Single-crystalline C60 nanostructures by sonophysical preparation: tuning hollow nanobowls as catalyst supports for methanol oxidation

Large-scale single-crystalline hollow nanobowls of pure C(60) were prepared by applying a sonophysical strategy in a binary organic solution. Through the simple adjustment of the concentration of the C(60) /m-xylene solution and the volume ratio of m-xylene to acetonitrile, C(60) nanorings, nanoplates, nanorods, and nanowires were also selectively synthesized. The promise of the C(60) hollow structures as Pt catalyst supports is heightened by the significantly enhanced catalytic activity toward methanol oxidation for a given amount of C(60) used, which demonstrates their potential application in fuel cells.     

Dealloying to Nanoporous Silver and Its Implementation as a Template Material for Construction of Nanotubular Mesoporous Bimetallic Nanostructures

Nanoporous silver (NPS) is fabricated by selectively dissolving Al from AgAl alloys in corrosive electrolytes at room temperature. Electron spectroscopy characterizations demonstrate that the NaOH electrolyte is beneficial to the formation of a three‐dimensional bicontinuous porous nanostructure with uniform and tunable pore and ligament dimensions of a few tens of nanometers, while processing in HCl electrolyte easily lead to coarsened porous nanostructures. The high‐surface‐area Ag nanostructures are demonstrated as novel effective template materials to the construction of nanotubular mesoporous Pt/Ag and Pd/Ag alloy structures, which are realized via room temperature galvanic replacement reactions with H₂PtCl₆ and K₂PdCl₄ solutions by adding a high concentration of Cl^? ions as a coordinating agent. Electrochemical measurements indicate that the resulting hollow and porous bimetallic nanostructures show enhanced electrocatalytic activities and CO‐tolerance with better durability toward methanol and formic acid oxidation due to alloying with Ag.     

Binding maps for the study and prediction of bimetallic catalyst surface reactions: The case of methanol oxidation

Focusing on the competing pathways of methanol oxidation on platinum and platinum/gold bimetallic catalysts, we explore a novel density functional theory (DFT)‐based approach to the study of reactions on catalyst surfaces. Traditionally, DFT has been used to compute binding energies of products and intermediates as proxies for catalytic activity, and to compute full reaction pathways and their activation energy barriers. Merging the computational simplicity and intuitive clarity of binding energy calculations with the site sensitivity of transition state calculations, we construct maps of the binding energies of relevant atoms and molecules at all sites on a surface. We show that knowledge of the arrangement of strong and weak binding sites on a surface is powerful in rationalizing the ease with which a reaction step proceeds on a given local motif of surface atoms. We highlight the prospects and challenges of this approach toward catalyst screening and prediction.     

Direct‐methanol Fuel Cell Based on Functionalized Graphene Oxide with Mono‐metallic and Bi‐metallic Nanoparticles: Electrochemical Performances of Nanomaterials for Methanol Oxidation

The catalysts based on 2‐aminoethanethiol functionalized graphene oxide (AETGO) with several mono‐metallic and bi‐metallic nanoparticles such as rod gold (rAuNPs), rod silver (rAgNPs), rod gold‐platinum (rAu‐Pt NPs) and rod silver‐platinum (rAg‐Pt NPs) were synthesized. The successful synthesis of nanomaterials was confirmed by various methods. The effective surface area (ESA) of the rAu‐Pt NPs/AETGO is 1.44, 1.64 and 2.40 times higher than those of rAg‐Pt NPs/AETGO, rAuNPs/AETGO and rAgNPs/AETGO, respectively, under the same amount of Pt. The rAu‐Pt NPs/AETGO exhibited a higher peak current for methanol oxidation than those of comparable rAg‐Pt NPs/AETGO under the same amount of Pt loading.     

中空树枝状三氧化钨载铂催化剂对甲醇的电催化氧化性能研究

采用水热法和牺牲模板法相结合制备具有中空树枝结构的三氧化钨载体(d-WO₃),在其表面进一步负载活性成分Pt,得到纳米Pt/d-WO₃复合催化剂。采用X射线粉末衍射(XRD)、透射电镜(TEM)和比表面积和孔结构分析(BET)等对催化剂的形貌和结构进行了表征。结果表明,三氧化钨具有长6 μm和宽2 μm的中空树枝状结构,孔径分布主要集中在20~120 nm,比表面积为24 m²/g,平均粒径为7.2 nm的Pt纳米粒子均匀分布在其表面。采用循环伏安和计时电流法研究了Pt/d-WO₃催化剂在酸性溶液中对甲醇的电催化氧化性能。结果表明,Pt/d-WO₃催化剂比Pt/C和Pt/WO₃催化剂对甲醇有更高的电催化氧化活性和稳定性。d-WO₃所具有的中空介孔结构和双功能作用机理有利于甲醇在铂表面的直接脱氢氧化过程。     

