甲醇燃料电池阳极催化剂的试验

用化学还原法制备了碳载镍、银、金三种金属单质催化剂,并研究其对甲醇电催化氧化的活性。用X射线衍射光谱（XRD）、X光电子能谱（XPS）表征催化剂的晶相结构、表面组成及价态形式。XRD测试表明均得到了纯度较高的金属单质,催化剂粒径大小在5 nm-11nm之间,颗粒分布均匀。用循环伏安法测定了不同催化剂对甲醇的电催化氧化的活性,结果表明碳载镍催化剂对甲醇氧化有较好的催化作用,而碳载银和碳载金对甲醇氧化几乎没有活性。     

Ni-Cr-Co氧化物纳米催化剂对甲醇阳极氧化的电催化性能研究

采用了热分解法合成Ni-Cr-Co氧化物纳米粒子,并用作直接甲醇燃料电池(DMFC)的阳极电催化剂。通过X射线衍射(XRD)、透射电子显微镜(TEM)和扫描电子显微镜(SEM)对催化剂进行表征,制得的纳米催化剂均匀分散,且粒径为25~50 nm。利用循环伏安法(CV)对不同金属摩尔比和焙烧温度下的催化剂在甲醇氧化反应中的活性进行了研究。结果表明,Ni-Cr-Co(摩尔比为1∶1∶1.5)的纳米氧化物对甲醇氧化反应的起始电位、峰值氧化电流密度和If/Ib分别为0.38 V,19.3 mA/cm2和1.72,表现了很好的电催化性能。     

碳化钨/碳气凝胶纳米复合材料增强Pt电催化甲醇性能的研究

以间苯二酚和甲醛为原料,采用溶胶-凝胶法原位合成WC纳米颗粒制备了碳化钨/碳气凝胶(WC/CAs);以WC/CAs为载体,利用微波加热乙二醇还原法制备了Pt/WC/CAs催化剂。运用循环伏安法(CV)、线性扫描(LSV)、计时电流法(CA)、能谱(EDS)、透射电子显微镜(TEM)和X射线衍射(XRD)等技术分析Pt/WC/CAs催化剂的组成、结构及其对甲醇的电催化氧化活性的影响。实验结果表明,载体中WC纳米颗粒的加入促进Pt贵金属颗粒对甲醇的电催化氧化活性,正扫电流峰ip与扫描速率的平方根v1/2线性相关,Pt/WC/C催化氧化甲醇的过程受扩散控制;且电催化活性比Pt/C要好。     

碳载Pt-TiO2催化剂对甲醇的电催化氧化

采用TiO2溶胶法,选用3种不同还原剂(甲酸、甲醛、硼氢化钠)制备了碳载Pt-TiO2催化剂。通过XRD衍射,循环伏安法(CV)和计时电流法(CA)对碳载Pt-TiO2催化剂的结构及其对甲醇的电氧化特性进行了研究。结果表明不同还原剂制备的催化剂中,TiO2的结晶度不同,Pt的粒径不同,电化学比表面不同,对甲醇的电催化氧化的催化活性也不同。其中用甲酸还原所制得的碳载Pt-TiO2催化剂对甲醇的电催化氧化活性分别是采用甲醛或硼氢化钠方法的1.41倍和1.76倍。     

乙二醇稳定的Pt/C催化剂的制备与表征

以乙二醇(EG)兼作溶剂和稳定剂,分别通过NaBH4和EG还原法制备了高度细化与分散的Pt/C催化剂,对其形貌、组成、结构和电化学活性比表面等进行了表征比较,并测试了它们对甲醇与乙醇电催化氧化的活性. 结果表明,2种催化剂中,Pt均为面心立方结构,粒径小且分布窄,在炭黑载体上分散均匀,单位质量Pt对甲醇与乙醇电催化氧化的活性相当;NaBH4还原法所制Pt/C催化剂中Pt0和Pt(220)晶面含量更高,Pt对甲醇与乙醇电催化氧化的峰电流密度分别为0.68与0.67 mA/cm2,分别是EG还原法所制Pt/C催化剂的1.2倍;2种催化剂对甲醇与乙醇电催化氧化的活性均与商品E-TEK催化剂相当.     

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.     

