JULIO NANDENHA
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Resumo IPEN-doc 26797 Development of nanomaterials for formate electrochemical oxidation aiming sustainable energy generation2019 - GUIMARÃES, V.P.; NANDENHA, J.; FATIBELLO-FILHO, O.; NETO, A.O.; VICENTINI, F.C.; ASSUMPÇÃO, M.H.M.T.The world energy system is highly depended of fossil fuels, which is not sustainable [1]. Thus, the use of alternative energy is crucial and fuel cells are being considered good options. In this context, this work aimed to develop electrocatalysts based on palladium nanoparticles (PdNPs) supported on the physical mixtures of carbon (Vulcan XC72) and titanium dioxide (P25) toward formate oxidation in alkaline medium and its application in formate fuel cells. The materials were synthesized by the borohydride reduction method [2] with 20% (m/m) of metal loading and in two batches. In the first batch, the PdNPs were reduced in the physical mixture of carbon (C) and titanium dioxide (TiO2), in different proportions of C and TiO2, identified as Pd/(C+TiO2), while in the second one, the PdNPs were reduced only in TiO2 with later incorporation of C which were identifies as Pd/TiO2-C. On both batches, the ratios between C and TiO2 used were 75:25, 50:50 and 25:75 (m/m). A reference material, complied of PdNPs supported just on C (Pd/C) was also prepared. All materials were characterized by X-ray diffraction, showing peaks of the face-centered-cubic (fcc) structure of the Pd, as well as TiO2 peaks of anatase and rutile phases. Transmission Electron Microscopy (TEM) were also evaluated showing an average particle size between 3 and 8 nm. Electrochemical experiments considering voltammetry and chronoamperometry showed that the materials with PdNPs reduced in the TiO2 (Pd/TiO2-C) were more promising when compared to Pd/(C+TiO2), and among them Pd/TiO2-C 75:25 presented the highest current observed in chronoamperometry. Comparing the Pd/(C+TiO2) materials, the Pd/(C+TiO2) 50:50 presented the highest current. Taking into account single cell experiments, although the electrochemical results evidenced the improvement toward formate with PdNPs deposited firstly in the TiO2, the fuel cell tests showed the opposite, presenting the best cell efficiencies with Pd/(C+TiO2) materials, where Pd/(C+TiO2) 75:25 (ratio between C and TiO2) was the best material with the highest power density obtained. This fact can be explained by the higher conductivity of C, in a higher proportion, coupled with the small amounts of TiO2, which provides oxygenated species that facilitate the formate oxidation.Resumo IPEN-doc 26699 Electrocatalytic oxidation of methane in an acidic electrolyte using PdMn/C-ITO electrocatalysts synthetized by sodium borohydride reduction process2019 - NANDENHA, JULIO; YAMASHITA, JESSICA Y.; FONTES, ERIC H.; FONSECA, FABIO C.; NETO, ALMIR O.Pd/C-ITO and PdMn/C-ITO electrocatalysts with different atomic ratio (90:10, 70:30 and 50:50) were synthetized by borohydride reduction method and characterized by X-ray diffraction, Transmission electronic microscopy and electrochemical studies (cyclic voltammetry). The electrochemical studies showed that PdMn(50:50)/C-ITO had superior performance for electrochemical oxidation of methane in an acidic electrolyte at 25 oC compared to others electrocatalysts prepared. The experiments in a single DMEFC also showed that the PdMn(70:30)/C-ITO electrocatalyst exhibited higher performance for methane oxidation in comparison with Pd/C-ITO, PdMn(90:10)/C-ITO and PdMn(50:50)/C-ITO electrocatalysts. These result indicated that the addition of Mn to Pd favor the electrochemical oxidation of Methane in acid medium, where this effect could be attributed to the synergy between the constituents of the binary electrocatalysts or to electronic modification of Pd atoms by the neighboring Mn atoms as the proximity of Pd and Mn atoms on the surface of the C-ITO (bifunctional mechanism - the presence of Pd and Mn oxides species).Resumo IPEN-doc 25501 Niobium as co-electrocatalyst for Pd in alkaline medium2018 - SOUZA, FELIPE M.; PARREIRA, LUANNA S.; OLIVEIRA, VITOR H.A.; PINHEIRO, VICTOR S.; BATISTA, BRUNO L.; NANDENHA, JULIO; NETO, ALMIR O.; SANTOS, MAURO C.Direct ethanol fuel cells (DEFC) have been evaluated as a possible alternative source of sustainable energy, because it can