A universal strategy for fast, scalable, and aqueous synthesis of multicomponent palladium alloy ultrathin nanowires

Selenium induced multicomponent platinum-based ultrathin nanowires with abundant grain boundaries and partial amorphous phase enable remarkable multifunctional electrocatalysis

Ultrafine platinum (Pt)-based nanowires (NWs) have emerged as a highly promising type of materials for multifunctional electrocatalysts. However, to achieve their synthesis presents significant challenges via relatively facile strategies, especially for multicomponent Pt-based NWs, due to the substantial variation in reduction potentials among different precursors and the tough coordination required for nanocrystal nucleation and growth. Herein, ultrathin NWs composed by Pt, Se, and Cd were realized via a facile one-pot synthesis where only involving precursors, reducing agent and solvent. Moreover, the prepared NWs embed the joint advantages of multicomponent, partial amorphous, ultrafine size, abundant grain boundaries and surface-defect-sites meanwhile. Thus, the ultrahigh methanol oxidation reaction (MOR) activity of 2.94 A mgPt-1 and superior catalytic stability were achieved for Pt-Se-Cd NWs, transcending the most of Pt-based catalysts. Density functional theory calculation suggests that the outstanding MOR activity was attributed to the weakened CO poisoning and optimized adsorption of *CH3OH. Apart from MOR, Pt-Se-Cd NWs are also with remarkable activities for ethanol oxidation reaction (EOR) and hydrogen evolution reaction (HER). Se precursor plays a key role on NWs formation and amorphous regulation, based on which more Pt-Se-M NWs (M = Zn, In, CdZn, ZnIn, CdInZn) were fabricated successfully, revealing a superior generalization in NW synthesis. The work may not only highlight a facile synthesis for ultrafine Pt-based NWs with abundant catalytic advantages, but also explore their potential applications in electrocatalysis and beyond.

Research progress of transition metal catalysts for electrocatalytic EG oxidation

Ethylene glycol (EG) is a small-molecule alcohol with a low oxidation potential and is a key monomer in the production of polyethylene terephthalate (PET). The efficient oxidation of EG can further enable the recycling of waste PET. Currently, there are many studies on catalysts for EG oxidation, among which transition metal catalysts (including traditional non-precious metals such as Fe, Co, Ni and other noble metals such as Pt and Pd) have good prospects for application in EG oxidation reactions due to their unique electronic structures. In this study, the synthesis strategy of transition metal catalysts for the electrocatalytic oxidation of EG is summarized and the performance of different types of catalysts in the EG oxidation reaction is reviewed. Advanced characterization methods were used to understand the oxidation mechanism of EG and to control the conversion of EGOR intermediates into target products. Therefore, we need to further explore efficient catalysts for EG oxidation to achieve efficient reactions.

Multi-Component Intermetallic Nanocrystals: a Promising Frontier in Advanced Electrocatalysis

As the latest representation of high-entropy materials, structurally ordered multi-component intermetallic (MCI) nanocrystals exhibit various attractive functional properties, exceptionally high activity, and durability in energy-related electrocatalytic applications. These properties are primarily attributed to their ordered superlattice structures and high-entropy effects in one sublattice. However, to date, MCI nanocrystals have not been systematically studied. This review comprehensively analyzes the structural characteristics of MCI nanocrystals and the thermodynamics and kinetics of their ordering transformation. Various synthesis strategies for constructing MCI nanocrystals are discussed, including traditional thermal annealing, the cutting-edge manufacturing protocol of Joule heating methods, and wet chemical synthesis, highlighting their advantages and limitations. Importantly, the electronic structure characteristics of MCI nanocrystals are analyzed, beginning with the orbital hybridization of platinum group elements with 3d-block, p-block, and f-block metals, and further discussing their roles in electrocatalytic reactions (oxygen reduction reaction, hydrogen evolution reaction, formic acid oxidation reaction, and methanol oxidation reaction). The focus is on how the optimized electronic structure of active sites in MCI nanocrystals and the shifting of the d-band center contribute to performance enhancement. Based on comprehensive analysis, this review summarizes the progress made in MCI nanocrystals to date and highlights the significant challenges faced by the scientific community.

High-Entropy PdRhFeCoMo Metallene With High C1 Selectivity and Anti-Poisoning Ability for Ethanol Electrooxidation

The urgent demand for designing highly efficient electrocatalysts for ethanol oxidation reaction (EOR) with elevated C1 selectivity, robust anti-poisoning capability, and high mass activity presents a formidable challenge. Herein, a novel two-dimentional (2D) high-entropy PdRhFeCoMo metallene (PdRhFeCoMo HEM) electrocatalyst is successfully synthesized via a mild one-step solvothermal method. The PdRhFeCoMo HEM, characterized by intentionally designed multi-metallic ensembles and ultra-thin graphene-like structures, delivers an impressive mass activity of 7.47 A mgPd+Rh -1 and specific activity of 25.5 mA cm-2. Furthermore, it can retain a mass activity of 0.56 A mgPd+Rh -1 after undergoing 20000 s of continuous testing, demonstrating outstanding resistance to poisoning. More significantly, the PdRhFeCoMo HEM demonstrates an elevated capacity for C─C bond cleavage with a superior C1 selectivity of up to 84.12%. In situ spectroscopy analysis, combined with theoretical calculations, reveals that the deliberate design of components and structures effectively regulate the electronic properties of the Pd site, thereby enhancing the adsorption of reactant and reducing the reaction barrier of the C1 pathway. Finally, a flexible solid-state ethanol fuel cell assembled by PdRhFeCoMo HEM presents a maximum power density of 20.1 mW cm-2 and can operate continuously by repeatedly adding ethanol fuel.

