SIRLANE GOMES DA SILVA

SIRLANE GOMES DA SILVA

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Borohydride reduction method for PdIn/C electrocatalysts synthesis towards glycerol electrooxidation under alkaline condition
2021 - NANDENHA, JULIO; RAMOS, CARLOS E.D.; SILVA, SIRLANE G. da; SOUZA, RODRIGO F.B. de; FONTES, ERIC H.; OTTONI, CRISTIANE A.; OLIVEIRA NETO, ALMIR
Pd−In/C electrocatalysts were synthesized by the adapted borohydride reduction method in different atomic ratios. Electrocatalysts were evaluated by conventional electrochemical techniques and direct glycerol fuel cells. X-ray diffraction profiles indicated the structure of Pd and In (fcc) phases, as well as the presence of In higher oxidation states. Regarding Transmission electron microscopy, it showed the particle‘s average diameters between 6.1–12.7 nm. All PdIn/C electrocatalysts showed high current values for −0.30 V vs. Ag/AgCl, which the best one was PdIn/C 90 : 10. Higher performance for glycerol oxidation was observed in polarization curves at 90 °C for PdIn/C (30 : 70) composition.
Fuel cell and electrochemical studies of the ethanol electro-oxidation in alkaline media using PtAuIr/C as anodes
2018 - SILVA, SIRLANE G.; FONTES, ERIC H.; SILVA, JULIO C.M.; ASSUMPÇAO, MONICA H.M.T.; OLIVEIRA NETO, ALMIR; LINARDI, MARCELO
The use of fossil fuels has resulted in an increase of CO2 concentration in the atmosphere . It is well known that CO2 emission from fossil fuels is one of the principals responsible for the greenhouse effect. Taking these aspects into account,fuel cells might bean excelente alternative to the current energy generation as a clean and eficiente power source. In this context, alkaline fuel cells have attracted worldwide attention due to its promise to produce clean energy with high efficiency [1], thus direct etanol fuel cell could offer an alternative for electrical energy generation. In this work, ethanol electrooxidation reaction was investigated considering conventional electrochemical experiments in alkaline media, direct ethanol fuel cell (DEFC), and in situ ATRFTIR. The working electrode/anodes were composed of monometallic Pt/C, Au/C, Ir/C, and trimetallic PtAuIr/C nanoparticles with atomic Pt/Au/Ir ratios of 40:50:10, 50:40:10, 60:30:10, 70:20:10, and 80:10:10. X-ray diffraction (XRD) suggests PtAuIr/C alloy formation, and according to transmission electron micrographs, the mean particle sizes are from 4 to 6 nm for all catalyst compositions. PtAuIr/C 40:50:10 showed the highest catalytic activity for ethanol electro-oxidation in the electrochemical experiments; using this material, the peak current density from ethanol electro-oxidation on cyclic voltammetry experimente was 50 Ma per g of Pt, 3.5 times higher than that observed with Pt/C. The fuel cell performance was superior using all PtAuIr/C compositions than using Pt/C. Au/C and Ir/C presented very poor catalytic activity toward etanol electro-oxidation. The improved results obtained using PtAuIr/C might be related to the OHads species formed at low overpotential on Ir and to the decrease on adsorption energy of poisoning intermediates on Pt sites, promoted by Au.
Glycerol and ethanol oxidation in alkaline medium using PtCu/C electrocatalysts
2018 - OTTONI, C.A.; RAMOS, C.E.D.; SOUZA, R.F.B. de; SILVA, S.G. da; SPINACE, E.V.; NETO, A.O.
The performance of platinum-copper electrocatalysts synthesized in different ratios (100:0, 90:10, 70:30, 50:50, and 0:100), using a borohydride reduction method for electrochemical oxidation of different fuels, was evaluated in an alkaline direct alcohol fuel cell. X-ray diffraction of Pt/C and PtCu/C showed a face-centered cubic structure (fcc) of the platinum and its alloys. Transmission electron microscopy analysis allowed us to see a good dispersion of metallic particles with some regions with clusters of nanoparticles, for all the synthesised materials in the presence of copper. Cyclic voltammetry and chronoamperometry tests demonstrated that the PtCu/C (50:50) and PtCu/C (70:30) electrocatalysts exhibited the highest activity and stability for the glycerol and ethanol oxidation, respectively. The tests made in fuel cells, directly fed with glycerol and ethanol, presented the PtCu/C (90:10) electrocatalyst as the most effective on the oxidation reaction of the fuels when compared with Pt/C and Cu/C.
