Controlled synthesis of Pt3Sn/C electrocatalysts with exclusive Sn-Pt interaction designed for use in direct methanol fuel cells

Alloy-type Sn-Pt/C electrocatalysts with Pt/Sn= 1.8-3.0 ratios and exclusive Sn-Pt interaction have been prepared by means of Controlled Surface Reactions (CSRs). As demonstrated by XRD the incorporation of Sn onto Pt/C was achieved satisfactorily yielding a near-stoichiometric fcc Pt3Sn alloy phase along with a certain amount of the Pt(1-x)Snx solid solution. The content and dispersion of the fcc Pt3Sn phase within the electrocatalysts can be controlled by tuning the reaction conditions of CSRs. No evidence of the presence of SnO2 phases in the Sn-modified Pt/C samples were found by means of the XRD and EDS analysis. According to in situ XPS studies the pre-treatment in hydrogen at 350°C resulted in complete reduction of tin to Sn0. These results demonstrate that the method of CSRs is a powerful tool to create of Pt-Sn bimetallic nanoparticles exclusively, without tin introduction onto the carbon support. The performance of the intermetallic SnPt/C catalysts in the CO and methanol electrooxidation reactions depends on the actual composition of the exposed surface and the size of bimetallic particles. In the consecutive tin introduction the decrease of the amount of SnEt4 precursor added per period, accompanied with an increase of the number of anchoring periods, resulted in an increase of the activity in both electrooxidation reactions as a consequence of an optimal balance of Pt/Sn ratio, the content of fcc Pt3Sn phase and metal particle size. It was demonstrated that the increasing tin content above a certain (optimal) amount gives rise to a negative effect on the catalyst performance in the CO and methanol electrooxidation

Formic acid oxidation over hierarchical porous carbon containing PtPd catalysts

The use of high surface monolithic carbon as support for catalysts offers important advantage, such as elimination of the ohmic drop originated in the interparticle contact and improved mass transport by ad-hoc pore design. Moreover, the approach discussed here has the advantage that it allows the synthesis of materials having a multimodal porous size distribution, with each pore size contributing to the desired properties. On the other hand, the monolithic nature of the porous support also imposes new challenges for metal loading. In this work, the use of Hierarchical Porous Carbon (HPC) as support for PtPd nanoparticles was explored. Three hierarchical porous carbon samples (denoted as HPC-300, HPC-400 and HPC-500) with main pore size around 300, 400 and 500 nm respectively, are used as porous support. PtPd nanoparticles were loaded by impregnation and subsequent chemical reduction with NaBH4. The resulting material was characterized by EDX, XRD and conventional electrochemical techniques. The catalytic activity toward formic acid and methanol electrooxidation was evaluated by electrochemical methods, and the results compared with commercial carbon supported PtPd. The Hierarchical Porous Carbon support discussed here seems to be promising for use in DFAFC anodes.Fil: Baena Moncada, Angélica María. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Departamento de Química; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Morales, Gustavo Marcelo. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Departamento de Química; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Barbero, César Alfredo. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Departamento de Química; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Planes, Gabriel Angel. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Departamento de Química; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Florez Montano, Jonathan. Universidad de la Laguna; EspañaFil: Pastor, Elena. Universidad de la Laguna; Españ

The mechanism for the electrooxidation of procarbazine pharmaceutical preparation in alkaline media and its mathematical description

The mechanism for the electrooxidation of procarbazine in alkaline media has been proposed. The process is realized completely on the electrode surface and is adsorption-controlled. The oscillatory behavior in this case is more probable, than for neutral media and may be caused by influences of electrochemical oxidation and salt dissolution from the electrode surface

Electrooxidation of formic acid on gold : An ATR-SEIRAS study of the role of adsorbed formate

