Alloy Nanodendrites Research Articles

Highly branched and ultrathin Au nanodendrites for reduction catalysis

Two-dimensional (2D) materials have garnered significant attention due to their distinctive physicochemical properties, with 2D noble metal nanodendrites being particularly intriguing in terms of their properties and functional prospects. However, the synthesis of ultrathin and highly branched gold nanodendrites (AuNDs) still poses challenges. In this study, we successfully achieved the synthesis of highly branched 2D AuNDs with a thickness of 4 nm by employing a carboxyl-functionalized C22-tailed surfactant along with the co-directing agent 2-mercaptonicotinic acid (2-MNA). The careful selection of specific thiol molecules such as 2-MNA is crucial for controlling the degree of branching and promoting the formation of ultrathin nanodendrites. Furthermore, we extended this method to synthesize alloy nanodendrites (AuAg NDs and AuCoAg NDs) using a similar approach. Due to their highly branched and ultrathin two-dimensional morphology, these prepared AuNDs exhibit excellent catalytic performance in the model reaction for 4-NP reduction. This thiol-induced synthesis strategy for AuNDs opens up new possibilities for designing other Au nanomaterials with an ultrathin morphology/structure.

The Effect of the Pd Precursors on the Shape of Hollow Ag-Pd Alloy Nanoparticles Using Ag Nanocubes as Seeds.

Hollow Ag-Pd nanoparticles have potentially high catalytic performance owing to their larger surface area compared to their corresponding solid nanoparticles. We successfully fabricated hollow Ag-Pd alloy nanodendrites and nanoboxes by using different Pd precursors (H2PdCl4 and Pd(acac)2) to achieve large surface area nanoboxes. Interestingly, the use of a H2PdCl4 precursor led to the formation of hollow nanodendrite structures, whereas the slower reduction of Pd(acac)2 led to the formation of hollow nanoboxes. The microstructure and chemical composition of Ag-Pd nanoparticles and properties of their growth solutions were investigated by transmission electron microscopy, energy-dispersive X-ray spectroscopy, and ultraviolet-visible spectroscopy.

Efficient promotion of ethanol complete electrooxidation by anti-poisoning rhodium-bismuth alloy nanodendrites

Alkaline direct ethanol fuel cells are promising future energy technologies with a high energy-density, while the lack of robust anodic electrocatalysts limits their energy conversion efficiency due to serious poisoning and weak selectivity to the C1 pathway of ethanol oxidation reaction (EOR). Herein, rhodium-bismuth alloy nanodendrites (RhBi-NDs) are applied as an efficient and anti-poisoning electrocatalyst for EOR, which exhibit superior electrocatalytic performance, including a mass activity of 1068.9 mA mgRh−1 at 0.71 V, a 31.1% Faradaic efficiency for the C1 product, and an excellent stability of 40 h. The mechanism study indicates that Bi improves the oxidation ability of Rh to toxic intermediates by providing oxygen-containing species. The theoretical calculations disclose the electronic interaction between Bi and Rh, which tunes the adsorption energy of intermediates such as CH3CH2OH*, and CH3CO*, resulting in the suppression of C2 pathway and the promotion of C1 pathway for EOR on RhBi-NDs.

Boosting Electrocatalytic Oxidation of Formic Acid on Ir(IV)-Doped PdAg Alloy Nanodendrites with Sub-5 nm Branches.

The formic acid oxidation reaction (FAOR) represents an important class of small organic molecule oxidation and is central to the practical application of fuel cells. In this study, we report the fabrication of Ir(IV)-doped PdAg alloy nanodendrites with sub-5 nm branches via stepwise synthesis in which the precursors of Pd and Ag were co-reduced, followed by the addition of IrCl3 to conduct an in situ galvanic replacement reaction. When serving as the electrocatalyst for the FAOR in an acidic medium, Ir(IV) doping unambiguously enhanced the activity of PdAg alloy nanodendrites and improved the reaction kinetics and long-term stability. In particular, the carbon-supported PdAgIr nanodendrites exhibited a prominent mass activity with a value of 1.09 A mgPd-1, which is almost 2.0 times and 2.7 times that of their PdAg and Pd counterparts, and far superior to that of commercial Pt/C. As confirmed by the means of the DFT simulations, this improved electrocatalytic performance stems from the reduced overall barrier in the oxidation of formic acid into CO2 during the FAOR and successful d-band tuning, together with the stabilization of Pd atoms. The current study opens a new avenue for engineering Pd-based trimetallic nanocrystals with versatile control over the morphology and composition, shedding light on the design of advanced fuel cell electrocatalysts.

