直接甲醇燃料电池电催化剂载体碳纳米带的合成与表征

 以间苯二酚和甲醛为碳前体,合成了一种新型碳纳米材料碳纳米带(CNRs), 并采用透射电镜(TEM)、 X射线衍射(XRD)及氮气吸附/脱附测试对CNRs进行了结构表征. 结果表明,所合成的CNRs具有很高的石墨化程度及较规则的带状结构,带宽约为8～20 nm, BET比表面积为283 m2/g, 氮气等温线为type-Ⅳ型,表明CNRs为中孔结构,平均孔径约为8.2 nm. 以CNRs为载体通过多元醇法制备了45%PtRu/CNRs电催化剂,该催化剂与以Vulcan XC-72R为载体的PtRu电催化剂相比,直接甲醇燃料电池单池性能得到明显提高.     

碳纳米管担载PtSn阳极催化剂对乙醇的电催化氧化性能研究

以多壁碳纳米管(MWNTs)为载体制备了担载型PtSn纳米催化剂,对其微观形貌和电催化性能进行了表征.透射电镜(TEM)及X射线衍射(XRD)测试结果表明,以MWNTs为载体提高了PtSn金属粒子的分散度,粒径分布范围在1.5-6.5nm之间,PtSn/MWNTs催化剂的平均粒径为3.6nm.循环伏安、计时电流及DEFC单池的实验结果表明,由于MWNTs具有独特的结构及丰富的表面基团和较高的导电率,PtSn/MWNTs催化剂对乙醇的催化氧化表现出比PtSn/XC-72更高的活性.     

石墨纳米纤维用作质子交换膜燃料电池催化剂载体

利用质子交换膜燃料电池用过的废旧碳纸,采用球磨法制备了石墨纳米纤维(GNF,BET比表面积为229·3m2/g),并以GNF作为载体制备了Pt/GNF催化剂(电化学比表面积为98m2/g).与传统的以VulcanXC-72碳黑为载体的Pt/XC-72催化剂相比,其电化学比表面积及Pt粒径大小相近.采用恒电位氧化法考察了GNF,XC-72,Pt/GNF和Pt/XC-72的电化学稳定性.结果表明,在相同条件下,XC-72的峰电流增加了60%,而GNF增加了2%;Pt/XC-72的腐蚀电流比Pt/GNF的大40%;恒电位氧化60h后,Pt/XC-72约有84·7%的电化学比表面积损失,Pt/GNF仅损失37·2%.这表明GNF的抗腐蚀性优于XC-72,有希望成为质子交换膜燃料电池抗腐蚀的催化剂载体.     

石墨化碳载体对Pt/C质子交换膜燃料电池

研究了碳载体Vulcan XC-72石墨化处理对Pt基催化剂稳定性的影响.在不同温度下对碳材料Vulcan XC-72进行了石墨化处理,并以处理后的材料为载体通过浸渍还原法制备了20%Pt/C催化剂.采用X射线衍射、氮气物理吸附/脱附等测试手段对碳载体材料进行表征,并用电化学实验和热重分析法考察了催化剂的稳定性.结果表明,碳材料在1 500℃左右开始石墨化,温度越高,石墨化程度越高,但比表面积逐渐减小;以石墨化的碳材料为载体的催化剂的稳定性明显优于普通Pt/C催化剂.     

制备方法对直接乙醇燃料电池阳极PtSn/C催化剂性能的影响

 对比研究了用三种液相沉积还原法制备的PtSn/C催化剂,并用X射线衍射、透射电镜和程序升温还原等技术表征了催化剂的形貌、结构及组成. 用乙二醇还原法制备的PtSn/C(EG)催化剂的平均粒径最小(约为1.8 nm), 且分布均匀, Sn以多种价态存在于PtSn/C(EG)中. 采用循环伏安法和直接乙醇燃料电池单池评价了三种PtSn/C催化剂对乙醇氧化反应的催化活性,探索了单池性能与催化剂粒径及组成的关系. 结果表明, PtSn/C(EG)催化剂具有较高的催化乙醇氧化活性. 这可能是因为PtSn/C(EG)催化剂的金属粒径较小, Pt晶格发生了适当的扩张以及SnO2能够在较低电位下提供含氧物种的缘故.     

