JULIO NANDENHA
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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 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.