JULIO NANDENHA
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Artigo IPEN-doc 29604 Effect of TiO2 and synthesis strategies on formate oxidation2023 - GUIMARAES, VITORIA P.; NANDENHA, JULIO; ORZARI, LUIZ O.; FATIBELLO-FILHO, ORLANDO; OLIVEIRA NETO, ALMIR; JANEGITZ, BRUNO C.; VICENTINI, FERNANDO C.; ASSUMPCAO, MONICA H.M.T.Direct formate fuel cells have gained increasing attention since formate can be obtained by CO2 reduction, being shown as a renewable power source. This paper reports the use of Pd nanoparticles supported on physical mixtures of Vulcan carbon and TiO2 in different ratios and different Pd reduction methodologies. The materials were prepared using sodium borohydride as a reducing agent and analyzed toward formate oxidation in alkaline media. The prepared electrocatalysts showed peaks of Pd face-centered cubic and TiO2 anatase and rutile phases and an average particle size between 3.7 and 7.9 nm. Experiments considering formate electro-oxidation (voltammetry and chronoamperometry) showed that the presence of TiO2 is favorably using both synthesis methodologies while single cells revealed Pd nanoparticles supported on physical mixtures of carbon and TiO2, in the proportion of 75:25 as the most efficient, which was explained by the carbon high electrical conductivity and small quantities of TiO2 working as co-catalyst.Artigo IPEN-doc 27782 Borohydride reduction method for PdIn/C electrocatalysts synthesis towards glycerol electrooxidation under alkaline condition2021 - NANDENHA, JULIO; RAMOS, CARLOS E.D.; SILVA, SIRLANE G. da; SOUZA, RODRIGO F.B. de; FONTES, ERIC H.; OTTONI, CRISTIANE A.; OLIVEIRA NETO, ALMIRPd−In/C electrocatalysts were synthesized by the adapted borohydride reduction method in different atomic ratios. Electrocatalysts were evaluated by conventional electrochemical techniques and direct glycerol fuel cells. X-ray diffraction profiles indicated the structure of Pd and In (fcc) phases, as well as the presence of In higher oxidation states. Regarding Transmission electron microscopy, it showed the particle‘s average diameters between 6.1–12.7 nm. All PdIn/C electrocatalysts showed high current values for −0.30 V vs. Ag/AgCl, which the best one was PdIn/C 90 : 10. Higher performance for glycerol oxidation was observed in polarization curves at 90 °C for PdIn/C (30 : 70) composition.Artigo IPEN-doc 27425 Methane activation on PdMn/C‑ITO electrocatalysts using a reactor‑type PEMFC2020 - NANDENHA, J.; YAMASHITA, J.Y.; SOUZA, F.M.; FONTES, E.H.; BATISTA, B.L.; SANTOS, M.C.; LINARDI, M.; NETO, A.O.Various palladium and manganese supported in a mix of carbon and indium thin oxide (PdMn/C-ITO) compositions were synthesized by a sodium borohydride reduction process for methane activation at low temperatures in a proton exchange membrane fuel cell (PEMFC) reactor. These electrocatalysts were characterized by X-ray diffraction, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy XPS, inductively coupled plasma mass spectrometry ICP-MS, attenuated total reflection-Fourier transform infrared spectroscopy, cyclic voltammetry and a PEMFC reactor. The diffractograms of PdMn/C-ITO electrocatalysts revealed the face-centered cubic structure of palladium and the bixbyite cubic structure of In2O3. TEM experiments showed mean nanoparticle sizes between 4.7 and 5.2 nm for all electrocatalysts. XPS results showed the presence of palladium and manganese oxides, as well as Pd0 species. Cyclic voltammograms of PdMn/C-ITO electrocatalysts showed an increase in current density values after the methane adsorption, this result is related to formation of methanol or formic acidic. Polarization curves at 80 °C acquired in a PEMFC reactor showed that PdMn(70:30)/C-ITO and PdMn(50:50)/C-ITO have superior performance when compared to Pd/C-ITO indicating the beneficial effect of adding Mn, this behavior can be attributed to the bifunctional mechanism or to the electronic effect of support.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.