Synthesis of Unsupported Pt-based Electrocatalysts and Evaluation of Their Catalytic Activity for the Ethylene Glycol Oxidation Reaction (original) (raw)
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Electrochemical study of PtRh/C and PtRhNi/C electrocatalysts for ethylene glycol oxidation
Journal of Solid State Electrochemistry, 2017
In the last decades, the ethylene glycol has been considered as another option of fuel, in both acid and alkaline solutions, for fuel cells application. Pt-based electrocatalysts are used in this type of technology but it is necessary to add a second or third oxophilic metal to form bimetallic or trimetallic alloys. Alloys with a second or a third metal modify electrocatalytic properties of Pt in order to overcome poisoning effects and enhancement of the ele ctro catalytic activity of platinu m-b ased electrocatalyst. PtRh/C and PtRhNi/C electrocatalysts were prepared by alcohol reduction method, and their catalytic activity and stability were evaluated by cyclic voltammetry and chronoamperometry, in alkaline medium using a KOH solution with ethylene glycol in concentrations of 0.5 and 1.0 mol L −1. The results showed that the binary electrocatalyst has a higher electrocatalytic performance and obtain about 90% more energy density than PtRhNi/C. This result indicates that the higher amount of Rh in the alloy presents a synergistic effect with Pt. Chronoamperometry tests show that both electrocatalysts have an active surface and tolerance to poisoning by intermediate products, and the presence of Ni in the ternary electrocatalyst contributes to raise this tolerance.
Journal of Colloid and Interface Science, 2008
The synthesis and characterization of catalysts based on nanomaterials, supported on multi-walled carbon nanotubes (CNT) for ethylene glycol (EG) oxidation is investigated. Platinum (Pt) and platinum–ruthenium (Pt–Ru) nanoparticles are deposited on surface-oxidized multi-walled carbon nanotubes [Pt/CNT; Pt–Ru/CNT] by the aqueous solution reduction of the corresponding metal salts with glycerol. The electrocatalytic properties of the modified electrodes for oxidation of ethylene glycol in acidic solution have been studied by cyclic voltammetry (CV), and excellent activity is observed. This may be attributed to the small particle size of the metal nanoparticles, the efficacy of carbon nanotubes acting as good catalyst support and uniform dispersion of nanoparticles on CNT surfaces. The nature of the resulting nanoparticles decorated multiwalled carbon nanotubes are characterized by scanning electron microscopy (SEM) and transmission electron microscopic (TEM) analysis. The cyclic voltammetry response indicates that Pt–Ru/CNT catalyst displays a higher performance than Pt/CNT, which may be due to the efficiency of the nature of Ru species in Pt–Ru systems. The fabricated Pt and Pt–Ru nanoparticles decorated CNT electrodes shows better catalytic performance towards ethylene glycol oxidation than the corresponding nanoparticles decorated carbon electrodes, demonstrating that it is more promising for use in fuel cells.TEM images of nanoparticles decorated MWCNT obtained by glycerol as reducing agent.
PtRu/C and PtSn/C electrocatalysts were prepared by the alcohol-reduction process with different atomic ratios. The electrocatalysts were characterized by EDAX, XRD, TEM and cyclic voltammetry and the electro-oxidation of ethylene glycol was studied by cyclic voltammetry and chronoamperometry using the thin porous coating technique. PtRu/C and PtSn/C electrocatalysts were found to be active for ethylene glycol oxidation, which starts at lower potentials by increasing the ruthenium and tin content. In the region of interest for direct alcohol fuel cell applications PtSn/C electrocatalysts were more active than PtRu/C electrocatalysts.
