抗甲醇中毒氧还原催化剂铂铋金属间化合物的研究

采用氩弧熔炼后热处理方法制备了PtBi金属间化合物材料.采用循环伏安和旋转圆盘电极手段进行电化学性能测试.通过在0.5mol/LH2SO4+0.25 mol/LCH3OH溶液中氧还原的起始电位和电流密度大小比较发现,与光滑铂电极相比,PtBi金属间化合物具有良好的氧还原催化性能和抗甲醇中毒性能.X射线光电子能谱(XPS)结果表明,PtBi材料中Pt的d电子空穴增加,可能是导致PtBi电极表面氧还原电流增大的原因.     

Nanocrystalline pyrochlore bonded to proton exchange membrane electrolyte as electrode material for oxygen reduction

The nanocrystalline Pb-Ru pyrochlore prepared by reverse microemulsion method has been used as the cathode electro catalyst for oxygen reduction reaction in proton exchange membrane (Nafion 117) medium. The oxide particles prepared were found to have nanosized spherical as well as filament type particles. The nanocrystalline Pb-Ru pyrochlore was found to exhibit comparable electrocatalytic activity and stability with commercial platinum catalyst, for oxygen reduction reaction.     

Symmetric growth of Pt ultrathin nanowires from dumbbell nuclei for use as oxygen reduction catalysts

This work demonstrates the synthesis of Pt ultrathin nanowires assisted by chromium hexacarbonyl [Cr(CO)₆]. The nanowires exhibit a uniform diameter of 2–3 nm. The length can reach up to several microns. It was found that Cr species produced dumbbell-like nuclei which play a pivotal role in the formation of the Pt nanowires. Such Pt nanowires can be tuned to nanocubes by simply decreasing the concentration of [Cr(CO)₆]. Compared to a commercial Pt/C catalyst (45 wt%, Vulcan, Tanaka) and Pt black (fuel cell grade, Sigma), the synthesized Pt nanowires exhibit superior performance in electrocatalytic oxygen reduction with a specific activity of 0.368 mA/cm², which was 2.7 and 1.8 times greater than that of Pt/C (0.138 mA/cm²) and Pt black (0.202 mA/cm²), respectively. The mass activity of Pt nanowires (0.088 mA/μg) is 2.3 times that of Pt black (0.038 mA/μg) and comparable to that of Pt/C (0.085 mA/μg).      

Zeolite-templated mesocellular graphene foam with adjustable defects as highly efficient catalysts for oxygen reduction reaction

In this study, zeolite-templated mesocellular graphene foam was facilely synthesized by pyrolysis under different temperatures for oxygen reduction reaction. Investigations found that MGF can be regulated with different structure properties by controlling the pyrolysis temperature, where the MGF-900 (pyrolyzed under 900 °C) possessed a large BET specific surface area (619 m² g^?1), a hierarchically micro–meso–macroporous carbon framework, and a better balance between conductivity and active sites than the other counterparts (MGF-800 and MGF-1000). As a result, MGF-900 had the most excellent catalytic activity, the most positive onset potential of ??0.1 V and the highest current density of 5.01 mA cm^?2 among the different samples and many other reported carbon-based catalysts. More importantly, despite no heterogeneous atoms doping, the catalytic activity of MGF-900 was nearly equal to that of commercial Pt/C catalyst. Regarding tolerance and stability, MGF-900 behaved even better. Therefore, as a superior metal-free electrocatalyst, MGF-900 is proved to be well applied in highly efficient oxygen reduction reaction.

     

Characterization of Pt-Cu binary catalysts for oxygen reduction for fuel cell applications

Nanostructured Pt-Cu/C alloy catalysts synthesized by a reduction procedure with different reducing agents are investigated to find the origin of the enhanced activity of the oxygen reduction reaction for fuel cell applications. Prepared catalysts are characterized by various techniques, such as energy dispersive X-ray spectrometry, X-ray diffraction, transmission electron microscopy (TEM) and cyclic voltammetry. XRD analysis shows that all prepared catalysts exhibit face-centered cubic structures and have smaller lattice parameters than pure Pt catalyst. TEM images show that the particle size of the catalysts increases with the heat treatment temperature, and that different reducing agent causes different particle size and dispersion of the binary catalysts on XC-72R. Using the polyol method with CuSO₄ as the precursor, the Pt-Cu/C sample is found to have good dispersion and high Cu loading. The Pt-Cu/C sample has a slightly higher specific activity value than that of Pt/C. The catalytic activity can be enhanced greatly with hydrogen reduction at 300 °C. Higher reduction temperatures cause the catalytic particles to agglomerate and therefore decreased catalytic activity.     

碳基非金属纳米材料用于二电子氧还原制备过氧化氢的研究进展

电催化二电子氧还原反应(2e-ORR)制备过氧化氢(H2O2)凭借其高效、安全和绿色特点,逐步发展为一种可能替代工业蒽醌法的新途径.碳基纳米材料具有电子导电性高、结构稳定性好、纳米结构调控容易、成本低等优势,是一类具有良好前景的2e-ORR制备H2O2的催化剂.针对该类碳基电催化材料的发展现状及相应材料上的活性中心和反...     

