, Ricardo Magno Lopes; Hashim, Hurraira; Roy, Deepto; Oliveira Fernandes, Carolina; Oliveira, Kevin; Leitão Pinheiro, Xavier Alexandre; Esteves, M. Alexandra; Capelo, Anabela; Donato, Mariana; Oliveira, Fernando; Ferreira, Cristina; Alves, Isabel N.; Cunha Diamantino, Teresa; Barreiros, Maria Alexandra; Rocha, Jorge; Passos Teixeira, Jennifer; Salomé, PedroABSTRACT: Structures such as OLEDs, perovskite solar cells, intumescent glasses, and other components in modern devices and buildings contain materials suscep-tible to degradation when exposed to UV radiation, requiring protection to with-stand outdoor environmental conditions. In this work, multilayer coating config-ured as a Bragg Reflector on glass is employed as spectral filtering to protect the intumescent component of fire-resistant glass from degradation due to prolonged UV solar radiation exposure. By alternating low-n (SiO2)/high-n (TiO2) dielectric layers through spin-coating, precise control over film thickness could be achieved, allowing the fabrication of thin (<700 nm) UV filters with high trans-mission of visible sunlight – 88% of the 780 to 380 nm wavelength range – while reflecting almost all the incident UV – 90% of the wavelength below 380nm. Using relatively simple techniques, high precision coating was successfully achieved, resulting in an effective UV radiation protective barrier applied to en-hance the durability of the components in fire-resistant glass.
- Electrocatalitic activity of platinum deposited on carbon functionalized with sulphonic groupsPublication . Capelo, Anabela; Esteves, M. Alexandra; Sá, A.I. 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 H2SO4 solution with added methanol or chloride demonstrating well defined features and stable voltammograms after cycling, with apparent higher currents when compared with commercial catalyst. The structure sensitive adsorption of anions on platinum is confirmed by either the blocking effect of chloride ions or methanol, evident in both anodic and cathodic features of the voltammograms. Optimal performance was found for a Nafion® concentration of 15-20 wt %.
- Enhancing Pt electrocatalytic activity by surface functionalization of carbon support with aromatic sulphonic groupsPublication . Capelo, Anabela; Esteves, M. Alexandra; de Sá, A.I.; Rangel, C. M.Preliminary results are presented for Pt deposited on 4-aminobenzenesulphonic acid-functionalized carbon, Pt/C_ABSA. Vulcan XC-72R was functionalized with the objective of influencing the dispersion of catalyst nanoparticles and to decrease the resistance of three phase boundaries, by introducing sulphonic groups. Electrochemical characterization of the supported catalyst was done in a 0.5 M sulphuric acid solution with added chloride and also using methanol demonstrating well defined features and stable voltammograms after 30 cycles, with apparent higher currents when compared with commercial catalyst. The structure sensitive adsorption of anions on platinum is confirmed by the blocking effect of chloride ions in the hydrogen adsorption-desorption region as well as by the consequent dissolution of platinum, evident in both anodic and cathodic features of the voltammograms regarding surface oxide formation and reduction. The partial reversibility of the effect of chloride ions is discussed. Research is in progress in order to accomplish a comprenhensive characterization of the synthesized catalyst and to ascertain the effect of the sulphonic groups.
- Evolution of atomically dispersed co-catalysts during solar or UV photocatalysis for efficient and sustained H2 productionPublication . Capelo, Anabela; Fattoruso, Domenico; Valencia-Valero, Laura; Esteves, M. Alexandra; Rangel, Carmen M.; Puga, AlbertoABSTRACT: The evolution of metal/titania photocatalysts during photocatalytic H-2 evolution is herein studied. Samples containing atomically dispersed Pt co-catalysts (single atoms, clusters and sub-nanoparticles) formed after calcination were compared to pre-reduced analogues mostly having metallic nanoparticles (diameters >1 nm) during ethanol photoreforming under either UV-rich irradiation or natural sunlight. Aggregation of ultra-dispersed oxidised platinum entities (Pt delta+) with concomitant reduction into Pt-0 nanoparticles (1-2 nm) was observed after UV irradiation by transmission electron microscopy (TEM), and diffuse reflectance UV-visible (DRUV-vis) and X-ray photoelectron (XPS) spectroscopies. A parallel, albeit slower, evolution trend was evidenced during solar photocatalysis. Conversely, atomically dispersed Cu co-catalyst species did not grow and became in-situ reduced into sub-nanometric Cu-0 under irradiation. Hydrogen production rates were remarkably high during initial stages of UV irradiation, and then declined to a sustained regime (approximate to 50 and 8 mmol g(-1) h(-1) for Pt/TiO2 or Cu/TiO2, respectively, for up to 24 h of irradiation). Steadier solar photoreforming was observed in experiments performed in a compound parabolic collector tubular reactor (approximate to 7.6 and 1.7 mmol g(-1) h(-1) for Pt/TiO2 or Cu/TiO2, respectively). Despite the non-negligible effect of co-catalyst rearrangement on activity rationalised herein, attenuated total reflectance Fourier-transform infrared (ATR-FTIR) spectroscopy measurements pre- and post-photocatalysis suggest that accumulation of strongly adsorbed degradation intermediates, chiefly acetate, is a major cause for rate decreases. Notwithstanding, this phenomenon did not result in total deactivation, so that sustained hydrogen production upon long-term irradiation was not compromised.