Rh–Cu alloy nano-dendrites with enhanced electrocatalytic ethanol oxidation activity

The application of direct ethanol fuel cell (DEFC) has been bottlenecked by the sluggish ethanol oxidation reaction (EOR). Efficient electrocatalysts for the C−C bond cleavage are essential to promote EOR with high efficiency and C1 selectivity. Here, we prepared Rh–Cu alloy nano-dendrites (RhCu NDs) with abundant surface steps through controlled co-reduction, which exhibited significantly enhanced activity and C1 selectivity (0.47 mA cm−2(ECSA), 472.4 mA mgRh−1, and 38.9%) than Rh NDs (0.32 mA cm−2(ECSA), 322.1 mA mgRh−1, and 21.4%) and commercially available Rh/C (0.18 mA cm−2(ECSA), 265.4 mA mgRh−1, and 14.9%). Theoretical calculations and CO-stripping experiments revealed that alloying with Cu could modulate the surface electronic structures of Rh to resist CO-poisoning while strengthening ethanol adsorption. In situ Fourier transform infrared spectroscopy (FTIR) indicated that the surface steps on RhCu NDs further promoted the C−C bond cleavage to increase the C1 selectivity. Therefore, optimizing the surface geometric and electronic structures of nanocrystals by rational composition and morphology control can provide a promising strategy for developing practical DEFC devices.

One-Pot Production of Pt–Ni Alloy Nanodendrites on Ceria Nanosheet Supporting Materials with High Electrocatalytic Performance Toward Methanol Oxidation and Oxygen Reduction

To create better fuel cell catalysts, effective approaches to generate hybrid materials comprised of intimately connected metal nanocatalysts and nonstoichiometric metal oxides with finely regulated topologies are very desirable. The production of closely connected metal (PtNi alloy)–metal oxide (CeOx, ceria) hybrid nanostructures is reported here using a simple one-pot synthesis technique. Heating a mixed metal (Pt, Ni, and Ce) precursor solution in oleylamine/oleic acid resulted in well-defined PtNi/ceria hybrids, in which PtNi alloy nanodendrites with multiple branches are evenly spread over small-grained ceria nanosheets. The ceria nanosheets in the hybrids have a large number of oxygen vacancies and a high conductivity due to their small grain size. In comparison to carbon-supported counterparts and a commercial catalyst, the prepared PtNi/ceria hybrids exhibited outstanding electrocatalytic activity and stability for both methanol oxidation and oxygen reduction reactions, which can be attributed to the synergistic effects of the Ni component and ceria on the enhancement of the electrocatalytic function. The current technique will be used to create the best multicomponent catalysts for specific processes.

Unveiling the Synergistic Effects of Monodisperse Sea Urchin-like PdPb Alloy Nanodendrites as Stable Electrocatalysts for Ethylene Glycol and Glycerol Oxidation Reactions.

