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.     

直接乙醇燃料电池阳极催化剂Pt-Ir-SnO2/C的制备与表征

采用改良的Bönnemann法合成了一系列Pt/C、Pt-Ir/C、Pt-SnO₂/C 和Pt-Ir-SnO₂/C 阳极电催化剂. 利用X射线衍射(XRD)、透射电子显微镜(TEM)以及X射线光电子能谱(XPS)对催化剂晶型结构、表面形貌、粒径尺寸和表面电子结构进行了表征. 运用线性扫描伏安(LSV)、循环伏安(CV)和电流密度-时间(j-t)曲线进行电化学测试, 研究了温度对乙醇电催化氧化活性的影响. XRD和TEM结果表明, Pt 纳米粒子均为面心立方结构且分散较均匀, 平均粒径为2-4 nm. 电化学结果表明, 上述催化剂随着温度的升高催化性能增强, 在相同条件下,Pt-Ir-SnO₂/C 催化剂的催化活性最佳. 通过阿仑尼乌斯公式计算结果得知, Ir 和Sn 的协同作用可以降低Pt-Ir-SnO₂/C 催化剂对乙醇氧化反应的活化能.     

反胶束法制备直接甲醇燃料电池Pt-Sn/C催化剂及其表征

在水/AOT/环己烷反胶束体系中, 制备了Pt-Sn/C催化剂, 研究了不同ω (反胶束溶液中水与表面活性剂的物质量之比)值对Pt-Sn粒径的影响. 并采用TEM, XRD, XPS, 循环伏安等技术对其进行表征. TEM结果表明合成的Pt-Sn纳米颗粒为球形, 在碳载体表面均匀分布, 粒径分布窄, 平均粒径为2.7 nm. Pt-Sn颗粒尺寸随着ω的增加而增大. XRD结果表明该催化剂中Pt具有面心立方结构且没有与Sn形成合金. XPS结果表明在该催化剂中, Pt主要以零价态存在. 在甲醇溶液中的循环伏安扫描结果表明, 甲醇氧化峰电位和峰电流随着ω的增加而减小, 说明反胶束方法可以通过控制颗粒尺寸, 从而影响催化剂的电氧化活性. 相对于商用Pt-Ru/Vulcan XC-72 (20 wt%, E-TEK公司), 该催化剂具有较低的峰电势以及较高的I_f/I_b (循环伏安曲线中正向扫描峰电流与反向扫描峰电流的比值), 这表明用此方法制备的Pt-Sn/C催化剂具有较好的抗中毒能力.     

甲醇氧化PtSnCo/C阳极催化剂

通过乙二醇液相分步还原法制备了金属质量分数为20%的PtSn/C二元及PtSnCo/C三元催化剂.采用X射线衍射(XRD)光谱法、能量散射谱(EDS)对催化剂进行了表征;通过阳极线性伏安扫描法(LSV)、连续循环伏安法(CV)、预吸附单层CO溶出法研究了其电化学性质.结果表明,PtSnCo/C三元催化剂较商业化JM-PtRu/C催化剂具有更好的氧化甲醇催化活性.循环伏安扫描100圈后发现,PtSn/C二元催化剂的甲醇氧化峰电流快速衰减到其初始氧化峰电流的11%左右,而PtSnCo/C三元催化剂仅衰减到其初始值的50%左右,这表明PtSnCo/C三元催化剂具有更好的化学稳定性.在PtSnCo/C催化剂上,甲醇氧化起始电位比直接吸附CO后的CO阳极溶出电位负,意味着甲醇在PtSnCo/C催化剂上氧化的中间产物不是CO,而是比CO更为活泼且易于氧化的中间物种.     

Ru, Sn和Co促进的Pt/C催化剂电催化氧化甲醇的性能

 采用溶胶法制备了用于阴离子膜直接甲醇燃料电池的Pt-M/C(M=Ru, Sn和Co)阳极电催化剂,并用X射线衍射和X射线能谱技术对催化剂进行了表征. 结果表明,制备的Pt-M合金颗粒分布均匀,粒径为2～6 nm, 其组成与前驱体中相应金属的原子比基本吻合. 用循环伏安法测定了催化剂在不同碱性条件下的活性. 结果显示,随着碱性的增加,甲醇的起始氧化电位降低,峰电流和催化剂的活性增大; 相同碱强度下催化剂活性顺序为Pt50Ru50/C>Pt50Sn50/C>Pt75Co25/C, 添加Ru可明显提高Pt/C催化剂的活性. Pt50Ru50/C在1.0 mol/L NaOH+1.0 mol/L CH3OH溶液中的峰电流密度可达634.7 mA/mg.     

