Three-dimensional Pd@Pt core−shell nanostructures with controllable shape and composition were synthesized by using a one-step microwave heating method. The nanostructures with the morphology, structure, and composition being easily controlled through adjusting the molar ratio between Pt and Pd precursor were characterized by transmission electronic microscopy (TEM), scanning electronic microscopy (SEM), X-ray powder diffraction (XRD), and energy-dispersive X-ray (EDX) techniques. In addition, the electrocatalytic characteristics of these prepared Pd@Pt electrocatalysts with different Pd/Pt molar ratio for oxygen electro-reduction reaction (ORR) and methanol electro-oxidation reaction (MOR) were systematically investigated by voltammetry. The results show that Pd@Pt electrocatalysts exhibit higher catalytic activity than pure Pd and pure Pt catalysts for both the ORR and MOR, and the highest activity is obtained at the Pd@Pt electrocatalyst with a Pd/Pt molar ratio of 1:3. This result demonstrates that a higher performance of ORR and MOR could be realized at the novel core−shell electrocatalyst while Pt utilization also could be diminished. This method may open a general approach for the shape-controlled synthesis of bimetallic Pt−M nanocatalysts, which can be expected to have promising applications in fuel cells.

close-packed structures with lower surface energy and anisotropy, leading to great challenges in stabilizing and synthesizing 2D noble metal nanomaterials. To this end, a variety of synthetic strategies, such as hard-template-directed synthesis, capping-agent-assisted synthesis, and secondary assembly methods, have been developed for the synthesis of 2D noble metal-based nanostructures. [2] As one of the alternatives, self-assembly from 0D or 1D primary building blocks has been identified as a sophisticated and reliable approach for the generation of 2D noble metal nanostructures. [3] Ultrathin noble metal nanowires with high surface-tovolume ratios and atom utilization efficiency hold promising applications in widespread fields, including catalysis, optics devices, and biomedicine, etc. [4] Rational engineering of 1D nanowires into 2D nanosheets may bring about many novel structural characteristics, including high porosity, large area per unit volume, good flexibility, and an interconnected open pore structure. [5] Therefore, succinct-operated and controllable synthesis of ultrathin free-standing 2D nanosheets with 1D primary building blocks would be of great significance for fundamental scientific interest and technological applications, yet still remains greatly challenging.Herein, for the first time, we present a novel and facile one-pot, simultaneous stepwise self-assembly approach for the synthesis of freestanding porous Pd nanosheets (≈2.5 µm in lateral size and 10 nm in thickness) with the assistance of a functional polymer, poly(diallyldimethylammonium chloride) (PDDA; Figure S1, Supporting Information). Essentially, the obtained porous Pd nanosheets are flexibly knitted by numerous interweaved ultrathin nanowires. Different from the previously reported 2D noble metal nanosheets with smooth surface, [6,7] the obtained Pd nanosheets with large porosity and rough surface are achieved by particle spontaneous attachment and subsequent self-assembly in the one-pot synthesis process. To the best of our knowledge, this is the first report that the construction of 2D sheet-like Pd porous nanostructures through such a simple and efficient approach so far, and the elaborate adoption of eco-friendly PDDA as a structuredirecting agent also plays a crucial role in the formation of the Freestanding ultrathin 2D noble metal nanosheets have drawn enormous attention due to their potential applications in various fields. However, the synthesis of 2D noble metal nanosheets still remains a great challenge due to the lack of an intrinsic driving force for anisotropic growth of 2D structures. Here, a facile one-pot synthesis of ultrathin freestanding porous Pd nanosheets (≈2.5 µm in lateral size and 10 nm in thickness) flexibly knitted by interweaved ultrathin nanowires with the assistance of poly(diallyldimethylammonium chloride) is presented. Nanoparticles attachment and subsequent self-assembly in the synthetic process are responsible for the formation of such intriguing nanostructures. Moreover, finely controlling the p...

