Methanol electro-oxidation on mesocarbon microbead supported Pt catalysts

Mesocarbon microbeads (MCMB) as Pt catalyst supports were characterized by X-ray electron diffraction, thermal field emission scanning electron microscope and electrochemical analysis. MCMB with different pretreatment were used as the catalyst supports. The XRD patterns show the existence of Pt and the micrograph of SEM shows Pt is absorbed uniformly on the surface of MCMB particles and the platinum grain size is ca. 3-5 nm. The effect of the pretreatment of the support on the catalyst performance of methanol electrooxidation was studied. Electrochemical analysis shows that MCMB are excellent candidates to be used as the support of catalyst for methanol electrochemical oxidation. The catalyst with MCMB boiled in KOH for 1 h as support exhibits a high catalytic activity during the electrooxidation of methanol.     

Synthesis of Mesoporous Carbon from Okara and Application as Electrocatalyst Support

Carbon materials derived from biomass are economical and simple. Here, a okara‐derived carbon (ODC) was prepared by carbonized cheap and abundant okara at 800 °C in N₂ atmosphere. A high degree of graphitization, mesoporous structure and large specific surface area of ODC were proved by Raman spectroscopy, nitrogen adsorption–desorption isotherms, X‐ray diffraction, Fourier transform infrared spectra and scanning electron microscope. The ODC can be used as support of platinum nanoparticles, and the catalytic performance for methanol electro‐oxidation of its was measured by cyclic voltammetry and CO stripping voltammetry. The results showed that Pt/ODC catalyst had higher electrocatalytic activity and the resistance to poisoning ability toward methanol electrooxidation than the Pt/C catalyst prepared under the same conditions.     

Fabrication of palladium coated nanoporous gold film electrode via underpotential deposition and spontaneous metal replacement: A low palladium loading electrode with electrocatalytic activity

An electrochemical approach to nanoporous film-based gold catalyst design using the underpotential deposition and redox replacement technique is presented. The procedure consisted of the underpotential deposition (UPD) of copper on the gold nanoporous film, with subsequent replacement of the copper by palladium at open circuit in a palladium containing solution. The resulting electrode was studied using cyclic voltammetry and scanning electron microscopy. The electrocatalytic activity of as-prepared palladium nanoporous gold film electrodes toward the oxygen reduction reaction is presented.     

Polyol synthesis of highly active PtRu/C catalyst with high metal loading

Highly loaded PtRu/C catalyst with high activity toward methanol electrooxidation was synthesized via a modified polyol process. XRD patterns indicated that the prepared catalyst was highly alloyed and TEM results showed that the metal nanoparticles were small and uniformly distributed on the carbon support despite the high metal loading. EDX results suggested that the two metals distributed uniformly in the catalyst. Electrochemical characterization and single cell test jointly showed that the prepared 40-20 wt.%PtRu/C catalyst possessed high activity toward methanol electrooxidation.     

Pt/C anodic catalysts with controlled morphology for direct dimethyl ether fuel cell: The role of consecutive surface

Two types of Pt nanowires (NWs)/C catalysts with different aspect ratios and one type of Pt nanoparticles/C catalyst are successfully synthesized, and DME electrochemical performance on different extent consecutive surfaces is investigated. The morphology and crystallization are confirmed with electron microscopes and XRD. The electrochemical tests show that the nanowire catalysts, especially the one with higher aspect ratio, possess higher electrochemical surface areas, higher absorption capacity of DME, higher CO tolerance, higher electron transfer coefficient, and higher activity towards DME electrooxidation than those of the nanoparticle catalyst. The results prove that the consecutive surface favors for direct dimethyl ether fuel cell (DDFC) anodic catalyst, which are contributive to the study of the mechanism of DME electrooxidation on Pt surface and designing an effective catalyst for anodic DDFC.     

Palladium nanoparticles supported on polymer: An efficient and reusable heterogeneous catalyst for the Suzuki cross-coupling reactions and aerobic oxidation of alcohols

Polymer supported palladium nanoparticle catalyst was synthesized and characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) techniques. This catalyst exhibits good activity and stability in Suzuki cross-coupling reaction of arylboronic acid with aryl halides and oxidation reaction of alcohols to corresponding aldehydes or ketones without over oxidation. After reaction, the catalyst can be separated by simple method and used many times in repeating cycles without considerable loss in its activity.     

