JULIO NANDENHA
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Artigo IPEN-doc 27220 Methane activation at low temperature in an acidic electrolyte using PdAu/C, PdCu/C, and PdTiO2/C electrocatalysts for PEMFC2020 - SOUZA, FELIPE de M.; SOUZA, RODRIGO F.B. de; BATISTA, BRUNO L.; SANTOS, MAURO C. dos; FONSECA, FABIO C.; OLIVEIRA NETO, ALMIR; NANDENHA, JULIOPd/C, PdAu/C, PdCu/C, and PdTiO2/ C electrocatalysts were prepared by a sodium borohydride reduction process for methane activation at low temperatures in a PEMFC reactor. These electrocatalysts were characterized by XRD, TEM, XPS, ICP-MS, ATR-FTIR, and cyclic voltammetry. The diffractograms of Pd/C, PdAu(50:50)/C, PdCu(50:50)/C, and PdTiO2( 50:50)/C electrocatalysts showed peaks associated with Pd face-centered cubic structure. PdAu(50:50)/C showed a small shift in the peak center when it was compared to Pd/C, while PdCu(50:50)/C showed a shift to higher angles when it was also compared to Pd/C. This effect can be due to the formation of an alloy between Pd and Au, and Pd and Cu. By TEM experiments, a mean nanoparticle size was observed between 6.9 and 8.9 nm for all electrocatalysts. Cyclic voltammograms of Pd/C, PdAu/C, PdCu/C and PdTiO2/ C electrocatalysts showed an increase in current density values after the adsorption of methane The ATR-FTIR experiments showed for all electrocatalysts the formation of methanol and formic acidic. Polarization curves at 80 °C acquired in a PEMFC reactor showed that PdAu(50:50)/C and PdTiO2( 50:50)/C had superior performance when compared to Pd/C, indicating the beneficial effect of adding the co-catalyst; this behavior has been attributed to the bifunctional mechanism or electronic effect.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).Artigo IPEN-doc 26619 Activation of methane on PdZn/C electrocatalysts in an acidic electrolyte at low temperatures2019 - NANDENHA, J.; NAGAHAMA, I.H.F.; YAMASHITA, J.Y.; FONTES, E.H.; AYOUB, J.M.S.; SOUZA, R.F.B. de; FONSECA, F.C.; NETO, A.O.PdZn/C electrocatalysts were prepared by sodium borohydride utilized as reducing agent for activation methane in an acidic medium at room temperature and in a proton exchange membrane fuel cell (PEMFC) at 80°C. The materials prepared were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The diffractograms of the PdZn/C electrocatalysts showed only peaks associated with Pd face-centered cubic (fcc) structure. Cyclic voltammograms (CV) of all electrocatalysts after adsorption of methane shown an increment in current during the anodic scan, this effect was more pronounced for Pd(70)Zn(30)/C. In situ ATR-FTIR (Attenuated Total Reflectance-Fourier Transform Infrared) experiments was not observed the formation of intermediates adsorbed for PdZn/C electrocatalysts, this behavior indicated that the methane oxidation occurs by parallel mechanisms. Polarization curves at 80°C in PEMFC show that Pd(90)Zn(10)/C has superior performance over the other electrocatalysts in methane oxidation.Artigo IPEN-doc 25122 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 process2018 - 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.