Displacement Plating of a Mesoporous Pt Skin onto Co Nanochains in a Low-Concentration Surfactant Solution

Pt-Co Alloy Nanoparticles on a γ-Al2 O3 Support: Synergistic Effect between Isolated Electron-Rich Pt and Co for Automotive Exhaust Purification

There is interest in minimizing or eliminating the use of Pt in catalysts by replacing it with more widely abundant and cost-effective elements. The alloying of Pt with non-noble metals is a potential strategy for reducing Pt use because interactions between Pt and non-noble metals can modify the catalyst structure and electronic properties. Here, a γ-Al₂ O₃ -supported bimetallic catalyst [Pt(0.1)Co(1)/Al₂ O₃ ] was prepared which contained 0.1 wt % Pt and 1 wt % Co and thus featured an extremely low Pt : Co ratio (<1 : 30 mol/mol). The Pt and Co in this catalyst formed alloy nanoparticles in which isolated electron-rich Pt atoms were present on the nanoparticle surface. The activity of this Pt(0.1)Co(1)/Al₂ O₃ catalyst for the purification of automotive exhaust was comparable to the activities of 0.3 and 0.5 wt % Pt/γ-Al₂ O₃ catalysts. Electron-rich Pt and metallic Co promoted activation of NO_x and oxidization of CO and hydrocarbons, respectively. This strategy of tuning the surrounding structure and electronic state of a noble metal by alloying it with an excess of a non-noble metal will enable reduced noble metal use in catalysts for exhaust purification and other environmentally important reactions.

A facile solvothermal synthesis of Pt1.2Co/C bimetallic nanocrystals as efficient electrocatalysts for methanol oxidation and hydrogen evolution reaction

A bimetallic alloyed Pt_1.2Co/C catalyst, which exhibited superior electrocatalytic performance for both MOR and HER, was synthesized by a one-pot solvothermal approach.

Self-standing hollow porous AuPt nanospheres and their enhanced electrocatalytic performance

In this paper, we present a template method to fabricate AuPt hollow nanospheres by depositing Au inner layer and dendritic Pt outer layer onto PS template. The as-prepared AuPt hollow nanospheres can form self-standing hollow nanostructures under thermal treatment which is confirmed by small-angle X-ray scattering results. We believe that the self-standing structural features of them result from different thermal stability of Au and Pt elements. The small-angle X-ray diffraction measurements and X-ray photoelectron spectroscopy of binding energies certify the existing interaction between Au and Pt. It is suggested that Pt mole contents of AuPt hollow nanospheres can be varied by changing H₂PtCl₄ concentration during chemical deposition process. The methanol electrochemical oxidation reaction indicates these as-prepared AuPt hollow nanospheres possessing excellent potential applications on catalysts. Moreover, synthesis of multilayer hollow porous nanospheres such as Pt@Au@Pt proves that our method greatly enriches the species of the self-standing, hollow and porous functional nanomaterials.

Controlled Synthesis of PtNi Hexapods for Enhanced Oxygen Reduction Reaction

Well-defined PtNi nanocrystals represent one of the most efficient electrocatalysts to boost the oxygen reduction reaction (ORR), especially in the shape of octahedrons, nanoframes, and nanowires. However, the synthesis of complex PtNi nanostructure is still a great challenge. Herein, we report a new class of PtNi hexapods with high activity and stability toward ORR. The hexapods are prepared by selective capping and simultaneous corrosion. By controlling the oxidative etching, PtNi polyhedrons and nanoparticles are obtained, respectively. The intriguing hexapods are composed of six nanopods with an average length of 12.5 nm. Due to their sharp tips and three-dimensional (3D) accessible surfaces, the PtNi hexapods show a high mass activity of 0.85 A mg Pt - 1 at 0.9 V vs. RHE, which are 5.4-fold higher than commercial Pt/C, also outperforming PtNi polyhedrons and PtNi nanoparticles. In addition, the mass activity of PtNi hexapods maintains 92.3% even after 10,000 potential cycles.

Dendritic Ternary Alloy Nanocrystals for Enhanced Electrocatalytic Oxidation Reactions

Engineering the morphology and composition of multimetallic nanocrystals composed of noble and 3d transition metals has been of great interest due to its high potential to the development of high-performance catalytic materials for energy and sustainability. In the present work, we developed a facile aqueous approach for the formation of homogeneous ternary alloy nanocrystals with a dendritic shape, Pt-Pd-Cu nanodendrites, of which synthesis is hard to be achieved because of synthetic difficulties. Proper choice of stabilizer and fine control over the amount of stabilizer and reductant allowed the successful formation of Pt-Pd-Cu nanodendrites with controlled sizes and compositions. The prepared ternary alloy nanodendrites exhibited considerably improved electrocatalytic performance toward methanol and ethanol oxidation reactions compared to their binary alloy counterparts and commercial Pt and Pd catalysts, as well as to previously reported Pt- and Pd-based nanocatalysts because of synergism between their morphological and compositional characteristics. We anticipate that the present approach will be helpful to develop efficient electrocatalysis systems for practical applications.