以多聚甲醛为还原剂制备新型阳极Pt/CMK-3催化剂

 以多聚甲醛为还原剂,采用液相还原法制备了Pt/CMK-3直接甲醇燃料电池(DMFC)阳极催化剂,并采用透射电镜和X射线衍射技术对其进行了表征. 结果表明,有序介孔碳CMK-3具有规整的二维有序孔道结构,为DMFC中电子和燃料的传输提供了方便的路径,同时它较大的比表面积使得Pt纳米粒子很好地分散在其表面; Pt/CMK-3催化剂中Pt粒子的平均粒径为2.8 nm, 小于E-TEK公司的商品化Pt/XC-72和以甲醇为还原剂制备的Pt/C-M催化剂,并且粒径分布范围窄,结晶度低. 察了Pt/CMK-3催化剂对甲醇的电催化氧化性能,发现Pt/CMK-3催化剂对甲醇氧化的电催化性能优于Pt/XC-72和Pt/C-M催化剂.     

高负载率纳米Pt-Ru/C催化剂的制备和表征

以Vulcan XC-72R碳黑为载体, 通过在含十二烷基硫酸钠(SDS)的乙二醇溶液中直接还原氯铂酸和三氯化钌, 制备了负载率为60%的纳米PtRu/C催化剂. 透射电镜(TEM)和X射线衍射(XRD)分析结果表明, SDS的加入可显著改善PtRu纳米颗粒在载体表面分散性, 平均粒径达到2.7 nm. 电化学循环伏安法(CV)测试的结果显示, 利用这种方法制备的纳米PtRu/C催化剂对于甲醇氧化具有较强的抗中毒能力和较高的电催化活性.     

Ir/CNTs催化剂的制备及对氨的电催化氧化

分别以碳纳米管(CNTs)和XC-72活性碳为载体制备了Ir/CNTs和Ir/C催化剂. X射线衍射(XRD)结果显示, CNTs拥有更高的石墨化程度. 电化学研究结果表明, 与Ir/C催化剂相比, Ir/CNTs对氨氧化具有更高的电流密度、更低的起始氧化电位和更好的稳定性. 同时, Ir/CNTs催化剂对氨检测的线性范围更宽, 灵敏度更高, 检出限更低.     

直接乙醇燃料电池PtSn/C电催化剂的合成表征和性能

采用多元醇法制备了n(Pt)/n(Sn)比为2:1,3:1,4:1的PtSn/C电催化剂.通过XRD,TEM、循环伏安和氢化学吸附技术对催化剂进行了表征.TEM和XRD结果表明,不同比例的PtSn/C金属粒子的平均粒径均小于4nm,且粒径分布较窄;该系列催化剂中Pt具有fcc结构;PtSn间的相互作用使Pt晶格参数增大.循环伏安和氢化学吸附实验结果表明,加入Sn可抑制Pt对氢的吸附,Pt3Sn/C对乙醇的氧化电流比Pt4Sn/C高约1倍.用不同n(Pt)/n(Sn)比的催化剂作为直接醇类燃料电池阳极电催化剂,在相同条件下,随着Sn含量的增加,单电池最大输出功率逐渐增大,当Sn含量继续增大时,单池性能反而下降.导致不同比例PtSn催化剂活性差别的原因可能是由于Sn与Pt间的合金化程度不同和催化剂粒子尺寸效应及Sn含量对电池阻抗等几方面因素所致.对40h寿命测试前后的阳极Pt3Sn/C催化剂的分析(EnergydispersiveX-rayanalysis,EDX)结果表明,PtSn含量在测试前后均有所降低,PtSn催化剂的寿命尚有待改善.     

微乳液法制备的PtSn/C催化剂对乙醇的电催化氧化性能

以甲酸钠为还原剂,在水/triton X-100/乙二醇/环己烷的W/O型微乳液中制备PtSn/C催化剂.采用X射线衍射（XRD）分析催化剂的结构,循环伏安法和电化学阻抗谱法测试催化剂对乙醇的催化氧化性能.结果表明,微乳法制备的PtSn/C催化剂部分合金化,与Pt/C相比,PtSn/C对乙醇的电催化氧化活性有明显提高,具有更高的抗CO中毒能力.     

