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1.
The kinetics of hydrogen oxidation reaction was studied in perchloric acid solution on carbon-supported Pt nanoparticles using the rotating disk electrode technique. Carbon cryogel and commercial carbon black. Vulcan XC-72 were used as catalyst supports. Pt/C catalysts were prepared by a modified polyol synthesis method in an ethylene glycol (EG) solution. Considerable effect has been observed for the specific surface area of carbon support on the fundamental properties of Pt/C catalyst, such as catalyst particle size distribution and dispersion as well as catalytic activity for the oxidation of hydrogen. X-ray diffraction (XRD) and transmission electron microscopy (TEM) images show that the particle size of the catalyst decreases with the increase of specific surface area of carbon support. Cyclic voltammetry (CV) was used for determination of the actual exposed surface area of catalyst particles. It was found that Pt catalyst prepared by using the novel carbon material displayed better hydrogen electrochemical oxidation activity than the catalyst prepared by using Vulcan XC-72.  相似文献   

2.
王亚琴  马腾 《工业催化》2018,26(8):31-35
利用紫外光电子能谱等表面科学方法,研究了Pt-Fe模型催化剂的次表层Fe结构[即Pt/Fe/Pt(111)结构]在不同条件下CO的吸附及其氧化反应。结果表明,Pt/Fe/Pt(111)结构在H_2气氛或者超高真空中是种稳定结构,最外层的原子与Pt(111)相同,是密排的铂原子面;但次表层的原子中有约0.5单层的铁原子,使费米边附近(0~2.0)e V的电子态密度明显低于Pt(111)表面,从而改变表面的CO和O_2吸附以及反应性能。程序升温的紫外光电子能谱结果显示,Pt/Fe/Pt(111)表面在(100~300)K,CO的吸附受温度的影响不明显,且O_2能够吸附、活化并使共吸附的CO发生氧化反应;当温度为300 K时,O_2无法在Pt/Fe/Pt(111)表面吸附、活化,所以CO氧化反应无法进行。Pt/Fe/Pt(111)结构虽然能有效地减弱CO的吸附从而避免CO毒化的问题,但O_2的吸附和活化也受到显著抑制并影响到一定条件下CO的氧化反应。  相似文献   

3.
In this work the activity of PtMo/C based materials prepared by the formic acid method was evaluated as electrocatalysts for the hydrogen oxidation reaction in the presence of CO, in polymer electrolyte fuel cells. A very high electrocatalytic activity was observed for an anode formed by PtMo/C (60:40) and supplied with H2 containing 100 ppm of CO, which presented an overpotential loss of 100 mV at 1 A cm−2, compared with pure hydrogen. Several electrode configurations based on Mo/C and PtMo/C CO filtering layers, having a Pt-based catalyst layer, were evaluated. In all cases an enhancement of electrocatalytic performance was observed, as compared with the standard Pt/C electrode. It is concluded that the CO tolerance is achieved through an electrochemical surface reaction of adsorbed CO with surface oxides, as proposed by the bifunctional mechanism, acting together with a heterogeneous chemical reaction of CO with water molecules catalyzed by Mo species and resulting in a lowering of the CO concentration in the gas channels of the electrode.  相似文献   

4.
In this work, Pt nanowire networks supported on high surface area carbon (Pt NWNs/C) are synthesized as electrocatalysts for direct methanol fuel cells (DMFCs). The electrocatalytic behavior of Pt NWNs/C catalysts for the methanol and adlayer CO oxidation reactions is investigated and the results are compared with the Pt nanoparticles (NPs) supported on carbon (Pt NPs/C). The results indicate that Pt NWNs are characterized by interconnected nanoparticles with large number of grain boundaries, downshifted d-band center and reduced oxophilicity, which results in the enhanced surface mobility of oxygen-containing species such as COads and OHads. The enhanced surface mobility of COads and OHads in turn facilitates the removal of intermediate CO species during the methanol oxidation. The activity of the Pt NWNs/C electrocatalyst for the methanol oxidation reaction and electrooxidation of adsorbed CO is also evaluated by cyclic voltammetry, CO stripping, and kinetic analysis. The results show that Pt NWNs/C catalysts have a significantly higher electrocatalytic activity for the methanol oxidation reaction as compared to Pt NPs/C catalysts. The enhanced electrocatalytic activity of Pt NWNs/C catalysts is mainly due to the existence of large number of the grain boundaries of the interconnected nanoparticles of the unique Pt NWN structure.  相似文献   

5.
运用电化学石英晶体微天平 (EQCM)研究了正丁醇在Pt、Pt/Sbad和Pt/Sad电极上的电氧化过程 ,结果表明正丁醇的氧化与电极表面氧化物种有着密切的关系。Pt电极表面Sb修饰原子能在较低的电位下吸附氧 ,催化正丁醇的氧化在较低电位下进行。相反 ,Pt电极表面S修饰原子的氧化会消耗表面氧化物种 ,从而抑制正丁醇的电氧化。  相似文献   