Estudo da oxidação eletroquímica do etanol em meio alcalino utilizando eletrocatalisadores PtAuIr/C e PdAuIr/C preparados via redução por borohidreto de sódio
2017 - SILVA, SIRLANE G. da
Eletrocatalisadores Pt/C, Pd/C, PtAu/C, PtIr/C, PdAu/C, PdIr/C, PtAuIr/C e PdAuIr/C foram preparados via redução por borohidreto de sódio em diferentes proporções atômicas, com 20% em massa de metal e suportados em carbono Vulcan XC72 de alta área superficial. Os materiais foram caracterizados pelas técnicas de espectroscopia de energia dispersiva de raios-X (EDX), análise de difração de raios-X (DRX) e microscopia eletrônica de transmissão (MET). A oxidação eletroquímica do etanol foi estudada por voltametria cíclica (VC) e cronoamperometria, utilizando a técnica do eletrodo de camada fina porosa e o estudo da oxidação eletroquímica de etanol \"in situ\" utilizando espectroscopia de infravermelho com transformada de Fourier (FTIR). Posteriormente os materiais foram testados em células à combustível alcalinas alimentadas diretamente com etanol. Os resultados demonstraram que houve formação de ligas, com tamanho médio de nanopartículas entre 4,0 - 10 nm. De acordo com os experimentos eletroquímicos os eletrocatalisadores ternários apresentaram maior atividade eletrocatalítica e os estudos em FTIR indicaram que o produto principal da oxidação eletroquímica de etanol em meio alcalino para todos eletrocatalisadores sintetizados foi o acetato, sugerindo que a oxidação ocorre de forma incompleta pelo mecanismo indireto. Os testes em célula mostraram os melhores resultados para PdAuIr/C (50:40:10) com o qual obteve-se potencial de circuito aberto de aproximadamente 0,78 V e densidade de potência máxima de aproximadamente 15 mW cm-2, cerca de 333% superior a Pd/C.
Fuel cell and electrochemical studies of the ethanol electro-oxidation in alkaline media using PtAuIr/C as anodes
2017 - SILVA, SIRLANE G. da; FONTES, ERIC H.; ASSUMPÇAO, MONICA H.M.T.; LINARDI, MARCELO; SPINACE, ESTEVAM; SILVA, JULIO C.M.; OLIVEIRA NETO, ALMIR
Ethanol electro-oxidation reaction was investigated considering conventional electrochemical experiments in alkaline media, direct ethanol fuel cell (DEFC), and in situ ATRFTIR. The working electrode/anodes were composed of monometallic Pt/C, Au/C, Ir/C, and trimetallic PtAuIr/C nanoparticles with atomic Pt/Au/Ir ratios of 40:50:10, 50:40:10, 60:30:10, 70:20:10, and 80:10:10. X-ray diffraction (XRD) suggests PtAuIr/C alloy formation, and according to transmission electron micrographs, the mean particle sizes are from 4 to 6 nm for all catalyst compositions. PtAuIr/C 40:50:10 showed the highest catalytic activity for ethanol electro-oxidation in the electrochemical experiments; using this material, the peak current density from ethanol electro-oxidation on cyclic voltammetry experiment was 50 mA per g of Pt, 3.5 times higher than that observed with Pt/C. The fuel cell performance was superior using all PtAuIr/C compositions than using Pt/C. Au/C and Ir/C presented very poor catalytic activity toward ethanol electro-oxidation. The improved results obtained using PtAuIr/C might be related to the OHads species formed at low overpotential on Ir and to the decrease on adsorption energy of poisoning intermediates on Pt sites, promoted by Au.
Performance of Pd electrocatalyst supported on a physical mixture indium Tin oxide–carbon for glycerol electro– oxidation in alkaline media
2017 - OTTONI, CRISTIANE A.; SOUZA, RODINEY R. de; SILVA, SIRLANE G. da; SPINACE, ESTEVAM V.; SOUZA, RODRIGO F.B. de; OLIVEIRA NETO, ALMIR
Palladium electrocatalysts, supported on Vulcan XC 72 carbon and indium tin oxide (ITO) with different ratios, were prepared by borohydride reduction method and analysed for glycerol electro-oxidation application in the presence of KOH solution. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) techniques were used to characterize the particle size and crystal electrocatalyst structures, whereas their catalytic activities regarding the glycerol electro-oxidation were evaluated by cyclic voltammetry (CV), chronoamperometry and tested in a direct alkaline glycerol fuel cell (DGFC) by electrochemical techniques. Micrographs results showed that the ITO presence promotes a large agglomeration of particles. Pd/C–ITO electrocatalysts showed peaks associated with the face-centered cubic (fcc) structure of palladium and several others peaks associated with ITO used as support. Similar performance was found on all Pd/ C–ITO electrocatalysts where measurements in CV were compared to Pd/C and Pd/ITO with Pd/C–ITO 50:50 chronoamperometry, presenting a better performance for glycerol electro-oxidation. When using Pd/C–ITO 85:15 electrocatalyst and 1.0 mol L 1 glycerol at 908C, the maximum power density found was 2,1 times higher than that obtained using Pd/C and Pd/CITO electrocatalysts. Therefore, the physical mixture of ITO and carbon, to be used as a support improves the electrocatalytic activity for glycerol oxidation reaction.
Use of PtAu/C electrocatalysts toward formate oxidation: electrochemical and fuel cell considerations
2016 - SILVA, SIRLANE G. da; SILVA, JULIO C.M.; BUZZO, GUILHERME S.; NETO, ALMIR O.; ASSUMPÇAO, MONICA H.M.T.
