Pt/C nanocatalysts for methanol electrooxidation prepared by water-in-oil microemulsion method (original) (raw)
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Journal of Power Sources, 2006
The organic sol method for preparing ultrafine transition metal colloid particles reported for the first time by Bonnemann et al. [H. Bonnemann, W. Brijoux, R. Brinkmann, E. Dinjus, T. Jouen, B. Korall, Angew. Chem. Int. Ed. Engl., 30 (1991) 1312] has been improved in this paper. The improved organic sol method uses SnCl 2 as the reductant and methanol as the organic solvent. Thus, this method is very simple and inexpensive. It was found that the average size of the Pt particles in the Pt/C catalysts can be controlled by adjusting the evaporating temperature of the solvent. Therefore, the Pt/C catalysts prepared by the same method are suitable for evaluating the size effect of the Pt particles on electrocatalytic performance for methanol oxidation. The results of the X-ray diffraction (XRD) and transmission electron microscopy (TEM) showed that when the evaporating temperatures of the solvent are 65, 60, 50, 40, and 30 • C, the average sizes of the Pt particles in the Pt/C catalysts prepared are: 2.2, 3.2, 3.8, 4.3, and 4.8 nm, respectively. The X-ray photoelectron spectroscopic (XPS) results demonstrated that the small Pt particles are easily oxidized and the decomposition/adsorption of methanol cannot proceed on the surfaces of Pt oxides. Thus, the Pt/C catalyst with small Pt particles has a low electrocatalytic activity for methanol oxidation. The Pt/C catalyst with a large average size of the Pt particles also possesses a small electrochemically active surface area. Therefore, only the Pt/C catalyst with a middle average size of Pt particles, such as 3.8 nm exhibited optimal electrocatalytic performance for methanol oxidation. Because the Pt/C catalysts with the different particle sizes were prepared with the same method, the size effect on the electrocatalytic performance of the catalysts could be reliably investigated.
Nano PtCuO particles were deposited on Vulcan XC-72R carbon black using the impregnation and microwave irradiation methods. The prepared catalysts were characterized by XRD, TEM and EDX analyses. TEM images indicated that the microwave method provides homogeneously distributed catalyst particles in smaller size, compared to the one prepared by the impregnation method. The electrocatalytic activity of Pt‒CuO/C electrocatalysts was investigated to oxidize methanol in 0.5 M H2SO4 solution by applying cyclic voltammetry and chronoamperometry techniques. The oxidation current density of Pt‒CuO/C electrocatalyst, prepared by the microwave method, showed two folds increment with a potential shift in the negative direction by 69 and 36 mV at the first and second oxidation peaks, respectively, relative to those at the catalyst prepared by the impregnation method. The effect of varying methanol concentration on the resulting oxidation current density of Pt‒ CuO/C electrocatalysts was studied. Some kinetic information about the reaction order with respect to methanol and Tafel slope values was calculated. Slower current density decay was observed in the chronoamperogram of Pt‒CuO/C electrocatalyst, prepared by the microwave method, reflecting a lower degree of surface poisoning.
iranian journal of catalysis, 2017
The impregnation method was used to synthesize Pt and Pt3Co supported on MWCNTs applying NaBH4 as the reducing agent. The structure, morphology, and chemical composition of the electrocatalysts were characterized through SEM, XRD, and EDX. X-ray diffraction showed a good crystallinity of the supported Pt nanoparticles on the composites and showed the formation of Pt3Co alloy. The SEM images revealed that the particles of Pt3Co were deposited uniformly on the surface of MWCNT with a diameter of 10 nm. EDX analysis confirmed the surface segregation of Co and Pt occurred (1:3 surface atomic ratio Pt-Co) for the Pt3Co/MWCNT nanocomposite. The Pt3Co/MWCNTs and Pt/MWCNTs electrocatalysts’ electrochemical performance was assessed against the methanol oxidation reaction (MOR) in 0.5 M H2SO4 solution using the chronoamperometry (CA) and the cyclic voltammetry (CV) methods. The minimum onset potential and the largest oxidation current density were obtained at Pt3Co/MWCNTs electrocatalyst. The...
