Alloy Nanocubes Research Articles

Dipole field as charge-transfer bridge between Cu atomic clusters/PtCu alloy nanocubes and nitrogen-rich C3N5 for superior photocatalytic hydrogen evolution

Utilizing spontaneous polarization field to harness charge transfer kinetics is a promising strategy to boost photocatalytic performance. Herein, a novel Cu atom clusters/PtCu alloy nanocubes coloaded on nitrogen-rich triazole-based C3N5 (PtCu-C3N5) with dipole field was constructed through facile photo-deposition and impregnation method. The dipole field-drive spontaneous polarization in C3N5 acts as a charge-transfer bridge to promote directional electron migration from C3N5 to Cu atom clusters/PtCu alloy. Through the synergistic effects between Cu atom clusters, PtCu alloy and dipole field in C3N5, the optimized Pt2Cu3-C3N5 achieved a record-high performance with H2 formation rate of 4090.4 μmol g−1 h−1 under visible light, about 154.4-fold increase compared with pristine C3N5 (26.5 μmol g−1 h−1). Moreover, the apparent quantum efficiency was up to 25.33 % at 320 nm, which is greatly superior than most previous related-works. The directional charge transfer mechanism was analyzed in detail through various characterizations and DFT calculations. This work offers a novel pathway to construct high-efficiency multi-metal photocatalysts for solar energy conversion.

Synergistic effect of bimetallic Pd-Pt nanocrystals for highly efficient methanol oxidation electrocatalysts.

Metal nanocrystals (NCs) with controlled compositional and distributional structures have gained increasing attention due to their unique properties and broad applications, particularly in fuel cell systems. However, despite the significant importance of composition in metal NCs and their electrocatalytic behavior, comprehensive investigations into the relationship between atomic distribution and electrocatalytic activity remain scarce. In this study, we present the development of four types of nanocubes with similar sizes and controlled compositions (Pd-Pt alloy, Pd@Pt core-shell, Pd, and Pt) to investigate their influence on electrocatalytic performance for methanol oxidation reaction (MOR). The electrocatalytic activity and stability of these nanocubes exhibited variations based on their compositional structures, potentially affecting the interaction between the surface-active sites of the nanocrystals and reactive molecules. As a result, leveraging the synergistic effect of their alloy nanostructure, the Pd-Pt alloy nanocubes exhibited exceptional performance in MOR, surpassing the catalytic activity of other nanocubes, including Pd@Pt core-shell nanocubes, monometallic Pd and Pt nanocubes, as well as commercial Pd/C and Pt/C catalysts.

Suspension Arrays Prepared from Nanofiber-Based Microparticles for a Platform of SERS-Based Multiplex Immunoassay

Electrospun nano- and microfibers have received considerable attention for various sensing applications owing to their three-dimensional porous structures with a high surface area that can increase the sensitivity of the sensor. Despite the successful use of electrospun fibers in the biosensing field, most applications have been based on a macroscopic fiber matrix, and the use of micrometer-scale fiber particles has not been reported. Here, we propose a simple method for fabricating shape-coded nanofiber microparticles using a water-soluble and photocrosslinkable polymer, poly(vinyl alcohol) N-methyl-4(4′-formylstyryl) pyridinium methosulfate acetal (PVA-SbQ). Electrospinning of PVA-SbQ and the subsequent photopatterning process generated photocrosslinked fibrous micropatterns that could be easily detached from the substrates and collected as nanofiber microparticles in an aqueous environment. The lateral dimensions and shapes of the microparticles were controlled by photomask design, and thickness of the microparticles was determined by electrospinning time. The resultant nanofiber microparticles were decorated with silver nanoparticles and served as capture substrates for a surface-enhanced Raman spectroscopy (SERS)-based immunoassay, where Au–Ag alloy nanocubes were used as SERS tags. Because suspension arrays consisting of nanofiber microparticles of various shapes can be prepared, highly sensitive SERS-based biosensing of multiple targets can be developed using shape-coded nanofiber microparticles. The performance of the devised immunosensor was demonstrated by the very low detection limit for biomolecules with high selectivity.