载体制备工艺对Pt/CA催化剂甲醇氧化催化性能的影响

比较研究了炭气凝胶(CA)的制备工艺条件对其表面微观结构及以其为载体的催化剂Pt/CA甲醇氧化催化活性的影响.结果表明,常压干燥制得的CA表面以微孔为主,而超临界CO2干燥制得的CA表面主要以中孔为主,而且比表面积、表面孔容和平均孔径更大;超临界CO2干燥比常压干燥更适合制备高活性甲醇氧化Pt/CA催化剂的载体材料;CA制备过程中催化剂Na2CO3的用量(常用R/C表示,其中R代表制备CA的原料间苯二酚,C代表制备CA的催化剂Na2CO3)为200至1000的范围内,R/C的增大会引起超临界CO2干燥制得CA的表面平均孔径随之增加,R/C为300时制得的CA具有最大的BET比表面积和表面孔容,以其为载体制得的催化剂具有最好的甲醇氧化催化性能.     

Pt-decorated nanoporous gold for glucose electrooxidation in neutral and alkaline solutions

Exploiting electrocatalysts with high activity for glucose oxidation is of central importance for practical applications such as glucose fuel cell. Pt-decorated nanoporous gold (NPG-Pt), created by depositing a thin layer of Pt on NPG surface, was proposed as an active electrode for glucose electrooxidation in neutral and alkaline solutions. The structure and surface properties of NPG-Pt were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray powder diffraction (XRD), and cyclic voltammetry (CV). The electrocatalytic activity toward glucose oxidation in neutral and alkaline solutions was evaluated, which was found to depend strongly on the surface structure of NPG-Pt. A direct glucose fuel cell (DGFC) was performed based on the novel membrane electrode materials. With a low precious metal load of less than 0.3 mg cm^-2 Au and 60 μg cm^-2 Pt in anode and commercial Pt/C in cathode, the performance of DGFC in alkaline is much better than that in neutral condition.     

Improving hydrogen storage/release properties of magnesium with nano-sized metal catalysts as measured by tapered element oscillating microbalance

An effective catalyst doping method was developed for directly depositing nano-particles of various metal catalysts (palladium, platinum and ruthenium) on the outer surface of magnesium powders through a wet chemistry process. The catalyst-doped magnesium was characterized by powder X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS). Catalysts of nano-meter size were uniformly deposited on the outer surface of the magnesium particles. The hydrogen storage and hydrogen release properties of magnesium and catalysts-doped magnesium were measured in situ by the tapered element oscillating microbalance (TEOM), and also by the volumetric method. Both the hydrogen absorption and hydrogen release kinetics of magnesium were significantly improved by doping the nano-particle catalysts. Among the three metals-doped and examined, palladium showed the best catalytic effect. Upon doping 0.5 mol% nano-particle palladium, the hydrogen absorption and hydrogen release rates of magnesium increased 1 and 14 times, respectively, as revealed by the dynamic measurement of storage/release by TEOM, which indicated a strong catalytic effect.     

Pd nanoparticles supported on carbon-modified rutile TiO2 as a highly efficient catalyst for formic acid electrooxidation

In this article, Pd nanoparticles supported on carbon-modified rutile TiO₂ (CMRT) as a highly efficient catalyst for formic acid electrooxidation were investigated. Pd/CMRT catalyst was synthesized by using liquid phase reduction method in which Pd nanoparticles was loaded on the surface of CMRT obtained through a chemical vapor deposition (CVD) process. Pd/CMRT shows three times the catalytic activity of Pd/C, as well as better catalytic stability towards formic acid electrooxidation. The enhanced catalytic property of Pd/CMRT mainly arises from the improved electronic conductivity of carbon-modified rutile TiO₂, the dilated lattice constant of Pd nanoparticles, an increasing of surface steps and kinks in the microstructure of Pd nanoparticles and slightly better tolerance to the adsorption of poisonous intermediates.     

Pd-Ag/C在硼氢化钠电氧化反应中的电化学行为

采用化学还原法制备了不同原子比的Pd-Ag/C催化剂。通过X射线衍射（XRD）表征了催化剂的晶体结构,并运用循环伏安、计时电流等电化学方法研究了其对硼氢化钠电氧化反应的催化活性。结果表明：适量Ag的掺杂不仅可以提高催化剂的催化活性,而且使得硼氢化钠电氧化反应过程中的转移电子数增加,其中Pd₇₅Ag₂₅/C的催化活性和转移电子数均为最高。     

Thiirane resins cured with polythiourethane hardeners as novel supports for metal complex catalysts

The application of thiirane resin cured with polythiourethane (PTU) hardeners as novel and efficient support for palladium complex catalyst is reported. Stability and activity efficiency in Heck reactions were determined. IR and X‐ray photoelectron spectroscopy provided information of metal coordination to the polymer matrix. Characterization of polymer supports and palladium catalysts has involved the measurements of the structural parameters in the dry state by the nitrogen BET adsorption, time‐of‐flight secondary ion mass spectrometry, scanning electron microscopy, and energy dispersive X‐ray analysis. The results of this study indicate that PTU used to cure thiirane resin can greatly affect the catalytic properties of the episufide resin‐supported palladium catalyst. These new type of polymer supports comparing to other organic carriers offers several practical advantages such as ability to control the crosslinking density, porosity and the chemical structure of the polymeric matrix, which influence the catalytic properties of the immobilized metal complex. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40330.     

