层级多孔碳载铂催化剂的制备及可达性

层级多孔碳作为氧还原铂基催化剂载体的选择之一, 简单的旋转圆盘电极(RDE)验证此类催化剂具有较高的氧还原活性, 但几乎都缺少膜电极(MEA)性能验证, 实用性无法保证. 本文设计制备了基于聚苯胺的层级多孔碳（NHPC）载铂催化剂（Pt/NHPC850）, 研究了其氧还原活性、 MEA质子传输和氧传输特性. RDE测试研究表明, Pt/NHPC850催化剂在低I/C（离聚物与碳载体质量比）时的面积活性低于实心碳载铂催化剂（Pt/XC-72）, 但当I/C增大到与膜电极中一致时, 由于Nafion树脂对Pt催化剂的毒化作用增强, 其面积活性反而优于 Pt/XC-72. Pt/NHPC850催化剂的高Pt分散性及其优异的抗Nafion毒化性能, 使其在I/C为0.8时的质量活性为Pt/XC-72催化剂的1.34倍. MEA质子传输研究表明, 即使在高加湿条件下, Pt/NHPC850质子电阻率仍高达72.6 mΩ·cm², 为Pt/XC-72的3倍. Pt/NHPC850制备的膜电极极化曲线在500 mA/cm²电流密度下性能迅速下降, Pt/NHPC850的氧增益电压达到144.4 mV, 比Pt/XC-72高56.7 mV. 表明Pt/NHPC850膜电极的质子传输和氧传输性能较差. 对比Pt/NHPC850催化剂的RDE和MEA的测试结果, 说明以层级多孔碳为载体的铂碳催化剂虽然耐Nafion毒化能力提高, 但是质子和氧气的氧传输性较差, 此类层级多孔碳还需进一步优化其结构, 才有可能满足低铂质子交换膜燃料电池（PEMFC）的应用需求.     

Pt纳米催化剂在质子交换膜燃料电池催化层中的尺寸效应研究

以XC-72碳黑为载体, H2[PtCl6]为前驱体, 采用浸渍还原法并结合后续高温处理, 制备出不同尺寸Pt颗粒(3～8 nm)的Pt/C催化剂. 在基于质子交换膜燃料电池(PEMFC)单电池的电化学电解池中, 对实际PEMFC催化层中燃料电池反应的Pt催化剂尺寸效应进行了研究. 结果表明, 在PEMFC催化层环境中, Pt/C纳米催化剂对氢氧化和氧还原反应均有显著的粒度尺寸效应. 随着Pt粒度减小, 氢氧化和氧还原反应的表面积活性均降低.     

纳米碳纤维载铂作为质子交换膜燃料电池阳极催化剂

采用化学还原法合成了微结构不同的纳米碳纤维(板式、鱼骨式、管式)载铂催化剂(分别记为Pt/p-CNF、Pt/f-CNF、Pt/t-CNF). 通过高分辨透射电镜(HRTEM)和X射线衍射(XRD)等分析技术对催化剂的微观结构进行了表征, 并利用循环伏安(CV)法分析了催化剂的电化学比表面积(ESA). 在此基础上, 制备了膜电极(MEA), 通过单电池测试了催化剂的电催化性能. 结果表明: 铂纳米粒子在不同的纳米碳载体上表现出不同的粒径, 在板式、鱼骨式和管式纳米碳纤维上的铂纳米粒子平均粒径分别为2.4、2.7和2.8 nm. 板式纳米碳纤维载铂催化剂作单电池阳极时表现出良好的电催化性能, 其对应的最高功率密度可达0.569 W·cm^-2, 高于鱼骨式纳米碳纤维载铂催化剂和管式纳米碳纤维载铂催化剂对应的最高功率密度(分别为0.550和0.496 W·cm^-2). 同时, 也制备了碳黑(Pt/XC-72)载铂催化剂. 相比于Pt/XC-72, 纳米碳纤维载体上的铂纳米颗粒有较小的粒径、较好的分散和较高的催化活性, 说明纳米碳纤维是质子交换膜燃料电池(PEMFCs)催化剂的良好载体.     

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.     