- Fire-resistant materials: characterization and thermal behavior of intumescent gels for fire resistant glass [Poster]Publication . Donato, Mariana; Esteves, M. Alexandra; Capelo, Anabela; Oliveira, Fernando; Ferreira, Cristina; Alves, Isabel N.; Morgado, Vanessa; Correia, Jose B.; Teixeira, Jennifer P.; Oliveira Fernandes, Carolina; Silva, Ricardo Magno Lopes; Rocha, Jorge; Salomé, Pedro; Cunha Diamantino, Teresa; Barreiros, Maria Alexandra
- Intumescent Gels for Fire-Resistant Glass: Thermal Insulation, UV Protection, and Durability Studies [Comunicação oral]Publication . Esteves, M. Alexandra; Capelo, Anabela; Donato, Mariana; Oliveira, Fernando; Ferreira, Cristina; Alves, Isabel N.; Correia, Jose B.; Silva, Ricardo Magno Lopes; Hashim, Hurraira; Roy, Deepto; Passos Teixeira, Jennifer; Rocha, Jorge; Salomé, Pedro; Cunha Diamantino, Teresa; Barreiros, Maria Alexandra
- Intumescent Gels for Fire-Resistant Glass: Thermal Insulation, UV Protection, and Durability Studies [Poster]Publication . Esteves, M. Alexandra; Capelo, Anabela; Donato, Mariana; Oliveira, Fernando; Ferreira, Cristina; Alves, Isabel N.; Correia, Jose B.; Silva, Ricardo Magno Lopes; Hashim, Hurraira; Roy, Deepto; Passos Teixeira, Jennifer; Rocha, Jorge; Salomé, Pedro; Cunha Diamantino, Teresa; Barreiros, Maria Alexandra
- Low load Pt catalyst with surface functionalised carbon supports for PEM fuel cells: half and full cell asssessmentsPublication . Capelo, Anabela; González, L.; Sá, A.I. De; Rangel, C. M.ABSTRACT: Current US DOE 2020 targets for electrocatalysts aim for a total platinum group metals (PGM) loading of 0.125 mgcm-2 on membrane-electrode assemblies. The catalysts are expected to endure an elevated number of load cycles in order to comply with the expected 5000 h stack lifetime. At the stated PGM low loading attributes of performance, power and durability, as well as costs, are simultaneously required. The present paper deals with performance assessment of new catalyst using Pt nanoparticles and a surface functionalized carbon support. Due to its relevance to fuel cell operation, the stability and durability were assessed in half cell mode, through the application of demanding aging cycling protocols (30000 cycles). Full fuel cell assessments were also conducted entailing power density curves and cell electrochemical impedance. Results denote significant improvements in cell performance as well as in catalyst stability, regarding a commercial catalyst tested in the same conditions, at Pt loadings of 0.1 mgcm-2.
- New hydroxypyrimidinone-sulfonamides as biatarget ligands for enzyme inhibitionPublication . Esteves, M. Alexandra; Olrtet, Osvaldo; Capelo, Anabela; Santos, Célia; Marques, Sérgio; Supuran, Claudiu; Santos, M. Amélia
- Novos nanocompósitos de óxido de titânio para a produção de hidrogénio solarPublication . Capelo, Anabela; Esteves, M. Alexandra; Fernandes, Vitor; Rangel, C. M.RESUMO: Neste trabalho foram sintetizados uma série de novos compósitos de TiO2-rGO e TiO2-g-C3N4, como base para o desenvolvimento de fotocatalisadores ativos na produção de hidrogénio solar a partir de soluções aquosas de etanol. Os compósitos foram dopados com metais nobres e de transição (Pt, Au e Cu), tendo sido estes fotodepositados a partir dos respetivos sais. Para 6 h de irradiação UV, o volume de gás produzido com os catalisadores TiO2-Pt1.5% e TiO2-Au1.5% é semelhante, embora com perfis de velocidade diferentes, que mostram 2 declives no caso da Pt. A substituição da Pt por Cu deu resultados promissores em termos de gás produzido, ainda que nas presentes condições experimentais não foi significativamente alterado pela presença de rGO ou g-C3N4. A irradiação contínua até 24 h evidenciou velocidades constantes para os fotocatalisadores TiO2-Cu contrariamente ao TiO2-rGO3%-Pt3.8% cuja produção de gás parou pelas 12 h, devido a envenenamento pelos produtos de oxidação do etanol. A substituição de Pt por Cu revela-se também vantajosa considerando as questões associadas à escassez e custo da Pt.