多尺度炭材料担载铂作为稳定的电催化剂用于氧还原反应

炭载体的稳定性对于燃料电池电催化剂是至关重要的. 本文中采用酚醛树脂作为前驱体,二氧化硅为模板剂,制备了多介孔且石墨化程度高的炭载体（HGMC）. 相比于商品Vulcan XC-72,HGMC具有中等的比表面积和高的石墨化程度,因此在电位循环扫描过程中具有较高的化学稳定性,然而HGMC碳层堆叠的结构不利于传质. 为克服这一劣势,多壁碳纳米管（MWCNTs）作为隔离物加入至HGMC中以构建具有三维多尺度结构的载体（MSGC）. 与HGMC为载体担载Pt以及商品催化剂Pt/C-JM相比,由于炭载体的具有高稳定性以及三维多尺度结构,MSGC担载Pt后不仅使电催化剂的电化学稳定性提高,且氧还原反应过程中传质得到显著改善.     

微乳法合成Pt/C、PtIr/C催化剂及其电化学性能表征

以碳纳米粉(XC-72R)作为载体,采用三种不同方法合成Pt/C负载型催化剂。利用X射线衍射(XRD)、透射电镜(TEM)、循环伏安法(CV)、恒电位测试(Potentiostatic)以及线性极化分析（Potentiodynamic polarization）等手段进行催化剂表征,结果表明,微乳法制得的负载型催化剂,活性组分的颗粒尺寸为5～10nm,且均匀地分散在载体表面,其电化学性能良好。而微乳法进一步制备的含不同比例的负载型的PtIr/C催化剂,其中以Pt85Ir15表现出更为较好的电化学综合性能。     

Electrochemical production, characterization, and application of MWCNTs

The subject of this study is production of carbon nanotubes (CNTs) using an original procedure of reduction of lithium molten salts onto graphite cathode; their structural characterization and application as support material for electrocatalysts aimed for hydrogen evolution. As-produced CNTs were characterized by means of scanning and transmission electron microscopy (SEM and TEM), Raman spectroscopy, and thermogravimetric and differential thermal analysis (DTA). SEM and TEM images have shown that nanotubes are mostly of curved shape with length of 1–20 μm and diameter of 20–40 nm. Raman peaks indicate that the crystallinity of produced nanotubes is rather low. The obtained results suggest that formed product contains up to 80 % multiwalled carbon nanotubes (MWCNTs), while the rest being non-reacted graphite and fullerenes. DTA curves show that combustion process of the nanotubes takes place in two stages, i.e., at 450 and 720 °C. At the lower temperature, combustion of MWCNTs occurs, while at higher one, fullerenes and non-reacted graphite particles burn. As-produced MWCNTs were used as electrocatalyst’s support materials and their performance was compared with that of traditional carbon support material Vulcan XC-72. MWNTs have shown almost twice higher real surface area, and electrocatalyst deposited on them showed better catalytic activity than corresponding one deposited on Vulcan XC-72.     

Kinetics and mechanism of oxygen electroreduction in alkaline solutions on xc-72r carbon black modified by products of pyrolysis of cobalt 5,10,15,20-tetrakis(4-methoxyphenyl)porphyrin

Cathodic oxygen reduction on XC-72R carbon black modified by products of pyrolysis of cobalt 5,10,15,20-tetrakis(4-methoxyphenyl)porphyrin (CoTMPP) (XC-72M) was studied. When XC-72R carbon black is modified, new active centers (ACs) are formed on the surface of the carbon support, on which the direct reaction to OH^- occurs, as shown using the rotating ring-disk electrode technique. The process of oxygen reduction on nonmodified carbon black occurs via the serial path. At low polarizations, the dependence of potential on pH corresponds to the slope of ??30 mV both for the carbon material and modified carbon black. This value is close to the coefficient in the Nernst equation for H₂/HO ₂ ^? . The slow stage of oxygen reduction is the transfer of the first or second electron to the adsorbed molecule. Herewith, the difference in the kinetics and mechanism of oxygen reduction on XC-72R and XC-72M is related to a stronger adsorption interaction of oxygen and ACs on XC-72M. The {ie1113-1} value in the pH range of 12?C14.6 is ?15 to ?20 mV both for XC-72R and XC-72M. In the case of the second halfwave potential on XC-72R, it is ?50 to ?60 mV. The observed effects are explained by a change in the surface state of catalysts at an increase in adsorption of OH^? ions at an increase in pH.     