Pt/碳纳米管电极的电化学稳定性

 研究了Pt/CNT(碳纳米管)电极在动电位和恒电位两种情况下的电化学稳定性. 在动电位条件(0.05～1.2 V vs RHE(可逆氢电极)循环伏安940次, 60 h)下, Pt/CNT电极的电化学表面积下降18.8%; 在恒电位条件(1.2 V vs RHE, 60 h)下, Pt/CNT电极的电化学表面积仅下降5.2%. 这表明Pt/CNT电极在动电位条件下性能衰减得更迅速. X射线光电子能谱分析表明,恒电位条件下载体碳纳米管被氧化的程度较大. X射线衍射分析计算表明,动电位和恒电位氧化后, Pt颗粒的平均粒径从3.8 nm分别增大到4.9和3.9 nm. Pt颗粒的长大可能是Pt/CNT电极性能衰减的主要原因之一,而载体的氧化不是Pt/CNT电极性能衰减的主要原因.     

微波功率和微波作用时间对脉冲微波辅助化学还原合成的Pt/C催化剂性能的影响

采用脉冲微波辅助化学还原法制备了质子交换膜燃料电池(PEMFC)用Pt/C催化剂.通过X射线衍射(XRD)和高分辨透射电镜(HRTEM)等分析技术对催化剂的微观结构和形貌进行了表征.利用循环伏安(CV)法计算了催化剂的电化学比表面积.在此基础上制备了膜电极(MEA)并组装成单电池,考察了制备的Pt/C催化剂作为单电池阴...     

新型钴-聚吡咯-碳载Pt燃料电池催化剂的制备与表征

采用脉冲微波辅助化学还原法制备了钴-聚吡咯-碳(Co-PPy-C)载Pt催化剂(Pt/Co-PPy-C),其中Pt的总质量占20%.利用透射电镜(TEM)、光电子射线能谱分析(XPS)和X射线衍射(XRD)研究了催化剂的结构,用循环伏安(CV)、线性扫描伏安(LSV)等方法考察了其电化学活性及氧还原反应(ORR)动力学特性及耐久性.Pt/Co-PPy-C电催化剂的金属颗粒直径约1.8 nm,略小于商用催化剂Pt/C(JM)颗粒尺寸(约2.5 nm);催化剂在载体上分散均匀,粒径分布范围较窄.Pt/Co-PPy-C的电化学活性比表面积(ECSA)(75.1 m2·g-1)高于商用催化剂的ECSA(51.3 m2·g-1).XPS测试表明,自制催化剂表面的Pt主要以零价形式存在.而XRD结果显示,自制催化剂中Pt(111)峰最强,Pt主要为面心立方晶格.Pt/Co-PPy-C具有与Pt/C(JM)相同的半波电位;在0.9 V下,Pt/Co-PPy-C的比活性(1.21 mA·cm-2)高于商用催化剂的比活性(1.04 mA·cm-2),表现出更好的ORR催化活性.动力学性能测试表明催化剂的ORR反应以四电子路线进行.CV测试1000圈后,Pt/Co-PPy-C和Pt/C(JM)的ECSA分别衰减了13.0%和24.0%,可见自制催化剂的耐久性高于商用Pt/C(JM),在质子交换膜燃料电池(PEMFC)领域有一定的应用前景.     

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.     

酸处理石墨化碳载体对燃料电池催化剂性能的影响

通过1700 ℃高温处理XC-72CB得到石墨化碳黑(GCB), 并采用酸处理对GCB碳载体进行官能团修饰. 透射电子显微镜(TEM)、 X射线粉末衍射(XRD)和拉曼光谱的结果显示, 酸处理后GCB的石墨化程度增加; N₂吸附-脱附结果证明GCB比表面积减小, 微孔数量减少; 热重分析结果表明, GCB热稳定性增强; 红外光谱和拉曼光谱结果显示, GCB表面引入了含氧官能团, 并同时保持了GCB的有序化结构. 采用循环伏安(CV)法和线性扫描伏安(LSV)法测试了不同预处理后催化剂的电化学性能, 表明其电化学活性表面积(ECSA, 75.25 m²/g)和质量比活性(MA, 0.093 A/mg)均高于商业Pt/C(JM)催化剂. TEM结果表明, 使用经过浓硫酸和浓硝酸混合酸处理的GCB(简称OGCB)作为载体得到的Pt/OGCB平均粒径为2.28 nm, 略小于商业Pt/C(JM)催化剂(约2.5 nm); 经5000周电化学循环伏安测试后, Pt/OGCB的电化学活性表面积衰减17.3%, 质量比活性衰减29.5%, 而Pt/C(JM)的ECSA衰减达到25.1%, MA衰减达到42.5%.     