A Facile and Green Eutectic Salt-Mediated Pyrolysis Strategy to Synthesize Hollow PtNi Alloy Nanocubes for Oxygen Reduction Reaction

A Facile and Green Eutectic Salt-Mediated Pyrolysis Strategy to Synthesize Hollow PtNi Alloy Nanocubes for Oxygen Reduction Reaction

Size-controlled, hollow and hierarchically porous Co2Ni2 alloy nanocubes for efficient oxygen reduction in microbial fuel cells

Schematic illustration of the fabrication of CoxNiy alloy nanocubes (ANCs) and hollow CoxNiy alloy nanocubes (HANCs).

Carbon nanorod supported metal alloy nanocubes using polydopamine as location reagent for water splitting

Transition metal catalysts were supposed to be the most likely substitute for commercial noble metal catalysts, and the development of highly active and long-term catalyst for water splitting are the future trend. Herein, Ni rectangular nitrogen doped carbon nanorods@Fe–Co nanocubes (Ni-CNRs@Fe–Co cubes) were fabricated via a facile template-free method. This simple strategy not only realizes the structure tailoring, but also achieves high-quality nitrogen-doping. Specifically, nickel dimethylglyoxime [Ni(dmg)2] with rectangular rodlike structure was firstly synthesized by solution method, then metal-organic frameworks Fe–Co nanocube with different contents were loaded on rectangular carbon nanorods with polydopamine as the locating and the connecting agent, and finally Ni-CNRs@xFe-Co cubes were obtained by a one-step calcination. A series of electrochemical tests were researched on materials with different metal contents in the 1 M KOH solution. The Ni-CNRs@Fe–Co cubes show excellent electrocatalytic activity in the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). For HER and OER, the Tafel slopes were 83.3 mV dec−1 and 71 mV dec−1, the onset potential were −167 mV and 1.62 V, and reached the current densities of 10 mA cm−2, the overpotential just needed 196 mV and 433 mV, respectively. This novel synthetic strategy will provide a template-free way for cheap electrocatalysts of non-precious metal for OER and HER.

Single-Crystalline Mesoporous Palladium and Palladium-Copper Nanocubes for Highly Efficient Electrochemical CO 2 Reduction

Single-Crystalline Mesoporous Palladium and Palladium-Copper Nanocubes for Highly Efficient Electrochemical CO ₂ Reduction

Bimetallic Ag–Au alloy nanocubes for SERS based sensitive detection of explosive molecules

We have fabricated Ag–Au alloy nanocubes using the galvanic replacement of silver nanocubes by aqueous HAuCl4 and investigated their morphological, structural, compositional and optical properties. The inter-diffusion between silver and gold at 100 °C leads to the formation of Ag–Au alloy nanocubes with hollow interiors. A broad tuning of the surface plasmon resonance (SPR) wavelength from 624 nm to 920 nm is obtained with the varying volume of HAuCl4. When excited at wavelength 785 nm, the bimetallic Ag–Au nanocubes with pinholes exhibit two-fold Raman intensity enhancement compared to pristine Ag nanocubes. The surface-enhanced Raman spectroscopy (SERS) substrate prepared with Ag–Au alloy nanocubes shows high-intensity enhancement factor of 1.9 × 107 for 11.2 wt% Au content. The SERS-active Ag–Au alloy nanocubes substrates were exploited for the detection of two explosive molecules; p-nitrobenzoic acid (PNBA) and picric acid (PA). Remarkable detection sensitivity and ultra-low detection limit of 1.7 × 10–14 M for PNBA and 4.1 × 10–11 M for PA were obtained, demonstrating the very high SERS detection capabilities of the as-prepared substrate.

Ternary PtNiCu self-assembled nanocubes for plasmon-enhanced electrocatalytic hydrogen evolution and methanol oxidation reaction in visible light

The strong interaction among metal components results in the change of the electronic structure (e.g. d-band energy level) of noble metal-based alloy structures which enables the increase of catalytic activity. In this paper, self-assembled ternary PtNiCu and binary PtCu alloy nanocubes are synthesized by a one-pot high-temperature chemical reduction method. The growth mechanism of the alloy is investigated. The alloy is applied to visible light-assisted electrocatalytic hydrogen production and methanol oxidation. The ternary PtNiCu alloy exhibits superior catalytic performance (a minimum over potential of 15 mV at a current density of 10 mA cm−2, a Tafel slope of 24.1 mV/dec, and more excellent mass specific activity under visible light irradiation about 3.3 A mgPt−1), because of its regular morphology, more surface active sites, and more intense interaction between metal elements. Especially the localized surface plasmon resonance effect of Cu largely increases the electron density (photoelectric effect) on Pt under illumination, thereby further improves the photo-assisted hydrogen production and methanol catalytic oxidation performance. The results will promote efficient and accurate electrocatalysis process, paving new way for a brighter further in rational design of ternary plasmonic electrocatalysts and photoelectrocatalysis field.