核壳结构C@WC载体的制备及Pd/C@WC催化剂对甲酸的电催化氧化

以活性碳为碳源,在碳表面原位生成碳化钨包覆的核壳结构的碳基材料(C@WC)。 TEM结果表明,制备的C@WC是具有核壳结构的碳材料,且WC中也有少量单质W。 BET比表面测量结果表明,C@WC较活性碳比表面小,但具有更多的介孔结构。 以C@WC为载体制备的Pd/C@WC催化剂电极的电化学比表积较大,为65.47 m2/g。 Pd/C@WC对甲酸的电催化氧化活性较高,氧化峰电流密度为0.222 A/cm2,比Pd/C电极上的氧化峰电流密度增加了0.128 A/cm2。 多周期循环伏安曲线的结果也表明,Pd/C@WC催化剂电极比Pd/C具有更高的活性和稳定性。     

Pd/TiO2/C复合催化剂的制备及其在碱性溶液中对乙醇氧化的电催化性能

钛酸四丁酯前驱体水热合成制备纳米TiO₂颗粒,在TiO₂和Vulcan XC-72活性炭复合载体上液相还原负载Pd纳米颗粒,制得Pd/TiO₂/C复合催化剂. 通过透射电镜（TEM）和X射线衍射（XRD）测试表明其具有面心立方结构,Pd金属粒子（粒径约3 ~ 4 nm）均匀分散在锐钛矿型的纳米TiO₂和活性炭的复合载体上. 循环伏安和计时电流曲线测试表明,与相同Pd载量的Pd/C相比,20% Pd载量的Pd/TiO₂/C颗粒在常温常压下对乙醇的电催化氧化有很高活性和稳定性. 这主要归功于纳米TiO₂改变了Pd表面的电子特性,且增大了其比表面积.     

High-loading Pt nanoparticles on mesoporous carbon with large mesopores for highly active methanol electro-oxidation

High metal-loading Pt/C electrocatalysts are important for the fabrication of thin-layered membrane electrode assemblies (MEAs). However, the preparation of high-loading Pt catalysts with a narrow size distribution of nanoparticles remains a challenge. Herein, ordered mesoporous carbon (OMC) with large mesopores (~15 nm) and a high surface area (1316.0 m² g^?1) was fabricated using a SiO₂ nanosphere array as a template. This material was developed to support a high loading of Pt nanoparticles (60 wt%) and was then used as an electrocatalyst for the methanol oxidation reaction (MOR). The prepared Pt/OMC contains Pt nanoparticles with an average size of ~1.9 nm that are uniformly dispersed on the mesoporous walls of the OMC. The Pt/OMC catalyst exhibits smaller Pt nanoparticle size, greater Pt dispersion, larger specific electrochemically active surface area (ECSA), and higher electrocatalytic activity for the MOR than the carbon black (Vulcan XC-72R)-supported Pt and the commercial Pt/C catalysts.     

微波辐射合成钌／碳纳米复合材料及其在电化学超级电容器的应用

以RuCl_3的乙二醇溶液作为产驱体，利用微波辐射技术合成了Ru/C(19.1 wt%) 纳米复合材料。TEM观察表明这些纳米粒子具有均匀的尺寸，其平均粒径为3.2 nm ，并均匀地分散在纳米碳的表面。Ru/C纳米复合在电化学氧化后可以作为电化学超 级电容器的电极材料，循环伏安实验表明其比电容为144 F/g，而未负载纳米钌的 XC-72碳的比电容为31 F/g。     

Direct ethanol oxidation fuel cell with anionite membrane and alkaline electrolyte

A number of cathode catalysts were synthesized from nitrogen-containing organic complexes on XC-72R carbon black for an alkaline electrolyte. The catalysts were studied by the rotating disc electrode (RDE) technique. The polyacrilonitrile (PAN), phthalocyanine (Pc), and cobalt tetra(methoxyphenyl)porphyrin (CoTMPP) systems showed the highest activity. The slope of the oxygen polarization curves in the first region in 1 M KOH was 35–40 mV; this corresponds to concentration polarization in an alkaline solution in the O₂-HO₂⁻ system. A cyclic voltammetry study demonstrated that the catalytic systems with the highest corrosion stability were Pc + Co + Fe/XC-72R and CoTMPP/XC-72R pyropolymer. The activity of the catalysts decreased by 20–25% compared with the initial current densities on average. An ethanol-oxygen fuel cell with a Fumasep FAA anionite membrane and nonplatinum catalysts was tested. The maximum power density was 32 mW/cm² at 40°C. The stability test of the fuel cell showed that the materials used for the membrane-electrode assembly allowed more than 100 h of continuous operation with constant working characteristics.