Nd^3＋对二甲氧基甲烷电氧化的促进作用

通过循环伏安法（CV）,计时电流法（CA）和线性扫描法（LSV）对DMM在Pt—Nd^3＋／C催化剂上的电氧化特性进行了研究。结果表明用Nd^3＋修饰的碳载铂基催化剂,能够提高催化剂对二甲氧基甲烷（DMM）的电催化氧化活性和稳定性。     

壳聚糖和硅钨酸共混修饰直接甲醇燃料电池PtRu催化剂的研究

用壳聚糖(Chitosan)和硅钨酸(HSiW_(12))共同修饰直接甲醇燃料电池(DMFC),制备了PtRu/[(CNT-CS)-Si W_(12)]催化剂。考察了其对甲醇的电催化氧化性能,并与PtRu/(CNT-CS)、PtRu/(CNT-SiW_(12))和PtRu/CNT催化剂进行比较。结果表明,与PtRu/(CNT-CS)、PtRu/(CNT-Si W_(12))和PtRu/CNT催化剂相比,PtRu/[(CNT-CS)-SiW_(12)]催化剂的甲醇氧化电流密度更大,具有更高的活性和稳定性。     

甲醇燃料电池纳米催化剂研制成功

厦门大学化学化工学院以XC-72R炭黑为载体,制备出直接甲醇燃料电池阳极PtRu／C纳米催化剂——纳米PtRu／C合金催化剂,其活性与目前商业化的催化剂相当,且有更加突出的抗CO中毒性能。采用该技术还可制备各种高性能多元合金的燃料电池纳米催化剂。     

科技信息

二甲醚制备新工艺；乙醛酸法合成甲／乙基香兰素氧化催化剂获专利；制备D-氨基酸的新技术；用废水发电的微生物燃料电池.     

纳米碳载Pt-TiO_2催化剂制备及对甲醇电催化氧化性能研究

炭载TiO_2与PEG混合,超声振荡1 h,80℃搅拌2 h。滴加氯铂酸,调节p H值,分别用Na BH4,甲醛及甲酸还原,制得Pt-TiO_2/C催化剂a,b及c。用循环伏安法研究甲醇及CO分别在25℃和60℃的0.5 mol/L H2SO4溶液中在Pt-TiO_2/C上的氧化情况。结果表明,甲醇在60℃的酸性溶液中氧化时3种催化剂的氧化峰电位增大,峰电流密度升高,起始峰电位负移,说明升高温度有利于甲醇氧化,并且无论在25℃还是在60℃,催化剂c的电氧化能力最好,起始氧化电位最低,峰电流和峰电位最大。60℃时CO的峰电流密度和25℃时相比无太大变化,但起始氧化电位和峰电位明显负移,说明升高温度对CO的电氧化很有利,催化剂c的抗CO能力比a,b强,活性最高。     

不同方法制备的Pt/C催化剂对乙醇的电催化氧化

选用不同方法制备Pt/C催化剂,运用循环伏安法、线性扫描法和计时电流法来检测乙醇及CO在不同方法制备的Pt/C催化剂上的电催化氧化情况。发现在酸性溶液中方法3制备的Pt/C催化剂对乙醇和COad的电氧化有良好的催化活性。     

三相床中合成气一步法制二甲醚的研究

在反应压力3－5MPa、温度230－270℃,以医药用石蜡油为惰性液相介质,C302铜基催化剂和CM－3－1改性分子筛组成的复合催化剂,在不同催化剂配比,研究了在三相搅拌釜中合成气（CO、CO2、H2）一步法合成二甲醚的反应。结果表明随着温度升高,碳的转化率增加、二甲醚的选择性增加、甲醇的选择性降低;随着压力的增加,碳的转化率升高,二甲醚的选择性增加、甲醇的选择性降低;合成二甲醚催化剂CM－3－1比例提高时,反应转化率降低,二甲醚的选择性提高。     

浆态床中合成二甲醚的研究

考察了浆态床中3种甲醇合成催化剂反应行为,考察了温度、压力、催化剂比例和种类对二甲醚合成的影响.结果表明,低压下甲醇合成催化剂中C30l活性最好,温度降低和压力升高有利于甲醇的合成.二甲醚合成中,不同脱水催化剂反应性能不同.在考察范围内,温度升高,CO转化率变化不大,二甲醚的选择性增加;压力升高,CO转化率和二甲醚选择性都随之升高;两种催化剂(C301Hβ)的质量比为41时,CO转化率和二甲醚选择性最高.     

