RICARDO MARCELO PIASENTIN

RICARDO MARCELO PIASENTIN

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Comparison of various atomic compositions of Au@Pd/C, Pd/C, and AuPd/C electrocatalysts for direct ethanol fuel cells
2020 - FONTES, ERIC H.; NANDENHA, JULIO; PIASENTIN, RICARDO M.; SOUZA, RODRIGO F.B. de; NETO, ALMIR O.
Pd/C, Au@Pd/C (core-shell), and AuPd/C (AR—consisting in Au microparticles) were used as electrocatalysts for ethanol oxidation in alkaline medium. A synergistic effect between Au and Pd atoms in Au@Pd/C makes the binding between ethanol and Au@Pd/C stronger. This leads to product formation in higher potentials and can be useful to select ethanol products. We also showed that the atomic composition of the electrocatalysts to be used in fuel cells and in powder form to be used in electrochemical experiments are very similar, reaching high values of correlation. The depth profiling X-ray photoelectron spectroscopy for the anode catalysts to be used in fuel cells can provide new insights about ethanol oxidation in direct ethanol fuel cells (DEFCs), for instance, metal oxide species can act in fuel cells environment. In terms of electric generation, Au@Pd/C presented a better performance in electrochemical experiments; the current density was about 1.6 times higher than the peak current density obtained for Pd/C. In terms of electrochemical stability, Au@Pd/C presented better final current density when compared to Pd/C and AuPd/C electrocatalysts. However, in DEFC experiments, Pd/C showed better performance.
Partial oxidation of methane and generation of electricity using a PEMFC
2019 - NANDENHA, J.; PIASENTIN, R.M.; SILVA, L.G.M.; FONTES, E.H.; NETO, A.O.; SOUZA, R.F.B. de
The aim of this work was to produce methanol through partial oxidation of methane. The gas fed in a solid membrane reactor- PEM fuel cell type (H2/H2O2 + CH4) has been used for electrosynthesis of methanol at room temperature, with electricity cogeneration as a benefit. It was observed that the current density measured when injected CH4 in the cathode decreased about 45%. This occurs due to the conversion of methane inmethanol in some ranges of potentials. In the other hand, in lower ranges of cell potential, formaldehyde was found. In this work, methane was injected on the cathode together with H2O2 solution, where it was observed that the catalytic layer adsorbed CH4 and H2O2 in active sites, which produced OH− radicals that reacted with the hydrocarbon.
Structural analysis of PdRh/C and PdSn/C and its use as electrocatalysts for ethanol oxidation in alkaline medium
2019 - FONTES, ERIC H.; RAMOS, CARLOS E.D.; NANDENHA, JULIO; PIASENTIN, RICARDO M.; OLIVEIRA NETO, ALMIR; LANDERS, RICHARD
The Pd/C, PdRh(50:50)/C and PdSn(50:50)/C nanomaterials were used as electrocatalysts for ethanol (EtOH) oxidation in Direct Ethanol Fuel Cell (DEFC) in an alkaline medium. This work aims to provide a complete physical characterization of the nanomaterials, elucidate the bifunctional mechanism concerning ethanol oxidation reaction and understand the influence of carbon e metal bonding in the electrochemical activity. These nanomaterials were investigated by X-ray photoelectron spectroscopy (XPS) and revealed that the atomic percentage of the surface is different of those obtained by Energy Dispersive X-ray spectroscopy (EDS). Raman spectroscopy showed a bonding between palladium and carbon atoms which can play a decisive role in the performance of the materials. Attenuated Total Reflectance technique coupled to the Fourier Transform Infrared spectroscopy (ATR-FTIR) made possible to investigate the oxidation products originated by the ethanol oxidation, and all the electrocatalysts showed the presence of acetaldehyde, carbonate ions, acetate and carbon dioxide, suggesting that the mechanism of oxidation is incomplete. Among all the nanomaterials studied, PdSn(50:50)/C showed the best electrochemical and Fuel Cell's results. It is about 33% better than Pd/C. The micrographs obtained by Transmission Electron Microscopy (TEM) revealed some agglomerate regions, but they are consistent with the literature data.