6.
The Pt-CO system is the only one in which a mere change of the potential at which the electrode is held while the compound to be oxidized is introduced in the cell dramatically affects the activity of the electrode. So, if the Pt electrode is held at a potential in the hydrogen region while CO is bubbled in the electrolyte, electrooxidation of dissolved CO occurs at a potential of 0.6 V vs the relative hydrogen electrode, which is considerably lower than the usual one of 0.9 V at which CO is oxidized when bubbled at open circuit. We have studied the dependence of this unique phenomenon on the number of Pt monolayers (MLs) deposited on Au. The peak potential in CVs of CO-stripping decreased with increasing number of Pt MLs, showing an increasing activity of the Pt film for CO oxidation. This is in agreement with the d-band model of Nørskov, which predicts that CO binds more strongly to a Pt ML on Au than to bulk Pt. Other contributing factor to the increasing activity of the Pt film with increasing number of Pt MLs is the increasing number of Pt atoms in step and kink positions, known to be active centres for the oxidation of both adsorbed and dissolved CO. This second factor is inferred from the monotonic increase of the hydrogen charge, which indicates that the second and successive MLs become increasingly rougher. As for the electrooxidation at low potentials of dissolved CO, it was completely absent with one Pt ML, and progressively emerged with increasing number of Pt MLs, a well-defined peak appearing with four MLs. The parallel evolution of the peak of dissolved CO oxidation and of the pre-peak in CO-stripping CVs confirms that dissolved CO oxidation takes place only on those Pt atoms that have become free of adsorbed CO by its oxidation in the pre-peak.  相似文献   

7.
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.  相似文献   

8.
Nanoclusters of Pt were electrochemically deposited on a conducting polymer, namely, poly(3,4-ethylenedioxythiophene) (PEDOT), which was also electrochemically deposited on carbon paper current collector. PEDOT facilitated uniform distribution of Pt nanoclusters, when compared with Pt electrodeposition on bare carbon paper substrate. Spectroscopy data indicated absence of any interaction between PEDOT and Pt. The electrochemically active surface area as measured from carbon monoxide adsorption followed by its oxidation was several times greater for Pt–PEDOT/C electrode in comparison with Pt/C electrode. The catalytic activity of Pt–PEDOT/C electrode for electrooxidation of formic acid was significantly greater than that of Pt/C electrode. Amperometry data suggested that the electrodes were stable for continuous oxidation of HCOOH.  相似文献   

9.
Pt/C electrocatalysts, aimed at maximizing the electrochemical surface area (ECSA) and consequently the specific mass activity of fuel cell reactions, are obtained by firstly depositing Pt nanoparticles on colloidal silica (Pt‐silica), followed by the adsorption of the latter onto a carbon support. This method of catalyst preparation increases Pt metal utilization and generates accessible void space in the interpenetrating particle network of carbon and silica for the facile transport of reactants and products. Both electrochemical hydrogen adsorption/desorption and CO oxidation measurements show an increase in the ECSA using this approach. Methanol electrooxidation is used as a test reaction to evaluate the catalytic activity. It is found that the silica modified catalyst is three times as active as a catalyst prepared without silica, under otherwise identical conditions.  相似文献   

10.
N. Zhang  S. Zhang  Y. Gao  G. Yin 《Fuel Cells》2013,13(5):895-902
In this work, Pt nanoparticles are deposited on NbO2‐modified carbon composites and evaluated as promising direct methanol fuel cell (DMFC) electrocatalysts. Transmission electron microscopy (TEM) and X‐ray diffraction (XRD) indicate that Pt nanoparticles (about 2.5 nm) are uniformly dispersed on NbO2‐modified carbon composites. Electrochemical measurements show that the mass activity toward methanol electrooxidation on Pt/NbO2‐C is as high as 3.0 times that of conventional Pt/C. Meanwhile, the onset potential of CO oxidation is negatively shifted by about 46 mV as compared with that of Pt/C, which means that the synergistic effect between NbO2 and Pt facilitates the feasible removal of poisoning intermediate CO during methanol electrooxidation. X‐ray photoelectron spectroscopy (XPS) characterizations reveal the electron transfer from Nb to Pt, which suppress the poisoning CO adsorption on Pt nanoparticles and facilitate methanol electrooxidation. NbO2 nanoparticles facilitate methanol electrooxidation on Pt/C catalyst by synergistic effect and electronic effect, which represents a step in the right direction for the development of excellent fuel cell anode electrocatalysts.  相似文献   