高分散在氮掺杂碳纳米管表面铂纳米粒子的高效甲醇电氧化性能

以氮掺杂碳纳米管（NCNT）为载体,利用掺杂氮原子的锚定作用,通过微波辅助乙二醇还原法方便地将Pt纳米粒子高分散地固载于NCNT表面,制得了Pt/NCNT系列催化剂,对催化剂制备规律、电催化甲醇氧化反应（MOR）性能及构效关系开展了系统深入的研究。结果表明,随Pt负载量在18.2%~58.7%（w/w,下同）范围增加,Pt纳米粒子的粒径在2.2~3.7 nm范围相应地逐渐增大。单位质量催化剂的MOR催化活性先增加后急剧减小,在负载量为47.8%时达到最大。Pt的质量比活性在中等负载量（27.6%~47.8%）区间出现高值平台。该变化规律源于Pt纳米粒子的MOR催化活性在3 nm前后的明显差异,即<3 nm时活性差,>3 nm时活性优异。高负载量（58.7%）时活性的急剧下降源于Pt纳米粒子因团聚引起的Pt利用率的降低。     

One‐Pot Self‐Templating Synthesis of Pt Hollow Nanostructures and Their Catalytic Properties for CO Oxidation

Nanoporous Pt hollow nanostructures with octahedral and hexagonal frame‐like morphologies were prepared by a novel one‐pot self‐templating route with no assistance from a preformed template or shape‐directing agent. The hexagonal frame‐like Pt hollow structures exhibited significantly enhanced catalytic activity toward CO oxidation reaction compared to the octahedral Pt hollow nanostructures due to the higher oxidation state of Pt.     

A general method for the synthesis of nanostructured large-surface-area materials through the self-assembly of functionalized nanoparticles

A general synthetic method for the preparation of nanostructured materials with large surface area was developed by using nanoparticle building blocks. The preparation route involves the self-assembly of functionalized nanoparticles in a liquid-crystal phase. These nanoparticles are functionalized by using difunctional amino acid species to provide suitable interactions with the template. Optimum interactions for self-assembly of the nanoparticles in the liquid-crystal phase were achieved with one -NH2 group anchored to the nanoparticle surface per 25 A(2). To maximize the surface area of these materials, the wall thicknesses are adjusted so that they are composed of a monolayer of nanoparticles. To form such materials, numerous parameters have to be controlled such as the relative volume fraction of the nanoparticles and the template and size matching between the hydrophilic component of the copolymer and nanoparticles. The surface functionalization renders our synthetic route independent of the nanoparticles and allows us to prepare a variety of nanostructured composite materials that consist of a juxtaposition of different discrete oxide nanoparticles. Examples of such materials include CeO2, ZrO2, and CeO2-Al(OH)3 composites.     

A spontaneous combustion reaction for synthesizing Pt hollow capsules using colloidal carbon spheres as templates

Here we report a spontaneous combustion reaction in synthesizing Pt hollow capsules. In brief, Pt nanoparticles were loaded on the surface of colloidal carbon spheres by wet-chemical impregnation. When Pt-loaded carbon spheres were taken out of an argon-filled tube furnace at room temperature and exposed to air, they underwent spontaneous combustion. The internal carbon spheres templates were removed to leave nanostructured Pt hollow capsules. There are at least two critical conditions for the occurrence of the spontaneous combustion: the Pt particle size is below 5.8 nm, and the hydrogen content in the carbon spheres is above 2.570 wt %. Such a reaction is interesting for the preparation of metal hollow spheres and is also relevant with respect to removal of accumulated carbon on catalysts and for soot oxidation at room temperature.     

Carbon Monoxide Oxidation on Pt Single Crystal Electrodes: Understanding the Catalysis for Low Temperature Fuel Cells

Herein the general concepts of fuel cells are discussed, with special attention to low temperature fuel cells working in alkaline media. Alkaline low temperature fuel cells could well be one of the energy sources in the next future. This technology has the potential to provide power to portable devices, transportation and stationary sectors. With the aim to solve the principal catalytic problems at the anode of low temperature fuel cells, a fundamental study of the mechanism and kinetics of carbon monoxide as well as water dissociation on stepped platinum surfaces in alkaline medium is discussed and compared with those in acidic media. Furthermore, cations involved as promoters for catalytic surface reactions are also considered. Therefore, the aim of the present work is not only to provide the new fundamental advances in the electrocatalysis field, but also to understand the reactions occurring at fuel cell catalysts, which may help to improve the fabrication of novel electrodes in order to enhance the performance and to decrease the cost of low temperature fuel cells.