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 28154 Addition of bismuth to Pt and Pd for electric power generation with selective cogeneration of acetate from ethanol in a fuel cell type reactor2021 - LIMA, F.S.; FONTES, E.H.; NANDENHA, J.; SOUZA, R.F.B. de; NETO, A.O.Pt/C, PtBi(95:5)/C, Pd/C, and PdBi(95:5)/C were synthesized by the sodium borohydride reducing method to produce metal nanoparticles with advanced electronic properties to enhance the ethanol oxidation reaction (EOR) mechanism. The Transmission Electron Microscopy (TEM) images and X-ray photoelectron spectroscopy (XPS) showed that a small Bi content does not affect the nanoparticle size PdBi/C; in contrast, it does affect the PtBi ones. The X-ray diffraction analysis revealed a lattice parameter modification by Bi dope in Pt crystalline structure. Furthermore, the ATR-FTIR results indicated the suppression of carbonate formation and increment in acetate production. The results of polarization and power density curves on DEFC, the material PtBi/C presented the more high power density, almost six times bigger than Pt/C. PtBi/C also has the highest current density (44 mW/cm2) and the lowest onset potential (−0.6 V) in linear sweep voltammetry experiments. It also has the highest final current density in current-time experiments. Hence, PtBi/C is a very promising electrocatalyst for DEFC.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.Artigo IPEN-doc 27171 Au core stabilizes CO adsorption onto Pd leading to CO2 production2020 - FONTES, E.H.; NANDENHA, J.; SOUZA, R.F.B. de; ANTONIO, F.C.T.; HOMEM-DE-MELLO, P.; NETO, A.O.Au core and Pd shell supported on carbon structure Au@Pd/C can cleave the CeC bond of ethanol molecules leading to the production of a relatively high amount of CO2 when compared with Pd/C electrocatalyst as the attenuated total reflectance - Fourier transform infrared (ATR-FTIR) experiment shows. Density functional theory (DFT) calculations showed that this could be explained by the oxidation of CO species adsorbed into Pd sites that has a modified electronic structure compared with Pd/C. In terms of DFT analysis, the highest thermodynamical stability of CO in Pd shell with Au core atoms, when compared with Pd/C is because of the increase of virtual orbital states near Fermi level that can be occupied by valence electrons of CO molecule. The d-band center shift is experimentally verified using the valence band X-ray photoelectron spectroscopy and theoretically predicted by the Generalized Koopmans’ Theorem. Besides that, Au@Pd/C electrocatalyst has a better electrochemical activity when compared with Pd/C.Artigo IPEN-doc 26874 High activity of Pt–Rh supported on C–ITO for ethanol oxidation in alkaline medium2020 - CAMARGO, V.F. de; FONTES, E.H.; NANDENHA, J.; SOUZA, R.F.B. de; NETO, A.O.PtRh/C–ITO electrocatalysts were prepared in a single-step method using H2PtCl6 ·6H2O and RhCl3 ·xH2O as metal sources, sodium borohydride as the reducing agent and a physical mixture of 85% Vulcan Carbon XC72 and 15% In2O3 ·SnO2 (indium tin oxide—ITO) as support. PtRh/C–ITO were characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy (XPS), cyclic voltammetry, chronoamperommetry, attenuated total reflectance, Fourier transform infrared spectroscopy and performance test on direct alkaline ethanol fuel cell. X-ray diffraction patterns for all PtRh/C–ITO indicated a shift in Pt (fcc) peaks, showing that Rh was incorporated into Pt lattice. Transmission electron microscopy for PtRh/C–ITO showed nanoparticles homogeneously distributed over the support with particles size between 3.0 and 4.0 nm. The XPS results for Pt70Rh30/C–ITO showed the presence of mixed oxidation states of Sn0 and SnO2 that could favor the oxidation of adsorbed intermediates by bifunctional mechanism. Pt90Rh10/C–ITO was more active in electrochemical studies, which could be associated with the C–C bond break. Experiments in direct alkaline ethanol