Perovskites containing ruthenium as catalysts for nitric oxide reduction

Ruthenium metal is an effective catalyst for the reduction of NO with H₂ and CO, but is volatile as RuO₄ in oxidizing atmosphere. Ru ions in the B sites of the perovskite-like ruthenates and manganites ABO₃ (A is La, Pb, Sr, K and B is Ru or Mn + up to 10 at % Ru) are shown to be very active for NO reduction. Losses of Ru by volatilization are substantially reduced. Ruthenates and Ru ions diluted in AMnO₃ have similar activities. The latter show lower NH₃ production. Substitution of 5% of the B-sites with Ni further increases the activity, but also the NH₃ yield. The mechanism of the NO reduction is discussed.     

Carbon nanotube/graphene nanocomposites built via surfactant-mediated colloid assembly as metal-free catalysts for the oxygen reduction reaction

Journal of Materials Science - The development of composites from 1D and 2D nanocarbon building blocks, namely carbon nanotubes and graphene layers, with enhanced properties or novel...     

New approach towards preparation of efficient gas diffusion-type oxygen reduction electrode

A novel method by combining NAC-FAS (NAnometer-sized Crystal Formation in Alcoholic Solutions) method and mechanical milling treatment was successfully applied for dispersing perovskite type oxide LaMnO₃ finely on carbon support. Microscopic observation revealed that nano-sized oxide particles were dispersed fairly well in the carbon support. The gas diffusion-type electrode prepared by means of reducing number and quantity of chemicals exhibited more excellent oxygen reduction activity than the electrodes containing LaMnO₃ prepared by RHP (Reverse Homogeneous Precipitation) method. It allowed current density as high as 300 mA cm⁻² at −80 mV (vs. Hg/HgO) in 8 M KOH at 60 °C under air flow.     

利用生物质材料合成高性能氢氧燃料电池氧还原催化剂（英文）

制备廉价、高活性氧还原催化剂对于发展氢氧燃料电池清洁能源极为重要.在本论文中,我们利用黑木耳作为生物质材料,通过一种便捷的方法合成了高活性氧还原催化剂.黑木耳经水热和热解两个步骤,碳化形成BF-N-950催化剂.该催化剂在酸性和碱性溶液中的半波电势分别为0.77和0.91 V.采用BF-N-950催化剂作为膜电极得到的氢氧燃料单电池,峰值功率可达255 mW cm^-2.本文提出了使用生物质材料合成高性能氧还原催化剂的方法,为氢氧燃料电池的应用提供了有益探索.     

A general strategy for bimetallic Pt-based nano-branched structures as highly active and stable oxygen reduction and methanol oxidation bifunctional catalysts

The morphology and size of Pt-based bimetallic alloys are known to determine their electrocatalytic performance in reactions relevant to fuel cells. Here, we report a general approach for preparing Pt-M (M = Fe, Co and Ni) bimetallic nano-branched structure (NBs) by a simple high temperature solution-phase synthesis. As-prepared Pt-M NBs show a polycrystalline structure and are rich in steps and kinks on the surface, which promote them favorable bifunctional catalytic properties in acidic electrolytes, specifically in terms of the oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR). Specially, Pt-Co NBs/C catalyst shows 6.1 and 5.3 times higher in specific activity (SA) and mass activity (MA) for ORR than state-of-the-art commercial Pt/C catalysts, respectively. Moreover, it exhibits a loss of 4.0% in SA and 14.4% in MA after 10,000 cycles of accelerated durability tests (ADTs) compared with the initial activities. In addition, we also confirmed the superior MOR activity of Pt-Co NBs/C catalyst in acidic electrolytes. For Pt-M NBs with other alloying metals, the ORR and MOR activities are both higher than commercial catalysts and are in the sequence of Pt-Co/C > Pt-Fe/C > Pt-Ni/C > commercial Pt/C (or PtRu/C). The improved activities and durability can benefit from the morphological and compositional effects. This synthesis approach may be applied to develop bifunctional catalysts with enhanced ORR and MOR properties for future fuel cells designs.

     

Self-supporting nanoporous gold-palladium overlayer bifunctional catalysts toward oxygen reduction and evolution reactions

The oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are crucial processes for energy conversion/storage systems, such as fuel cells, metal–air batteries, and water splitting. However, both reactions are severely restricted by their sluggish kinetics, thus requiring highly active, cost-effective, and durable electrocatalysts. Herein, we develop novel bifunctional nanocatalysts through surface nanoengineering of dealloying-driven nanoporous gold (NPG). Pd overlayers were precisely deposited onto the NPG ligament surface by epitaxial layer-by-layer growth. More importantly, the obtained NPG-Pd overlayer nanocatalysts exhibit remarkably enhanced electrocatalytic activities toward both the ORR and OER in alkaline media, benchmarked against a stateof- the-art Pt/C catalyst. The improved electrocatalytic performance is rationalized by the unique three-dimensional nanoarchitecture of NPG, enhanced Pd utilization efficiency from precise control of the Pd overlayers, and change in electronic structure, as revealed by density functional theory calculations.