The synthesis of Pt nanocrystals with controlled size and morphology has drawn enormous interest due to their particular catalytic activity. We present a facile and green hydrothermal method for synthesizing monodisperse Pt nanocubes (Pt-NCs) with polyallylamine hydrochloride (PAH) as a complex-forming agent, capping agent and facet-selective agent, and formaldehyde as a reductant. The formation mechanism, particle size and surface composition of the Pt-NCs were investigated by Ultraviolet and visible spectroscopy (UV-vis), Fourier transform infrared (FT-IR), transmission electron microscopy (TEM), selected area electron diffraction (SAED), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS), etc. In the proposed PAH-K(2)PtCl(4)-HCHO synthesis system, the raw material could be reutilized to re-synthesize the Pt-NCs, and the particle size of the Pt-NCs could be readily controlled by the reduction rate of the Pt(II) species in the Pt(II)-PAH complex. After UV/Ozone and electrochemical cleaning, the residual PAH on the Pt-NC surfaces still strongly influenced the d-band centre of Pt due to the strong N-Pt interaction. The as-prepared 6 nm Pt-NCs showed superior electrocatalytic activity (mass activity and specific activity) and stability towards the oxygen reduction reaction (ORR) in both H(2)SO(4) and HClO(4) electrolytes compared to the commercial E-TEK Pt black, owing to the combination of the facets effect and electronic effect.

Noble metallic nanocrystals (NMNCs) with highly branched morphologies are an exciting new class of nanomaterials because of their great potential application in catalysis, sensing, optics, and electronics originating from their unique structures. Herein, we report a facile water-based method to synthesize high-quality palladium (Pd) tetrapods with the assistance of arginine molecule, which is more economical and environmentally friendly than the previous reported carbon monoxide (CO)-assisted synthesis in the organic system. During the synthesis, arginine molecule plays an essential role in controlling the tetrapod-like morphology. The as-synthesized Pd tetrapods have a potential application in the formic acid (HCOOH)-induced reduction of highly toxic hexavalent chromium (Cr(VI)) owing to their improved catalytic performance for the HCOOH decomposition.

The rational design of economical and high‐performance nanocatalysts to substitute Pt for the oxygen reduction reaction (ORR) is extremely desirable for the advancement of sustainable energy‐conversion devices. Isolated single atom (ISA) catalysts have sparked tremendous interests in electrocatalysis due to their maximized atom utilization efficiency. Nevertheless, the fabrication of ISA catalysts remains a grand challenge. Here, a template‐assisted approach is demonstrated to synthesize isolated Fe single atomic sites anchoring on graphene hollow nanospheres (denoted as Fe ISAs/GHSs) by using Fe phthalocyanine (FePc) as Fe precursor. The rigid planar macrocycle structure of FePc molecules and the steric‐hindrance effect of graphene nanospheres are responsible for the dispersion of Fe–Nx species at an atomic level. The combination of atomically dispersed Fe active sites and highly steady hollow substrate affords the Fe ISAs/GHSs outstanding ORR performance with enhanced activity, long‐term stability, and better tolerance to methanol, SO2, and NOx in alkaline medium, outperforming the state‐of‐the‐art commercial Pt/C catalyst. This work highlights the great promises of cost‐effective Fe‐based ISA catalysts in electrocatalysis and provides a versatile strategy for the synthesis of other single metal atom catalysts with superior performance for diverse applications.

In this work, the soluble cobalt phthalocyanine functionalized multiwalled carbon nanotubes (MWCNTs) are synthesized by π-π stacking interaction between tetrakis (3-trifluoromethylphenoxy) phthalocyaninato cobalt(II) (CoPcF) complex and MWCNTs. The physical properties of CoPcF-MWCNTs hybrids are evaluated using spectroscopy (UV-vis, XPS, and Raman) and electron microscopy (TEM and SEM). Subsequently, an amperometric nitrite electrochemical sensor is designed by immobilizing CoPcF-MWCNTs hybrids on the glassy carbon electrode. The immobilized CoPcF complex shows the fast electron transfer rate and excellent electrocatalytic activity for the oxidation of nitrite. Under optimum experimental conditions, the proposed nitrite electrochemical sensor shows the fast response (less than 2 s), wide linear range (9.6 × 10(-8) to 3.4 × 10(-4) M) and low detection limit (6.2 × 10(-8) M) because of the good mass transport, fast electron transfer rate, and excellent electrocatalytic activity.

Highly selective carbonylative Suzuki reactions of aryl iodides with arylboronic acids using an in situ generated nanopalladium system furnished products in high yields. The reactions were performed under ambient conditions and in the absence of an added ligand. The key to success is the addition of pivalic acid, which can effectively suppress undesired Suzuki coupling. The synthesis can be easily scaled up, and the catalytic system can be reused up to nine times. The nature of the active catalytic species are discussed.

A highly enantioselective (S)-diphenylpyrrolinol triethylsilyl ether promoted tandem oxa-Michael-aldol reaction of alpha,beta-unsaturated aldehydes with salicylaldehydes has been developed; the method affords one-pot access to chiral and synthetically useful chromenes in high yields and high enantioselectivities from readily available compounds.