Direct oxidation of methane at low temperature using Pt/C, Pd/C, Pt/C-ATO and Pd/C-ATO electrocatalysts prepared by sodium borohydride reduction process
2018 - NANDENHA, J.; FONTES, E.H.; PIASENTIN, R.M.; FONSECA, F.C.; NETO, A.O.
The main objective of this paper was to characterize the voltammetric profiles of the Pt/C, Pt/C-ATO, Pd/C and Pd/C-ATO electrocatalysts and study their catalytic activities for methane oxidation in an acidic electrolyte at 25°C and in a direct methane proton exchange membrane fuel cell at 80°C. The electrocatalysts prepared also were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The diffractograms of the Pt/C and Pt/C-ATO electrocatalysts show four peaks associated with Pt face-centered cubic (fcc) structure, and the diffractograms of Pd/C and Pd/C-ATO show four peaks associated with Pd face-centered cubic (fcc) structure. For Pt/C-ATO and Pd/C-ATO, characteristic peaks of cassiterite (SnO2) phase are observed, which are associated with Sb-doped SnO2 (ATO) used as supports for electrocatalysts. Cyclic voltammograms (CV) of all electrocatalysts after adsorption of methane show that there is a current increase during the anodic scan. However, this effect is more pronounced for Pt/C-ATO and Pd/C-ATO. This process is related to the oxidation of the adsorbed species through the bifunctional mechanism, where ATO provides oxygenated species for the oxidation of CO or HCO intermediates adsorbed in Pt or Pd sites. From in situ ATR-FTIR (Attenuated Total Reflectance-Fourier Transform Infrared) experiments for all electrocatalysts prepared the formation of HCO or CO intermediates are observed, which indicates the production of carbon dioxide. Polarization curves at 80°C in a direct methane fuel cell (DMEFC) show that Pd/C and Pt/C electroacatalysts have superior performance to Pd/C-ATO and Pt/C-ATO in methane oxidation.
Effect of Sn loading on the characteristics of Pt electrocatalysts supported on reduced graphene oxide for application as direct ethanol fuel cell anode
2017 - CORDEIRO, GUILHERME L.; USSUI, VALTER; MESSIAS, NILDEMAR A.; PIASENTIN, RICARDO M.; LIMA, NELSON B. de; NETO, ALMIR O.; LAZAR, DOLORES R.R.
The effect of Sn loading (5–30 mol %) on Pt catalysts supported on reduced graphene oxide was investigated for ethanol electro-oxidation in acidic medium. Reduced graphene oxide was synthesized via graphite oxidation–exfoliation process in liquid phase and chemical reduction. Pt and PtxSny catalysts were deposited on reduced graphene oxide by a NaBH4 impregnation–reduction method. The adopted procedures allowed the synthesis of graphene-like nanosheets where single Sn-doped Pt nanoparticles were impregnated. Pt lattice parameter and micro-strain increased with Sn addition, confirming the formation of a solid solution. Concerning ethanol electro-oxidation, Pt was more active when supported on reduced graphene oxide whereas the introduction of Sn enhanced the catalyst activity, leading to lower ethanol oxidation potentials and higher current densities.
The effect of antimony-tin and indium-tin oxide supports on the catalytic activity of Pt nanoparticles for ammonia electro-oxidation
2016 - SILVA, JULIO C.M.; PIASENTIN, RICARDO M.; SPINACE, ESTEVAM V.; NETO, ALMIR O.; BARANOVA, ELENA A.