Electrochemistry Communications, 2011
Unsupported nanostructured PtRu electrocatalysts were synthesized using a spray pyrolysis process with varying atomic compositions. A ruthenium rich and platinum rich PtRu were compared to supported E-Tek PtRu on Vulcan XC-72 at a pH range from 5 to 8 for the oxidation of ethylene glycol and glycerol. Oxalic acid is also evaluated as a fuel because it is a terminal oxidation product of glycerol oxidation that enzymes cannot successfully oxidize electrochemically. The nanostructured catalysts were evaluated by SEM and exhibited a sponge-like morphology that helped to increase the metal utilization despite its low surface area. In situ FTIR spectroscopy was used to probe the reaction to determine if complete oxidation occurred by monitoring the production of CO 2 . The nanostructured catalyst successfully oxidized each fuel (oxalic acid, ethylene glycol, glycerol) to CO 2 with no indication of CO formation. This presents an interesting opportunity to combine enzymatic catalysts with metallic Pt-based catalysts for oxidation of more complex fuels.
Journal of Electroanalytical Chemistry, 2021
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Electrochimica Acta, 2011
Electrocatalytic activities of Pt/C, Pt-Ru/C, and Pt-Ni/C for the oxidation of ethylene glycol in a basic solution are evaluated by cyclic voltammetry and quasi-steady state polarization. Based on the results of Tafel slopes from quasi-steady state polarization, the catalytic activities for ethylene glycol oxidation are in the order of Pt-Ru/C > Pt-Ni/C > Pt/C. The analysis of intermediate products for ethylene glycol oxidation by higher performance liquid chromatograph (HPLC) demonstrates that the degree of ethylene glycol oxidation is dependent on catalysts. Pt-Ru/C shows the highest current densities for ethylene glycol oxidation, but shows lower fuel utilization. On the other hand, Pt-Ni/C shows higher ability to cleavage CC bonds, but is suffered from catalyst poisoning. To improve the tolerance for catalyst poisoning, we construct a novel Pt-Ni-SnO 2 /C catalyst, compare its catalytic activities, and evaluate the intermediates. Pt-Ni-SnO 2 /C shows superior catalytic activities for ethylene glycol oxidation, resulting in the highest degree of complete electro-oxidation of ethylene glycol to CO 2 .
Electrochimica Acta, 2009
Present paper reports kinetics of electro-oxidation of ethanol (EtOH) and ethylene glycol (EG) onto Pt and PtRu nanocatalysts of different compositions in the temperature range of 298-318 K. These catalysts have been characterized by SEM, EDX, XRD, CV and amperometry. It has been observed that apparent activation energies for oxidation of EtOH and EG pass through a minimum at about 15-20 at.% of Ru in the PtRu alloy catalysts. Anodic peak current vs. composition curve also shows a maximum around this composition. The results have been explained by a geometric model, which proposes requirement of an ensemble of three Pt atoms with an adjacent Ru atom onto PtRu surface for an efficient electro-oxidation of EtOH or EG. This is further supported from statistical data analysis of probability of occurrence of such ensembles onto PtRu alloy surface. Present results also suggest that electro-oxidation of EG onto nano-PtRu catalyst surfaces follows a different path from that of EtOH at alloy composition less than 15 at.% of Ru.
Ethylene glycol oxidation on ternary PtRhNi/C electrocatalyst with different metal compositions
Matéria (Rio de Janeiro), 2017
Direct Alcohol Fuel Cells (DAFC's) are an alternative to fuel cell systems and when is used alkaline medium this has an increase performance. The alkaline direct alcohol fuel cells (ADAFC's) have some advantages such as low-emission, high energy efficiency, improved oxidation kinetics, low crossover and in addition there is a broad range of materials that can be used as catalysts. The ethylene glycol (EG) has received attention in recent decades as an alternative fuel for ADAFC, but like others alcohols must be completed oxidized to generate full power energy. In this study we analyzed ternary PtRhNi/C electrocatalysts with different compositions, synthesized by alcohol reduction method, and compared to Pt/C ETEK. The active area, catalytic activity and stability of catalysts for ethylene glycol oxidation in alkaline medium were studied by cyclic voltammetry, CO stripping voltammetry and chronoamperometry tests. XRD technique was applied to physical characterization and it was observed the formation of alloy. The average crystallite size was calculated from the Scherrer equation. The Pt 92 Rh 7 Ni 1 /C electrocatalyst shows a larger electrochemically active area and consequently higher catalytic activity for EG oxidation. This response was attributed to improvement in the synergistic effect provided by the reduction of the amount of Rh and Ni in the ternary alloy when compared to Pt 80 Rh 15 Ni 5 /C and Pt/C ETEK electrocatalysts. However, Pt 80 Rh 15 Ni 5 /C electrocatalyst showed greater tolerance to poisoning by intermediate species due to the presence of Rh in greater quantity, leading to a formation of adsorbed OH species in potentials smaller than those for platinum.
