WC/C制备条件对甲醇电氧化特性的影响研究

以钨酸铵为前躯体,采用程序升温控制还原法（TPR）制备了WC／C纳米颗粒,在碳载体存在的情况下,研究了钨源前躯体碳化过程中CH4与H2流量比对单-WC晶相以及Pt／WC／C电催化氧化甲醇性能的影响。XRD测试结果发现：仅在CH4：H2流量比为2时可获得单一WC多晶,其平均粒径为11．3nm。循环伏安实验结果证实：10wt％Pt-10wt％WC／C电催化氧化cH,OH的比质量活性达到875mA·mg^-1,远远高于10wt％Pt／C的658mA·mg^-1,且起始氧化电位负移80mV。计时电流法实验表明Pt／WC／C在酸性介值中稳定性高于Pt／C催化剂。     

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.     

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。     

微波法制备的Pt/C催化剂对甲醇和CO的电催化氧化

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。     

新型rGO-PtNPs材料对甲醇的电催化研究

本文以1-芘甲醛作为氧化石墨烯的还原剂,通过一步法制备了羧基功能化的且高度还原的还原态石墨烯(rGO),并以其载体原位还原了高度分散的铂纳米颗粒负载的新型催化剂(rGO-PtNPs)。采用扫描电镜对其形貌进行了表征,发现用1-芘甲醛作为还原剂可以均匀地还原氧化石墨烯并为纳米颗粒Pt的负载提供了位点。利用循环伏安法和计时电流法分别研究该催化剂对甲醇具有优良的电催化氧化活性及稳定性。     

负载途径对炭气凝胶载Pt催化剂性能的影响

选择孔隙率高、孔隙尺寸小、比表面积大、电导率高、孔径大小及分布可控的新型炭材料炭气凝胶(CAs)为载体,通过在成品CAs表面负载和在CAs制备过程中同步负载两种途径制备了CAs负载的Pt催化剂,利用XRD、TEM、ICP及电化学循环伏安测试等手段对比讨论了负载途径对CAs载Pt催化剂物化性能及甲醇氧化催化活性的影响。结果表明,同步负载虽然可以简化制备工艺,但所制得的催化剂样品中催化活性组分Pt颗粒大、团聚严重、分散性差、负载量低,而且有许多Pt颗粒被包裹在CAs内部,因而导致了催化剂的有效利用率和催化性能降低。相反,通过在成品CAs表面负载的方法可以制得Pt颗粒小、分散均匀、实际负载量接近理论设计的高性能催化剂。     

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。     

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。     

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C掺杂多孔纳米TiO2,以其为载体制备了一种RuAg/TiO2-C催化剂.采用XRD、TEM、EDS、XPS及电化学分析对催化剂的结构和性能进行了表征,测定了其对甲醇的电催化氧化性能.结果表明,RuAg的负载和C的掺杂提高了TiO2对甲醇的电催化性能,RuAg/TiO2-C对甲醇电...     

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。     

Durable Transition‐Metal‐Carbide‐Supported Pt–Ru Anodes for Direct Methanol Fuel Cells

Molybdenum carbide (MoC) and tungsten carbide (WC) are synthesized by direct carbonization method. Pt–Ru catalysts supported on MoC, WC, and Vulcan XC‐72R are prepared, and characterized by X‐ray diffraction, X‐ray photoelectron spectroscopy, and transmission electron microscopy in conjunction with electrochemistry. Electrochemical activities for the catalysts towards methanol electro‐oxidation are studied by cyclic voltammetry. All the electro‐catalysts are subjected to accelerated durability test (ADT). The electrochemical activity of carbide‐supported electro‐catalysts towards methanol electro‐oxidation is found to be higher than carbon‐supported catalysts before and after ADT. The study suggests that Pt–Ru/MoC and Pt–Ru/WC catalysts are more durable than Pt–Ru/C. Direct methanol fuel cells (DMFCs) with Pt–Ru/MoC and Pt–Ru/WC anodes also exhibit higher performance than the DMFC with Pt–Ru/C anode.     

纳米碳化钨的合成及其电催化活性研究

以钨酸和丙烯腈为原料,采用共沉淀法合成碳化钨（WC）前驱体,于H₂和Ar混合气氛中高温还原碳化制备纳米WC。采用傅立叶红外光谱、X射线衍射及扫描电镜等对试样进行表征,在酸性介质中采用循环伏安法测试Pt/WC电化学催化活性。结果表明,实验合成了较纯的纳米碳化钨,其颗粒形貌近似球形,粒径80 nm左右。Pt/WC的电化学表面积（ESA）较传统的Pt/C有较大提高,10%Pt/WC电流密度为51.2 mA·cm^-2。     

Facile synthesis of tungsten carbide-carbon composites for oxygen reduction reaction

Tungsten carbide-carbon composite (XWC-C, where X=10 or 30 represents the tungsten content) supports were prepared by pyrolyzing tungsten-adsorbed poly(4-vinylpyridine)-functionalized carbon. The supports were used to prepare Pt catalysts (Pt/XWC-C) for oxygen reduction reactions (ORR) in alkaline solution. Prepared XWC-C revealed highly dispersed tungsten carbide species composed of WC and W₂C phases. The tungsten carbide species proved to have a positive effect on the dispersion of Pt particles. Compared to the Pt catalyst supported on carbon (Pt/ C), Pt/XWC-C showed higher ORR performance. In addition, the catalytic performance of Pt/XWC-C was enhanced with increasing tungsten carbide content. The highest ORR activity was achieved for the Pt/30WC-C catalyst, which had a 2.9-fold enhanced performance (at 0.8V vs. RHE) compared to that of Pt/C. It is believed that the unique interaction between Pt and the tungsten carbide species was responsible for the enhanced ORR performance of the Pt/XWC-C catalysts.     

