RITA MARIA DE SOUSA RODRIGUES

RITA MARIA DE SOUSA RODRIGUES

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Preparation of PtRu/C Electrocatalysts by borohydride reduction for methanol oxidation in acidic and alkaline medium
2017 - SANTOS, MONIQUE C.L. dos; DUTRA, RITA M.; RIBEIRO, VILMARIA A.; SPINACE, ESTEVAM V.; OLIVEIRA NETO, ALMIR
PtRu/C electrocatalysts were performed according to the borohydride reduction method and characterized by X–ray diffraction (XRD), energy dispersive analysis (EDX), transmission electron microscopy, cyclic voltammetry (CV) and polarization curves in alkaline and acidic medium. The X-ray diffraction (XRD) of PtRu/C showed Pt peaks attributed to the face-centered cubic (fcc) structure and a shift in Pt(fcc) peaks indicated that Ru was incorporated into Pt lattice. TEM results showed mean particles sizes in the range of 2.0-4.0nm for all electrocatalysts prepared: therefore, the borohydride reduction process was considered effective for the preparation of PtRu/C electrocatalysts with a different atomic ratio. The activity for the methanol oxidation in acidic and alkaline media was investigated at room temperature, by cyclic voltammetry and chronoamperometry. Cyclic voltammetry and chronoamperometry studies showed that PtRu/C (50:50) had superior performance for methanol oxidation, compared with other electrocatalysts prepared considering acidic and alkaline studies. The currents values observed for alkaline media were higher than those observed for acidic media. Polarization curves, also, showed PtRu/C (50:50) with superior performance for methanol oxidation, when compared with Pt/C, and this improvement of performance could be associated with the occurrence of the bifunctional mechanism and electronic effect.
Estudo da oxidação eletroquímica do etanol em meio acido utilizando os eletrocatalisadores PtSnAuRh/C e PtRuAuRh/C
2016 - DUTRA, RITA M.
Os eletrocatalisadores quartenários PtSnAuRh/C e PtRuAuRh/C foram preparados nas proporções 50:40:5:5, 60:30:5:5, 70:20:5:5, 80:10:5:5, 90:4:3:3 e para as composições terciárias PtSnAu/C, PtSnRh/C, PtRuAu/C, PtRuRh/C preparados na proporção atômica 50:45:5 com (20% em massa) pelo método da redução por álcool utilizando H2PtCl6.6H2O, RuCl3·xH2O, SnCl2.2H2O, HAuCl4.3H2O e RhCl3.xH2O, como fonte de metais e carbono Vulcan XC72 como suporte e, por último, etileno glicol como agente redutor. Os eletrocatalisadores obtidos foram caracterizados fisicamente por difração de raios-X (DRX), energia dispersiva de raios X (EDX) e microscopia eletrônica de transmissão (MET). As análises por EDX mostraram que as razões atômicas dos diferentes eletrocatalisadores, preparados pelo método da redução por álcool, foram similares às composições nominais de partida indicando que esta metodologia é eficiente para a preparação destes eletrocatalisadores. Em todos os difratogramas para os eletrocatalisadores preparados observa-se um pico largo em aproximadamente 2θ = 25°, o qual é associado ao suporte de carbono e quatro outros picos de difração em aproximadamente 2θ = 40°, 47°, 67° e 82°, que por sua vez são associados aos planos (111), (200), (220) e (311), respectivamente, da estrutura cúbica de face centrada (CFC) de platina. Os resultados de difração de raios X apresentaram tamanhos médios de cristalitos entre 2,0 e 5,2 nm para PtSnAuRh/C, PtSnAu/C, PtSnRh/C e 2,0 a 2,6 nm para PtRuAuRh/C, PtRuAu/C, PtRuRh/C. Os estudos para a oxidação eletroquímica do etanol em meio ácido foram realizados utilizando as técnicas de voltametria cíclica e de cronoamperometria em uma solução 0,5 mol.L-1 H2SO4, + 1,0 mol.L-1 de C2H5OH. As curvas de polarização obtidas na célula a combustível unitária, alimentada diretamente por etanol, estão de acordo com os resultados de voltametria e cronoamperometria constatando o efeito benéfico da adição do ouro e ródio na composição dos eletrocatalisadores.