Ethanol oxidation reaction on PtCeO 2/C electrocatalysts prepared by the polymeric precursor method
Applied Catalysis B-environmental, 2009
This paper presents a study of the electrocatalysis of ethanol oxidation reactions in an acidic medium on Pt-CeO 2 /C (20 wt.% of Pt-CeO 2 on carbon XC-72R), prepared in different mass ratios by the polymeric precursor method. The mass ratios between Pt and CeO 2 (3:1, 2:1, 1:1, 1:2, 1:3) were confirmed by Energy Dispersive X-ray Analysis (EDAX). X-ray diffraction (XRD) structural characterization data shows that the Pt-CeO 2 /C catalysts are composed of nanosized polycrystalline non-alloyed deposits, from which reflections corresponding to the fcc (Pt) and fluorite (CeO 2 ) structures were clearly observed. The mean crystallite sizes calculated from XRD data revealed that, independent of the mass ratio, a value close to 3 nm was obtained for the CeO 2 particles. For Pt, the mean crystallite sizes were dependent on the ratio of this metal in the catalysts. Low platinum ratios resulted in small crystallites, and high Pt proportions resulted in larger crystallites. The size distributions of the catalysts particles, determined by XRD, were confirmed by Transmission Electron Microscope (TEM) imaging. Cyclic voltammetry and chronoamperometic experiments were used to evaluate the electrocatalytic performance of the different materials. In all cases, except Pt-CeO 2 /C 1:1, the Pt-CeO 2 /C catalysts exhibited improved performance when compared with Pt/C. The best result was obtained for the Pt-CeO 2 /C 1:3 catalyst, which gave better results than the Pt-Ru/C (Etek) catalyst. ß
Journal of the Brazilian Chemical Society, 2012
Este trabalho teve como objetivo desenvolver eletrocatalisadores plurimetálicos contendo Pt, Ru, Ni e Sn suportados em C pelo método de decomposição de precursores poliméricos (DPP), na razão metal:carbono de 40:60% em massa, para aplicação em célula a combustível de etanol direta (DEFC). As nanopartículas obtidas foram caracterizadas físico-quimicamente por difração de raios X (DRX) e energia dispersiva de raios X. Os resultados de DRX revelaram cristalitos com estrutura cúbica de face centrada da Pt com evidências de que os átomos de Ni, Ru e Sn foram incorporados à estrutura da Pt. A caracterização eletroquímica das nanopartículas foi realizada por voltametria cíclica e cronoamperometria em meio ácido (H 2 SO 4 0,05 mol L -1 ), na ausência e presença de etanol. A adição de Sn para os catalisadores PtRuNi/C deslocou significativamente o potencial de início de oxidação de etanol e CO para valores mais baixos, aumentando assim a atividade catalítica, especialmente para a composição Pt 64 Sn 15 Ru 13 Ni 8 /C. Eletrólises de solução de etanol em 0,4 V vs. ERH permitiram a determinação de acetaldeído e ácido acético como principais produtos da reação. A presença de Ru nas ligas favoreceu a formação de ácido acético como produto principal da oxidação do etanol. O catalisador Pt 64 Sn 15 Ru 13 Ni 8 /C exibiu o melhor desempenho para DEFC.