XC-72碳和碳纳米管负载PtRu纳米粒子的微波快速合成及其对甲醇的电化学氧化

利用微波辐射加热技术快速合成了XC-72碳和碳纳米管(CNTs)负载的PtRu合金纳米粒子,合金负载的质量分数为20%,Pt和Ru的原子比接近于1:1.透射电镜观察表明微波合成的PtRu合金纳米粒子具有细小的粒径和狭窄的尺寸分布,所合成的PtRu合金纳米粒子高度分散在XC-72碳和CNTs的表面,其平均粒径分别为3.3 nm和2.8 nm.电化学实验表明微波合成的PtRu/XC-72和PtRu/CNTs纳米催化剂比用湿化学方法以KBH₄还原制备的催化剂对甲醇的电化学氧化具有更高的催化活性.     

炭黑负载Pt-Sn双金属催化剂对乙醇的电催化氧化性能

采用一步还原法(乙二醇为还原剂)与两步还原法(在聚乙烯吡咯烷酮PVP保护下,先用硼氢化钠还原制备Sn溶胶,沉积Pt后用乙二醇还原)制备了炭黑负载Pt-Sn双金属催化剂,利用循环伏安法和计时电流法考察了催化剂制备方法、Pt/Sn原子比、溶液p H值、PVP/Sn质量比、反应介质等对乙醇室温电催化氧化活性和稳定性的影响.以X光衍射、透射电镜及电化学活性面积测定对所得催化剂进行了表征.发现引入Sn明显提高了Pt催化剂对乙醇的电催化活性与稳定性,两步还原法得到的Pt3Sn/C催化剂具有更小的颗粒尺寸,更大的电化学活性面积及更高的乙醇氧化活性与稳定性.与酸性介质相比,该催化剂在碱性介质中的电化学活性更好.     

Remarkable support effect of SWNTs in Pt catalyst for methanol electrooxidation

Carbon nanotubes have been proposed as advanced metal catalyst support for electrocatalysis. In this work, different carbon support materials including single-walled carbon nanotubes (SWNTs), multi-walled carbon nanotubes (MWNTs) and XC-72 carbon black, were compared in terms of their electrochemical properties using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The SWNTs is found to exhibit the highest accessible surface area in electrochemical reactions and the lowest charge transfer resistance at the SWNTs/electrolytes. These carbon materials are then loaded with varying amount of Pt by the electrodeposition technique to prepare carbon supported Pt catalysts. Electrochemical measurements of methanol oxidation reveal that the SWNTs supported Pt catalyst exhibits the highest mass activity (mA/mg-Pt). In comparison with Pt-XC-72 and Pt-MWNTs, the remarkably enhanced electrocatalytic activity of the Pt-SWNTs maybe attributed to a higher dispersion and utilization of the Pt particles, which are directly related to the electrochemical characteristics of SWNTs. The high concentration of oxygen-containing functional groups, high accessible surface area, low charge transfer resistance at the carbon/electrolyte interfaces can be important for the Pt dispersing and strong metal-support interaction in the Pt-SWNTs catalyst.     

Durability investigation of graphene-supported Pt nanocatalysts for PEM fuel cells

We report graphene nanosheets as a durable alternative support material for Pt nanoparticle catalysts for oxygen reduction in proton exchange membrane (PEM) fuel cells and compared them to XC-72. The materials were characterized by X-ray diffraction and transmission electron microscopy. Electrochemical surface oxidation of XC-72 and graphene, and of Pt/XC-72 and Pt/graphene has been compared following treatments for up to 120 h. The electrochemical performance of the specimens was evaluated by cyclic voltammetry and linear sweep voltammetry at different surface oxidation time intervals. Electrochemical measurements indicate that the graphene exihibits greatly enhanced electrochemical durability. It is suggested that graphene nanosheet is a promising, low-cost, and durable electrocatalyst support for oxygen reduction in the PEM fuel cell.     