Preparação do eletrocatalisador PtSn/C+Er2O3 pelo método da redução por álcool para a eletro-oxidação do etanol
2010 - RODRIGUES, RITA M. de S.; SPINACE, ESTEVAM V.; LINARDI, MARCELO; OLIVEIRA NETO, ALMIR
Preparation of Pt rate earth/C electrocatalysts using the alcohol-reduction process ethanol electro-oxidation
2008 - RODRIGUES, RITA M. de S.; RIBEIRO, VILMARIA A.; BRANDALISE, MICHELE; TUSI, MARCELO M.; LINARDI, MARCELO; FORBICINI, CHRISTINA A.L.G.O.; SPINACE, ESTEVAM V.; OLIVEIRA, ALMIR
Fuel cell employing alcohols directly as combustible (Direct Alcohol Fuel Cell - DAFC) are attractive as power sources for mobile, stationary and portable applications. Compared to hydrogen-fed fuel cells which need a reforming system, or have hydrogen storage problems, DAFC uses a liquid fuel simplifying the fuel system. Methanol has been considered the most promising fuel, because it is more efficiently oxidized than others alcohols, however, slow anode kinetics are observed and it is a toxic product. Ethanol offers an attractive alternative in relation to methanol as a fuel in low temperature fuel cells because it can be produced in large quantities from agricultural products and it is the major renewable biofuel from the fermentation of biomass. However, its complete oxidation to CO2 is more difficult than that of methanol due to the difficulty in C–C bond breaking and to the formation of CO-intermediates that poison the platinum anode catalysts. In this context, more active electrocatalysts are essential to enhance the ethanol electro-oxidation. In recent years, it is found that certain metal oxides, such as RuO2, SnO2 and CeO2, can enhance the catalytic activity for ethanol or methanol electro-oxidation through synergetic interaction with Pt. Among those, rare earth oxides exhibit a number of characteristics that make them interesting for catalytic studies. In this work, Pt Rare Earth/C electrocatalysts (Rare Earth = La, Ce, Pr, Nd, Sm, Tb, Dy, Ho Er, Tm and Lu) were prepared in a single step by an alcohol reduction process using ethylene glycol as reduction agent and solvent and Vulcan XC 72 as support. The obtained materials were tested for ethanol oxidation in acid medium using cyclic voltammetry and chronoamperometry. The EDX analysis showed that the Pt:RE atomic ratios obtained for all electrocatalysts were approximately 60:40 and were similar to the ones used in the preparations. The X-ray diffractograms of Pt Rare Earth/C electrocatalysts showed the typical fcc structure of platinum and the presence of rare earth (III) hydroxides. The average particle size were calculated using Scherrer equation using the reflections of Pt(220) peak and the values are in the range of 6-15 nm. The final current values after holding the cell potential at 0.5V versus RHE for 30 min are following: PtLu/C> PtTb/C > PtEr/C ≈ PtNd/C ≈ PtCe/C > PtHo/C > PtLa/C >PtDy/C > PtTm/C > PtPr/C > PtSm/C > Pt/C. The superior activity of Pt Rare Earth/C electrocatalysts in relation Pt/C could be attributed probably to the bi-functional mechanism were Pt acts on ethanol adsorption and dissociation and Rare Earth provides oxygenated species at lower potentials for oxidative removal of adsorbed CO.
Preparacao de eletrocatalisadores PtRu/C + terras raras pelo metodo da reducao por alcool para a eletro-oxidacao do etanol
2010 - TUSI, M.M.; RODRIGUES, R.M.S.; SPINACE, E.V.; OLIVEIRA NETO, A.
Preparação e caracterização de eletrocatalisadores PtSn/C-terras raras e PtRu/C-terras raras para a eletro-oxidação do etanol
2011 - RODRIGUES, RITA M. de S.
Os eletrocatalisadores PtRu/C-terras raras e PtSn/C-terras raras (20% em massa) foram preparados pelo método da redução por álcool utilizando H2PtCl6.6H2O RuCl3·xH2O, SnCl2.2H2O como fonte de metais, 85 % Vulcan - 15 % de terras raras como suporte e, por último, etileno glicol como agente redutor. Os eletrocatalisadores obtidos foram caracterizados fisicamente por difração de raios-X (DRX), energia dispersiva de raios X (EDX) e microscopia eletrônica de transmissão (MET). As análises por EDX mostraram que as razões atômicas dos diferentes eletrocatalisadores, preparados pelo método da redução por álcool, são similares às composições nominais de partida indicando que esta metodologia é promissora para a preparação destes eletrocatalisadores. Em todos os difratogramas para os eletrocatalisadores preparados observa-se um pico largo em aproximadamente 2θ = 25o, o qual é associado ao suporte de carbono e quatro outros picos de difração em aproximadamente 2θ = 40o, 47o, 67o e 82o, que por sua vez são associados aos planos (111), (200), (220) e (311), respectivamente, da estrutura cúbica de face centrada (CFC) de platina. Os resultados de difração de raios X também mostraram tamanhos médios de cristalitos entre 2,0 e 4,0 nm para PtSn e 2,0 a 3,0 para PtRu. Os estudos para a oxidação eletroquímica do etanol em meio ácido foram realizados utilizando a técnica de cronoamperometria em uma solução 0,5 mol.L-1 H2SO4, + 1,0 mol.L-1 de C2H5OH. As curvas de polarização obtidas na célula a combustível unitária, alimentada diretamente por etanol, estão de acordo com os resultados de voltametria e cronoamperometria constatando o efeito benéfico das terras raras na preparação dos eletrocatalisadores e atestando que os eletrocatalisadores de PtSn/C são mais efetivos que PtRu/C para a oxidação do etanol.