Oscillatory behaviour during the oxidation of methane over palladium metal catalysts

Oscillatory reactions over palladium foil and wire catalysts during the oxidation of methane have been investigated over a wide range of reaction temperatures and argon/methane/oxygen feed gas compositions. Characterisation of the catalyst has also been carried out using scanning electron microscopy (SEM) techniques, which revealed the presence of a porous surface. This suggested that the metal surface has undergone a change since the reaction commenced, and using X-ray powder diffraction (XRD) techniques the palladium phase was shown to be the dominant phase present. Hysteresis phenomena were observed in the activity of the reaction as the temperature was cycled up and down, showing that the metal surface was continually changing throughout the reaction. The activation energies of the reaction during the high reactivity mode, PdO, and low reactivity mode, Pd, were also calculated. Oscillation rates were observed to depend on the dominant surface. Oscillations were frequent when the high reactivity mode was dominant while the activation energy of this mode was found to be low. When the low reactivity mode was dominant, the oscillations were slower and the activation energy was three times larger. The results obtained imply that the behaviour of the palladium surface, switching back and forth from the reduced state to the oxidised state, is responsible for the oscillatory behaviour seen in this system.     

Effect of Surface Activation Treatment on Pt/C Catalyst for Electrooxidation of Ethylene Glycol and Adsorbed CO

It was reported for the first time that the electrocatalytic activity of the Pt/C electrode for the oxidation of ethylene glycol (EG) could be dramatically improved after the new surface treatment of the Pt/C electrode. It was also found that the surface treatment of the Pt/C electrode could greatly promote the electrooxidation of CO adsorbed on the Pt/C electrode. Promoting the electrooxidation of CO would lead to the acceleration of the electrooxidation of EG because CO is an intermediate product of the oxidation of EG and it would be strongly adsorbed on the Pt catalyst, leading the poison of the Pt/C catalyst.     

Enhanced electrooxidation of methanol,ethylene glycol,glycerol, and xylitol over a polypyrrole/manganese oxyhydroxide/palladium nanocomposite electrode

A small quantity of palladium metal (Pd, 5 wt%) nanoparticles supported by a polypyrrole/manganese oxyhydroxide (PPy/MOH) nanocomposite was developed and investigated as an electrocatalyst for the alcohol electrooxidation reaction in alkaline media. In voltammetric studies, the PPy/MOH/Pd catalyst, compared to C/Pd, exhibited improved electrocatalytic activity for methanol electrooxidation. The peak current density ratios (j ^f/j ^b) for the C/Pd and PPy/MOH/Pd nanocomposite electrodes were 0.67 and 2.43, respectively, indicating that the PPy/MOH/Pd nanocomposite electrode was much more resistant to catalytic poisoning. The electrooxidation of ethylene glycol (EG), glycerol, and xylitol was also tested using the PPy/MOH/Pd nanocomposite electrode. Among these alcohol electrooxidations, that of EG exhibited the maximum power density of 430 mA cm^?2. The intermediates formed during the electrooxidation reactions were removed by increasing the upper sweep potential from +0.2 to +1.0 V. The catalytic performance of the PPy/MOH nanocomposite is discussed in detail. The study results demonstrate that PPy/MOH acts as a superior catalytic supporting material for alcohol electrooxidation reactions in alkaline media.     

Synthesis of cenosphere supported heterogeneous catalyst and its performance in esterification reaction

A heterogeneous catalyst has been developed from cenosphere, a byproduct generated in thermal power plant. The performance of catalyst was investigated in the esterification of propionic acid and ethanol. The catalyst was characterized by FTIR, X-ray diffraction, field emission scanning electron microscope, and Brunauer–Emmett–Teller surface area and surface acidity analysis. The response surface methodology (RSM) with the Box–Behnken design was employed to design the experiments as well as to optimize the various process parameters such as catalyst loading, alcohol/acid molar ratio, and reaction temperature. The characterization revealed that the cenosphere supported catalyst possessed increased amounts of silica content, surface hydroxyl groups, surface area as well as surface acidity as compared with that of pristine cenosphere. The catalyst showed an excellent activity in the esterification reaction with a maximum conversion up to 91%. The RSM model well fitted the experimental data and predicted optimal conditions which were validated experimentally with a good agreement. The recyclability study showed a significant catalytic stability up to three reaction cycles. This study reveals that the cenosphere supported catalyst can be used as a potential catalyst in the esterification reaction may replace the conventional homogeneous acid catalyst.     