Funding from the DGI (Spanish Ministry of Education and Science) through Projects CTQ2009-07017 and PLE2009-0008 is gratefully acknowledged. M.E.-E. acknowledges an FPI fellowship from the Spanish Ministry of Science and Innovation and an accommodation grant at the Residencia de Estudiantes from the Madrid City Council. C. V.-D. acknowledges a JAE-Doc fellowship from CSIC.Peer reviewedPostprin

Super-Nernstian Shifts of Interfacial Proton-Coupled Electron Transfers : Origin and Effect of Noncovalent Interactions

The support of the University of Aberdeen is gratefully acknowledged. C.W. acknowledges a summer studentship from the Carnegie Trust for the Universities of Scotland. E.P.M.L. acknowledges SeCYT (Universidad Nacional de Cordoba), ́ CONICET- PIP 11220110100992, Program BID (PICT 2012-2324), and PME 2006-01581 for financial support.Peer reviewedPostprin

Understanding the Influence of the Biomass-Derived Alcohols on the Activity and Stability of Pt Nanoparticles Supported on Graphene Nanoribbons

We produced Pt/GNRs by a one-step synthesis procedure and evaluated their electroactivity and stability towards glycerol electrooxidation reaction (GEOR) for the first time. We compared the electrocatalytic performance of GEOR with methanol and ethanol electrooxidation on Pt/GNRs at identical experimental conditions. The activities and stabilities for the electrooxidation of these biomass-derived alcohols on Pt/GNRs were compared to commercial Pt/C. The synthesis of the Pt/GNRs was confirmed by transmission electron microscopy, x-ray diffractometry, ultraviolet spectrophotometry, and Raman spectroscopy. We found that the activities of Pt/GNRs for these reactions are comparable to Pt/C, with improvement in terms of current density for methanol electrooxidation. Comparing potentiostatic measurements, we found that glycerol produces lower pseudo-stationary current densities than ethanol and methanol on both catalysts, with greatest values found for methanol electrooxidation on Pt/C. Otherwise, the GNRs remarkably enhance the stability of the catalyst for all the reactions, by increasing the stability of the current density during successive potential cycles, and by preventing the loss of electrochemically active surface area by avoiding carbon corrosion and Pt detachment. Moreover, we showed that the stability of the NPs depends on the biomass-derived alcohol used. The solution containing methanol reveals itself the most aggressive electrochemical environment to the catalyst, impacting in the decrease of surface area, while glycerol is less aggressive. Hence, the different products formed at the interface electrode/solution might lead to a different electrochemical environment, which plays an important role on the stability of the catalysts.The authors acknowledge financial assistance from CNPq (grant no. 454516/2014-2), FUNDECT (grant no. 026/2015), FAPESP (grant no. 2016/01365-0), CAPES, FINEP, and FAPESP.Peer reviewe

Electro-oxidation of Ethanol on Carbon Supported PtSn and PtSnNi Catalysts

Even though platinum is known as an active electro-catalyst for ethanol oxidation at low temperatures (< 100 oC), choosing the electrode material for ethanol electro-oxidation is a crucial issue. It is due to its property which easily poisoned by a strong adsorbed species such as CO. PtSn-based electro-catalysts have been identified as better catalysts for ethanol electro-oxidation. The third material is supposed to improved binary catalysts performance. This work presents a study of the ethanol electro-oxidation on carbon supported Pt-Sn and Pt-Sn-Ni catalysts. These catalysts were prepared by alcohol reduction. Nano-particles with diameters between 2.5-5.0 nm were obtained. The peak of (220) crystalline face centred cubic (fcc) Pt phase for PtSn and PtSnNi alloys was repositioned due to the presence of Sn and/or Ni in the alloy. Furthermore, the modification of Pt with Sn and SnNi improved ethanol and CO electro-oxidation. Copyright © 2016 BCREC GROUP. All rights reserved Received: 10th November 2015; Revised: 1st February 2016; Accepted: 1st February 2016 How to Cite: Hidayati, N., Scott, K. (2016). Electro-oxidation of Ethanol on Carbon Supported PtSn and PtSnNi Catalysts. Bulletin of Chemical Reaction Engineering & Catalysis, 11 (1): 10-20. (doi:10.9767/bcrec.11.1.394.10-20) Permalink/DOI: http://dx.doi.org/10.9767/bcrec.11.1.394.10-2