Synthesis of sub-nanosized Pt particles on mesoporous SBA-15 material and its application to the CO oxidation reaction

In this work, we show that the size and shape of Pt nanoparticles in SBA-15 can be controlled through vacuum and air calcination. The vacuum-calcination/H2-reduction process is used to thermally treat a 0.2 wt% Pt(4+)/SBA-15 sample to obtain small 2D clusters and single atoms that can significantly increase Pt dispersion in SBA-15. Compared with thermal treatments involving air-calcination/H2-reduction, which result in ∼4.6 nm rod-like Pt particles, vacuum-calcination/H2-reduction can dramatically reduce the size of the Pt species to approximately 0.5-0.8 nm. The Pt particles undergoing air-calcination/H2-reduction have poor conversion efficiency because the fraction of terrace sites, the major sites for CO oxidation, on the rod-like Pt particles is small. In contrast, a large amount of low-coordinated Pt sites associated with 2D Pt species and single Pt atoms in SBA-15 is effectively generated through the vacuum-calcination/H2-reduction process, which may facilitate CO adsorption and induce strong reactivity toward CO oxidation. We investigated the effect of vacuum-calcination/H2-reduction on the formation of tiny 2D clusters and single atoms by characterizing the particles, elucidating the mechanism of formation, determining the active sites for CO oxidation and measuring the heat of CO adsorption.

Preparation of a platinum electrocatalyst by coaxial pulse arc plasma deposition

We have developed a new method of preparing Pt electrocatalysts through a dry process. By coaxial pulse arc plasma deposition (CAPD), highly ionized metal plasma can be generated from a target rod without any discharged gases, and Pt nanoparticles can be deposited on a carbon support. The small-sized Pt nanoparticles are distributed over the entire carbon surface. From transmission electron microscopy (TEM), the average size of the deposited Pt nanoparticles is estimated to be 2.5 nm, and their size distribution is narrow. Our electrocatalyst shows considerably improved catalytic activity and stability toward methanol oxidation reaction (MOR) compared with commercially available Pt catalysts such as Pt black and Pt/carbon (PtC). Inspired by its very high efficiency toward MOR, we also measured the catalytic performance for oxygen reduction reaction (ORR). Our PtC catalyst shows a better performance with half-wave potential of 0.87 V, which is higher than those of commercially available Pt catalysts. The higher performance is also supported by a right-shifted onset potential. Our preparation is simple and could be applied to other metallic nanocrystals as a novel platform in catalysis, fuel cells and biosensors.

Ultralong mesoporous ZnO nanowires grown via room temperature self-assembly of ZnO nanoparticles for enhanced reversible storage in lithium ion batteries

Template-free synthesis of ultralong mesoporous ZnO nanowires (up to 50 μm) was developed. Compared to ZnO powder, the obtained porous ZnO nanowires show enhanced reversible storage as lithium ion battery anodes.

Synthesis and characterization of Pt nanoparticles with different morphologies in mesoporous silica SBA-15 for methanol oxidation reaction

Mesoporous SBA-15 silica materials functionalized with and without carboxylic acid groups were used to effectively control the morphology of Pt crystals, and the materials thus obtained were applied to methanol oxidation reactions. The Pt particles aggregated to form long spheroids inside the channels in pure SBA-15. When carboxylic acid groups were utilized, the SBA-15(-COOH) material facilitated the formation of higher Pt surface area, smaller Pt nanoparticles and nearly spherical shape due to the strong interaction between Pt(4+) ions and carboxylic acid on SBA-15. The Pt(4+) ions on the SBA-15(-COOH) material can be directly transformed to reduced Pt particles during calcination. The methanol oxidation activity on a Pt surface is strongly dependent on the shape of Pt particles. The near-spherical Pt nanoparticles on the SBA-15(-COOH) exhibited higher catalytic activity during methanol oxidation than Pt catalysts on unmodified SBA-15. The near-spherical Pt particles on the SBA-15(-COOH) contained large numbers of terrace sites on their surfaces, which led to high efficiency during methanol oxidation.