Room-Temperature Synthesis of Thioether-Stabilized Ruthenium Nanocubes and Their Optical Properties

Controlling the nucleation and growth processes for nanoparticle synthesis allows the development of well-defined structures that offer unique chemical and physical properties. Here, we report a wet chemical reduction method for synthesizing ruthenium nanocubes (Ru NCs) that display plasmonic properties at room temperature (RT). The growth of the particles to form nanostructured cubes was established by varying the carbon chain length of the thioether stabilizing ligands and the reaction time to produce stable and controlled growth. In this study, we found that the longer the thioether chain length, the less isotropic the shape of the particles. Short chain lengths of thioethers (ethyl sulfide and butyl sulfide) produced spherical nanoparticles, whereas longer chain lengths (hexyl sulfide and octyl sulfide) produced cubic nanoparticles. In addition, parameters such as the ligand to precursor ratio also played an important role in the homogeneity of the nanocubes. The Ru NCs were characterized by UV-visible absorbance spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS), which supported a face-centered cubic (fcc) structure. Moreover, to demonstrate catalytic efficiency, we studied their ability to reduce benzaldehyde to benzyl alcohol, and the Ru NCs demonstrated an overall 78% efficiency at room temperature.

Promoting the Electrocatalytic Ethanol Oxidation Activity of Pt by Alloying with Cu

The development and commercialization of direct ethanol fuel cells requires active and durable electro-catalysts towards the ethanol oxidation reactions (EOR). Rational composition and morphology control of Pt-based alloy nanocrystals can not only enhance their EOR reactivity but also reduce the consumption of precious Pt. Herein, PtCu nanocubes (NCs)/CB enclosed by well-defined (100) facets were prepared by solution synthesis, exhibiting much higher mass activity (4.96 A mgPt−1) than PtCu nanoparticles (NPs)/CB with irregular shapes (3.26 A mgPt−1) and commercial Pt/C (1.67 A mgPt−1). CO stripping and in situ Fourier transform infrared spectroscopy (FTIR) experiments indicate that the alloying of Cu enhanced the adsorption of ethanol, accelerated the subsequent oxidation of intermediate species, and increased the resistance to CO poisoning of PtCu NCs/CB, as compared with commercial Pt/C. Therefore, alloying Pt with earth-abundant Cu under rational composition and surface control can optimize its surface and electronic structures and represents a promising strategy to promote the performance of electro-catalysts while reduce the use of precious metals.

Platinum-Based Electrocatalysts for Direct Alcohol Fuel Cells: Enhanced Performances toward Alcohol Oxidation Reactions

In the past few decades, Pt-based electrocatalysts have attracted great interests due to their high catalytic performances toward the direct alcohol fuel cell (DAFC). However, the high cost, poor stability, and the scarcity of Pt have markedly hindered their large-scale utilization in commerce. Therefore, enhancing the activity and durability of Pt-based electrocatalysts, reducing the Pt amount and thus the cost of DAFC have become the keys for their practical applications. In this minireview, we summarized some basic concepts to evaluate the catalytic performances in electrocatalytic alcohol oxidation reaction (AOR) including electrochemical active surface area, activity and stability, the effective approaches for boosting the catalytic AOR performance involving size decrease, structure and morphology modulation, composition effect, catalyst supports, and assistance under other external energies. Furthermore, we also presented the remaining challenges of the Pt-based electrocatalysts to achieve the fabrication of a real DAFC.

Nanocatalysts for Electrocatalytic Oxidation of Ethanol

The use of ethanol as a fuel in direct alcohol fuel cells depends not only on its ease of production from renewable sources, but also on overcoming the challenges of storage and transportation. In an ethanol-based fuel cell, highly active electrocatalysts are required to break the C-C bond in ethanol for its complete oxidation at lower overpotentials, with the aim of increasing the cell performance, ethanol conversion rates, and fuel efficiency. In recent decades, the development of wet-chemistry methods has stimulated research into catalyst design, reactivity tailoring, and mechanistic investigations, and thus, created great opportunities to achieve efficient oxidation of ethanol. In this Minireview, the nanomaterials tested as electrocatalysts for the ethanol oxidation reaction in acid or alkaline environments are summarized. The focus is mainly on nanomaterials synthesized by using wet-chemistry methods, with particular attention on the relationship between the chemical and physical characteristics of the catalysts, for example, catalyst composition, morphology, structure, degree of alloying, presence of oxides or supports, and their activity for ethanol electro-oxidation. As potential alternatives to noble metals, non-noble-metal catalysts for ethanol oxidation are also briefly reviewed. Insights into further enhancing the catalytic performance through the design of efficient electrocatalysts are also provided.