In recent times, the fabrication of noble metal-based catalysts with controllable morphologies has become a research hotspot. Electrocatalytic devices with excellent catalytic performance and enhanced durability for the ethylene glycol oxidation reaction (EGOR) and the glycerol oxidation reaction (GOR) are significant for commercial direct fuel cells. Herein, a series of PdPb sea urchin-like nanodendrite (ND) structures with controllable molar ratios were synthesized as EGOR and GOR electrocatalysts of high efficiency. The optimized structurally regular Pd3Pb NDs exhibit the best electrocatalytic activity and outstanding stability compared to other samples and commercial Pt/C. In addition, the integrated Pb on Pd3Pb NDs can mitigate the bond energy the intermediates generate and further boost the electrooxidation of the intermediates by supplying enough active sites without considering its intrinsic structure, which is beneficial to the enhanced EGOR and GOR activity and stability. With the assistance of electrochemical measurement, the mechanism of the enhanced alloy was further investigated. This paper presents a promising strategy to fabricate catalysts with stable structures, which will elucidate a very promising approach for developing Pd-based catalysts for further applications in fuel cells.

Fabrication of bimetallic Au–Pt NSs for the catalytic reduction of nitroarenes

Abstract This work is based on the preparation of Au–Pt NSs (Nano stars) @Au core, Au–Pt NSs@Au1Pt3 core, Au–Pt NSs@Au1Pt1 core, Au–Pt NSs@Au3Pt1 core and Au@Pt NCs (Nano cubes) by a seed-mediated synthesis route. The characterizations of the prepared bimetallic NSs and NCs were conducted with ultraviolet-visible spectroscopy, X-ray diffraction, transmission electron microscopy, and inductively coupled plasma optical emission spectroscopy. The catalytic activities of the prepared Au–Pt NPs for 2-nitrophenol (2NP), 3-nitrophenol (3NP), 4-nitrophenol (4NP), 2-nitroresorcinol (2NR), and 4-nitrocatchol (4NR) reduction have been investigated. The results evidently demonstrated that the superior catalytic activities of Au–Pt alloy nano-dendrites can be attributed to the metal–metal connection (synergy between Au and Pt) in the catalysts.

Dendric nanoarchitectonics of PtRu alloy catalysts for ethylene glycol oxidation and methanol oxidation reactions

Designing and modulating the morphological structure of catalysts is of great significance to improve their catalytic activity and stability. In this work, PtRu alloy nanodendrites with tunable components were constructed by the introduction of Ru. Owing to the presence of electron transfer in the alloy nanocatalysts and their unique nanodendritic structures, Pt0.8Ru0.2 alloy nanocatalysts with optimal composition exhibited excellent electrocatalytic activity and stability in ethylene glycol oxidation reaction (EGOR) and methanol oxidation reaction (MOR). Among the nano-catalysts, mass activities of Pt0.8Ru0.2 nanodendritic catalysts to EGOR and MOR were 6.1 A mg−1 and 4.6 A mg−1, and the specific activities were 11.5 mA cm−2 and 8.68 mA cm−2, respectively, much better than those of commercial Pt/C catalysts. This work provides a strategy for designing efficient PtRu catalysts for fuel cells.

Precisely modulated 2D PdCu alloy nanodendrites as highly active peroxidase mimics for the elimination of biofilms.

Pd-based nanomaterials are good candidates for antibacterial applications because of their high catalytic activity and good biocompatibility. Nonetheless, there is still much work to do to improve the catalytic activity of Pd nanomaterials as antibacterial agents, particularly for anti-biofilms. In this work, Cu was introduced into Pd to form a series of 2D PdCu alloy nanodendrites (PdCu NDs) as high-performance peroxidase mimics based on flexible control of compositions. Remarkably, catalytic kinetics show that the composition-dependent synergy in the PdCu NDs strongly enhances the peroxidase-like activity. The detailed theoretical study reveals that the tuning of the electrostatic adsorption and dissociative chemisorption of the H2O2 molecule on PdCu ND surfaces by the precise introduction of Cu plays a key role in obtaining superior peroxidase-like catalytic activity. Significantly, the distinct peroxidase-like properties of the fine-tuned PdCu NDs endow them with excellent biofilm elimination capability via the generation of hydroxyl radicals. This work offers a great opportunity to design noble metal nanozymes with enhanced performance, which might advance the development of nanozymes as a new class of highly efficient antibacterial agents.

Two-Dimensional Palladium-Copper Alloy Nanodendrites for Highly Stable and Selective Electrochemical Formate Production.

