Electrocatalytic Oxidation Of Ethylene Glycol Research Articles

Electrocatalytic oxidation of ethylene glycol at palladium-bimetallic nanocatalysts (PdSn and PdNi) supported on sulfonate-functionalised multi-walled carbon nanotubes

Electrocatalytic oxidation of ethylene glycol (EG) in alkaline medium using nano-scaled palladium-based bimetallic catalysts (PdM, where M=Ni and Sn) supported on sulfonated multi-walled carbon nanotubes (SF-MWCNTs) is compared. The bimetallic mixture (i.e., SF-MWCNT–PdSnmix and SF-MWCNT–PdNimix) showed better electrocatalysis towards EG oxidation than the SF-MWCNT–Pd. At the SF-MWCNT–PdSnmix platform, oxidation of EG occurred at lower onset and peak potentials, higher current density, and faster kinetics (lower impedance) than at the SF-MWCNT–PdNimix platform. EG oxidation at the SF-MWCNT–PdNimix is more stable than at the SF-MWCNT–PdSnmix. Indeed, Sn is a more favoured co-catalyst with Pd in EG electro-oxidation.

Electrocatalytic oxidation of ethylene glycol (EG) on supported Pt and Au catalysts in alkaline media: Reaction pathway investigation in three-electrode cell and fuel cell reactors

Carbon supported Pt and Au nanoparticles with small sizes (2.4nm for Pt/C, and 3.5nm for Au/C) and narrow size distributions were prepared though a modified solution-phase reduction method, and served as the working catalysts for an investigation of electrocatalytic oxidation of EG in alkaline media. Our three-electrode cell with an on-line sample collection system showed that with applied potential increasing, glycolic acid, oxalic acid and formic acid were sequentially produced from EG oxidation on Pt/C, while only glycolic acid and formic acid were detected on Au/C. Oxalic acid is a fairly stable product, and Pt/C is inactive to its further oxidation reaction. On Au/C, glycolic acid is the primary product, and no oxalic acid was found at specified test conditions. We clarified that formic acid was produced preferably from direct CC bond cleavage of EG not glycolic acid on both Pt/C and Au/C catalysts. The single anion exchange membrane-direct EG fuel cell (AEM-DEGFC) with Pt/C and Au/C anode catalysts showed consistent results with the three-electrode cell tests. The AEM-DEGC with Pt/C anode catalyst demonstrated a peak power density of 71.0mWcm−2, which is much higher than that with the Au/C (only 7.3mWcm−2) at 50°C. With the fuel cell operation voltage decreasing (anode overpotential increasing), deeper-oxidized products oxalic acid and formic acid were generated in the Pt/C anode AEM-DEGFC with higher selectivity. No formic acid was detected in the Pt anode AEM-DEGFC when glycolic acid was employed as fuel. On Au/C anode catalyst, very high selectivity to glycolic acid (>98%) was achieved. The AEM-DEGFC results confirmed the EG electro-oxidation pathways proposed by using an on-line sample collection system.

Platinum modification of gold and electrocatalytic oxidation of ethylene glycol on Pt-modified Au electrodes

The surface modification of gold electrodes with platinum and the electrocatalytic oxidation of ethylene glycol on Pt-modified Au electrodes are investigated by cyclic voltammetry. Platinum modification is performed by the electrochemical deposition of platinum on polycrystalline gold electrodes, and the Pt-modified Au electrodes with different amount of the deposited platinum are used for the ethylene glycol oxidation in alkaline and acidic solutions. It is shown that oxidation potential for the ethylene glycol oxidation on the Pt-modified Au electrodes shifts significantly negative compared with that on Au electrodes, nearly same oxidation potentials as that on Pt electrodes are observed, and peak current density of the ethylene glycol oxidation is dependent on the amounts of the deposited platinum on gold surface, much higher peak current densities than that on Au and Pt electrodes can be obtained. The low oxidation potential and high peak current density indicate the enhanced reactivity of Au electrodes by the platinum modification. The characteristics of the Pt-modified Au electrodes are found to be similar to that of Pt electrodes, and the reactivity of the Pt-modified Au electrodes is mainly attributed to the deposited platinum.

