Electrocatalytic oxidation of methanol and ethanol at carbon ceramic electrode modified with platinum nanoparticles

The use of carbon ceramic electrode (CCE) modified with platinum particles was studied for the electrocatalytic oxidation of methanol and ethanol by cyclic voltammetry and chronoamperometry. After preparation of a carbon ceramic as an electrode matrix by sol–gel technique, its surface was potentiostatically coated with Pt nanoparticles at −0.2 V vs. SCE in an aqueous solution of 0.1 M H₂SO₄ containing 0.002 M H₂PtCl₆. The electrocatalyst was characterized by XRD, SEM and cyclic voltammetry. The effective parameters on electrocatalytic oxidation of the alcohols, i.e. the amount Pt loadings, medium temperature and working potential limit in anodic direction were investigated and the results were discussed. This modified electrode showed an enhanced current density over the other Pt-modified electrodes making it more attractive for fuel cell applications.     

Magnetron sputtering of platinum nanoparticles onto vertically aligned carbon nanofibers for electrocatalytic oxidation of methanol

The electrochemical activities of Pt-sputtered electrodes based on vertically aligned carbon nanofibers (Pt/VACNFs) directly grown on the carbon paper are investigated. Different Pt loading (0.01 mg cm⁻², 0.025 mg cm⁻² and 0.05 mg cm⁻²) electrodes are developed. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) results show that the Pt nanoparticles are homogeneously dispersed on the surface of vertically aligned carbon nanofibers. TEM and X-ray diffraction (XRD) results reveal the Pt nanoparticles diameter increase with increasing Pt loading. The Pt/VACNFs electrodes show good electrochemical active surface area, methanol oxidation peak current density and CO tolerance. The electrochemical catalyst activities weaken as the diameter grows larger. Compared to common electrodes prepared by commercial catalyst in a conventional ink-process, the performance improvement suggests that unique structure of Pt/VACNFs electrode ensures the electronic pathway and Pt nanoparticles exposed to three-phase boundary, which leads to a significant improvement of the Pt utilization and a potential application in direct alcohol fuel cells.     

Novel conjugated polymer/graphene/platinum composite for enhancing electrocatalytic oxidation of methanol

A novel conjugated polymer containing electron transport groups with high electron affinity, denoted POXD was synthesized upon polycondensation. The polymer was characterized by Fourier transform infrared (FTIR) spectra and ¹H nuclear magnetic resonance (¹H NMR) spectroscopy. Furthermore, the conjugated polymer/graphene (POXD/RGO) composite film was prepared, which was subsequently used as the support for the electrodeposition of platinum. The microstructure and morphology of the prepared samples were characterized by X‐ray photoelectron spectroscopy (XPS) and field emission scanning electron microscopy (FE‐SEM). The electrocatalytic activity for the oxidation of methanol was investigated through cyclic voltammogram method. The POXD/RGO composite film can facilitate the electrodeposition of Pt nanoparticles compared with graphene (RGO) support. The POXD/RGO/Pt composite exhibits more excellent electrocatalytic property for the oxidation of methanol, such as lower oxidation potential and higher current intensity, which might be attributed to the high electron affinity of the polymer and the interaction of the Pt nanoparticles with polymer. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Controlled platinum nanoparticles uniformly dispersed on nitrogen-doped carbon nanotubes for methanol oxidation

This work presents the synthesis of platinum nanoparticles (Pt NPs) and their subsequent deposition on the nitrogen-doped carbon nanotubes, which have been directly grown on a carbon cloth (CNT-CC electrode). The CNT-CC electrode provides a fast electron-transfer path to the carbon cloth, resulting in energy-loss reduction and enhancing catalytic activity of Pt NPs. The N-dopants in CNT serve as the defect sites to enhance nucleation of Pt particles. The reduction of the Pt precursor salt was carried out in the ethylene glycol solution at an elevated temperature. In order to control the Pt NP size, the pH of the reaction solution was controlled by the addition of NaOH. Zeta potential measurements of the as-prepared sample indicate that a higher zeta potential results in a smaller particle size, due to a stronger electrostatic repulsion between NPs. This serves a powerful tool for size control of the Pt nanoparticle. The Pt NPs dispersed on the CNT-CC have an average size of 2.81 nm (Pt/CNT-CC) prepared using 15 mM NaOH, with high uniformity under electron microscopy. Cyclic voltammetry measurements of the electrocatalytic activity of the Pt/CNT-CC for methanol oxidation indicate that it exhibits excellent electrocatalytic activity and are ideal for direct methanol fuel cell applications.     