Pd is the only metal that can catalyze electrochemical CO2 reduction to formate at close-to-zero overpotential. It is unfortunately subjected to severe poisoning by trace CO as the side product and suffers from deteriorating stability and selectivity with increasing overpotential. Here, we demonstrate that alloying Pd with Cu in the form of two-dimensional nanodendrites could enable highly stable and selective formate production. Such unique bimetallic nanostructures are formed as a result of the rapid in-plane growth and suppressed out-of-plane growth by carefully controlling a set of experimental parameters. Thanks to the combined electronic effect and nanostructuring effect, our alloy product catalyzes CO2 reduction to formate with remarkable stability and selectivity under the working potential as cathodic as -0.4 V. Our results are rationalized by computational simulations, evidencing that Cu atoms weaken the *CO adsorption and stabilize the *OCHO adsorption on neighboring Pd atoms.

Pt-based (Zn, Cu) nanodendrites with enhanced catalytic efficiency and durability toward methanol electro-oxidation via trace Ir-doping engineering

Pt-based alloy nanomaterials with nanodendrites (NDs) structures are efficient electrocatalysts for methanol oxidation reaction (MOR), however their durability is greatly limited by the issue of transition metals dissolution. In this work, a facile trace Ir-doping strategy was proposed to fabricate Ir-PtZn and Ir-PtCu alloy NDs catalysts in aqueous medium, which significantly improved the electrocatalytic activity and durability for MOR. The as-prepared Ir-PtZn/Cu NDs catalysts showed distinct dendrites structures with the averaged diameter of 4.1 nm, and trace Ir doping subsequently improved the utilization of Pt atoms and promoted the oxidation efficiency of methanol. The electrochemical characterizations further demonstrated that the obtained Ir-PtZn/Cu NDs possessed enhanced mass activities of nearly 1.23 and 1.28-fold higher than those of undoped PtZn and PtCu, and approximately 2.35 and 2.67-fold higher than that of Pt/C in acid medium. More excitingly, after long-term durability test, the proposed Ir-PtZn and Ir-PtCu NDs still retained about 88.9% and 91.6% of its initial mass activities, which further highlights the key role of Ir-doping in determining catalyst performance. This work suggests that trace Ir-doping engineering could be a promising way to develop advanced electrocatalysts toward MOR for direct methanol fuel cell (DMFC) applications.

Boosting Pd-catalysis for electrochemical CO2 reduction to CO on Bi-Pd single atom alloy nanodendrites

Pd is a catalyst for electrochemical CO2 reduction to CO but often disturbed by H2 and formate formation at low overpotentials due to its strong affinity to H atoms. Herein, guided by density functional theory (DFT) calculations, Bi-Pd single atom alloy (SAA) nanodendrites (NDs) with Bi atomically dispersed in Pd matrices have been developed for efficient CO2 reduction to CO. The Faradic efficiencies (FEs) of CO on the Bi6Pd94-SAA ND catalyst reach 90.5 % and 91.8 % in H-type and gas diffusion flow cells with overpotentials of only 290 and 200 mV, respectively, which are among the best of the reported Pd-based electrocatalysts. The greatly enhanced CO formation on the Bi6Pd94-SAA NDs can be attributed to the increased reaction barriers for H2 formation due to a lower H coverage resulted from Bi doping, and the decreased free energy for *COOH generation which is a key intermediate for CO production.

