JULIO NANDENHA

JULIO NANDENHA

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Borohydride reduction method for PdIn/C electrocatalysts synthesis towards glycerol electrooxidation under alkaline condition
2021 - NANDENHA, JULIO; RAMOS, CARLOS E.D.; SILVA, SIRLANE G. da; SOUZA, RODRIGO F.B. de; FONTES, ERIC H.; OTTONI, CRISTIANE A.; OLIVEIRA NETO, ALMIR
Pd−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.
Methane activation on PdMn/C‑ITO electrocatalysts using a reactor‑type PEMFC
2020 - 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.
High CO tolerance of Pt nanoparticles synthesized by sodium borohydride in a time-domain NMR spectrometer
2020 - RAMOS, A.S.; SANTOS, M.C.L.; GODOI, C.M.; QUEIROZ, L.C. de; NANDENHA, J.; FONTES, E.H.; BRITO, W.R.; MACHADO, M.B.; NETO, A.O.; SOUZA, R.F.B. de
The CO poisoning effect was overcome using a novel synthesis method. This method consists of using sodium borohydride reducing agent assisted by magnetic field and radiofrequency pulses in the time-domain NMR spectrometer. This synthesis was useful to disperse the Pt nanoparticles over the carbon support and to compress the lattice strain of the Pt crystalline structure. Besides that, Pt/C MFP90° showed a multi-CO oxidation component in cyclic voltammetry, and this can avoid the poisoning effect by creating a large availability of CO species to be adsorbed, desorbed, and re-adsorbed. Pt/C MFP90° has also shown the best performance in the PEMFC regarding H2 and CO + H2 experiments.
Methane activation at low temperature in an acidic electrolyte using PdAu/C, PdCu/C, and PdTiO2/C electrocatalysts for PEMFC
2020 - SOUZA, FELIPE de M.; SOUZA, RODRIGO F.B. de; BATISTA, BRUNO L.; SANTOS, MAURO C. dos; FONSECA, FABIO C.; OLIVEIRA NETO, ALMIR; NANDENHA, JULIO
Pd/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.
High activity of Pt–Rh supported on C–ITO for ethanol oxidation in alkaline medium
2020 - 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.
Activation of methane on PdZn/C electrocatalysts in an acidic electrolyte at low temperatures
2019 - 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.
Methanol oxidation in acidic and alkaline electrolytes using PtRuIn/C electrocatalysts prepared by borohydride reduction process
2018 - SANTOS, M.C.L.; NANDENHA, J.; AYOUB, J.M.S.; ASSUMPÇAO, M.H.M.T.; NETO, A.O.
PtRuIn/C electrocatalysts (20% metal loading by weight) were prepared by sodium borohydride reduction process using H2PtCl66H2O, RuCl3xH2O and InCl3xH2O as metal sources, borohydride as reducing agent and Carbon Vulcan XC72 as support. The synthetized PtRuIn/C 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 XRD patterns show Pt peaks are attributed to the face-centered cubic (fcc) structure, and a shift of Pt (fcc) peaks indicates that Ru or In is incorporated into Pt lattice. TEM micrographs show metal nanoparticles with an average nanoparticle size between 2.7 and 3.5 nm. Methanol oxidation in acidic and alkaline electrolytes was investigated at room temperature, by CV and CA. PtRu/C (50:50) shows the highest activity among all electrocatalysts in study considering methanol oxidation for acidic and alkaline electrolyte. Polarization curves at 80°C show PtRuIn/C (50:25:25) with superior performance for methanol oxidation, when compared to Pt/C, PtIn/C and PtRu/C for both electrolytes. The best performance obtained by PtRuIn/C (50:25:25) in real conditions could be associated with the increased kinetics reaction and/or with the occurrence simultaneously of the bifunctional mechanism and electronic effect resulting from the presence of Pt alloy.
Electrocatalytic performance of PtSn/C-In2O3 center dot SnO2 nanoparticles prepared by sodium borohydride reduction process for ethanol oxidation in acidic and alkaline electrolytes
2018 - 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.
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 process
2018 - 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.
Estudo da oxidação eletroquímica do ácido fórmico utilizando eletrocatalisadores Pd/C-Sb2O5.SnO2, PdAu/C-Sb2O5.SnO2, PdIr/C-Sb2O5.SnO2 e PdAulr/C-Sb2O5.SnO2 preparados via redução por borohidreto de sódio
2016 - NANDENHA, JÚLIO
Os eletrocatalisadores Pd/C, Pd/C-15%ATO, PdAu/C-15%ATO (90:10, 70:30 e 50:50), PdIr/C-15%ATO (90:10, 70:30 e 50:50) e PdAuIr/C-15%ATO (90:5:5, 70:20:10 e 50:45:5) foram preparados pelo método de redução por borohidreto de sódio. Esses eletrocatalisadores foram caracterizados por espectroscopia de energia dispersiva de raios X (EDX), difração de raios X (DRX) e microscopia eletrônica de transmissão (MET), enquanto que as atividades eletrocatalíticas para a oxidação eletroquímica do ácido fórmico em meios ácido e alcalino foram investigadas por voltametria cíclica, cronoamperometria e experimentos em células a combustível de ácido fórmico direto (DFAFC) em meios ácido e alcalino a 100 ºC e 60 ºC, respectivamente. Os difratogramas de raios X dos eletrocatalisadores PdAu/C-15%ATO, PdIr/C-15%ATO e PdAuIr/C-15%ATO mostraram a presença de fase de estrutura cúbica de Pd (cfc), ligas de Pd-Au, Pd-Ir e Pd-Au-Ir, fases de carbono e SnO2. As micrografias eletrônicas de transmissão indicaram que as nanopartículas foram bem distribuídas sobre o suporte C-ATO e apresentaram alguns aglomerados. Os estudos eletroquímicos para oxidação de ácido fórmico foram realizados utilizando a técnica de camada fina porosa. Todos os eletrocatalisadores preparados foram testados em células a combustível unitárias alimentadas diretamente por ácido fórmico. Nos estudos comparativos entre os melhores eletrocatalisadores, o eletrocatalisador PdAuIr/C-15%ATO (50:45:5) em meios ácido e alcalino apresentou uma atividade eletrocatalítica superior para a oxidação eletroquímica do ácido fórmico em temperatura ambiente em comparação com o eletrocatalisador Pd/C-15%ATO e os outros eletrocatalisadores binários e ternários preparados. Os experimentos em uma DFAFC unitária ácida e alcalina, também, indicaram que o eletrocatalisador PdAuIr/C-15%ATO (90:5:5) apresentou melhor desempenho para oxidação eletroquímica do ácido fórmico a 100 ºC (meio ácido) e a 60 ºC (meio alcalino), respectivamente, em comparação com os demais eletrocatalisadores sintetizados. Esses resultados indicaram que a adição de Au e Ir ao Pd favorece a oxidação eletroquímica do ácido fórmico, esse efeito pode ser atribuído ao mecanismo bifuncional (a presença de ATO (Sb2O5·SnO2), óxidos de Au e Ir) associados ao efeito eletrônico (ligas de Pd-Au-Ir (cfc)).

JULIO NANDENHA

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