Au/C catalyst prepared by polyvinyl alcohol protection method for direct alcohol alkaline exchange membrane fuel cell application

An Au/C catalyst was prepared by means of the polyvinyl alcohol-protected Au sol method. Highly dispersed Au nanoparticles with an average particle size of around 3.7 nm were obtained as confirmed by transmission electron microscopy. The cyclic voltammogram of Au/C was similar to that of a bulk Au electrode, but a small shift of Au oxide reduction and oxidation potential peaks were observed. The electrooxidation of methanol, ethanol, ethylene glycol, and glycerol on the Au/C catalyst in an alkaline solution was analyzed. Using a cyclic voltammogram, the maximum current density toward alcohol electrooxidation was found to decrease in the order of glycerol > ethylene glycol > ethanol, while methanol was not oxidized. Compared with PtRu/C, the maximum current densities obtained from the Au/C catalyst for ethylene glycol and glycerol electrooxidation were increased by 1.6 and 3.3 times, respectively. The reaction heavily progressed through a C–C bond dissociation path. It was found that main product of glycerol electrooxidation was formic acid, which accounted for more than 60 % of the total product. Using chronoamperometry, the Au/C catalyst showed much better stability than that of PtRu/C for the reaction without C–C bond dissociation and better stability for the reaction with C–C bond dissociation.     

The enhancement effect of MoOx on Pd/C catalyst for the electrooxidation of formic acid

Molybdenum oxide (MoO_x) was added to a Pd/C catalyst using a novel two-step procedure. The enhancement effect of MoO_x on Pd/C catalyst for the electrooxidation of formic acid was verified by electrochemical experiments. Compared to the Pd/C catalyst, the experimental results showed that the addition of MoO_x could significantly enhance the electrocatalytic performances for the electrooxidation of formic acid. Significant improvements in electrocatalytic activity and stability were primarily ascribed to the effect of MoO_x on the Pd catalyst. In addition to the large specific surface area, the hydrogen spillover effect is speculated to have accelerated the electrooxidation rate of formic acid in the direct pathway.     

Electrocatalytic Oxidation of Formaldehyde onto Carbon Paste Electrode Modified with Nickel Decorated Nanoporous Cobalt‐Nickel Phosphate Molecular Sieve for Fuel Cell

Nanoporous cobalt‐nickel phosphate VSB‐5 molecular sieve (CoVSB‐5) was synthesized by conventional heating for 48 h in the presence of (2‐hydroxyethyl) trimethylammonium hydroxide as template. Then, a novel, cheap and efficient catalyst was developed for formaldehyde electrooxidation by decorating Ni²⁺ ions on the surface of CoVSB‐5 modified carbon paste electrode (CoVSB‐5/CPE). The electrochemical behavior of the Ni‐CoVSB‐5/CPE electrode towards the formaldehyde oxidation was evaluated by cyclic voltammetry (CV) as well as chronoamperometry methods. An oxidation peak was observed at 0.60 V in 0.1M NaOH solution for electrocatalytic oxidation of formaldehyde with EC′ mechanism. It has been observed that CoVSB‐5 at the surface of CPE can improve catalytic efficiency of the dispersed nickel ions toward oxidation of formaldehyde. The values of electron transfer coefficient, the mean value of catalytic rate constant and diffusion coefficient for formaldehyde and redox sites were obtained to be 0.66, 1.80 × 10⁵ cm³ mol⁻¹ s⁻¹ and 3.62 × 10⁻⁴ cm² s⁻¹, respectively. Obtained results from cyclic voltammetry (CV) and chronoamperometry techniques specified that the electrode reaction is a diffusion‐controlled process. The good catalytic activity, high sensitivity, good selectivity and stability and easy in preparation rendered the Ni‐CoVSB‐5/CPE to be a capable electrode for formaldehyde electrooxidation.     

Electrocatalytic activity of Pt/C catalysts for methanol electrooxidation promoted by molybdovanadophosphoric acid

A Pt/C catalyst modified by the Keggin-structure molybdovanadophosphoric acid (PMV) is prepared by cyclic voltammetry and the modified Pt/C catalyst is studied for methanol electrooxidation. The results show that the PMV modified Pt/C catalyst has increased the electron transfer coefficient of the rate-determining step and diminished the adsorption of CO on Pt/C catalysts. Significant improvements in the catalytic activity and stability for methanol electrooxidation are observed, and it indicates that the PMV combined with Pt/C catalyst can be considered as a good electrocatalyst material for potential application in direct methanol fuel cells.