JULIO NANDENHA
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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.