JULIO NANDENHA
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Artigo IPEN-doc 29047 Pd, Ag and Bi carbon-supported electrocatalysts as electrochemical multifunctional materials for ethanol oxidation and dopamine determination2022 - ORZARI, LUIZ O.; ASSUMPCAO, MONICA H.M.T.; NANDENHA, JULIO; OLIVEIRA NETO, ALMIR; MARCOLINO JUNIOR, LUIZ H.; BERGAMINI, MARCIO; JANEGITZ, BRUNO C.This manuscript describes the investigation towards the multifunctional synthesis, characterization, and application of different Pd, Ag and Bi-carbon black supported electrocatalysts in two different fields in electrochemistry: fuel cells and electrochemical sensors. Throughout morphological and electrochemical characterizations, comprising scanning and transmission electron microscopies, X-ray powder diffraction, electrochemical impedance spectroscopy, and cyclic voltammetry techniques, the materials were characterized to better understand their properties towards proposed applications. Afterward, the materials were employed for ethanol oxidation in alkaline media, with investigations by chronoamperometry, cyclic voltammetry, and by closing a direct alkaline fuel cell, which the Pd50Ag45Bi05/C composite presented attractive ethanol catalysis behavior, with a maximum power density of 19.70 mW cm−2, at 30.59 mA cm−2. Also, the proposed device was applied for dopamine determination by square wave voltammetry. In this sense, two linear behaviors, respectively ranging from 0.2 to 1.0 and 4.0 to 40 μmol L−1 were obtained, due to two distinctive mechanisms. This higher activity has been attributed to the synergism among the used metals and proportions contributing to the bifunctional and electronic effects. As synthetic samples investigations were accomplished, data reinforces the proposed material as a possible interfacing composite in electrochemistry.Artigo IPEN-doc 27219 The effect of support on Pd1Nb1 electrocatalysts for ethanol fuel cells2020 - SOUZA, FELIPE M.; NANDENHA, JULIO; OLIVEIRA, VITOR H.A.; PAZ, EDSON C.; PINHEIRO, VICTOR S.; AVEIRO, LUCI R.; PARREIRA, LUANNA S.; SILVA, JULIO C.M.; BATISTA, BRUNO L.; NETO, ALMIR O.; SANTOS, MAURO C.Pd1Nb1/C on different kinds of carbon black were prepared by a modified sol-gel method. The alkaline direct ethanol fuel cell (ADEFC) performance was performed first with the Pd1Nb1 electrocatalysts and then by varying the fuel concentration. In CV, Pd1Nb1/Printex 6L (50:50 wt%) exhibited 2.2 times higher mass activity than that of the Pd/C (Alfa Aesar); their mass activities were 1300 and 590 mA mg 1 Pd , respectively. The best performance for the ADEFC was obtained using Pd1Nb1/Printex 6L, which yielded a maximum power density and cell voltage of 28 mW cm 2 and 1.17 V, respectively. The Pd1Nb1/Printex 6L electrocatalyst exhibited a more negative onset potential for the CO stripping reaction. We suggest that the higher hydrophilicity (contact angle) and higher degree of disorder of Printex 6L (Raman) corroborates these results. In addition, both bifunctional and electronic effects operated on the electrocatalyst due to the presence of metal oxides and alloys of PdNb (XRD), respectively, in the synthesized electrocatalysts. Therefore, it was notable that the support has an essential roledas important as the cocatalystdin the electrocatalytic performance.