Dynamics of Electrocatalytic Oxidation of Ethylene Glycol, Methanol and Formic Acid at MWCNT Platform Electrochemically Modified with Pt/Ru Nanoparticles

AbstractComparative electrocatalytic behavior of functionalized multiwalled carbon nanotubes (fMWCNTs) electrodecorated with Pt/Ru nanoparticles towards the oxidation of methanol (MeOH), ethylene glycol (EG) and formic acid (FA) has been investigated. The catalytic current density decreased approximately as MeOH≈EG>FA. Result revealed that BPPGE‐fMWCNT‐Pt/Ru tolerates CO poisoning for FA electrooxidation than when used for the oxidation of the EG or MeOH. Electrochemical impedance spectra are dependent on the oxidation potentials, with equivalent circuit models characteristic of adsorption‐controlled charge transfer kinetics. The results provide important insights into the electrochemical response of these small organic molecules useful in fuel cell technology.

A comparative study of the electrocatalytic oxidation of ethylene glycol on PtAu nanocomposite catalysts in alkaline, neutral and acidic media

Electrocatalytic oxidation of ethylene glycol on platinum–gold nanocomposite catalysts is investigated by cyclic voltammetry. Platinum–gold nanoparticles are prepared by chemical reduction, and cyclic voltammograms of carbon-supported platinum–gold nanocomposite catalysts show significant differences in alkaline, neutral and acidic solutions. The catalysts exhibit high electrocatalytic activity and stability in alkaline solution, showing oxidation peaks at low potentials with high current densities. Oxidation peaks at higher potentials with significant current declines are observed in neutral solution, and further positive shifts in peak potential are observed in acidic solution. The concentrations of ethylene glycol and the supporting electrolytes also affect the reaction. A higher alkaline concentration is favorable for oxidation at low potential with high current density. Increased phosphate concentration in neutral buffer solution yields a negative shift in peak potential and minor enhancement in peak current density. Changes in the sulfuric acid concentration mainly affect peak current density. Factors such as the synergic catalysis effect and increased active surface area are thought to be responsible for the reactivity of the platinum–gold nanocomposite catalysts.

Electrocatalytic oxidation of ethylene glycol on Pt and Pt–Ru nanoparticles modified multi-walled carbon nanotubes

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.

Pd-Ni/MWCNT Electrocatalysts for Ethylene Glycol Electro-oxidation in Alkaline Medium

The MWCNT (multi-walled carbon nanotube) electrocatalysts with different Pd/Ni atomic ratios were prepared by microwave reduction method. XRD, TEM, and EDS measurements were used to characterize the composition, particle size, and crystallinity of the catalysts. It showed that the Pd-Ni nanoparticles supported on MWCNTs were small and well dispersed on the surface of MWCNTs. The electrocatalytic oxidation of ethylene glycol (EG) was studied by cyclic voltammetry (CV), linear sweep voltammetry (LSV), chronoamperometry (CA) and electrochemical impendance spectroscopy (EIS). It was found that the performance of ethylene glycol electro-oxidation on Pd-Ni/MWCNT electrocatalysts with a Pd/Ni atomic ratio of 3∶1 was the best.

Electrocatalytic Oxidation of Ethylene Glycol in Alkaline Solution

The electrochemical oxidation of ethylene glycol in alkaline solution was investigated using , and ultrafine gold deposited on electrodes. The ultrafine gold particles prepared in the present study were in diameter. These catalysts enhanced the activity in ethylene glycol oxidation in lower potential regions. In particular, the electrode showed the highest catalytic activity in ethylene glycol oxidation in a less noble potential region ( vs. RHE).