11.
The factors controlling the behavior and the stability of electrocatalysts based on Pt, Ru and Mo nanoparticles during exhaustive electrochemical treatment are examined. Along this treatment, it has been observed that in the case of ternary catalysts there are pronounced changes in the structure of their surface resulting in electrode activation for methanol and CO electrooxidation, whereas the activity of binary PtRu/C and PtMo/C catalysts decreases. Therefore, the role of both Ru and Mo is crucial for the electrochemical activation of the catalyst, though metal losses do occur during electrochemical process. For the first time a detailed study of this phenomenon is presented, including characterization by HRTEM, TXRF, XRD, electrochemical measurements and in situ Fourier transform infrared spectroscopy (FTIR). In order to get a deeper insight into the surface structure, chemical state, and stability of the electrocatalyst under reaction conditions, a combination of cyclic voltammetry, chronoamperometry and X-ray photoelectron spectroscopy (XPS) has been used. By comparing bulk and surface composition, our results point out to the key role of the geometric effect enhanced by previous reduction of the nanoparticles. At the end of the electrochemical treatment, Mo-PtRu/C catalysts surface was restructured with substantial enrichment in Pt and a less pronounced Mo surface enrichment, while Ru is incorporated into the Pt-Mo overlayer. These results underline the possibility of further optimization of the surface structure and composition producing PtRuMo nanoparticles with high methanol and CO oxidation activity.  相似文献   

12.
Electrochemical oxidation of HCOOH in H2SO4 and HClO4 solutions was examined on thin film Pt2Ru3/C electrode. XRD pattern revealed that Pt2Ru3 alloy consisted of the solid solution of Ru in Pt and the small amount of Ru or solid solution of Pt in Ru. According to STM images, Pt2Ru3 particles size was between 2 and 6 nm. It was established that electrochemical oxidation of HCOOH commenced at −0.1 V versus SCE at Pt sites in the catalyst. Kinetic parameters indicated that dehydrogenation path was predominant. Dehydration occurs in parallel, but without significant poisoning by COad owing to oxidative removal by OH species on Ru atoms. The coverage of Pt2Ru3 surface by CO preadsorbed from the solution was found to be 24% lower when the surface was modified by irreversibly adsorbed Bi. Modification by Bi also shifted the onset potential for HCOOH oxidation for about 50 mV towards more negative values and consequently, increased the reaction rate for a factor of two. It was proposed that Ru acts through bifunctional mechanism, i.e. OH species adsorbed on Ru oxidizes COad from Pt sites, while Bi hinders the adsorption of CO on Pt sites via electronic and/or ensemble effects.  相似文献   

13.
This work provides a detailed electrochemical impedance study for formic acid electro-oxidation on size-controlled Pd/C nanoparticles, the synthesis of which was done by a simple protocol using ethylene glycol as a reducing agent. By controlling KOH concentration, this strategy provides a synthesis method for Pd nanoparticles with a selective size range of 3.9–7.5 nm. The as-prepared Pd nanoparticles exhibited size-dependent electrochemical property and electrochemical characterizations of four different Pd/C nanocatalysts (3.9, 5.2, 6.1, and 7.5 nm) showed that Pd particle with average size of 6.1 nm has the highest formic acid oxidation activity. Electrochemical impedance-based characterizations of formic acid oxidation on Pd/C suggested that at high potentials the adsorbed oxygen species could block the catalyst surface and inhibit the oxidation reaction, as reflected by the negative polarization resistance. Unlike Pd/C, the intermediate adsorbed CO species (COads) plays a critical role for formic oxidation on Pt/C and thus the impedance spectra of Pd/C and Pt/C appear different potential-dependent patterns in the second quadrant. The issue of CO was investigated by an impedance investigation of Pd/C in a mixture of formic acid containing dissolved CO.  相似文献   

14.
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.  相似文献   

15.
Carbon supported Au-PtRu (Au-PtRu/C) catalysts were prepared as the anodic catalysts for the direct methanol fuel cell (DMFC). The procedure involved simple deposition of Au particles on a commercial Pt-Ru/C catalyst, followed by heat treatment of the resultant composite catalyst at 125, 175 and 200 °C in a N2 atmosphere. High-resolution transmission electron microscopy (HR-TEM) measurements indicated that the Au nanoparticles were attached to the surface of the Pt-Ru nanoparticles. We found that the electrocatalytic activity and stability of the Au-PtRu/C catalysts for methanol oxidation is better than that of the PtRu/C catalyst. An enhanced stability of the electrocatalyst is observed and attributable to the promotion of CO oxidation by the Au nanoparticles adsorbed onto the Pt-Ru particles, by weakening the adsorption of CO, which can strongly adsorb to and poison Pt catalyst. XPS results show that Au-PtRu/C catalysts with heat treatment lead to surface segregation of Pt metal and an increase in the oxidation state of Ru, which militates against the dissolution of Ru. We additionally find that Au-PtRu/C catalysts heat-treated at 175 °C exhibit the highest electrocatalytic stability among the catalysts prepared by heat treatment: this observation is explained as due to the attainment of the highest relative concentration of gold and the highest oxidation state of Ru oxides for the catalyst pretreated at this temperature.  相似文献   