Palladium/Copper Alloy Hollow Nanocubes Supported on Sulfur‐doped Graphene as Highly Efficient Catalyst for Ethylene Glycol Oxidation

AbstractTo control and regulate both the shape and size of metal nanoparticles is essential for the design and preparation of active and stable catalysts for fuel cell reactions such as the ethylene glycol (EG) electrooxidation reaction, which is highly sensitive to the structure of the catalysts. We report the synthetic strategy of PdCu alloy hollow nanocube supported on sulfur‐doped graphene (H‐PdCu/SG) catalyst through a self‐assembled hydrothermal process for ethylene glycol (EG) electrooxidation reaction. The as‐prepared hollow PdCu alloy nanocubes are well distributed on the SG surface with a relatively small particle size distribution. Additionally, the H‐PdCu/SG catalyst shows a superior electrocatalytic activity and stability toward EG oxidation.

Cyanogel auto-reduction induced synthesis of PdCo nanocubes on carbon nanobowls: a highly active electrocatalyst for ethanol electrooxidation.

Direct ethanol fuel cells (DEFCs) with a high conversion efficiency are quite promising candidates for energy conversion devices. Herein, we have successfully synthesized PdCo alloy nanocubes supported on carbon nanobowl (denoted as Pd2Co1/CNB) nanohybrids by using the cyanogel auto-reduction method at high temperature. The morphology, composition and structure of Pd2Co1/CNB nanohybrids are characterized in detail, revealing that PdCo nanocubes have a high alloying degree and special {110} facets. In cyclic voltammetry measurements, Pd2Co1/CNB nanohybrids show a mass activity of 1089.0 A g Pd-1 and a specific activity of 40.03 mA cm-2 for ethanol electrooxidation at peak potential, which are much higher than that of the commercial Pd/C electrocatalyst (278.2 A gPd-1 and 8.22 mA cm-2). Additionally, chronoamperometry measurements show that Pd2Co1/CNB nanohybrids have excellent durability for ethanol electrooxidation. A high alloying degree, special {110} facets and the CNB supporting material contribute to the high activity and durability of Pd2Co1/CNB nanohybrids, making them a highly promising Pt-alternative electrocatalyst for ethanol electrooxidation in DEFCs.

Sophisticated Construction of Binary PdPb Alloy Nanocubes as Robust Electrocatalysts toward Ethylene Glycol and Glycerol Oxidation.

The design of nanocatalysts by controlling pore size and particle characteristics is crucial to enhance the selectivity and activity of the catalysts. Thus, we have successfully demonstrated the synthesis of binary PdPb alloy nanocubes (PdPb NCs) by controlling pore size and particle characteristics. In addition, the as-obtained binary PdPb NCs exhibited superior electrocatalytic activity of 4.06 A mg-1 and 16.8 mA cm-2 toward ethylene glycol oxidation reaction and 2.22 A mg-1 and 9.2 mA cm-2 toward glycerol oxidation reaction when compared to the commercial Pd/C. These astonishing characteristics are attributed to the attractive nanocube structures as well as the large number of exposed active areas. Furthermore, the bifunctional effects originated from Pd and Pb interactions help to display high endurance with less activity decay after 500 cycles, showing a great potential in fuel cell applications.

Electroreduction of Oxygen on PdPt Alloy Nanocubes in Alkaline and Acidic Media

AbstractThe electrochemical kinetic behavior of the oxygen reduction reaction (ORR) on PdPt alloy nanocubes of various compositions is investigated in 0.1 M KOH and 0.1 M HClO4 solutions, adopting the rotating disk electrode (RDE) configuration. The PdPt nanocubes are prepared in the presence of polyvinylpyrrolidone and identified by using transmission electron microscopy (TEM). TEM images reveal that the PdPt alloy nanoparticles have a preferential cubic shape and the average particle size is approximately 8–10 nm. CO‐stripping and cyclic voltammetry (CV) experiments are used for electrochemical cleaning and characterization of metal nanoparticles. The CV responses indicate alloy formation. In acidic media, Pd36Pt64 shows the highest specific activity (SA) for the ORR from the alloyed catalysts studied, but this activity is similar to that found with Pt and Pd nanocubes. However, in alkaline solution, the SA value for Pd72Pt28 is about two times higher than that of Pd and Pt nanocubes. The mechanistic pathway of O2 reduction on PdPt alloy nanocubes is analogous to that of pure Pd and Pt catalysts and the ORR proceeds via a 4‐electron pathway in both electrolyte solutions.