锡负载量对PtSn/Al2O3催化丙烷脱氢性能的影响

采用羰基合成-浸渍法制备了不同Pt/Sn摩尔比(3:1, 1:1, 1:2和1:3)的PtSn/Al₂O₃催化剂, 利用N₂吸附-脱附实验、 X射线衍射(XRD)、 透射电子显微镜(TEM)、 吡啶吸附红外光谱(Py-IR)和热重-差热分析(TG-DTA)等手段对其进行了表征, 研究了Sn负载量对PtSn/Al₂O₃的结构性质及催化丙烷脱氢性能的影响. 结果表明, 制备的PtSn/Al₂O₃具有较高的丙烯选择性和稳定性. 当Pt/Sn摩尔比为3:1和1:1时, 铂和锡在催化剂上主要以Pt₃Sn和PtSn合金形式存在, 合金的形成明显改善了催化剂的脱氢性能, 可抑制金属颗粒的高温烧结; 当Pt/Sn摩尔比为1:2和1:3时, 铂主要以金属形式存在. 随着Sn负载量的增加, 催化剂上L酸性位逐渐减少, 丙烷转化率降低, 丙烯选择性增加, 同时促使反应积炭从金属表面向载体迁移, 改善了催化剂的稳定性.     

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.     

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.     

质子交换膜燃料电池Pd修饰Pt/C催化剂的电催化性能

通过对Pt催化剂表面进行Pd修饰提高质子交换膜燃料电池阴极催化剂的氧还原反应(ORR)活性. 采用乙二醇还原法制备了不同比例的Pd修饰Pt/C催化剂. 透射电镜(TEM)和X射线衍射(XRD)测试结果表明, 制备的催化剂贵金属颗粒粒径主要分布在1.75～2.50 nm之间, 并均匀地分散在碳载体表面. 循环伏安方法(CV)研究表明Pd修饰Pt/C催化剂的电化学活性面积低于传统的Pt/C催化剂. 但通过旋转圆盘电极(RDE)测试研究发现, 制备的催化剂具有比传统Pt/C催化剂高的ORR活性.     

化学镀制备高性能直接乙醇燃料电池(DEFC)阳极催化剂PtRu/C和PtRuSn/C

应用化学镀方法,以活化-敏化处理的活性炭作载体,制备高分散催化剂PtRu/C和PtRuSn/C.XRD、TEM及电化学测试表明,该催化剂Pt、Ru、Sn形成合金.金属颗粒的平均粒径约为3 nm.PtRu/C和PtRuSn/C二者对乙醇的阳极氧化都具有良好的催化活性和稳定性.     

Microwave-assisted polyol synthesis of carbon-supported platinum-based bimetallic catalysts for ethanol oxidation

High surface area carbon-supported Pt, PtRh, and PtSn catalysts were synthesized by microwave-assisted polyol procedure and tested for ethanol oxidation in perchloric acid. The catalysts were characterized by thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning tunnelling microscopy (STM), TEM, and EDX techniques. STM analysis of unsupported catalysts shows that small particles (～2?nm) with a narrow size distribution are obtained. TEM and XRD examinations of supported catalysts revealed an increase in particle size upon deposition on carbon support (diameter?～?3?nm). The diffraction peaks of the bimetallic catalysts in X-ray diffraction patterns are slightly shifted to lower (PtSn/C) or higher (PtRh/C) 2θ values with respect to the corresponding peaks at Pt/C catalyst as a consequence of alloy formation. Oxidation of ethanol is significantly improved at PtSn/C with the onset potential shifted for?～?150?mV to more negative values and the increase of activity for approximately three times in comparison to Pt/C catalyst. This is the lowest onset potential found for ethanol oxidation at PtSn catalysts with a similar composition. Chronoamperometric measurements confirmed that PtSn/C is notably less poisoned than Pt/C catalyst. PtRh/C catalyst exhibited mild enhancement of overall electrochemical reaction in comparison to Pt/C.     

