One‐Pot Synthesis and Electrocatalytic Properties of Pd@Pt Core‐Shell Nanocrystals with Tailored Morphologies

Pd@Pt core‐shell nanocrystals consisting of well‐defined Pd nanocube cores and dendritic Pt shells were prepared by a new facile aqueous one‐pot synthetic method. The prepared Pd@Pt nanocrystals exhibited efficient catalytic activity and stability toward methanol electrooxidation, and their catalytic function was highly dependent on their Pt shell thickness due to the different synergism between Pt and Pd.     

Platinum–Copper Nanoframes: One‐Pot Synthesis and Enhanced Electrocatalytic Activity

Platinum–copper nanoframes were produced from copper nanoparticles by a one‐pot synthesis method. The growth mechanism was thoroughly studied by experiment and theoretical calculations. Owing to the unique structure, Pt‐Cu nanoframes exhibited significantly enhanced catalytic activity toward the electro‐oxidation of methanol compared to commercial Pt black.     

Excavated Cubic Platinum–Tin Alloy Nanocrystals Constructed from Ultrathin Nanosheets with Enhanced Electrocatalytic Activity

Excavated polyhedral noble‐metal materials that were built by the orderly assembly of ultrathin nanosheets have both large surface areas and well‐defined facets, and therefore could be promising candidates for diverse important applications. In this work, excavated cubic Pt–Sn alloy nanocrystals (NCs) with {110} facets were constructed from twelve nanosheets by a simple co‐reduction method with the assistance of the surface regulator polyvinylpyrrolidone. The specific surface area of the excavated cubic Pt–Sn NCs is comparable to that of commercial Pt black despite their larger particle size. The excavated cubic Pt–Sn NCs exhibited superior electrocatalytic activity in terms of both the specific area current density and the mass current density towards methanol oxidation.     

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.     

Pt‐Pd‐Co Trimetallic Alloy Network Nanostructures with Superior Electrocatalytic Activity towards the Oxygen Reduction Reaction

Pt alloy nanostructures show great promise as electrocatalysts for the oxygen reduction reaction (ORR) in fuel cell cathodes. Herein, three‐dimensional (3D) Pt‐Pd‐Co trimetallic network nanostructures (TNNs) with a high degree of alloying are synthesized through a room temperature wet chemical synthetic method by using K₂PtCl₄/K₃Co(CN)₆–K₂PdCl₄/K₃Co(CN)₆ mixed cyanogels as the reaction precursor in the absence of surfactants and templates. The size, morphology, and surface composition of the Pt‐Pd‐Co TNNs are investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected‐area electron diffraction (SAED), energy dispersive spectroscopy (EDS), EDS mapping, X‐ray diffraction (XRD), and X‐ray photoelectron spectroscopy (XPS). The 3D backbone structure, solid nature, and trimetallic properties of the mixed cyanogels are responsible for the 3D structure and high degree of alloying of the as‐prepared products. Compared with commercially available Pt black, the Pt‐Pd‐Co TNNs exhibit superior electrocatalytic activity and stability towards the ORR, which is ascribed to their unique 3D structure, low hydroxyl surface coverage and alloy properties.     

A Facile One‐Pot Synthesis and Enhanced Formic Acid Oxidation of Monodisperse Pd–Cu Nanocatalysts

Highly monodisperse spherical 3 nm Pd–Cu alloy nanoparticles (NPs) were synthesized in high yield through the coreduction of [Pd(acac)₂] (acac=acetylacetonate) and [Cu(acac)₂] in nonhydrolytic solutions by using trioctylamine and oleic acid. The relative compositions of Pd and Cu could be tuned by controlling the molar ratios between the metal precursors in the raw solutions. The carbon‐supported Pd–Cu NPs (Pd–Cu/C) were chemically dealloyed by acetic acid washing, which resulted in the formation of porous structures. The prepared Pd–Cu/C catalysts exhibited at least threefold enhancement of Pd mass activities compared with a commercial Pd/C catalyst toward formic acid oxidation in an acidic medium, and also showed outstanding electrocatalytic stabilities. The improved electrocatalytic properties of the Pd–Cu NPs are attributed to the presence of a large number of active sites on their surfaces owing to their small particle sizes and chemically dealloyed porous structures.     

