Temperature dependence on methanol oxidation and product formation on Pt and Pd modified Pt electrodes in alkaline medium (original) (raw)
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Electrochemistry Communications, 2011
The oxidation of methanol, ethanol and iso-propanol and their respective product formation on platinum and palladium electrodes in alkaline solution are studied by voltammetry combined with high performance liquid chromatography. The oxidation products observed at platinum are formaldehyde and formate for methanol, acetaldehyde and acetate for ethanol and acetone for iso-propanol oxidation. On palladium, the same products (except formaldehyde) are detected. Palladium appears to be a better catalyst for the selective oxidation of the alcohol group in alkaline media, but as soon as poisoning by adsorbed carbon monoxide plays a significant role, such as in methanol oxidation, platinum is the preferred catalyst.
Electrochemical oxidation of methanol on Pt3Co bulk alloy
Journal of the Serbian Chemical Society, 2003
The electrochemical oxidation of methanol was investigated on a Pt 3 Co bulk alloy in acid solutions. Kinetic parameters such as transfer coefficient, reaction orders with respect to methanol and H + ions and energy of activation were determined. It was found that the rate of methanol oxidation is significantly diminished by rotation of the electrode. This effect was attributed to the diffusion of formaldehyde and formic acid from the electrode surface. Stirring of the electrolyte also influenced the kinetic parameters of the reaction. It was speculated that the predominant reaction pathway and rate determining step are different in the quiescent and in the stirred electrolyte. Cobalt did not show a promoting effect on the rate of methanol oxidation on the Pt 3 Co bulk alloy with respect to a pure Pt surface.
Methanol and ethanol electroxidation using Pt electrodes prepared by the polymeric precursor method
The results of methanol and ethanol oxidation in acidic medium on Pt electrodes deposited on Ti substrate using the Pechini method are presented. In this route the metallic salts were dissolved in a mixture of ethylene glycol (EG) and citric acid (CA) forming a polyester network, which is painted onto a Ti substrate and then heat treated at 600 • C in order to obtain the metallic Pt thin films. The X-ray diffraction analysis showed the presence of Pt pattern peaks. The presence of the (4 2 0) plane in a higher amount compared to bulk Pt was observed and the peak position of the planes (2 0 0) and (4 2 0) were displaced by approximately −0.3 • . The roughness data presented almost the same values for Ti and Ti/Pt. The electrochemical characterization of the electrodes in 0.1 M HClO 4 showed a typical Pt voltammetric profile. Although the voltammetric profiles of Ti/Pt and bulk Pt were the same, the electrocatalytical behavior for methanol oxidation showed an enhancement of the oxidation current density peak, which increased by 170% compared to bulk platinum. Although, the current density peak for ethanol oxidation on Ti/Pt is smaller than for Pt, it began at 0.11 V less positive than the same process on bulk Pt. The chronoamperometric experiments for methanol and ethanol oxidation on Ti/Pt increased by almost 934% and 440%, respectively, compared with Pt bulk.
Electrochimica Acta, 2010
Ethanol has been recognized as the ideal fuel for direct alcohol fuel cell (DAFC) systems due to its high energy density, non-toxicity and its bio-generation. However the complete conversion of ethanol to CO 2 is still met with challenges, due to dearth of suitable catalysts for the electro-oxidation. In the present work the effect of temperature on the catalytic oxidation of ethanol in alkaline medium over electrodeposited Pt and Pt-Pd alloyed nano particles on carbon support and also on the product formation during the course of reaction have been studied within the temperature range of 20-80 • C. The information on surface morphology, structural characteristics and bulk composition of the catalyst was obtained using SEM, XRD and EDX. BET surface area and pore widths of the catalyst particles were calculated by applying the BET equation to the adsorption isotherms. The electrochemical techniques like cyclic voltammetry, chronoamperometry and impedance spectroscopy were employed to investigate the electrochemical parameters related to electro-oxidation of ethanol in alkaline pH on the catalyst surfaces under the influence of temperature. The results show that the oxidation kinetics of ethanol on the alloyed Pt-Pd/C catalysts is significantly improved compared to that on Pt alone. The observations were interpreted in terms of the synergistic effect of higher electrochemical surface area, preferred OH − adsorption on the surface and the ad-atom contribution of the alloyed matrix. A pronounced influence of temperature on the reaction kinetics was manifested in the diminution of charge transfer resistance and activation energy of the ethanol oxidation with Pd incorporation into the Pt matrix, ensuring greater tolerance of the alloyed catalyst towards ethanolic residues. The higher yield of the reaction products like acetate and CO 3 −2 on the alloyed catalyst compared to Pt alone in alkaline medium, as estimated by ion chromatography, further substantiates the catalytic superiority of the Pt-Pd/C catalyst over Pt/C.
Chinese Journal of Chemical Physics, 2014
Methanol oxidation reaction (MOR) at Pt and Pt electrode surface deposited with various amounts of Ru (denoted as Pt x Ru y , nominal coverage y is 0.17, 0.27, and 0.44 ML) in 0.1 mol/L HClO 4 +0.5 mol/L MeOH has been studied under potentiostatic conditions by in situ FTIR spectroscopy in attenuated-total-reflection configuration and differential electrochemical mass spectrometry under controlled flow conditions. Results reveal that (i) CO is the only methanol-related adsorbate observed by IR spectroscopy at all the Pt and PtRu electrodes examined at potentials from 0.3 V to 0.6 V (vs. RHE); (ii) at Pt 0.56 Ru 0.44 , two IR bands, one from CO adsorbed at Ru islands and the other from CO L at Pt substrate are detected, while at other electrodes, only a single band for CO L adsorbed at Pt is observed; (iii) MOR activity decreases in the order of Pt 0.73 Ru 0.27 >Pt 0.56 Ru 0.44 >Pt 0.83 Ru 0.17 >Pt; (iv) at 0.5 V, MOR at Pt 0.73 Ru 0.27 reaches a current efficiency of 50% for CO 2 production, the turnover frequency from CH 3 OH to CO 2 is ca. 0.1 molecule/(site•sec). Suggestions for further improving of PtRu catalysts for MOR are provided.