PdCu@Pd Nanocube with Pt-like Activity for Hydrogen Evolution Reaction.

The electronic properties of metal surfaces can be modulated to weaken the binding energy of adsorbed H-intermediates on the catalyst surface, thus enhancing catalytic activity for the hydrogen evolution reaction (HER). Here we first prepare PdCu alloy nanocubes (NCs) by coreduction of Cu(acac)2 (acac = acetylacetonate) and Na2PdCl4 in the presence of oleylamine (OAm) and trioctylphosphine (TOP). The PdCu NC coated glassy carbon electrode is then anodized at a constant potential of 0.51 V vs Ag/AgCl at room temperature in 0.5 M H2SO4 solution for 10 s, which converts PdCu NCs into core@shell PdCu@Pd NCs that show much enhanced Pt-like activity for the HER and much more robust durability. The improvements in surface property and HER activity are rationalized based on strain and ligand effects that enhance the activity of the edge-exposed Pd atoms on core@shell PdCu@Pd structure. This work opens up a new perspective for simultaneously reducing metal Pd cost and achieving excellent performance toward the HER.

Chemical etching of graphene-supported PdPt alloy nanocubes into concave nanostructures for enhanced catalytic hydrogen production from alkaline formaldehyde aqueous solution

Graphene-supported PdPt concave nanostructures with different degrees of concavity were synthesized by etching PdPt nanocubes for enhanced catalytic hydrogen production from alkaline formaldehyde aqueous solution.

Controlled synthesis of sponge-like porous Au–Ag alloy nanocubes for surface-enhanced Raman scattering properties

The sponge-like Au–Ag alloy nanocubes (NCs) showed excellent SERS performance derived from high-density “hotspots” in nanopores, sharp corners and edges, and synergistic effect between Au and Ag species.

Quantitative Analysis of the Reduction Kinetics Responsible for the One-Pot Synthesis of Pd-Pt Bimetallic Nanocrystals with Different Structures.

We report a quantitative understanding of the reduction kinetics responsible for the formation of Pd-Pt bimetallic nanocrystals with two distinctive structures. The syntheses involve the use of KBr to manipulate the reaction kinetics by influencing the redox potentials of metal precursor ions via ligand exchange. In the absence of KBr, the ratio between the initial reduction rates of PdCl4(2-) and PtCl4(2-) was about 10.0, leading to the formation of Pd@Pt octahedra with a core-shell structure. In the presence of 63 mM KBr, the products became Pd-Pt alloy nanocrystals. In this case, the ratio between the initial reduction rates of the two precursors dropped to 2.4 because of ligand exchange and, thus, the formation of PdBr4(2-) and PtBr4(2-). The alloy nanocrystals took a cubic shape owing to the selective capping effect of Br(-) ions toward the {100} facets. Relative to the alloy nanocubes, the Pd@Pt core-shell octahedra showed substantial enhancement in both catalytic activity and durability toward the oxygen reduction reaction (ORR). Specifically, the specific (1.51 mA cm(-2)) and mass (1.05 A mg(-1) Pt) activities of the core-shell octahedra were enhanced by about four- and three-fold relative to the alloy nanocubes (0.39 mA cm(-2) and 0.34 A mg(-1) Pt, respectively). Even after 20000 cycles of accelerated durability test, the core-shell octahedra still exhibited a mass activity of 0.68 A mg(-1) Pt, twice that of a pristine commercial Pt/C catalyst.

Cubic superstructures composed of PtPd alloy nanocubes and their enhanced electrocatalysis for methanol oxidation.

Three-dimensional (3D) cubic superstructures of PtPd nanocubes were achieved by spontaneous adjustment of PtIV reduction kinetics, and exhibited enhanced catalytic activity and long-term durability towards methanol oxidation compared with the state-of-the-art Pt/C. This work demonstrates the first example of designing 3D shaped architectures of PtPd nanocubes for methanol electrooxidation.