Catalysis Today, 2020
In this work, anodic electrocatalyst (20%wt of metal loading) as PtCo nanoparticles (atomic ratio of 48:52) on micro/nano-structured pyrolytic carbon (MNC) was synthesized by sequential impregnation method and chemical reduction route using citric acid and Ar-H 2 static atmosphere. MNC sample was synthesized via nanocasting process with anhydrous pyrolysis at 800°C using SBA-15 as hard template and refined sugar as carbon source. SBA-15 was prepared via sol gel using pluronic P-123 as surfactant and tetraethoxysilane as silica precursor. The prepared materials were characterized by means of N 2 physisorption, X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy and high resolution transmission electron microscopy. The performance of PtCo/MNC for methanol oxidation reaction (MOR) was measured by cyclic voltammetry, chronoamperometry. The electrochemical characterization techniques revealed that the mass activity of PtCo/ MNC and the commercial electrocatalyst Pt/C (20%wt of Pt loading) at 20 cycles were 481 and 372 mA/mg Pt respectively as well as the resistance to the accumulation intermediate carbonaceous species (methoxy, aldehyde, formaldehyde and carbon monoxide) denoted by the ratio I f /I b for these catalysts were 1.30 and 0.76 respectively. PtCo/MNC exhibit better electrocatalytic performance, electrochemical stability and best resistance to carbonaceous intermediates species in the electro-oxidation of methanol.
Journal of Solid State Electrochemistry, 2019
We studied the effect of the organic solvent on the synthesis of platinum nanoparticles anchored on the surface of multi-wall carbon nanotubes (Pt NPs/MWCNT) by the reverse microemulsion method. For oil phase, three organic solvents of the same alkane chain length (six carbon atoms) were tested: hexane, cyclohexane, and 2,2,4-trimethylpentane. The total metallic content was characterized by thermogravimetric analysis (TGA), and Pt NPs were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The chemical structure of the oil phase influences the Pt loading and crystallite size. The catalyst prepared with 2,2,4-trimethylpentane showed the highest electrochemical active surface area, enhancing the mass and specific activity compared to the commercial electrocatalyst (Pt/C) in the methanol oxidation reaction (MOR).
Enhancing by Weakening: Electrooxidation of Methanol on Pt3Co and Pt Nanocubes
Angewandte Chemie International Edition, 2010
Direct methanol fuel cells (DMFCs) are attractive energy conversion devices for powering portable electronics by converting the chemical energy of methanol directly into electricity. To increase the methanol oxidation activity and to reduce platinum loading, bimetallic catalysts of platinum alloyed with a less expensive metal M are often used. Among different bimetallic catalysts, Pt/Ru has attracted most attention owing to its strong methanol oxidation enhancement. The improved catalytic activity is explained by the bifunctional mechanism and the electronic effect. In the bifunctional mechanism, the platinum sites are responsible for methanol oxidation to form adsorbed carbon monoxide (CO ads ), which poisons the catalyst surface for further fuel oxidation; the ruthenium sites provide adsorbed hydroxyl groups (OH ads ), which is the oxidant for the removal of CO ads , at a much lower potential than on platinum. In the electronic effect, the presence of ruthenium changes the electronic structure of platinum in such a way that it lowers the CO adsorption energy. These two mechanisms often operate concurrently and are often invoked to explain the activity enhancement of other Pt/M alloys. Herein we present methanol oxidation on Pt 3 Co nanocubes (NCbs), in which the enhanced methanol oxidation arises solely from the electronic effect.