Carbon-supported PdSn nanoparticles as catalysts for formic acid oxidation

Pd and PdSn nanoparticles supported on Vulcan XC-72 carbon are prepared by a microwave-assisted polyol process. The catalysts are characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), linear sweeping voltammetry, and chronoamperometry. The results show that the Pd and PdSn nanoparticles, which are uniformly dispersed on carbon, are 2–10 nm in diameters. All Pd/C and PdSn/C catalysts display the characteristic diffraction peaks of a Pd face-centered cubic (fcc) crystal structure. It is found that the addition of Sn to Pd can increase the lattice parameter of Pd (fcc) crystal. The PdSn/C catalysts have higher electrocatalytic activity for formic acid oxidation than a comparative Pd/C catalyst and show great potential as less expensive electrocatalyst for formic acid electrooxidation in DFAFCs.     

Colloidal synthesis and structural control of PtSn bimetallic nanoparticles

PtSn bimetallic nanoparticles with different particle sizes (1-9 nm), metal compositions (Sn content of 10-80 mol %), and organic capping agents (e.g., amine, thiol, carboxylic acid and polymer) were synthesized by colloidal chemistry methods. Transmission electron microscopy (TEM) measurements show that, depending on the particle size, the as-prepared bimetallic nanocrystals have quasi-spherical or faceted shapes. Energy-dispersive X-ray (EDX) analyses indicate that for all samples the signals of both Pt and Sn can be detected from single nanoparticles, confirming that the products are actually bimetallic but not only a physical mixture of pure Pt and Sn metal nanoparticles. X-ray diffraction (XRD) measurements were also conducted on the bimetallic particle systems. When compared with the diffraction patterns of monometallic Pt nanoparticles, the bimetallic samples show distinct shifts of the Bragg reflections to lower degrees, which gives clear proof of the alloying of Pt with Sn. However, a quantitative analysis of the lattice parameter shifts indicates that only part of the Sn atoms are incorporated into the alloy nanocrystals. This is consistent with X-ray photoelectron spectroscopy (XPS) measurements that reveal the segregation of Sn at the surfaces of the nanocrystals. Moreover, short PtSn bimetallic nanowires were synthesized by a seed-mediated growth method with amine-capped bimetallic particles as precursors. The resulting nanowires have an average width of 2.3 nm and lengths ranging from 5 to 20 nm.     

Carbon-supported IrSn catalysts for a direct ethanol fuel cell

Carbon-supported Ir₃Sn/C and Ir/C catalysts were simply prepared with NaBH₄ as a reducing agent under the protection of ethylene glycol at room temperature. TEM and X-ray diffraction (XRD) data showed that the catalysts with small particle size exhibited the typical characteristic of a crystalline Ir fcc structure. Their electro-catalytic activities in comparison with Pt/C and Pt₃Sn/C catalysts also prepared by the NaBH₄ reduction process were characterized by cyclic voltammetry (CV), linear sweep voltammetry (LSV) and chronoamperometry (CA) techniques. The results indicated that Ir-based catalysts showed superior electro-catalytic activity towards ethanol oxidation to Pt/C and Pt₃Sn/C catalysts, mainly at low potential region. During single-cell tests at 90 °C, better performances of Ir-based catalysts as anodes were obtained compared to that of Pt/C catalyst. The comparable overall performance of Ir₃Sn/C to Pt₃Sn/C makes it a promising alternative choice of anode catalyst for direct ethanol fuel cells.     

Effect of thermal treatment on phase composition and ethanol oxidation activity of a carbon supported Pt50Sn50 alloy catalyst

A carbon supported Pt–Sn electrocatalyst in the Pt/Sn atomic ratio 50:50 was prepared by the reduction of Pt and Sn precursors with formic acid and thermally treated at 200 °C (i.e., in the presence of solid tin) and 500 °C (in the presence of molten tin) in flowing hydrogen. In the absence of thermal treatment, X-ray diffraction (XRD) analysis showed a solid solution of Sn in the face centered cubic (fcc) Pt and SnO₂. After thermal treatment, the formation of a main phase of hexagonal PtSn (niggliite) and a secondary phase of cubic Pt₃Sn was observed in the Pt50Sn50 catalyst. The relative amount of the PtSn phase increased with increasing thermal treatment temperature. The presence of molten tin gave rise to the formation of some big particles during annealing at 500 °C. The activity for the ethanol oxidation reaction (EOR) of the as-prepared catalyst was higher than that of both thermally treated catalysts and Pt75Sn25/C and Pt50Ru50/C by E-TEK. The higher activity for the EOR of the as-prepared Pt–Sn catalysts was ascribed to the presence of a large amount of SnO₂. Dedicated to Teresa Iwasita’s 65th birthday.     