16.
M.H. Shao 《Electrochimica acta》2005,50(12):2415-2422
The electrooxidation of ethanol was investigated on a Pt thin film electrode in a HClO4 solution using surface enhanced infrared absorption spectroscopy (SEIRAS) with the attenuated total reflection (ATR) technique. The spectra indicate that during this reaction acetate and CO adsorbates are formed. The intensity of symmetric OCO stretching band of adsorbed acetate correlates well with voltammetry in the potential range between −0.1 and 0.85 V. The CO stretching band for adsorbed acetaldehyde and/or acetyl also was observed; these compounds are the reaction intermediates whose oxidation generates COad and acetic acid. We also explored the oxidation behavior of adsorbed residues. The oxidation of acetaldehyde was studied for comparison.  相似文献   

17.
CO tolerance of H2-air single cell with phosphoric acid doped polybenzidazole (PA-PBI) membrane was studied in the temperature range 140-180 °C using either dry or humidified fuel. Fuel composition was varied from neat hydrogen to 67% (vol.) H2-33% CO mixtures. It was found that poisoning by CO of Pt/C and Pt-Ru/C hydrogen oxidation catalysts is mitigated by fuel humidification. Electrochemical hydrogen oxidation at Pt/C and Pt-Ru/C catalysts in the presence of up to 50% CO in dry or humidified H2-CO mixtures was studied in a cell driven mode at 180 °C. High CO tolerance of Pt/C and Pt-Ru/C catalysts in FC with PA-PBI membrane at 180 °C can be ascribed to combined action of two factors—reduced energy of CO adsorption at high temperature and removal of adsorbed CO from the catalyst surface by oxidation. Rate of electrochemical CO oxidation at Pt/C and Pt-Ru/C catalysts was measured in a cell driven mode in the temperature range 120-180 °C. Electrochemical CO oxidation might proceed via one of the reaction paths—direct electrochemical CO oxidation and water-gas shift reaction at the catalyst surface followed by electrochemical hydrogen oxidation stage. Steady state CO oxidation at Pt-Ru/C catalyst was demonstrated using CO-air single cell with Pt-Ru/C anode. At 180 °C maximum CO-air single cell power density was 17 mW cm−2 at cell voltage U = 0.18 V.  相似文献   

18.
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.  相似文献   

19.
VOC deep oxidation over Pt catalysts using hydrophobic supports   总被引:7,自引:0,他引:7  
The active hydrophobic-supported Pt catalysts were synthesized for VOC deep oxidation at low temperature (less than 200°C). The destruction of VOC could cost less at lower temperature due to less energy consumption. The advantage using hydrophobic support was that moistures from atmosphere and oxidation would not be adsorbed on the surface. Thus the active sites would not be cloaked and catalyst activity could be maintained, especially at low temperature. The hydrophobicity of supports was characterized by wetting angles. Porous SDB (styrene divinylbenzene copolymer) was found near 113°, indicating high hydrophobicity. Three Pt catalysts were prepared on SDB and activated carbons by incipient wetness method. Specific surface areas were measured by nitrogen adsorption. The thermal stability of SDB catalyst was examined by TGA, and found no degradation below 200°C in air. The surface compositions of catalysts were analyzed by EDS. XRD showed that Pt was well dispersed on supports after hydrogen reduction at 160°C. The chemical states of Pt were investigated by XPS, and suggested that the oxidized PtIV might be the active sites in the reaction. The deep oxidation of toluene/air mixture was carried out to test the activity of catalysts. Pt/SDB showed the highest activity among the catalysts and could completely oxidize 90 ppm toluene/air at VHSV=21 000 h−1, 150°C. Redox mechanism was proposed to reveal the enhanced kinetic rates. The results suggested that the rate of toluene oxidation might be enhanced due to the fact that water, one of the products, was expelled from the hydrophobic surface.  相似文献   

20.
用微波间断升温法制备了3种Pt/C催化剂,运用循环伏安和线行扫描方法测试甲醇和吸附态CO在不同方法制备的Pt/C催化剂上的电催化氧化情况。发现在酸性溶液中,对于相同Pt载量的Pt(2)和Pt(3)催化剂,Pt(3)具有较小的Pt平均粒径及较高的电催化活性;对于具有较高Pt载量的Pt(1)催化剂,具有最小的平均粒径和最高的电催化活性。  相似文献   

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