Journal of Molecular Liquids, 2016
The acidified, functionalized carbon black supported Pt nanocatalyst (Pt@f-VC) was prepared by the modified ethylene glycol reduction method. The functionalized carbon black serves as a stabilizer to prevent agglomeration of the platinum nanoparticles and ensures that Pt NPs have superficially greater dispersion. The prepared nanoparticles have been characterized by Transmission Electron Microscopy (TEM), X-ray Photoelectron Spectroscopy (XPS), X-ray Diffraction (XRD), Raman Spectroscopy (RS) etc. XRD and TEM results showed that Pt NPs have uniform distribution on functionalized carbon support and the average particle sizes of Pt NPs were measured as 3.5 nm. Methanol electrooxidation reaction results showed that Pt@f-VC catalyst has higher catalytic activity and surface area
Electrochimica Acta, 2009
PtCo and PtMn electrocatalyst particles were successfully synthesized on Ti substrate by the electrodepostion method. PtCo particles deposited are star-shaped particles with size of 100–200 nm and very porous with many slices of ∼10 nm. On the other hand, PtMn particles are spherical and have no obvious conglomeration, and the particle is in the range of 100–200 nm. The results reveal that the effect of the incorporation of Co and Mn on the electrochemical active surface area of Pt nanoaprticles is very small. However, incorporation of trace Co and Mn in Pt (e.g., Pt1000Co and Pt1000Mn) has dramatic effect on the electrochemical oxidation reaction of alcohol. The mass specific peak current for the methanol oxidation in alkaline media is 49 mA cm−2 and 39 mA cm−2 on Pt10000Mn and Pt1000Co, which is three and two times higher, respectively, than that on pure Pt electrocatalyst nanoparticles. PtMn and PtCo electrocatalysts also show significant enhanced stability for methanol oxidation. However, the electrocatalytic enhancement of Co or Mn to Pt is relatively small for the electrooxidation reactions of ethanol in alkaline media.
International Journal of Hydrogen Energy, 2010
Pt catalyst supported on Vulcan XC-72R containing 5 wt% NiO (Pt/NiO-C) showed larger electrochemical active surface area and higher electrochemical activity for methanol oxidation than Pt catalyst supported on Vulcan XC-72R using polyol method without NiO addition. Prepared Pt/NiO-C electrocatalyst was heat-treated at four temperatures (200, 400, 600, and 800 C) in flowing N 2. X-ray diffraction and temperature-programmed desorption results indicated that NiO was reduced to Ni in inert N 2 during heat-treatments at temperatures above or equal to 400 C, while oxygen from NiO reacted with carbon support due to the catalytic effect of Pt. The reduced Ni formed an alloy with Pt, which, according to the X-ray photoelectron spectroscopy data, resulted in a shift to a lower binding energy of Pt 4f electrons. The Pt/NiO-C electrocatalyst heat-treated at 400 C showed the best activity in methanol oxidation due to the change in Pt electronic structure by Ni and the minimal aggregation of Pt particles.
Preparation and characterization of Pt/TiO 2 nanotubes catalyst for methanol electro-oxidation
Applied Catalysis B-environmental, 2011
Titanium dioxide nanotubes were prepared via a hydrothermal treatment of TiO 2 powder (Degussa P25). Obtained samples were analyzed by various techniques, such as transmission electron microscopy (TEM) and X-ray diffraction (XRD), which revealed that the crystal structure of the obtained materials was similar to that of H 2 Ti 2 O 5 ·H 2 O nanotubes, and were about 50 nm in length and 20 nm in diameter. Nitrogen adsorption-desorption isotherms indicated that synthesized solids are mesoporous materials with a multi-walled nanotubular structure and high specific surface area. The methanol oxidation reaction was investigated on platinum nanoparticles supported TiO 2 nanotubes (XC72). The electrocatalytic activity of the catalyst was measured by cyclic voltammetry. CO stripping voltammetry in acidic solutions was investigated to study the reaction of the catalysts towards poisoning by carbonyl compounds. The results demonstrated that Pt/TiO 2 nanotubes catalyst exhibits the best activity for methanol oxidation and were favorable for improving the tolerance to poisoning species.