活性炭载碳化钨复合材料的制备及其对对硝基苯酚的电催化性能

以浓度为10%的偏钨酸铵溶液为前驱体、CH4/H2为还原碳化气氛,采用表面修饰技术和还原碳化技术制备了碳化钨(WC)/活性炭(C)复合材料。通过FT-IR、XRD、SEM等对制备的WC/C材料进行表征,结果表明,酸处理后的活性炭外表面大幅度增加了羟基和羰基,WC/C复合材料是由WC、W2C和C三相组成,碳化钨均匀地分散于活性炭表面,粒径约50～100nm。采用循环伏安法研究了碱性介质中WC/C-PME对对硝基苯酚的电还原行为,结果表明,该材料对对硝基苯酚的电催化活性优于WC和C,且WC/C材料在对硝基苯酚电还原过程中保持良好的化学稳定性。     

Precursor synthesis and properties of nanodispersed tungsten carbide and nanocomposites WC:nC

Nanoscale tungsten carbide (WC) and WC:nC nanocomposites have been synthesized by the precursor method. The precursor, obtained in the form of a glassy mass by thermal treatment of a mixture of (NH₄)₁₀W₁₂O₄₁∙7H₂O and glycerol, was heated in inert gaseous atmosphere up to 1050–1100 °C. The concentration of chemically active carbon in the precursor and nanocomposites depends on the W/C ratio in the initial mixture. At W/C=1/3 pure tungsten carbide is formed; at W/C>1/3 composites of WC and free carbon (WC:nC) are formed. Heating of the precursor with W/C=1/6 up to 1100 °C in helium atmosphere results in the formation of carbon-encapsulated tungsten carbide nanoparticles. An increase in the precursor-heating rate leads to the formation of chain-like structures. Each chain consists of hexagonal WC grains with unit cell parameters a=2.93 Å and c=2.83 Å. Free carbon in WC:nC composites forms agglomerates of carbon “nano-onions” of spherical or multi-layered tubular shapes.     

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.     

A Combined Surface Science and Electrochemical Study of Tungsten Carbides as Anode Electrocatalysts

An effective anode electrocatalyst in direct methanol fuel cell (DMFC) should have high activity for the oxidation of methanol and the decomposition of water, while remaining stable under the relatively harsh anode environment. Although the Pt/Ru bimetallic alloy is currently the most effective anode electrocatalyst, both Pt and Ru are expensive due to limited supplies and both are susceptible to CO poisoning. Consequently, the discovery of less expensive and more CO tolerant alternatives to the Pt/Ru catalysts would help facilitate the commercialization of DMFC. In this paper we will discuss the possibility of using tungsten carbides (WC) and Pt-modified WC as potential anode electrocatalysts in DMFC. We will provide an overview of our recent work, using a combined approach of fundamental surface science studies and in-situ electrochemical evaluation of the activity and stability of tungsten carbides. We will demonstrate the feasibility to bridge fundamental surface science studies on single crystals with the electrochemical evaluation on polycrystalline WC films. We will also discuss the synergistic effect by supporting low coverages of Pt on the WC substrate to further enhance the electrochemical performance of WC.     

碳化钨载铂的制备及其对硝基苯的电催化还原

以偏钨酸铵（AMT）为钨源前驱体,气流式喷雾干燥仪造粒,得到空心球状结构偏钨酸铵,固定床气固反应,以CO/CO₂为还原碳化气氛在800℃下制备了介孔空心球状碳化钨。采用氯铂酸作为铂源,用浸渍、气相还原法制备了Pt/WC粉末催化剂。通过XRD和SEM测试手段对Pt/WC粉末样品进行了表征,表明Pt成功负载在介孔WC材料上。采用循环伏安法、以Pt/WC粉末微电极为工作电极,研究了Pt/WC对在质子惰性介质中硝基苯的硝基还原的催化作用。结果表明,Pt/WC催化剂对硝基还原有着良好的电催化活性和化学稳定性。     

A Novel Carbon‐Encapsulated Cobalt‐Tungsten Carbide as Electrocatalyst for Oxygen Reduction Reaction in Alkaline Media

Carbon‐encapsulated cobalt‐tungsten carbides (CoWC@C) were synthesized by reduction and carbonization method and used as the electrocatalyst for oxygen reduction reaction (ORR) in direct methanol fuel cells. The as‐prepared samples were characterized by transmission electron microscope, X‐ray diffraction, and X‐ray photoelectron spectroscopy. The results show that CoWC@C consists of outer layer carbon and internal Co₃W₃C, WC, and Co. The cyclic voltammetry results show that CoWC@C has high ORR activity, long‐term durability, and good methanol‐tolerant performance. It is revealed that the main active phase for ORR of CoWC@C is Co₃W₃C, and the outer layer carbon plays the role in improving the durability of the catalyst.