Ultrasonic synthesis of highly dispersed Pt nanoparticles supported on MWCNTs and their electrocatalytic activity towards methanol oxidation

A new method of synthesis of highly dispersed Pt nanoparticles with large catalytic surface area on multi-walled carbon nanotubes (MWCNTs) under high-intensity ultrasonic field was developed. The method, with low processing temperature at 25 °C, took only about 5 min. The surface characterization of MWCNTs was carried out by fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy methods. The electrochemical surface area and pore volume of MWCNTs were also examined. The result showed that functional groups of the MWCNTs which favored the high loading and high dispersion of particles and electrochemical surface area of MWCNTs were reinforced in the case of high-intensity ultrasonic field. The Pt/MWCNT catalysts were characterized by energy dispersion X-ray spectra analysis (EDX), transmission electron microscopy (TEM) and X-ray diffraction (XRD) measurements. The prepared Pt nanoparticles were uniformly dispersed on the MWCNT surface. The mean size of Pt particles was 3.4 ± 0.2 nm. The electrocatalytic properties of Pt/MWCNT composites and kinetic characterization for methanol electro-oxidation were investigated by cyclic voltammetry. The Pt/MWCNT catalysts prepared for 5 min in ultrasonic field present excellent electrochemical activities. The schematic of the reaction was also introduced.     

A novel electrocatalytic polyaniline electrode for methanol oxidation

Pt clusters were electrodispersed on polymeric films to obtain catalytic electrodes for methanol oxidation. The electrodeposit was built up by applying either a constant potential or a repetitive square wave potential routine. The performance of the electrodes was followed by measuring the stripping peak potential of adsorbed CO, each assembly metal/Pani/Pt being characterized by SEM and EDAX. Polymeric electrodes, modified with Pt electrodeposited by the programmed potential variation had a better electrocatalytic activity for CO and methanol oxidation. The novel tailored electrode is the result of a balance between a particular morphology and the number of particles of the catalytic material on the conductive polyaniline matrix.     

The use of nitrogen-doped graphene supporting Pt nanoparticles as a catalyst for methanol electrocatalytic oxidation

Nitrogen-doped graphene (N-G) was prepared by thermal annealing of graphene oxide in ammonia at different temperatures. The resultant N-G was used as a conductive support for Pt nanoparticles (Pt/N-G) and the electrocatalytic activity of the Pt/N-G catalysts towards methanol oxidation was examined. To investigate the microstructure and morphology of the synthesized catalysts, X-ray diffraction, scanning and transmission electron microscopy and X-ray photoelectron spectroscopy were used. The catalytic activity of the catalysts towards the oxidation of methanol was evaluated by cyclic voltammetry. Compared to a control catalyst of Pt loaded on undoped graphene, the Pt/N-G materials show higher electrochemical activity towards methanol oxidation. The excellent electrochemical performance of Pt/N-G is mainly attributed to the nitrogen doping and the uniform distribution of Pt particles on the doped graphene support. These results indicate that N-doped graphene has great potential as a high-performance catalyst support for fuel cell electrocatalysis.     

Enhanced electrocatalytic activity for the oxidation of liquid fuels on PtSn nanoparticles

PtSn nanoparticles with different Pt/Sn ratio have been prepared by a chemical reduction method. XRD data indicate that Sn atom is introduced into the Pt lattice. Their electrocatalytic activity is evaluated using cyclic voltammetry (CV), differential electrochemistry mass spectrometry (DEMS), and rotating disk electrode (RDE) experiments. The Pt₉Sn₁ nanoparticles exhibit higher electrocatalytic activity than commercial Pt nanoparticles (E-TEK) for the oxidation of ethanol. The rate constants for the oxidation of formic acid, formaldehyde, methanol, ethanol, glycol, and glycerol on Pt₉Sn₁ electrocatalyst are much higher than that on Pt. The results indicate that Pt₉Sn₁ is an excellent electrocatalyst for the oxidation of liquid fuels. The activation energy studies show that the higher electrocatalytic activity of PtSn catalyst can be ascribed to the bifunctional mechanism, instead of the dilation of Pt crystal structure.     