The role of carbon support morphology in the formation of catalytic layer of solid-polymer fuel cell

The Pt/C catalysts with similar morphology of active catalytic phase (platinum nanoparticles), which were deposited on the supports with different types of carbon structures (Vulkan XC-72 carbon black, Taunit carbon tubes, and Timrex HSAG-300 carbon support with graphite structure), were fabricated by the method of electrochemical dispersion. The effect of the carbon structure type on the electrocatalytic properties of Pt/C catalysts was studied in their operation in the three-electrode cell and in-service in the membrane-electrode assembly of air-hydrogen solid-polymer fuel cell. The Pt/C catalyst based on the Vulkan XC-72 carbon support showed the best performance. The anisotropic shape of Taunit carbon nanotubes and the microstructure of Timrex HSAG-300 carbon support do not allow us to form a catalytic layer with a large active platinum surface area and a structure, which provides an effective ionic transport and mass exchange near the platinum surface.     

Graphene supported electrocatalysts for methanol oxidation

Graphene nanosheet was prepared by modified Hummer’s chemical method and utilized as a catalyst support of PtRu nanoparticles for the electro-oxidation of methanol. Home-made graphene nanosheet was clearly characterized by Raman spectroscopy and we applied colloidal method to synthesize with high metal content of 80 wt.% Pt–Ru catalyst, which is extensively clarified by HR-TEM and XRD analysis. 80 wt.% Pt–Ru/graphene nanosheet catalyst showed superior electrochemical activity toward methanol oxidation compared to Pt–Ru/Vulcan XC-72R. It is due to the significant increase of electrochemical active surface area for better catalyst utilization.     

Carbon nanotubes as a support for Pt-and Pt-Ru-catalysts of reactions proceeding in fuel cells

Comparative study of two types of single-wall carbon nanotubes and standard carbon black Vulcan XC-72 as supports for catalysts of reactions proceeding in fuel cells is carried out. The nanotubes were prepared by arc method; they differed in the degree of their purifying from amorphous carbon and metal impurities. The structure and hydrophobic-hydrophilic properties of these carbon supports are studied by etalon porosimetry. The effect of the supports’ specific surface area on the deposited catalyst particles size and specific surface area is studied. The catalysts (Pt-Ru and Pt) were deposited from aqueous solutions of their salts. Platinum was also deposited by thermal decomposition of ethoxy clusters. It is shown that in methanol oxidation reaction at the Pt-Ru catalysts the current values per unit true surface area do not depend on the support nature, provided the catalyst loading is equal and the particle size is similar. When oxygen is reduced at platinum deposited onto purified nanotubes and the carbon black Vulcan XC-72, specific kinetic currents also are close to each other. It is shown that the degree of nanotubes purification and their structure affect the kinetics of this reaction significantly.     

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.     

Electrocatalytic oxidation of methanol on Pt-Pd nanoparticles supported on honeycomb-like porous carbons in alkaline media

Honeycomb-like porous carbons (PCs) were synthesized using a facile self-assembly method with phenolic resin as the carbon source and tetraethyl orthosilicate (TEOS) as the silica source. The PCs were found to have a large BET surface area of 458 m² g^?1 and a partially graphitized structure. The obtained PCs were used as a support for various Pt-Pd bimetallic alloy catalysts employed for methanol oxidation in alkaline media. Compared with Pt supported on commercial Vulcan XC-72R carbon (Pt/C) and with the other Pt-Pd bimetallic alloy catalysts on PCs, Pt₃Pd₁ on PCs displayed the most negative onset potential for methanol oxidation and the highest steady-state current (2.04 mA cm^?2). This may be because the Pt₃Pd₁/PCs catalyst has the largest electrochemical active surface area (ESA), and because adding Pd to the catalyst improves the ability of the intermediate species to tolerate oxidation. The results show that the prepared Pt-Pd/PCs is a potential candidate for application as a catalyst in alkaline direct methanol fuel cells.     

电化学方法制备高分散Pt/CMK-3及其对甲醇电化学催化性能

采用直接电化学还原法在介孔碳(CMK-3)载体上直接电沉积高分散的铂纳米颗粒,制备CMK-3复合铂纳米颗粒电极(Pt/CMK-3)。 通过透射电子显微镜分析发现,铂纳米颗粒非常均匀的分布在CMK-3上,平均粒径约5 nm。 通过循环伏安测试,分析了催化剂不同负载铂含量时氯铂酸的利用率,在理论铂质量分数为20%时,这种方法制备的Pt/CMK-3所使用的氯铂酸的利用率最高,在1 mol/L CH3OH+0.5 mol/L H2SO4溶液中循环伏安测试电流密度达到382 A/g。 在相同实验条件下,Pt/CMK-3电极对甲醇电催化活性远高于Pt/XC-72(炭黑)电极和用常规电沉积方法制备的Pt/CMK-3电极。