Open image in new window

     

Janus electrode with simultaneous management on gas and liquid transport for boosting oxygen reduction reaction

Nano Research - Oxygen reduction efficiency holds the key for renewable energy technologies including fuel cells and metal-air batteries, which involves coupling diffusion-reaction-conduction...     

Cobalt nanoparticles as reusable catalysts for reduction of 4-nitrophenol under mild conditions

Facile reduction of p-nitrophenol to p-aminophenol by sodium borohydride catalysed by cobalt nanoparticles (CoNPs) has been discussed. A simple approach has been made to synthesize highly active and ordered structures of CoNPs. The air-stable nanoparticles were prepared from cobalt sulphate using tetrabutyl ammonium bromide as surfactant and sodium borohydride as reductant. The cobalt nanocolloids in aqueous medium were found to be efficient reusable catalysts for the p-nitrophenol reduction. Palladium nanoparticles prepared from palladium chloride and the same surfactant were found to reduce p-nitrophenol but lose their catalytic efficiency after recovery. Based on chemical and kinetic studies, an attempt has been made to elucidate the mechanism of p-nitrophenol reduction using these nanoclusters.     

Designing three-dimensional hierarchical porous chrysanthemum flower-like CoNiFe2O4/carbon spheres as high-performance electrode for supercapacitors and oxygen reduction reaction

Journal of Materials Science: Materials in Electronics - Novel three-dimensional electrode materials with high capacitance, long cycle stability and electrocatalytic activity are designed through...     

Inside-out dual-doping effects on tubular catalysts:Structural and chemical variation for advanced oxygen reduction performance

Dual-doping of carbon,especially the combination of nitrogen and a secondary heteroatom,has been demonstrated efficient to optimize the oxygen reduction reaction(ORR)performance.However,the optimum dual-doping is still not clear due to the lack of strong experimental proofs,which rely on a reliable method to prepare carbon materials that can rule out the interference factors and then emphasize only the doping effects.In this work,an inside-out doping method is reported to prepare carbon submicrotubes(CSTs)as a material to study the principles of designing dual-doping catalysts for ORR.The interference factors including the metal impurities and doping gradient in the bulk phase are excluded,and the doping effects including the structural and chemical variation of carbon are studied.P-doping exhibited a higher pore-forming ability to perforate carbon and a lower doping content,but a higher ORR catalytic activity as compared with S-and B-doped N-CSTs,demonstrating the N,P co-doping is more efficient in making carbon-based catalysts for ORR.First-principle calculations reveal that the edge C situated around the oxidized P site nearby a graphitic N atom is the active site that shows the lowest ORR overpotential comparable to Pt-based catalysts.This study suggests that the catalytic activity of dual-heteroatoms-doped carbons not only depends on the intrinsic chemical bonding between heteroatoms and carbon,but also is affected by the structural variation generated by introducing different atoms,which can be extended to the study of other kinds of functionalization of carbon and potential reactions besides ORR.     

Active catalysts based on cobalt oxide@cobalt/N-C nanocomposites for oxygen reduction reaction in alkaline solutions

Over the past few years, electrocatalysis for the oxygen reduction reaction in alkaline solutions has undergone tremendous advances, and non-precious metal catalysts are of prime interest. In this study, we present a highly promising CoO@Co/N-C （where N-C represents a N-doped carbon material） catalyst, achieving an onset potential of 0.99 V （versus the reversible hydrogen electrode （RHE）） and a limiting current density of 7.07 mA-cm-2 （at 0.3 V versus RHE） at a rotation rate of 2,500 rpm in an O2-saturated 0.1 M KOH solution, comparable to a commercial Pt/C catalyst. The H2--O2 alkaline fuel cell test of CoO@Co/N-C as the cathode reveals a maximum power density of 237 mW.cm 2. Detailed investigation clarifies that a synergistic effect, induced by C-N, Co-N-C, and CoO/Co moieties, is responsible for the bulk of the gain in catalytic activity.     

Carboxyl groups trigger the activity of carbon nanotube catalysts for the oxygen reduction reaction and agar conversion

Ozone treatment is a common way to functionalize commercial multi-walled carbon nanotubes (CNTs) with various oxygen functionalities like carboxyl, phenol and lactone groups, in order to enhance their textural properties and chemical activity. In order to detail the effect of each functional group, we correlated the activity with the surface density of each group, and found that the carboxyl groups play a pivotal role in two important catalytic reactions, namely the electrochemical oxygen reduction reaction (ORR) and agar conversion to 5-hydroxymethylfurfural (HMF). During the processes, the hydrophilic surface provides a strong affinity for reaction substrates while the improved porosity allows the efficient diffusion of reactants and products. Furthermore, the activity of functionalized CNTs for agar conversion remained almost unchanged during nine cycles of reaction. This work highlights a strategy for improving the activity of CNTs for electrochemical ORR and agar conversion reactions, as well a promising application of carboxyl-rich CNTs as a solid acid catalyst to produce high-purity HMF—an important chemical intermediate.

Open image in new window