室温制备高合金化Pt-Ru/CMK-3催化剂及其对甲醇的电催化氧化

通过低温络合反应制备了高分散高合金化的Pt-Ru固溶体, 并将其均匀地担载在有序介孔碳CMK-3上, 以形成二元复合金属催化剂. XRD谱图表明,fcc结构的Pt原子部分被hcp结构的Ru原子取代形成置换固溶体， 而且几乎没有未形成合金的Ru存在. TEM和XRD研究结果表明， Pt-Ru/CMK-3催化剂中Pt-Ru合金粒子的平均粒径为27 nm, 且具有良好的均一度. 还研究了催化剂对甲醇的电催化氧化性能, 并与E-TEK公司同类催化剂进行了对比, 研究结果表明, Pt-Ru/CMK-3催化剂具有较大的电化学活性面积, 对甲醇的电催化氧化性能和抗CO中毒能力明显优于其它同类催化剂.     

PtSn/Al2O3/MCM-41催化剂的丙烷脱氢催化性能

用微型催化反应装置评价, 并结合X射线粉末衍射(XRD)、表面积和孔结构测试、程序升温还原(TPR)、氢化学吸附和热重分析等方法研究了负载型PtSn/γ-Al2O3, PtSn/MCM-41和PtSn/Al2O3/MCM-41催化剂的丙烷脱氢反应催化性能. 发现PtSn/Al2O3/MCM-41催化剂具有较PtSn/MCM-41催化剂高的丙烷脱氢反应活性和较PtSn/γ-Al2O3催化剂高的反应稳定性. 实验结果表明, 纯硅MCM-41载体表面的锡物种因与载体相互作用较弱故易被还原, 导致铂金属分散度和催化剂的丙烷脱氢活性较低. 用Al2O3修饰MCM-41可以增强Sn物种与Al2O3/MCM-41载体之间的相互作用, 提高PtSn/Al2O3/MCM-41催化剂铂金属分散度和丙烷脱氢催化活性. 并且, 积炭后的PtSn/Al2O3/MCM-41催化剂具有较高的铂金属表面裸露度, 故具有较高的丙烷脱氢反应稳定性. PtSn/Al2O3/MCM-41催化剂优良的丙烷脱氢催化性能可能不仅与Sn-载体Al2O3/MCM-41较强的相互作用有关, 而且与Al2O3/MCM-41载体的介孔结构有关.     

Methanol oxidation in acidic and alkaline electrolytes using PtRuIn/C electrocatalysts prepared by borohydride reduction process

PtRuIn/C electrocatalysts( 20% metal loading by weight) were prepared by sodium borohydride reduction process using H_2PtCl6·6H_2O,RuCl_3·xH_2O and InCl_3·xH_2O as metal sources,borohydride as reducing agent and Carbon Vulcan XC72 as support. The synthetized PtRuIn/C electrocatalysts were characterized by X-ray diffraction( XRD),energy dispersive analysis( EDX),transmission electron microscopy( TEM),cyclic voltammetry( CV),chronoamperommetry( CA) and polarization curves in alkaline and acidic electrolytes( single cell experiments). The XRD patterns showPtpeaks are attributed to the face-centered cubic( fcc) structure,and a shift of Pt( fcc) peaks indicates that Ru or In is incorporated into Ptlattice. TEMmicrographs showmetal nanoparticles with an average nanoparticle size between 2.7 and 3.5 nm. Methanol oxidation in acidic and alkaline electrolytes was investigated at room temperature,by CV and CA. PtRu/C( 50 ∶ 50) shows the highest activity among all electrocatalysts in study considering methanol oxidation for acidic and alkaline electrolyte. Polarization curves at 80 ℃ showPtRuIn/C( 50 ∶ 25 ∶ 25)with superior performance for methanol oxidation,when compared to Pt/C,PtIn/C and PtRu/C for both electrolytes. The best performance obtained by PtRuIn/C( 50 ∶ 25 ∶ 25) in real conditions could be associated with the increased kinetics reaction and/or with the occurrence simultaneously of the bifunctional mechanism and electronic effect resulting from the presence of Ptalloy.