Controlling Palladium Nanocrystals by Solvent-Induced Strategy for Efficient Multiple Liquid Fuels Electrooxidation

Pd has been considered as the possible economical substitute of rare Pt for catalyzing the liquid fuels electrooxidation reaction. However, the biggest problem of Pd nanocatalysts for alcohol oxidations is that they show the limited stability and activity, greatly impacting the development of liquid fuels-based fuel cell technology. We report herein a new solvent-induced procedure for making distinct Pd NCs with geometry tuning from Pd nanosheets, Pd tetrapods, to Pd concave tetrahedra by switching the solvent from 1-methyl-2-pyrrolidone, formamide, to acetylacetonate. The key features for the preparation of dimension-controlled Pd NCs herein are that the use of molybdenum carbonyl (Mo(CO)6) determines the exposed {111} facet in the final Pd NCs, while different solvents control the reduction kinetics to induce the growth of Pd NCs with distinct morphologies. The as-prepared distinct Pd NCs show the interesting shape-dependent electrocatalytic activities toward multiple liquid fuels electrooxidation reactions including ethylene glycol oxidation reaction, glycerol oxidation reaction, ethanol oxidation reaction, and also methanol oxidation reaction with Pd nanosheets exhibiting higher activity than all the other Pd catalysts and higher activity than the commercial Pd/C and also Pd black due to the thin character of Pd nanosheets. Most importantly, the Pd nanosheets exhibit much higher stability for multiple liquid fuels electrooxidation than all the other Pd catalysts tested. The present work gives the first example in exploring the effect of solvent in tuning the dimensions of Pd NCs, and thus optimizing the electrocatalytic performance for liquid fuels electrooxidation.

Preparation and characterization of PtIr alloy dendritic nanostructures with superior electrochemical activity and stability in oxygen reduction and ethanol oxidation reactions

PtIr alloy dendritic nanostructures with high surface area exhibit superior electrocatalytic properties in ethanol oxidation and oxygen reduction reactions.

Synthesis of Pt dendritic nanocubes with enhanced catalytic properties

Pt dendritic nanocubes (DNCs) were successfully synthesized in oleylamine under a 1 bar H₂ atmosphere. The catalytic activity of Pt DNCs was much greater than conventional Pt nanoparticles (NPs) for methanol electrooxidation.

Electrochemical and in situ ATR-SEIRAS investigations of methanol and CO electro-oxidation on PVP-free cubic and octahedral/tetrahedral Pt nanoparticles

The adsorbed PVP enhances further the MOR activity on the O/T but suppresses it on the cubic Pt NPs.

Facile synthesis of high-quality Pt nanostructures with a controlled aspect ratio for methanol electro-oxidation

Pt nanobars with different aspect ratios were synthesized and exhibited remarkably excellent electrocatalytic performance for methanol oxidation.

Polyallylamine-directed green synthesis of platinum nanocubes. Shape and electronic effect codependent enhanced electrocatalytic activity

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.

In situ shaping of Pt nanoparticles directly overgrown on carbon supports

Pt cubes immobilized on carbon supports were synthesized by a one pot process in the presence of anchoring agents. The anchoring agents provide nucleating sites on the support, and also act as shape-controlling agents. In situ shaped cubic Pt/C showed superior activity and long-term stability for oxygen reduction reaction without an organic removal process.

Electrochemical detection of dopamine in the presence of ascorbic acid using PVP/graphene modified electrodes

Graphene (GR) was synthesized through electrochemical reduction of graphene oxide and characterized by spectroscopic and electrochemical techniques. Polyvinylpyrrolidone (PVP)/graphene modified glassy carbon electrode (PVP/GR/GCE) was prepared and applied for the fabrication of dopamine (DA) sensors without the interference of ascorbic acid (AA). Compared to bare GCE, an increase of current signal was observed, demonstrating that PVP/GR/GCE exhibited favorable electron transfer kinetics and electrocatalytic activity towards the oxidation of dopamine. Furthermore, PVP/GR/GCE exhibited good ability to suppress the background current from large excess ascorbic acid. Amperometric response results show that the PVP based sensor displayed a wide linear range of 5×10(-10) to 1.13×10(-3) mol/L DA with a correlation coefficient of 0.9990 and a detection limit of 0.2 nM (S/N=3). The determination of dopamine in urine and human serum samples were studied.