One‐Step Synthesis of Self‐Supported Nickel Phosphide Nanosheet Array Cathodes for Efficient Electrocatalytic Hydrogen Generation

Nickel phosphide is an emerging low‐cost, earth‐abundant catalyst that can efficiently reduce water to generate hydrogen. However, the synthesis of nickel phosphide catalysts usually involves multiple steps and is laborious. Herein, a convenient and straightforward approach to the synthesis of a three‐dimensional (3D) self‐supported biphasic Ni₅P₄‐Ni₂P nanosheet (NS) array cathode is presented, which is obtained by direct phosphorization of commercially available nickel foam using phosphorus vapor. The synthesized 3D Ni₅P₄‐Ni₂P‐NS array cathode exhibits outstanding electrocatalytic activity and long‐term durability toward the hydrogen evolution reaction (HER) in acidic medium. The fabrication procedure reported here is scalable, showing substantial promise for use in water electrolysis. More importantly, the approach can be readily extended to synthesize other self‐supported transition metal phosphide HER cathodes.     

Solution‐Based Evolution and Enhanced Methanol Oxidation Activity of Monodisperse Platinum–Copper Nanocubes

Shape‐controlled catalysis : High‐quality Pt–Cu nanocubes with an average size of about 8 nm (see picture, scale bar=20 nm) were synthesized from a high‐temperature organic solution system in the presence of various capping ligands. These cubic Pt–Cu nanocrystals terminated with {100} facets demonstrated a superior catalytic activity towards methanol oxidation compared to similar sized Pt–Cu and Pt nanospheres.

     

High Electrocatalytic Activity of Pt–Pd Binary Spherocrystals Chemically Assembled in Vertically Aligned TiO2 Nanotubes

To obtain noble metal catalysts with high efficiency, long‐term stability, and poison resistance, Pt and Pd are assembled in highly ordered and vertically aligned TiO₂ nanotubes (NTs) by means of the pulsed‐current deposition (PCD) method with assistance of ultrasonication (UC). Here, Pd serves as a dispersant which prevents agglomeration of Pt. Thus Pt–Pd binary catalysts are embed into TiO₂ NTs array under UC in sunken patterns of composite spherocrystals (Sps). Owing to this synthesis method and restriction by the NTs, the these catalysts show improved dispersion, more catalytically active sites, and higher surface area. This nanotubular metallic support material with good physical and chemical stability prevents catalyst loss and poisoning. Compared with monometallic Pt and Pd, the sunken‐structured Pt–Pd spherocrystal catalyst exhibits better catalytic activity and poison resistance in electrocatalytic methanol oxidation because of its excellent dispersion. The catalytic current density is enhanced by about 15 and 310 times relative to monometallic Pt and Pd, respectively. The poison resistance of the Pt–Pd catalyst was 1.5 times higher than that of Pt and Pd, and they show high electrochemical stability with a stable current enduring for more than 2100 s. Thus, the TiO₂ NTs on a Ti substrate serve as an excellent support material for the loading and dispersion of noble metal catalysts.     

One‐Pot Synthesis of Carbon‐Supported Dendritic Pd‐Au Nanoalloys for Electrocatalytic Ethanol Oxidation

One‐pot synthesis of carbon‐supported Pd‐Au alloy nanoparticles with well‐defined dendritic shape (Pd‐Au_den/C) was achieved by co‐reduction of K₂PdCl₄/HAuCl₄ mixtures in a molar ratio of 1:1 with hydrazine in the presence of Vulcan XC‐72R. The prepared Pd‐Au_den/C exhibited significantly enhanced performance in the electrocatalytic oxidation of ethanol compared with dendritic Pd nanoparticles and a commercial Pd/C catalyst. Pd‐Au_den/C even showed higher durability in electro‐oxidation of ethanol than the supported catalyst prepared by the deposition of presynthesized dendritic Pd‐Au nanoparticles on the carbon support. The experimental results clearly indicate that enhanced interaction between nanoparticle catalysts and carbon support through the one‐pot synthesis protocol can improve the durability of the electrocatalysts.     