石墨烯基直接甲醇燃料电池催化剂的制备

通过浸渍还原法以乙二醇为还原剂制备了石墨烯及石墨烯负载的铂催化剂(Pt/Graphene),通过XRD、SEM、Raman对材料进行了分析,通过电化学测试与Pt黑催化剂对比,试验数据表明:Pt/Graphene比Pt黑催化剂电化学活性面积提高了28%,对甲醇电催化氧化峰电流提高了52%,电化学活性面积和甲醇氧化反应的稳定性均有所提高。     

液相羰基法合成碳酸二甲酯的铜络合催化剂

用溴化铜和季铵盐制备了络合催化剂,并考察了几种无机盐助荆对催化剂性能的影响.结果表明.络合催化剂CuxBrnLm对甲醇液相氧化羰化合成碳酸二甲酯(DMC)具有良好的催化活性,以碳酸钾为助剂时,甲醇转化率达到了26.9%,DMC选择性达到97.8%.采用傅立叶红外光谱(FT-IR)、X射线衍射(XRD)、元素分析(EA)和电感耦合等离子发射光谱(ICP-AES)对合成的催化剂进行表征,结果表明,络合催化剂的分子式为Cu2Br62,配位剂和无机盐助剂有助于形成甲醇选择性氧化羰基合成DMC的活性物种Cu(I),而Cu(I)是催化剂活性中心.     

RuAg/TiO2-C催化剂的制备及对甲醇的电催化氧化性能

采用改性溶胶凝胶法和水热合成法制备了掺C多孔纳米TiO2,并以其为载体制备了一种RuAg/TiO2-C甲醇催化剂。采用X射线衍射（XRD）、透射电镜（TEM）、X射线能谱（EDS）和X射线光电子能谱（XPS）等对催化剂进行了表征,测定了其对甲醇的电催化氧化性能。实验结果表明,RuAg的负载和C的掺杂能提高TiO2对甲醇的电催化性能,RuAg/TiO2-C对甲醇电催化的循环伏安曲线中未见甲醇氧化中间产物的氧化峰,0.544 V处有一个较大的甲醇氧化峰,其峰电流密度5.8 mA/cm2,RuAg/TiO2-C比商用PtRu/C催化剂具有更高的催化活性和抗毒性,RuAg合金的负载以及RuAg合金与掺C多孔纳米TiO2载体之间较强的相互作用是其对甲醇催化性能提高的主要因素。     

F掺杂TiO_2的制备及其甲醇电氧化性能研究

采用水热法制备了F掺杂的TiO2,将其与碳黑机械混合制成复合载体,采用微波辅助加热乙二醇法制备了载Pt电催化剂。通过X射线衍射(XRD)和扫描电镜(SEM)对F-TiO2进行了表征,结果表明,F掺杂后,TiO2仍然呈锐钛矿结构,形貌呈纳米片层结构。Pt/F-TiO2-C催化剂表现出很好的催化活性和稳定性,循环伏安法和计时电流法的测试结果表明,复合载体中F的加入有利于甲醇的电催化氧化,提高了Pt对甲醇氧化的抗毒化能力,使其质量比活性是商业Pt/C催化剂的1.2倍。     

Carbon-supported Pt(Cu) electrocatalysts for methanol oxidation prepared by Cu electroless deposition and its galvanic replacement by Pt

Bimetallic Pt–Cu carbon-supported catalysts (Pt(Cu)/C) were prepared by electroless deposition of Cu on a high surface area carbon powder support, followed by its partial exchange for Pt; the latter was achieved by a galvanic replacement process involving treatment of the Cu/C precursor with a chloroplatinate solution. X-ray diffraction characterization of the Pt(Cu)/C material showed the formation of Pt-rich Pt–Cu alloys. X-ray photoelectron spectroscopy revealed that the outer layers are mainly composed of Pt and residual Cu oxides, while metallic Cu is recessed into the core of the particles. Repetitive cyclic voltammetry in deaerated acid solutions in the potential range between hydrogen and oxygen evolution resulted in steady-state characteristics similar to those of pure Pt, indicating the removal of residual Cu compounds from the surface (due to electrochemical treatment) and the formation of a compact Pt outer shell. The electrocatalytic activity of the thus prepared Pt(Cu)/C material toward methanol oxidation was compared to that of a commercial Pt/C catalyst as well as of similar Pt(Cu)/C catalysts formed by simple Cu chemical reduction. The Pt(Cu)/C catalyst prepared using Cu electroless plating showed more pronounced intrinsic catalytic activity toward methanol oxidation than its counterparts and a similar mass activity when compared to the commercial catalyst. The observed trends were interpreted by interplay between mere surface area effects and modification of Pt electrocatalytic performance in the presence of Cu, both with respect to methanol oxidation and poisonous CO removal.     