Electrooxidation of ethanol using Pt rare earth-C Electrocatalysts prepared by an alcohol reduction process
2008 - OLIVEIRA NETO, ALMIR; WATANABE, ANDRE Y.; RODRIGUES, RITA M. de S.; LINARDI, MARCELO; FORBICINI, CHRISTINA A.L.G.O.; SPINACE, ESTEVAM V.
Pt rare earth–C electrocatalysts (rare earth = La, Ce, Pr, Nd, Sm, Tb, Dy, Ho, Er, Tm, and Lu) were prepared by an alcohol reduction process using ethylene glycol as reduction agent and solvent and Vulcan XC 72 as support. The electrocatalysts were characterized by energy-dispersive X-ray analysis, X-ray diffraction (XRD), and cyclic voltammetry. The electrooxidation of ethanol was studied in acid medium by cyclic voltammetry and chronoamperometry using thin porous coating technique. The XRD patterns indicate that all electrocatalysts present the facecentered cubic structure of Pt and the presence of rare earth hydroxides. All electrocatalysts prepared by this methodology showed superior performance for ethanol electrooxidation at room temperature compared to Pt–C.
Preparation and characterization of Pt-rare earth/C electrocatalysts using and alcohol reduction process for methanol electro-oxidation
2009 - OLIVEIRA NETO, ALMIR; WATANABE, ANDRE Y.; BRANDALISE, MICHELE; TUSI, MARCELO M.; RODRIGUES, RITA M. de S.; LINARDI, MARCELO; SPINACE, ESTEVAM V.; FORBICINI, CHRISTINA A.L.G.O.
Pt-Rare Earth/C electrocatalysts (Rare Earth = La, Ce, Pr, Nd, Sm, Tb, Dy, Ho and Er) were prepared by an alcohol reduction process using ethylene glycol as reduction agent and solvent and Vulcan XC72 as support. The electrocatalysts were characterized by energy dispersive X-ray analysis (EDX), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The electro-oxidation of methanol was studied in acid medium by cyclic voltammetry and chronoamperometry using thin porous coating technique. The XRD patterns indicate that all electrocatalysts present the face-centered cubic (fcc) structure of Pt and the presence of Rare Earth hydroxides. PtEr/C, PtTb/C, PtLa/C, PtDy/C and PtNd/C electrocatalysts prepared by this methodology showed superior performance for methanol electro-oxidation at room temperature compared to Pt/C.
Preparation and characterization of PtSn/C-rare earth using an alcohol reduction process for ethanol electro-oxidation
2010 - BRANDALISE, MICHELE; TUSI, MARCELO M.; RODRIGUES, RITA M.S.; SPINACE, ESTEVAM V.; OLIVEIRA NETO, ALMIR
PtSn/C, PtSn/Er2O3-C, PtSn/CeO2–C, PtSn/La2O3–C and PtSn/Nd2O3–C electrocatalysts were prepared by an alcohol-reduction process using H2PtCl6.6H2O and SnCl2.2H2O as metal sources, ethylene glycol as solvent and reducing agent, 85% Vulcan XC72-15% rare earth (Er2O3, CeO2, La2O3 and Nd2O3) as support. The platinum and tin metal loadings were always kept at 20 wt%. The electrocatalysts were characterized by EDX, XRD and TEM, while that the performance for ethanol oxidation was investigated by cyclic voltammetry and cronoamperommetry at room temperature. The PtSn/Er2O3–C electrocatalyst showed an increase of performance for ethanol oxidation in relation to PtSn/C electrocatalyst. The final current values after holding the cell potential at 0.5 V versus RHE for 30 min were the following: PtSn/Er2O3–C > PtSn/CeO2–C > PtSn/Nd2O3–C > PtSn/La2O3–C > PtSn/C. In the tests at 100oC on a single cell of a direct ethanol fuel cell (DEFC), the PtSn/Er2O3–C electrocatalyst also showed the best performance in relation to the others electrocatalysts.
Preparation and characterization of PtRu/C-rare earth using an alcohol-reduction process for ethanol electro-oxidation
2011 - RODRIGUES, R.M.S.; TUSI, M.M.; CHIKASAWA, M.H.; FORBICINI, C.A.L.G.O.; LINARDI, M.; SPINACE, E.V.; OLIVEIRA NETO, A.