This study reports the use of PtAu/C electrocatalysts with different atomic ratios (90:10, 70:30 and 50:50) supported on Vulcan XC 72 carbon and prepared by the sodium borohydride method toward formate electrooxidation in alkaline media. The materials were characterized by X-ray diffraction, showing peaks characteristics of Pt and Au face-centered-cubic structures, and also by transmission electron micrographs that show the nanoparticles well dispersed on carbon and a mean particle size between 4 and 5 nm for all electrocatalysts. Electrochemical experiments show PtAu/C as promising catalysts toward formate oxidation, while single cell experiments reveal PtAu/C 90:10 as the best material since it provides a power density higher than Pt/C. The incorporation of Au could increase formate oxidation for more than one reason: (i) a facilitated rupture of C–H bond; (ii) the Au/oxide interface or (iii) by regenerating active sites.
Methanol oxidation in alkaline medium using PtIn/C electrocatalysts
2016 - SANTOS, M.C.L.; OTTONI, C.A.; SOUZA, R.F.B. de; SILVA, S.G. da; ASSUMPÇAO, M.H.M.T.; SPINACE, E.V.; NETO, A.O.
Pt/C and PtIn/C with atomic ratios of 90:10, 70:30, and 50:50 were investigated for methanol electro-oxidation in alkaline media by using cyclic voltammetry (CV), chronoamperometry (CA), and direct methanol alkaline fuel cell (DMAFC). All electrocatalysts were synthesized using sodium borohydride method with 20 wt% of metals loading on carbon. X-ray diffraction (XRD) analysis revealed that bimetallic PtIn had faced centered cubic structure and, also, confirmed alloy formation for PtIn/C nanoparticles. Transmission electron micrographs showed metal nanoparticles with average particle size between 3.0 and 5.0 nm; however, the particle size increases when the In content was increased in PtIn/C. In the CV experiments, the onset potential of methanol electro-oxidation shifted to lower values as the indium content increased. Chronoamperometry experiments and direct methanol alkaline fuel cell suggested PtIn/C (70:30) as the most promising material for methanol electrooxidation: this result could be explained by the presence of Pt and In in close contact (electronic effect) as the occurrence of oxy-hydroxy interactions.
Glycerol and methanol electro-oxidation at Pt/C-ITO under alkaline condition
2016 - OTTONI, CRISTIANE A.; RAMOS, CARLOS E.D.; SILVA, SIRLANE G. da; SPINACE, ESTEVAN V.; SOUZA, RODRIGO F.B. de; OLIVEIRA NETO, ALMIR
A physical mixture composed by carbon Vulcan XC 72 and indium tin oxide (ITO) with different ratios (85 : 15; 50 : 50; 85 : 15) was used as support for platinum nanoparticles synthesis by borohydride reduction method. The characterization of this electrocatalyst was performed by transmission electron microscopy (TEM), X-ray diffraction (XRD), electrochemical techniques cyclic voltammetry (CV), chronoamperometry and performance test on direct alkaline glycerol/methanol fuel cell (DGFC/ DMFC). According to TEM micrographs, Pt/C-ITO nanoparticles analysis revealed the presence of large agglomerations of particles. Moreover, it was possible to observe Pt deposition on ITO and also in the carbon surface. The electrochemical studies showed that Pt/C-ITO (85 : 15) had superior performance for glycerol electro-oxidation, whereas Pt/C-ITO (15 : 85) was the most promising in the methanol oxidation. A comparative study using direct alkaline fuel cells revealed Pt-C-ITO (15 : 85) electrocatalyst to be the best material for glycerol and methanol oxidation, specifically when being at open circuit potential about 0.95 V, maximum power density of 16 mW cm2 for glycerol and circuit potential 0.95 V, and maximum power density of approximately 20 mW cm2 for methanol.
In situ ATR-FTIR studies of ethanol electro-oxidation in alkaline medium on PtRh/C electrocatalyst prepared by an alcohol reduction process
2016 - FONTES, E.H.; SILVA, SIRLANE G. da; SPINACE, E.V.; NETO, A.O.; SOUZA, R.F.B. de
Anion exchange membrane fuel cell is a new chance to produce a functional and portable fuel cell; however, the studies are still at an early stage with few reports regarding the AEMFC. PtRh/C electrocatalysts with different Pt:Rh atomic ratios were prepared by an alcohol reduction process. X-ray diffraction patterns for all PtRh/C materials indicated no shift in Pt(fcc) peaks showing that Rh did not incorporated into Pt lattice; however, the analysis of lattice parameter showed that some Pt atoms are added to Rh(fcc) structure. The mean particle sizes were in the range of 4–5 nm. Electrochemical experiments showed that PtRh/C electrocatalyst with Pt:Rh atomic ratio of 70:30 had superior performance exhibiting a current density of 5.0 mA mgmetal−1 . From in situ ATR-FTIR experiments, it was observed that PtRh/C electrocatalyst with Pt:Rh atomic ratio of 70:30 produced more acetate ions than other ones, while the material prepared with Pt:Rh atomic ratio of 50:50 was more selective to CO2 as observed in acid media.