Hollow PdCu nanocubes supported by N-doped graphene: A surface science and electrochemical study

N doped graphenes (NGs) are believed to be promising materials for constructing novel hybrid composites with desirable functionalities and applications in many fields. Therefore, a better understanding of the NGs holds the key to a better performance of the hybrid properties. A facile and low-cost preparation of NGs supported hollow PdCu alloy nanocubes (H–PdCu) catalysts were introduced in this paper. To increase the stability and efficiency of the catalysts, a two-step strategy was employed, which included the preparation of NGs and the synthesis of hollow PdCu alloy nanocube catalysts. A series of NGs using melamine, polypyrrole (ppy) and polyaniline (PANI) as nitrogen source, respectively. The influence of the different N species (pyridinic N, pyrrolic N and graphite N) on the morphologies and corresponding electrical properties of H–PdCu nanoparticles were studied. The results indicate that NGs are successfully synthesized, and hollow PdCu alloy nanocubes are well-dispersed on the surface of them with a relatively narrow particle size distribution. Electrochemical characterizations reveal that the H–PdCu/melamine-NG catalyst has excellent catalytic activity and stability toward alcohols oxidation in alkaline electrolyte, which can serve as promising anode catalysts in direct alcohols fuel cells (DAFCs).

Pdpt Alloy Nanocubes As Electrocatalysts for Oxygen Reduction Reaction in Acid Media

Platinum-based catalysts are the best electrocatalysts for oxygen reduction reaction (ORR) in fuel cells.1 However, because of the high price and limited supply of Pt, numerous researches have focused on finding a way to reduce its amount in the catalysts. One way to decrease Pt loading is to replace it partially by other metals. Pd is a promising substitute due to the similar properties to the Pt (same group of the periodic table, similar atomic size and crystalline structure).2 In this work, PdPt alloy nanocubes with different metal ratios were synthesized in the presence of polyvinylpyrrolidone.3 The surface morphology of the PdPt samples was characterized by transmission electron microscopy (TEM). TEM images showed that PdPt nanoparticles were cubic-shaped and the average size of the cubes was about 8–10 nm. TEM image for sample Pd54Pt46 is shown in Fig. 1a. Electrochemical measurements were performed to explore the electrocatalytic properties of the PdPt alloy nanocubes toward the ORR in 0.5 M H2SO4 using the rotating disk electrode (RDE) method. CO stripping and cyclic voltammetry (CV) were used for cleaning and characterizing the surface of catalysts. The CV responses showed improvement in surface cleanness after CO oxidation compared with those CVs initially measured. Comparison of polarization curves received from RDE measurements at 1900 rpm are presented in Fig. 1b. The half-wave potentials (E 1/2) for O2 reduction on PdPt alloys were found to be higher than that of Pd nanocubes and were comparable with that of Pt nanocubes. The onset potential for Pd36Pt64 was the highest. The RDE data were analyzed using the Koutecky-Levich (K-L) equation and from the slopes the number of transferred electrons (n) was found. The value of n was close to four for all the catalysts studied. For better comparison of the kinetic parameters of all the electrodes the Tafel plots were constructed from the RDE data (Fig. 1c). Two regions with distinct slope values were observed. In the low overpotential region the slope value was close to -60 mV dec‒ 1 and at high overpotentials the Tafel slope value was over -130 mV dec‒ 1. All the alloyed catalysts showed enhanced electrocatalytic activity for ORR as compared to the monometallic cubic Pd nanoparticles. From the alloyed catalysts Pd36Pt64 exhibited the highest specific activity, which was only slightly lower than that of cubic Pt nanoparticles. Work is in progress to study the electroreduction of oxygen on PdPt alloy nanocubes in 0.1 M KOH solution using the RDE method. Single-waved polarization curves with well-defined current plateaus were observed. The E 1/2 values for PdPt alloys in alkaline solution were comparable. The K-L analysis showed that O2 reduction on these alloys proceeds via 4-electron pathway in 0.1 M KOH. The Tafel analysis revealed that the mechanism of O2 reduction on PdPt alloy nanocubes in alkaline media is similar to that in acid media. The PdPt alloy nanocubes exhibit good electrocatalytic activity for the electroreduction of oxygen in both electrolytes. This indicates a great promise of these materials as cathode catalysts for low-temperature fuel cells.