One‐Pot Solvothermal Synthesis of Highly Water‐Dispersible Size‐Tunable Functionalized Magnetite Nanocrystal Clusters for Lipase Immobilization

A facile one‐pot synthesis of highly water‐dispersible size‐tunable magnetite (Fe₃O₄) nanocrystal clusters (MNCs) end‐functionalized with amino or carboxyl groups by a modified solvothermal reduction reaction has been developed. Dopamine and 3,4‐dihydroxyhydroxycinnamic acid were used for the first time as both a surfactant and interparticle linker in a polylol process for economical and environment‐friendly purposes. Morphology, chemical composition, and magnetic properties of the prepared particles were investigated by several methods, including FESEM, TEM, XRD, XPS, Raman, FTIR, TGA, zeta potential, and VSM. The sizes of the particles could be easily tuned over a wide range from 175 to 500 nm by varying the surfactant concentration. Moreover, ethylene glycol/diethylene glycol (EG/DEG) solvent mixtures with different ratios could be used as reductants to obtain the particles with smaller sizes. The XRD data demonstrated that the surfactants restrained the crystal growth of the grains. The nanoparticles showed superior magnetic properties and high colloidal stability in water. The cytotoxicity results indicated the feasibility of using the synthesized nanocrystals in biology‐related fields. To estimate the applicability of the obtained MNCs in biotechnology, Candida rugosa lipase was selected for the enzyme immobilization process. The immobilized lipase exhibited excellent thermal stability and reusability in comparison with the free enzyme. This novel strategy would simplify the reaction protocol and improve the efficiency of materials functionalization, thus offering new potential applications in biotechnology and organocatalysis.     

One‐Pot Hydrothermal Synthesis of Heterostructured ZnO/ZnS Nanorod Arrays with High Ethanol‐Sensing Properties

ZnO/ZnS heterostructured nanorod arrays with uniform diameter and length were synthesized from zinc substrates in a one‐pot procedure by using a simple hydrothermal method. Structural characterization by HRTEM indicated that the heterostructured nanorods were composed of parallel segments of wurtzite‐type ZnO and zinc‐blende ZnS, with a distinct interface along the axial direction, which revealed the epitaxial relationship, ZnO (10$\bar 1$ 0) and ZnS ($\bar 1$ 1$\bar 1$ ). The as‐prepared ZnO/ZnS nanorods showed only two green emissions at around 523 nm and 576 nm. We also found that the nanorods exhibited high sensitivity to ethanol at relatively low temperatures, owing to their smaller size and structure.     

Simplifying the Creation of Hollow Metallic Nanostructures: One‐Pot Synthesis of Hollow Palladium/Platinum Single‐Crystalline Nanocubes

Efficiency simplified : A synthetic strategy has been developed to prepare single‐crystalline hollow Pd/Pt nanocubes (right, see picture; left: nanocubes). Compared to the solid Pd/Pt nanocubes of similar sizes, the hollow Pd/Pt nanocubes increase accessible surface area and therefore improve electrocatalytic activity in formic acid oxidation.

     

One‐Pot Template‐Free Synthesis of Monodisperse Zinc Sulfide Hollow Spheres and Their Photocatalytic Properties

Little hollow! Monodisperse ZnS hollow nanospheres (see figure) of about 200 nm in size have been fabricated on a large scale by a hydrothermal method and they show good photocatalytic activity in the decolorization of an aqueous solution of rhodamine B under UV irradiation.