Preparation of methanol oxidation electrocatalysts: ruthenium deposition on carbon-supported platinum nanoparticles

Methanol oxidation electrocatalysts were prepared from Ru electrochemical or spontaneous deposition on commercial-grade carbon-supported Pt nanoparticles (Pt-Vulcan XC72, E-TEK). The resulting Ru coverage was estimated by cyclic voltammetry in supporting electrolyte. The maximum electrocatalytic activity for methanol oxidation at room temperature was observed at lower Ru coverage for spontaneous deposition than for electrodeposition; _Ru 10% vs 20%, respectively. On the other hand, higher current densities for methanol oxidation were obtained in the case of electrodeposited Ru. These two results were related to the presence of non-reducible ruthenium oxides in the spontaneous deposit. The present work provides evidence that (i) efficient DMFC electrocatalysts can be achieved by Ru deposition on Pt nanoparticles, and (ii) formation of a PtRu alloy is not a required condition for effective methanol electrooxidation.     

Electrocatalytic oxidation of methanol on platinum nanoparticles electrodeposited onto porous carbon substrates

To achieve methanol fuel cell electrodes allowing a high catalyst use, thin layers of various carbon powders and recast Nafion® were electrochemically plated with platinum. The resulting Pt deposits were characterized by hydrogen and carbon monoxide electrosorption, as well as by transmission electron microscopy. Methanol oxidation was then carried out using cyclic voltammetry. The influence of the amount of carbon surface oxides and the effect of Pt specific surface area on the Pt catalytic activity were thus investigated.     

Sonochemical synthesis of Pt-doped Pd nanoparticles with enhanced electrocatalytic activity for formic acid oxidation reaction

Pt-doped Pd nanoparticle catalysts (Pd _n Pt, n is 12, 15 and 19) supported on carbon were synthesized by an ultrasound assisted polyol method. The catalysts were characterized by X-ray diffraction, transmission electron microscopy, and energy dispersive X-ray spectroscopy. The electrochemical activity of the electrocatalysts was investigated in terms of formic acid oxidation reaction (FAOR) at low concentration of formic acid in 0.1 M perchloric acid at room temperature. Formic acid oxidation on the Pd _n Pt/C commences at lower potential than a commercial Pt/C. Pd₁₉Pt/C catalyst showed the highest catalytic activity in FAOR compared to that of other catalysts. The obtained electrochemical results from voltammograms indicate that Pt-doped Pd catalysts can be a promising candidate for the anode material in direct formic acid fuel cells. The synthesis procedure is not only a very facile route but also a mass producible method for preparing carbon supported alloy nanoparticles.     

Platinum and platinum-ruthenium nanoparticles supported on ordered mesoporous carbon and their electrocatalytic performance for fuel cell reactions

Highly ordered meso-porous carbon, denoted CMK-3 was synthesized by using mesoporous silicates, SBA-15 as the starting templating materials. The ordered mesoporous carbon was loaded with platinum and platinum-ruthenium nanoparticles using alternative synthesis techniques. The metal loaded ordered mesoporous carbon powders were characterized by transmission electron microscopy (HRTEM), energy dispersive X-ray analysis (EDX), X-ray diffraction, and nitrogen adsorption isotherm experiments. Micrometer-scale and centimeter-scale electrodes containing the mesocarbon/nanometal electrocatalysts were tested for some typical fuel cell reactions. While the nanometal/mesocarbon catalysts have well-defined and uniform properties in the nanometer scale, they have mixed electrocatalytic performance. A synthesized Pt/mesocarbon electrocatalyst outperformed a commercial electrocatalyst for oxygen reduction on a gas-diffusion electrode. The Pt-Ru/mesocarbon electrocatalyst synthesized, however, was not as effective for methanol oxidation.     

Gold and platinum catalysed oxidation of methanol

A comparative study was made of the vapour phase oxidation of methanol in presence of gold and platinum, using a flow system at temperatures below 500°C. Over gold there is a stoichiometric conversion to formaldehyde and water. In presence of platinum, the reaction is the same up to 200°C, but at higher temperatures other oxidation products appear. Mechanisms are suggested involving interaction between chemisorbed oxygen and methanol fragments.     

碳化钨纳米晶薄膜电极的制备及其对甲醇电氧化性能

引　言碳化钨具有与金属铂相类似的表面电子结构[1], 因此, 人们一直在探索碳化钨在化学领域中的催化性能, 期望利用矿藏丰富、价格低廉的钨矿优势, 用碳化钨来替代资源稀缺、价格昂贵的铂及铂基合金催化剂. 研究表明, 碳化钨在烷烃重整、异构化反应以及在氢析出反应等方面具有     

Highly dispersed Pt nanoparticles on nitrogen-doped magnetic carbon nanoparticles and their enhanced activity for methanol oxidation