Facile synthesis of platinum-rhodium alloy nanodendrites as an advanced electrocatalyst for ethylene glycol oxidation and hydrogen evolution reactions

Direct ethylene glycol fuel cells (DEGFCs) and water splitting devices have received intensive interest during the past few decades. However, the commonly used Pt catalysts are seriously restricted by the high cost and very low resistance to CO-like intermediates during the catalysis. Herein, a general and simple solvothermal method was developed to synthesize three-dimensional (3D) bimetallic alloyed PtRh nanodendrites (NDs) for ethylene glycol oxidation reaction (EGOR) and hydrogen evolution reaction (HER). Citric acid (CA) and cetyltrimethylammonium chloride (CTAC) played important roles in formation of such dendritic structures. The optimized Pt56Rh44 NDs displayed the greatest mass activity (MA) for EGOR in 0.5 M KOH, which was 2.6-fold higher than commercial Pt black, coupled with the remarkable increase in the HER activity with a decayed overpotential of 20.0 mV to drive a current density of 10 mA cm−2 relative to the homemade Pt41Rh59 NDs (26.2 mV), Pt81Rh19 NDs (26.2 mV), Pt black (44.3 mV), Pt/C (44.4 mV) and Rh NFs (37.3 mV). This work offers some constructive guidelines for synthesis of advanced Pt-based catalysts in such energy devices.

PtRhCu ternary alloy nanodendrites with enhanced catalytic activity and durability toward methanol electro-oxidation

Despite the great progress has been made in the research of Pt-based catalysts toward methanol oxidation reaction (MOR), it is still remaining a great challenge for direct methanol fuel cells (DMFCs) to simultaneously satisfy both excellent activity and good durability. Herein, we report a facile one-pot approach for the successful fabrication of PtRhCu ternary alloy nanodendrites. For the methanol oxidation reaction (MOR), the electrocatalytic performances of the as-prepared nanocrystals can be optimized by simply varying the amount of Rh precursor. The mass activity and specific activity of the as-obtained Pt47Rh8Cu45 nanodendrites are 2.9 and 5.8 times as high as that of commercial Pt/C catalyst, respectively. Besides, after the accelerated durability test (ADT) for 1500 cycles, the remaining specific activity of Pt47Rh8Cu45 nanodendrites is 7.8 folds enhancement compared to commercial Pt/C, indicating the excellent stability of the PtRhCu catalyst. We believe that the improved electrochemical activity and stability could be resulted from the highly dendritic nanostructure and the synergetic effect of the three metallic elements in the alloy.

One-pot Synthesis of N-doped Reduced Graphene Oxide Decorated with Au-Pd@Au Alloy Nanodendrites for Electrochemical Detection of Chrysophanol

One-pot Synthesis of N-doped Reduced Graphene Oxide Decorated with Au-Pd@Au Alloy Nanodendrites for Electrochemical Detection of Chrysophanol

Facile fabrication of hierarchical Rh2Ir alloy nanodendrites with excellent HER performance in a broad pH range

Hierarchical Rh2Ir alloy nanodendrites were prepared via a facile oil-bath method, which exhibits excellent HER performance in a broad pH range.

One-pot production of ceria nanosheet-supported PtNi alloy nanodendrites with high catalytic performance toward methanol oxidation and oxygen reduction

The production of high-performance electrocatalysts consisting of intimately coupled PtNi nanodendrites and ceria nanosheets was realized by a one-pot method.

Ir3Pb alloy nanodendrites with high performance for ethanol electrooxidation and their enhanced durability by alloying trace Au

Porous Ir3Pb nanodendrites exhibit excellent activity and superior CO2 selectivity for the EOR under acidic conditions, and their durability can be enhanced dramatically by alloying trace Au.

Ultrafine PtRu Dilute Alloy Nanodendrites for Enhanced Electrocatalytic Methanol Oxidation.

Dilute alloy nanostructures have been demonstrated to possess distinct catalytic properties. Noble-metal-induced reduction is one effective synthesis strategy to construct dilute alloys and modify the catalytic performance of the host metal. Herein, we report the synthesis of ultrafine PtRu dilute alloy nanodendrites (PtRu NDs, molar ratio Ru/Pt is 1:199) by the reduction of RuIII ions induced by Pt metal. For the methanol oxidation reaction, PtRu NDs showed the highest forward peak current density (2.66 mA cm-2 , 1.14 A/mgPt ) and the best stability compared to those of pure-Pt nanodendrites (pure-Pt NDs), commercial PtRu/C and commercial Pt/C catalysts.