Methanol-tolerant PdPt/C alloy catalyst for oxygen electro-reduction reaction

A carbon-supported Pd-based PdPt catalyst (PdPt/C) with a small amount of Pt was prepared by borohydride reduction method and its activity in the oxygen electro-reduction reaction (ORR) was investigated in acidic conditions both with and without methanol. For comparison, carbon-supported Pt (Pt/C) and Pd (Pd/C) catalysts were prepared and the ORR activities were compared. Results revealed that the PdPt/C catalyst showed slightly lower ORR activity in terms of onset potential of oxygen reduction than Pt/C catalyst in 0.1M HClO₄. However, PdPt/C catalyst exhibited enhanced activity toward selective ORR with methanol-tolerant characteristics in 0.1M HClO₄ in the presence of methanol. The PdPt/C catalyst prepared here is suitable for use as a cathodic electrocatalyst in direct alcohol fuel cells after addition of small amount of expensive Pt metal.     

Electrocatalytic activity of carbon-supported Pt-Au nanoparticles for methanol electro-oxidation

Pt-modified Au nanoparticles on carbon support were prepared and analyzed as electrocatalysts for methanol electro-oxidation. In this paper, a novel chemical strategy is described for the preparation and characterization of carbon-supported and Pt-modified Au nanoparticles, which were prepared by using a successive reduction process. After preparing Au colloid nanoparticles (∼3.5 nm diameter), Au nanoparticles were supported spontaneously on the surface of carbon black in the aqueous solution. Then a nanoscaled Pt layer was deposited on the surface of carbon-supported Au nanoparticles by the chemical reduction. The structural information and electrocatalytic activities of the Pt-modified Au nanoparticles were confirmed by transmission electron microscopy (TEM), X-ray diffractometry (XRD) and cyclic voltammetry (CV). The results indicate that carbon-supported Au nanoparticles were modified with the reduced Pt atoms selectively. The Pt-modified Au nanoparticles showed the higher electrocatalytic activity for methanol electro-oxidation reaction than the commercial one (Johnson-Matthey). The increased electrocatalytic activity might be attributed to the effective surface structure of Pt-modified Au nanoparticles, which have a high utilization of Pt for surface reaction of methanol electro-oxidation.     

Catalysts for Direct Methanol Fuel Cells

The activity of in house prepared carbon-supported Pt-Ru catalysts for methanol oxidation and carbon-supported RuSe for the oxygen reduction reaction in direct methanol fuel cells (DMFCs) was investigated. The composition of Pt-Ru/C was varied both in terms of weight loading (ratio of total metal content to carbon) as well as the ratio of Pt to Ru. The measurements were carried out in a half cell arrangement in sulphuric acid at various temperatures. The weight loading and ratio of Pt to Ru were varied in order to find out the optimum weight loading of precious metal and the temperature dependence of Pt to Ru ratio on methanol oxidation reaction. It has been found that there exists an optimum in the weight loading at 60 wt.% for carbon-supported Pt-Ru catalyst towards its maximum mass activity. While 1:1 Pt to Ru ratio exhibits a higher activity than 3:2 Pt:Ru above 60 °C, 3:2 ratio exhibits a higher activity at lower temperature. It has been observed that RuSe is inactive towards methanol and it is realised that RuSe is a potential candidate as methanol tolerant oxygen reduction catalyst. The activity of carbon supported RuSe for oxygen reduction reaction (ORR) was tested in sulphuric acid in the presence of methanol. Even though the mass specific activity of the RuSe catalyst is somewhat lower than that of Pt/C, the surface activity of carbon-supported RuSe is superior than that of carbon supported Pt which indicate the unfavourable size distribution of RuSe/C catalyst.     