fuel cells showed that the power density values obtained for Pt70Rh30/C–ITO and Pt90Rh10/C–ITO were higher than Pt/C, indicating the beneficial effect of Rh addition to Pt and the use of C–ITO support.Artigo IPEN-doc 25213 Electrocatalytic performance of PtSn/C-In2O3 center dot SnO2 nanoparticles prepared by sodium borohydride reduction process for ethanol oxidation in acidic and alkaline electrolytes2018 - PEREIRA, C.V.; FONTES, E.H.; NANDENHA, J.; ASSUMPCAO, M.H.M.T.; NETO, A.O.PtSn/C-In2O3.SnO2 electrocatalysts were prepared by the borohydride reduction method in the single step using H2PtCl6.6H2O and SnCl2.2H2O as metal sources, sodium borohydride as reducing agent and a physical mixture of 85% Vulcan Carbon XC72 and 15% In2O3.SnO2 (indium tin oxide – ITO) as support. PtSn/C-In2O3.SnO2 electrocatalysts were characterized by X–ray diffraction (XRD), energy dispersive analysis (EDX), transmission electron microscopy (TEM), cyclic voltammetry (CV), chronoamperommetry (CA) and polarization curves in alkaline and acidic electrolytes (single cell experiments). The diffractograms of PtSn/C-In2O3.SnO2 electrocatalysts showed peaks associated to the face-centered cubic (fcc) structure of platinum, peaks which could be identified as a cassiterite SnO2 phase or with Indium-doped SnO2 (ITO) used as supports. TEM micrographs showed metal nanoparticles with average nanoparticle size between 2.4 and 2.7 nm. Ethanol oxidation in acidic and alkaline electrolytes was investigated at room temperature, by chronoamperommetry (CA), where PtSn/C-In2O3.SnO2 (70:30) showed the highest activity among all electrocatalysts in study considering ethanol oxidation for acid electrolyte, while for alkaline electrolyte the highest activity was observed for PtSn/C-In2O3.SnO2 (50:50). Polarization curves at 100oC showed PtSn/C-In2O3.SnO2 (70:30) with superior performance for ethanol oxidation for acidic electrolyte and PtSn/C (70:30) for alkaline electrolyte, when compared to Pt/C for both electrolytes. The best performance obtained by PtSn/C-In2O3.SnO2 (70:30) in real conditions could be associated with the occurrence simultaneously of the bifunctional mechanism and electronic effect resulting from the presence of PtSn alloy or a synergetic effect between PtSn and In2O3.Artigo IPEN-doc 24800 PdxNby electrocatalysts for DEFC in alkaline medium2018 - SOUZA, F.M.; NANDENHA, J.; BATISTA, B.L.; OLIVEIRA, V.H.A.; PINHEIRO, V.S.; PARREIRA, L.S.; NETO, A.O.; SANTOS, M.C.PdxNby/C binary electrocatalysts supported on Vulcan carbon XC72 were prepared by the sol-gel method. The materials are characterized by transmission electron microscopy, X-ray diffraction analysis, inductively coupled plasma–mass spectrometry and contact angle measurements. The electrocatalytic activity for ethanol electrooxidation reaction was studied by cyclic voltammetry, chronoamperometry, Tafel slope and accelerated durability testing. The direct ethanol performance and the products after the experiments were studied by Fourier transform infrared spectroscopy. Pd1Nb1/C (50:50 wt%) shows superior activity for ethanol oxidation compared to the other electrocatalysts prepared in this work. All electrocatalysts containing Nb show the highest current exchange density. The Tafel slope results suggest that the Nb modified the Pd-electrocatalyst to obtain a reaction path with high selectivity with only a single determining step with low production of the intermediates for the ethanol oxidation reaction. The best performance is obtained using Pd1Nb1/C 18.11 mW cm−2. The Pd1Nb1/C electrocatalyst displays the highest production of CO2 and the lowest production of acetaldehyde. Pd1Nb1/C shows the highest peak current density during 1000 cycles of the experiment and the lowest mass loss of Pd after the cycling test. We find that the Nb modifies the Pd electrocatalysts from the bifunctional mechanism and reduces the loss of Pd during the accelerated durability test.