碳载PdCo合金催化剂对甲酸的电催化氧化

用间歇式微波法制备了不同Pt：Co原子比的碳载PdCo合金催化剂（PdCo／C）,发现在酸性溶液中Pd：Co原子比2：1催化剂对甲酸的电氧化有良好的催化活性和稳定性。从H在电极表面的吸脱附峰计算出来的结果表明,催化剂中加入一定比例的金属Co能够增加催化剂的电化学比表面。     

甲醇在不同方法制备的碳载Pt-TiO_2催化剂上的电催化氧化

采用TiO2溶胶法,在不同条件下制备了碳载Pt-TiO2催化剂.通过循环伏安法(CV),计时电流法(CA)对碳载Pt-TiO2催化剂在甲醇上的电氧化特性进行了研究.结果表明不同条件制备的催化剂对甲醇的电催化氧化的催化活性不同.其中加入聚乙二醇所制得的Pt-TiO2/C催化剂对甲醇的氧化具有最佳的电催化活性和稳定性.     

Stabilization and dispersion of PtRu and Pt nanoparticles on multiwalled carbon nanotubes using phosphomolybdic acid,and the use of the resulting materials in a direct methanol fuel cell

PtRu and Pt nanoparticles were deposited on the surface of multiwalled carbon nanotubes (MWCNTs) with the assistance of phosphomolybdic acid (PMo) by a one-pot hydrothermal reduction strategy. Transmission electron microscopy shows a high-density PtRu (or Pt) nanoparticles uniformly dispersed on the surface of the MWCNTs with an average diameter of 1.8 nm for PtRu nanoparticles and 2.4 nm for Pt nanoparticles. Moreover, the as-prepared PMo/PtRu/MWCNT and PMo/Pt/MWCNT electrocatalysts are highly electroactive for the electrochemical oxidation of methanol. Cyclic voltammograms show a high electrochemical surface area (ESA) and a large current density for methanol oxidation at the modified electrode by PMo/PtRu/MWCNT and PMo/Pt/MWCNT electrocatalysts. Electrochemical impedance spectroscopy reveals a high CO tolerance for PMo/PtRu/MWCNT and PMo/Pt/MWCNT electrocatalysts in the electrochemical catalysis of methanol oxidation. For comparison, PtRu/MWCNT and Pt/MWCNT electrocatalysts were prepared in control experiments without PMo. The results demonstrate that PtRu and Pt nanoparticles deposited on MWCNTs in the presence of PMo were superior to those on MWCNTs without PMo in several respects including: (1) a smaller size and a higher dispersion; (2) a higher ESA; (3) a larger current density for methanol oxidation; (4) a higher tolerance for CO poisoning.     

Electro-oxidation of dimethyl ether on Pt/C and PtMe/C catalysts in sulfuric acid

The electro-oxidation of dimethyl ether (DME) on PtMe/Cs (Me = Ru, Sn, Mo, Cr, Ni, Co, and W) and Pt/C electro-catalysts were investigated in an aqueous half-cell, and compared to the methanol oxidation. The addition of a second metal enhanced the tolerance of Pt to the poisonous species during the DME oxidation reaction (DOR). The PtRu/C electro-catalyst showed the best electro-catalytic activity and the highest tolerance to the poisonous species in the low over-potential range (<0.55 V, 50 °C) among the binary electro-catalysts and the Pt/C, but at the higher potential (>ca. 0.55 V, 50 °C), the Pt/C behaved better than PtRu/C. The apparent activation energy for the DOR decreased in the order: PtRu/C (57 kJ mol⁻¹) > Pt₃Sn/C (48 kJ mol⁻¹) ≈ Pt/C (46 kJ mol⁻¹). On the other hand, the activation energy for the MOR showed a different turn, decreased in the following order: Pt/C (43 kJ mol⁻¹) > Pt₃Sn/C (35 kJ mol⁻¹) ≈ PtRu/C (34 kJ mol⁻¹). The temperature dependence of the DOR was greater than that of the oxidation of methanol (MOR) on the PtRu/C.     