Microwave activation of electrochemical processes: enhanced PbO2 electrodeposition, stripping and electrocatalysis

Microwave activation of electrochemical processes has recently been introduced as a new technique for the enhancement and control of processes at electrode|solution (electrolyte) interfaces. This methodology is extended to processes at glassy carbon and boron-doped diamond electrodes. Deposition of both Pb metal and PbO2 from an aqueous solution of Pb2+ (0.1 M HNO3) are affected by microwave radiation. The formation of PbO2 on anodically pre-treated boron-doped diamond is demonstrated to change from kinetically sluggish and poorly defined at room temperature to nearly diffusion controlled and well defined in the presence of microwave activation. Calibration of the temperature at the electrode|solution (electrolyte) interface with the Fe3+/2+ (0.1 M HNO3) redox system allows the experimentally observed effects to be identified as predominantly thermal in nature and therefore consistent with a localized heating effect at the electrode|solution interface. The microwave-activated deposition of PbO2 on boron-doped diamond remains facile in the presence of excess oxidizable organic compounds such as ethylene glycol. An increase of the current for the electrocatalytic oxidation of ethylene glycol at PbO2/boron-doped diamond electrodes in the presence of microwave radiation is observed. Preliminary results suggest that the electrodissolution of solid microparticles of PbO2 abrasively attached to the surface of a glassy carbon electrode is also enhanced in the presence of microwave radiation.

Lead Dioxide Deposition and Electrocatalysis at Highly Boron-Doped Diamond Electrodes in the Presence of Ultrasound

Boron-doped diamond (BDD) is a versatile and novel electrode material which, due to its mechanical and chemical robustness, wide potential window, low background interference, and ease of chemical modification, is becoming an interesting alternative to conventional electrodes for a wide range of electrochemical applications. It is shown in this study that BDD is a good substrate for the ultrasound-enhanced electrodeposition of lead dioxide, producing strongly adhered electrically conducting deposits. Power ultrasound is used to enhance both the efficiency of the deposition procedure and the rate of the electrocatalytic ethylene glycol oxidation process at the -modified BDD electrode. The presence of high levels of aqueous organic material is shown to interfere with the lead dioxide deposition process. Under optimized insonation conditions the deposit, quantified by using cathodic stripping voltammetry, is shown to be mechanically stable. When used in conjunction with power ultrasound to perform the electrocatalytic oxidation of ethylene glycol two distinct types of oxidation processes at chemically rate limited and electrochemically rate limited, are observed. © 2001 The Electrochemical Society. All rights reserved.

Electrocatalytic Oxidation of Ethylene Glycol on Dispersed Pt: Determination of the Reaction Products

Comparative studies of electrocatalytic ethylene glycol oxidation on bulk and dispersed Pt in acidic aqueous solutions have been performed. A quantitative method has been developed to determine all organic oxidation products using high-performance liquid chromatography with appropriate derivatising reagents.

Effects of microstructure in ethylene glycol oxidation on graphite supported platinum electrodes

Activities of graphite supported and polycrystalline Pt in electrocatalytic oxidation of ethylene glycol in neutral unbuffered Na 2SO 4 solutions have been compared. Morphology and microstructure of supported Pt electrodes have been studied using scanning electron microscopy, high-resolution transmission electron microscopy and X-ray diffraction. Specific activity of Pt electrodes and sensitivity to poisoning has been found to depend strongly on their microstructure. Supported electrodes appear to be from four to six times less active than polycrystalline Pt in the potential region between 0.3 and 0.9 V vs. SHE but much more stable to self-poisoning. The electrode microstructure has much less effect on the activity at high (over 0.9 V vs. SHE) anodic potentials.

Electrocatalytic oxidation of ethylene glycol in 0.5 M H 2SO 4 and 0.5 M NaOH solutions at a bimetallic deposited electrode

The activity of Pt, Pt + Pb and Pt + Ir deposits on Ti, for ethylene glycol (EG) oxidation, was studied in both 0.5 M H 2SO 4 and 0.5 M NaOH solutions. The metallic deposits were prepared by electrolysis at constant current on Ti, with their morphology studied by scanning electron microscopy. These electrodes revealed higher activities in alkaline medium than in acid solutions, the Pt deposits being the most active for EG electro-oxidation. In acid medium, although the electrodes generally showed low electrocatalytic activities, among them Pt + Ir codeposits presented the best performance. Additionally, from activity measurements in acid medium, a synergistic effect for Pt + Ir electrodes was observed. The effect of the supporting electrolyte on the activity of these electrodes is discussed in terms of a reaction path, which is dependent on the OH − anions in alkaline solutions and on the adsorbed (OH) ad species in sulfuric acid solution.