Platinum nanoparticles supported on carbon (Pt/C) and carbon with addition of ITO (Pt/C-ITO (In2O3)(9)center dot(SnO2)(1)) and ATO (Pt/C-ATO (SnO2)(9).(Sb2O5)(1)) oxides were prepared by sodium borohydride reduction method and used for ammonia electro-oxidation reaction (AmER) in alkaline media. The effect of the supports on the catalytic activity of Pt for AmER was investigated using electrochemical (cyclic voltammetry and chronoamperometry) and direct ammonia fuel cell (DAFC) experiments. X-ray diffraction (XRD) showed Pt peaks attributed to the face-centered cubic (fcc) structure, as well as peaks characteristic of In2O3 in ITO support and cassiterite SnO2 phase of ATO support. According to transmission electron micrographs the mean particles sizes of Pt over carbon were 5.4, 4.9 and 4.7 nm for Pt/C, Pt/C-ATO and Pt/C-ITO, respectively. Pt/C-ITO catalysts showed the highest catalytic activity for ammonia electrooxidation in both electrochemical and fuel cell experiments. We attributed this to the presence of In2O3 phase in ITO, which provides oxygenated or hydroxide species at lower potentials resulting in the removal of poisonous intermediate, i.e., atomic nitrogen (N-ads) and promotion of ammonia electrooxidation. (C) 2016 Elsevier B.V. All rights reserved.
Oxidação da amônia em células e combustível de baixa temperatura utilizando-se PtRh/C como eletrocatalisadores
2015 - NETO, A.O.; ASSUMPCAO, M.H.M.T.; PIASENTIN, R.M.; HAMMER, P.; SPINACE, E.V.; SANTOS, M.C.; SILVA, J.C.M.
Electrochemical and in situ ATR-FTIR studies of ethanol electro-oxidation in alkaline medium using PtRh/C electrocatalysts
2015 - FONTES, E.H.; PIASENTIN, R.M.; AYOUB, J.M.S.; SILVA, J.C.M. da; ASSUMPCAO, M.H.M.T.; SPINACE, E.V.; NETO, A.O.; SOUZA, R.F.B. de
PtBi/C electrocatalysts for formic acid electro-oxidation in acid and alkaline electrolyte
2015 - YOVANOVICH, M.; PIASENTIN, R.M.; AYOUB, J.M.S.; NANDENHA, J.; FONTES, E.H.; SOUZA, R.F.B. de; BUZZO, G.S.; SILVA, J.C.M.; SPINACE, E.V.; ASSUMPCAO, M.H.M.T.; NETO, A.O.; SILVA, S.G. da
Oxidation of ammonia using PtRh/C electrocatalysts: fuel cell and electrochemical evaluation
2015 - ASSUMPCAO, MONICA H.M.T.; PIASENTIN, RICARDO M.; HAMMER, PETER; SOUZA, RODRIGO F.B. de; BUZZO, GUILHERME S.; SANTOS, MAURO C.; SPINACE, ESTEVAM V.; OLIVEIRA NETO, ALMIR; SILVA, JULIO C.M. da
This study reports on the use of PtRh/C electrocatalysts prepared by the borohydride reduction method with different Pt:Rh atomic ratios: (90:10, 70:30 and 50:50) which was investigated toward the ammonia electro-oxidation considering electrochemical and also direct ammonia fuel cell (DAFC) experiments. The DAFC experiments were conducted using different proportions of NH4OH and KOH as fuels. X-ray diffraction showed the formation of PtRh alloy while transmission electron micrographs showed the particles sizes between 4.1 and 4.5 nm. Among the different NH4OH and KOH concentrations the combination of 3 mol L−1 NH4OH and 3 mol L−1 KOH was the most favorable due to the higher KOH concentration, which increased the electrolyte conductivity, thus, improving the ammonia oxidation. Moreover, among the PtRh/C electrocatalysts the Pt:Rh ratio of 90:10 showed to be the best suited one since it showed a power density almost 60% higher than Pt. X-ray photoelectron spectroscopy results revealed for this catalyst that the nanoparticles contain a high proportion of metallic Pt and Rh phases, supporting the alloy formation between Pt and Rh. The improved fuel cell efficiency can be related to the combination of different effects: the alloy formation between Pt and Rh (electronic effect), suppressing the adsorption strength of poisonous intermediates, and a synergic effect between Pt and Rh at this composition.