The inclusion of Mo, Nb and Ta in Pt and PtRu carbon supported electrocatalysts in the quest for improved CO tolerant PEMFC anodes

The effect of the inclusion of Mo, Nb and Ta in Pt and PtRu carbon supported anode electrocatalysts on CO tolerance in proton exchange membrane fuel cells (PEMFC) has been investigated by cyclic voltammetry and fuel cell tests. CO stripping voltammetry on binary Pt_xM/C (M: Mo, Nb, Ta) reveals partial oxidation of the CO adlayer at low potential, with PtMo (4:1)/C exhibiting the lowest value. At 80 °C, the operating temperature of the fuel cell, CO oxidation was observed at potentials close to 0 V versus the reversible hydrogen electrode (RHE). No significant difference for CO electro-oxidation at the lower potential limit, compared to PtRu/C, was observed for PtRuM_y/C (M: Mo, Nb). Fuel cell tests demonstrated that while all the prepared catalysts exhibited enhanced performance compared to Pt/C, only the addition of a relatively small amount of Mo to PtRu results in an electrocatalyst with a higher activity, in the presence of carbon monoxide, to PtRu/C, the current catalyst of choice for PEM fuel cell applications.     

Niobium Dioxide Facilitating Methanol Electrooxidation on Pt/C Catalyst by Synergistic Effect

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.     

Increased Metal Utilization in Carbon‐Supported Pt Catalysts by Adsorption of Preformed Pt Nanoparticles on Colloidal Silica

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.     

Influence of the Temperature for the Ethanol Oxidation Reaction (EOR) on Pt/C,Pt‐Rh/C and Pt‐Rh‐SnO2/C

The electrocatalytic activity of Pt/C, Pt‐Rh/C and Pt‐Rh‐SnO₂/C electrocatalysts toward the ethanol oxidation reaction (EOR) was investigated in a three‐electrode assembly at 25 °C, 40 °C and 70 °C in acidic medium. The 10 wt.% electrocatalysts were prepared with a modified polyol method and physically characterized by both X‐Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM). The CO‐stripping study revealed that CO_ad oxidation initiates at lower potential on Pt‐Rh/C and Pt‐Rh‐SnO₂/C than on Pt/C and shifts negatively when the temperature increases. The positive effect of the temperature is maintained for the EOR: the three electrocatalysts exhibit a higher activity and a negative shift of the EOR wave at higher temperature. Pt‐Rh‐SnO₂/C demonstrates the lowest EOR onset potential of the three electrocatalysts. The steady‐state Tafel slopes and apparent activation energies E_a were determined in 0.5 M H₂SO₄ + 0.1 M EtOH between E = 0.4 and 0.7 V vs. RHE in the temperature range 25–70 °C. The results show rather comparable rate determining steps (rds) for the ethanol electrooxidation on Pt/C and Pt‐Rh/C in the ranges of potential and temperature studied. The EOR on Pt‐Rh‐SnO₂/C seems less influenced by the potential than on Pt/C and Pt‐Rh/C electrocatalysts, but is more temperature sensitive.     

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.     

Surfactant stabilized Pt and Pt alloy electrocatalyst for polymer electrolyte fuel cells

A simple process for the synthesis of carbon supported Pt and Pt/Ru electrocatalysts was investigated. Borrowing from the homogeneous catalyst preparation, this process uses a surfactant as a stabilizer which prevents the metal colloids from aggregation during the reduction process without influencing the deposition of the colloids onto the carbon support. Chemical, morphological and crystallographic properties of the newly prepared electrocatalysts were characterized using various surface techniques including X-ray diffraction (XRD), Transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). These techniques show that mono-size, well-dispersed metal colloids can be formed and successfully supported on the carbon black. Moreover, the size of metallic colloids prepared by this method can be manipulated by controlling the synthesis temperature and is independent of the catalyst loading. Electrochemical characterizations show that in comparison with commercial E-TEK electrocatalysts, surfactant-based Pt/C electrocatalysts possess similar catalytic activity in terms of oxygen reduction and higher CO tolerance performance can be obtained by the surfactant stabilized Pt,Ru/C.     

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.     

甲醇氧化电催化剂Pt、Ru和PtRu的性能研究

应用恒电位沉积法制得Pt、Ru和PtRu直接甲醇燃料电池阳极催化剂,并对三种催化剂的甲醇氧化活性和稳定性进行了考察。动电位和恒电位实验结果均表明,Ru的加入使PtRu的甲醇起始氧化电位相对于Pt催化剂负移,催化活性和稳定性得到明显的改善。