Carbon cryogel as support of platinum nano-sized electrocatalyst for the hydrogen oxidation reaction

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.     

CaO/MgO混合催化剂的制备及催化合成生物柴油

采用溶胶-凝胶法制备纳米CaO,采用溶胶-凝胶自蔓延燃烧法制备纳米MgO,并通过TG-DSC、XRD和SEM对制备的CaO和MgO晶体结构、形貌特性及热稳定性等进行表征。采用固体研磨法将纳米CaO和纳米MgO混合制备催化剂,并应用于大豆油与甲醇的酯交换反应中制备生物柴油。结果表明,纳米CaO和纳米MgO按质量比0.7∶0.5混合的催化剂具有良好的催化活性,在催化剂用量为大豆油质量的3%、甲醇与大豆油物质的量比为12∶1和回流状态下反应4h条件下,大豆油酯化率可达88.58%。     

Highly active carbon-supported PdNi catalyst for formic acid electrooxidation

A new carbon-supported PdNi (PdNi/C) catalyst is prepared by a simple simultaneous reduction reaction with sodium borohydride in glycol solution. The results show that the performance of PdNi/C catalyst for formic acid oxidation is greatly improved compared with that of Pd/C. X-ray diffraction (XRD) results show that Ni exists in the catalyst both as NiO and as PdNi alloy. The value of the apparent activation energy shows that the activity of formic acid oxidation on the PdNi/C is more sensitive to temperature compared with Pd/C.     

Low-Pt Content Carbon-Supported Pt–Ni–TiO2 Nanotube Electrocatalyst for Direct Methanol Fuel Cells

Low-Pt content (5%) carbon-supported Pt–Ni–TiO₂ nanotube electrocatalysts were prepared via a microwave-assisted polyol strategy. Physical and morphological properties of these electrocatalysts were characterized by X-ray diffraction (XRD), high resolution transmission electron microscope (HRTEM), and energy dispersive X-ray spectroscopy (EDX). Cyclic voltammetry and chronoamperometry studies clearly suggested that the Pt(5%)–Ni(10%)–TiO₂ nanotube (10%) supported by Vulcan XC-72 is better than the commercial 20% Pt/C electrocatalyst for methanol electro-oxidation in direct methanol fuel cells (DMFCs).     

Investigation of Ti mesh-supported anodes for direct borohydride fuel cells

The use of titanium mesh-supported gold and silver anodes in direct borohydride fuel cells (DBFCs) is reported. The anodes were prepared by either thermal decomposition or electrochemical deposition and were characterised by scanning electron microscopy and X-ray diffraction analyses. The performance of the mesh electrodes was compared with that for carbon-supported electrodes. The mesh anodes gave current densities, for borohydride oxidation, up to 50% greater and cell power densities up to 20% greater than those obtained with carbon-supported anodes. The effects of catalyst loading and fuel cell operating conditions are also reported. Electrode stability was examined over a prolonged period.     

Effect of the amount of reducing agent on surface structures, electrochemical activity and stability of PtRu catalysts

The effect of the amount of reducing agent used in the synthesis of PtRu alloy catalysts on their surface structure was investigated, and the prepared catalysts were characterized using transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, cyclic voltammetry, and potential cycling. The alloying degree of the catalysts was essentially the same for all of the catalysts studied, despite the use of different amounts of reducing agent. Varying the amount of reducing agent resulted in changes in the surface composition of the catalysts, wherein the surfaces were found to be composed of several PtRu domains that differed in local inhomogeneity and hence showed differences in activity for CO_ad oxidation. The highest activity for methanol oxidation was obtained when there was moderate Ru enrichment of the catalyst. The electrochemical stability of the catalysts was also investigated via potential cycling in a methanol-containing electrolyte solution. The electrochemical stability under methanol oxidation was enhanced by Ru-enrichment at the catalyst surface, because the Ru-rich surface had sufficient Ru atoms near the Pt atoms to act as a bifunctional catalyst, even though the Ru atoms were leached out by potential cycling. The most Ru-rich catalyst exhibited an increase in methanol oxidation current in the middle of potential cycling whereas the other catalysts showed a monotonic decrease.