Pt nanoparticles dispersed nitrogen-doped magnetic carbon nanoparticles (N-MCNPs) were prepared by chemical method, conventional sodium borohydride reduction. Then, those probable applications were evaluated for a support material comparing with Vulcan XC-72 for polymer electrolyte membrane fuel cell. N-MCNPs-supported Pt nanoparticles show a better activity of methanol oxidation reaction compared to Vulcan XC-72-supported one in terms of both mass and electrochemical surface area (ESA) normalized current density. In particular, Pt/N-MCNPs show more enhanced activity based on the mass normalized specific activity rather than ESA normalized activity. For investigation of physical characterizations of Pt/N-MCNPs, and Pt/Vulcan XC-72, X-ray diffraction (XRD), high resolution-transmission electron microscopy (HR-TEM), and X-ray photoelectron spectroscopy (XPS) likes various experiments were performed. Especially, to identify the role of nitrogen in the N-MCNPs for Pt nanoparticles dispersion, specific investigation of N 1s XP spectra with peak deconvolution were performed on N-MCNPs support material of the before and after chemical reduction of Pt nanoparticles.     

Radiolysis route to Pt nanodendrites with enhanced comprehensive electrocatalytic performances for methanol oxidation

Unique Pt nanodendrites with controlled size were prepared by a rapid radiolysis route. The Pt nanodendrites display drastically enhanced electrochemical catalytic performances toward methanol oxidation. They exhibit a better CO tolerance for methanol oxidation compared with commercial catalysts and other nanodendritic Pt-based catalysts.     

Methanol oxidation on gold nanoparticles in alkaline media: Unusual electrocatalytic activity

Methanol oxidation on gold nanoparticles has been studied using cyclic voltammetry in alkaline media. The onset for methanol oxidation in 0.1 M NaOH solutions is at ca. 0.3 V (RHE) and the currents reach a maximum value at 0.8 V. In 1 M NaOH solutions, oxidation currents are measured at potentials as low as 0.1 V. Although the currents are significantly smaller than the expected limiting diffusion current for methanol oxidation, oxidation currents are partially controlled by diffusion, as revealed by rotating disk experiments. This suggests that only a small fraction of the nanoparticles is active for the oxidation. It is proposed that formate is the final product of the oxidation and formaldehyde is an active intermediate in the process.     

Optimization of the dispersion of gold and platinum nanoparticles on indium tin oxide for the electrocatalytic oxidation of cysteine and arsenite

Gold and platinum nanoparticles (NPs) were prepared by chemical reduction of the corresponding metal complex bound by ion-exchange to generation-4 poly(amidoamine) dendrimers (PAMAM). Arrays of the NPs on indium tin oxide (ITO) electrodes were formed by adsorbing a monolayer comprising a controlled ratio of NP-PAMAM to PAMAM on ITO that was modified with 3-aminopropyl triethoxysilane; subsequently, the organic components were thermally destroyed. Varying the above-defined ratio resulted in a commensurate change of the density of the NPs on the surface. Using an electrode modified in a solution with a mole fraction of Au-PAMAM (relative to total of Au-PAMAM and PAMAM) of 0.06, which gave NPs separated by 200 nm, the current for the catalytic oxidation of cysteine reached a value that did not increase when more nanoparticles were present. The analogous experiment on the oxidation of As^III with PtNPs as the catalyst was optimized at a mole fraction of 0.2. Calculations assuming hemispherical diffusion suggested that the diffusion domains during cyclic voltammetry at 5 mV s⁻¹ were less than the distance between the NPs.     

Electrocatalytic activity of Pt nanoparticles on bamboo shaped carbon nanotubes for ethanol oxidation

Recently, bamboo shaped carbon nanotubes (BCNTs) have received increased attention for its bamboo shaped structure associated properties and its application in direct methanol/ethanol fuel cell. In this work, the potential to use BCNTs as the support material of high loaded Pt nanoparticles for improving the efficiency of ethanol/methanol fuel cell is explored. The structure and nature of the resulting Pt-BCNTS composite were characterized by transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS) spectrum, it was found that Pt nanoparticles were homogeneously dispersed on the BCNTs surfaces with 23.5% by weight. Cyclic voltammogram (CV) indicated that the Pt-BCNTs catalyst displayed excellent electrocatalytic activity and long-term stability toward ethanol oxidation. The excellent performance may be attributed to the high dispersion of nanoscale Pt catalysts and the unique nature of BCNTs. The results imply that doping N atom introduces some defective sites and active sites onto the surface of CNTs. In general, this paper demonstrates that BCNTs are promising support material for Pt-nanoparticles catalyst and can be used to enhance the efficiency of fuel cell.