reach high current densities with minimal pollutant production [1]. In this work, we report the synthesis of PdxNby/C binary electrocatalysts supported on Vulcan XC-72 carbon by the sol-gel method [2]. These synthesized electrocatalysts were physically characterized by DRX, EDS, ICP-MS, XPS and TEM. Their electrochemical activities (CV and CA) were evaluated as already reported by Souza [2]. Here, we reported new results from Tafel plots and FTIR ex situ experiments for ethanol oxidation reaction using those electrocatalysts. Pd/C electrocatalyst has the EOR governed by two determining steps since it showed two straight lines between 570 mV and 730mV, presenting also two different slopes (a and b, in Figure 1). Unlike the other electrocatalysts, with Nb in their chemical composition, that the EOR occurs by one determining step since there is just one slope. The exchange current densities (A cm-2) were 2.3x10-17, 2.7x10-12, 6.6x10-10, 3.6x10-11 and 7.3x10-11 for Pd/Ca, Pd/Cb, Pd1Nb1/C, Pd3Nb1/C and Pd1Nb3/C, respectively. This shows that Nb increases the electron exchange rate at the analyte/electrode interface, improving the kinetics of the EOR reaction [3]. FTIR experiments strengthened the evidence that Nb modifies the Pd mechanism for EOR electrocatalysis to a mechanism that present almost no formation of acetaldehyde, avoiding the reaction ... The FTIR spectra showed that Pd1Nb1/C displays the highest production of CO2 and the lowest production of acetaldehyde. Furthermore, the ADT experiments with ICP-MS analysis indicated that Pd1Nb1/C obtained the highest peak current density during 1000 cycles of the experiment, presenting the lowest Pd mass loss after the ADT.Resumo IPEN-doc 25485 Carbon supported hybrids nanostructures PtSn with CeO2 nanorods for Direct Ethanol Fuel Cells2018 - GENTIL, TUANI C.; PARREIRA, LUANNA S.; SOUZA, FELIPE M. de; PINHEIRO, VICTOR S.; NANDENHA, JULIO; OLIVEIRA NETO, ALMIR; SANTOS, MAURO C. dosNew energetic sources have been the focus of current researches, including on fuel cells. This device has as its operating principle the conversion of chemical energy into electrical energy, making possible the use of renewable energy sources [1]. In the fuel cells operation are applied nanostructured electrocatalysts capable of oxidizing organic molecules such as ethanol [2]. This work was carried out using PtSn-based electrocatalysts with ceria nanorods (CeO2), synthesized by chemical reduction method via sodium borohydride [2], and supported on carbon Vulcan XC 72 (20% w/w). The synthesized materials have the following mass metal ratios: Pt/C; Pt3Sn1/ C and Pt3Sn1_20%NR/ C, with % of the Pt3Sn1 load replaced by ceria nanorods in the last nanomaterial, in order to reduce the costs of noble metals such as platinum. The evaluation of the activity for ethanol oxidation is given by polarization and power density curves, according to Figure 1. From the polarization curve it was observed that the Pt3Sn1_20%NR/ presented higher open circuit potential value (572 mV), and power density higher than the Pt/C composite material. The Pt3Sn1/C material presented a higher value of power density related to the others, but Pt3Sn1_20%NR/C generated a power density for ethanol oxidation relatively close to the best activity material, by the supply of oxygenated species improved the electrocatalytic activity for CO oxidation, making its application possible.Resumo IPEN-doc 20770 Electro-oxidation of formic acid on PdIr/C-Sbsub(2)Osub(5)-SnOsub(2) electrocatalysts prepared by borohydride reduction.2014 - NANDENHA, JULIO; ASSUMPCAO, MONICA H.M.T.; SILVA, JULIO C.M.; SPINACE, ESTEVAM V.; OLIVEIRA NETO, ALMIRResumo IPEN-doc 20217 O efeito da concentração de etanol na performance e na distribuição de produtos em uma DEFC: um estudo utilizando o acessório DEFC/ATR-FTIR2014 - ASSUMPCAO, MONICA H.M.T.; NANDENHA, JULIO; BUZZO, GUILHERME S.; SILVA, JULIO C.M.; SPINACE, ESTEVAM V.; NETO, ALMIR O.; SOUZA, RODRIGO F.B. deResumo IPEN-doc 17628 Enhanced CO tolerance in PEM fuel cell using Pt - dopped ceria electrocatalyst system2011 - ARICO, E.M.; LINARDI, M.; NARDENHA, J.Resumo IPEN-doc 19074 Estudo da oxidação de etanol sobre Pt usando ATR-FTIR em condições realistas de uma DEFC2013 - OLIVEIRA NETO, ALMIR; NANDENHA, JULIO; LINARDI, MARCELO; SPINACE, ESTEVAM V.; SOUZA, RODRIGO F.B. de