Electrolytically co-deposited platinum—palladium electrodes and their electrocatalytic activity for ethylene glycol oxidation: a synergistic effect

The electrocatalytic oxidation of ethylene glycol has been investigated on platinumpalladium alloy electrodes of different compositions in alkaline aqueous solution. The surface characteristics of the alloys in contact with electrolytic solution have been studied using cyclic voltammetry. X-ray diffraction studies are interpreted to verify homogeneity of electrolytically co-deposited alloys. Enhanced electrocatalytic activity at about 20 at.% in Pd is obtained when compared to pure metals, thus leading to a synergistic effect. An explanation of these effects is suggested on the basis of a decrease of strongly bound residue of ethylene glycol.

Electrocatalytic oxidation of ethylene glycol: Part III. In-situ infrared reflectance spectroscopic study of the strongly bound species resulting from its chemisorption at a platinum electrode in aqueous medium

The adsorption of ethylene glycol (EG) at a platinum electrode in aqueous medium was investigated using Electrochemically Modulated Infrared Reflectance Spectroscopy. The adsorption appears to the dissociative at any pH. However, striking changes occur in the composition of the adsorbed layer when the pH is varied from acid to alkaline solutions. Thus, linearly bonded CO is dominant at pH ∼ 1, whereas almost equal amounts of bridge-bonded and linearly bonded CO species are found at pH ∼ 13. No other adsorbed residue has been detected in the experimental conditions observed and for the wavelength ranges investigated. But detailed analysis of the spectroscopic data leads to the conclusion that other adsorbed organic species might be present on the electrode surface, at least in acid medium.

Electrocatalytic oxidation of organic molecules in alkaline solutions—II. Electroadsorption and electrooxidation of ethylene glycol at platinum

The electrocatalytic oxidation of ethylene glycol (EG) at polycrystalline platinum in 1 M KOH was studied under potentiodynamic and potentiostatic conditions. EG electroadsorption processes were clearly distinguished from the oxidation of EG electroadsorbed residues by using the flux technique after adsorption. The maximum adsorption potential was between 0.3 and 0.4 V in the H-adatoms potential region. An electroadsorbed residue which oxidizes at more positive potentials was formed. The (eps) ads and (eps) ox values were independently determined by the potentiostatic i/t transients at 0.35 V and the potentiodynamic oxidation profiles at low sweep rates respectively. The experimental values obtained allowed to postulate a plausible reaction pathway sequence. The comparison of EG with electroadsorbed 1,3 dioxolane and adsorbed CO electrooxidation spectra showed similar surface oxidation behavior.

Electrocatalytic oxidation of ethylene-glycol: Part I. Behaviour of platinum ad-atom electrodes in acid medium

The influence of six different foreign metal ad-atoms (Cd, Re, Pb, Cu, Bi, Tl) on the electrocatalytic activity of a platinum-based electrode was investigated in the case of the oxidation of ethylene-glycol in acid medium. Only Cd and Re ad-atoms lead to an electrocatalytic effect, mainly due to a cathodic shift of the whole polarization curve. An explanation of the different behaviour of these six ad-atoms is given on the basis of their potential range of redissolution, compared to the potential range of the first anodic peak of ethylene-glycol electrooxidation. As far as metal ad-atoms remain present on the platinum surface in the potential range of the hydrogen region, they prevent the formation of adsorbed hydrogen and thus the occurrence of a strongly bound intermediate.

Electrocatalytic oxidation of ethylene glycol in alkaline medium on paltinum-gold alloy electrodes modified by underpotential deposition of lead adatoms

Electrocatalytic oxidation of ethylene glycol in alkaline medium on paltinum-gold alloy electrodes modified by underpotential deposition of lead adatoms