Fast synthesis of platinum nanopetals and nanospheres for highly-sensitive non-enzymatic detection of glucose and selective sensing of ions

Novel methods to obtain Pt nanostructured electrodes have raised particular interest due to their high performance in electrochemistry. Several nanostructuration methods proposed in the literature use costly and bulky equipment or are time-consuming due to the numerous steps they involve. Here, Pt nanostructures were produced for the first time by one-step template-free electrodeposition on Pt bare electrodes. The change in size and shape of the nanostructures is proven to be dependent on the deposition parameters and on the ratio between sulphuric acid and chloride-complexes (i.e., hexachloroplatinate or tetrachloroplatinate). To further improve the electrochemical properties of electrodes, depositions of Pt nanostructures on previously synthesised Pt nanostructures are also performed. The electroactive surface areas exhibit a two order of magnitude improvement when Pt nanostructures with the smallest size are used. All the biosensors based on Pt nanostructures and immobilised glucose oxidase display higher sensitivity as compared to bare Pt electrodes. Pt nanostructures retained an excellent electrocatalytic activity towards the direct oxidation of glucose. Finally, the nanodeposits were proven to be an excellent solid contact for ion measurements, significantly improving the time-stability of the potential. The use of these new nanostructured coatings in electrochemical sensors opens new perspectives for multipanel monitoring of human metabolism

Methanol Electrooxidation on Pt-Ru Catalysts Dispersed in Conducting Polyaniline Films

Methanol electrooxidation was investigated on tailored Pt-Ru-polyaniline catalysts prepared applying dynamic potential routines. The electrodes characterized by SEM, EDX and TEM present a uniform distribution of metal particles about 100 nm in size, composed of Ru and Pt on the fibrous polymer matrix. The effect of concentration in the range 0.05-1 M and temperature in the range 20 to 60 °C on the methanol electrooxidation rate was determined. The apparent activation energy depends on the catalyst Ru content.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Oscillatory instabilities during the electrocatalytic oxidation of methanol on platinum

It is described in this paper the experimental observation of oscillatory dynamics during the electrocatalytic oxidation of methanol on platinum. Besides the previously reported potential oscillations, current oscillations obtained under potentiostatic control are also presented. The existence region of current oscillations is mapped in an applied voltage x resistance bifurcation diagram. Conjointly with electrochemical investigations, in situ FTIR spectroscopy was also employed in the present studies. Although we were not able to follow eventual intermediate coverage changes during the oscillations, those experiments revealled that the mean coverage of adsorbed carbon monoxide remains appreciably high along the oscillations. Results are discussed and compared with the oscillations observed in the electrooxidation of formic acid, a system whose behavior is more understood and widely supported by in situ spectroscopic data.Descreve-se neste artigo a observação experimental de dinâmica oscilatória durante a oxidação eletrocatalítica de metanol sobre platina. Além das, previamente relatadas, oscilações de potencial, oscilações de corrente obtidas sob controle potenciostático também são apresentadas. A região de existência de oscilações de corrente é mapeada no plano de bifurcação voltagem aplicada x resistência. Conjuntamente com investigações eletroquímicas, espectroscopia FTIR in situ também foi aplicada nestes estudos. Apesar de não ter sido possível acompanhar eventuais variações de intermediários reacionais durante as oscilações, tais experimentos revelaram que a cobertura média de monóxido de carbono permanece consideravelmente alta durante as oscilações. Os resultados são discutidos e comparados com as oscilações observadas na eletrooxidação de ácido fórmico, um sistema cujo comportamento é mais entendido e amplamente fundamentado por dados espectroscópicos obtidos in situ.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)CNP