Morphology Variation of Ternary PdCuSn Nanocrystalline Assemblies and Their Electrocatalytic Oxidation of Alcohols

Metal alloys not only increase the composition and spatial distribution of elements but also provide the opportunity to adjust their physicochemical properties. Recently, multimetallic alloy nanocatalysts have attracted great attention in energy applications and the chemical industry. This work presents the production of three ternary PdCuSn nanocrystalline assemblies with similar compositions via a one-step hydrothermal method. The shape variation of assembly units from nanosheets and nanowires to nanoparticles were realized by adjusting the percentage of Sn in metal precursors. Experimental data show that PdCuSn nanowire networks showed the best catalytic activity by virtue of their optimized morphological characteristics and microscopic electronic structure. With electrooxidation of methanol, ethanol, ethylene glycol, and glycerol at 30 °C, PdCuSn nanowire networks demonstrated catalytic activity of 1129, 2111, 2540, and 1445 mA mg-1, respectively. The catalytic activity for alcohol oxidation is attributed to the production of the electronic structure and morphology features that are most suitable. This is achieved by introducing the proper quantities of Cu and Sn components in the first stage of synthesis. This study would help with the construction of high-efficiency nanostructured alloy catalysts by regulating the electronic structure and morphology.

One-pot Synthesis of PdCuAg and CeO2 Nanowires Hybrid with Abundant Heterojunction Interface for Ethylene Glycol Electrooxidation

Introducing CeO2 into Pd-based nanocatalysts for electrocatalytic reactions is a good way to solve the intermediate toxicity problem and improve the catalytic performance. Here we reported a simple strategy to synthesize the PdCuAg and CeO2 nanowires hybrid via a one-pot synthesis process under strong nanoconfined effect of specific surfactant as templates. Owing to the structural (ultrathin nanowires, abundant heterojunction/interfaces between metal and metal oxide) and compositional (Pd, Cu, Ag, CeO2) advantages, the hybrid showed significantly enhanced catalytic activity (6.06 A mgPd -1) and stability, accelerated reaction rate, and reduced activation energy toward electrocatalytic ethylene glycol oxidation reaction.

Facile Synthesis of High-Entropy Alloy Nanowires for Electrocatalytic Alcohol Oxidation

Considering the structural and compositional advantages of high-entropy alloy (HEA) as high-efficient electrocatalysts, we here present a facile method to prepare high-entropy alloy nanowires with seven elements in an aqueous solution. The as-synthesized PdPtCuAgAuPbCo nanowires possess dispersed one-dimensional morphology and exhibit enhanced electrocatalytic performance with the mass activity of 9.9 A mgPd+Pt -1 toward ethanol electrooxidation. The HEA nanowires also perform superior stability, resistance to CO poisoning, and good electrocatalytic activities toward other alcohols (e. g., ethylene glycol and methanol) oxidation. The synthesis strategy is easy to operate with low cost and has wide application prospects for preparing desired electrocatalysts for fuel cells.

Ultrathin RhCo alloy nanowires with defect-rich active sites for alkaline hydrogen evolution electrocatalysis

One-dimensional RhCo alloy nanowires (NWs) with an ultrathin thickness (2.6 nm) and abundant defect sites were prepared in an aqueous solution by a nanoconfined attachment growth route within assembled columnar micelles. Thanks to dual synergies between advantageous anisotropic ultrathin structures and alloy compositions, they endowed one-dimensional RhCo NWs with superior activity and high stability for alkaline hydrogen evolution electrocatalysis.

Ultrathin RhCuAgPd/Pd nanowire heterostructures for ethylene glycol electrooxidation

Ultrathin RhCuAgPd/Pd nanowire heterostructures were prepared by a seed-mediated growth method. Due to the synergistic structural (including ultrathin NWs and interfaces) and compositional (Pd, Rh, Cu and Ag) advantages, the RhCuAgPd/Pd NWs exhibit superior electrocatalytic performance toward ethylene glycol oxidation under alkaline conditions, including high mass activity (6.63 A mg_Pd^-1), fine stability/durability and resistance to CO poisoning, favourable electrocatalytic kinetics and low activation energy values (18.64 kJ mol^-1).

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.

Assembly of Alloyed PdCu Nanosheets and Their Electrocatalytic Oxidation of Ethanol

Two-dimensional (2D) nanostructured catalysts have attracted great attention in many important fields, including energy applications and chemical industry. In this study, PdCu nanosheet assemblies (NSAs) have been synthesized and investigated as electrocatalysts for direct ethanol fuel cells in an alkaline medium. A great number of active sites on the nanosheets of PdCu NSAs for ethanol electro-oxidation are exposed, where the electron structures are optimized combined with the second element copper. Electrochemical measurements show that PdCu NSA1 exhibits excellent catalytic activity (2536 mA mg^-1) and cyclic stability compared to PdCu NSA2 (1700 mA mg^-1) and PdCu NSA3 (1436 mA mg^-1), much higher than commercial Pd/C. Kinetics studies on the electrolysis of ethanol suggest that PdCu NSAs should be more favorable at higher catalytic temperatures, higher concentrations of ethanol, and low pH value environments. The unique composition and structures PdCu NSA1 would result in the lowest energy barrier in the rate-controlling step of the ethanol oxidation reaction (EOR), confirmed by density functional theory (DFT). The formation mechanism of PdCu NSAs and their excellent electrocatalytic activity toward EOR have been discussed and analyzed.

Chiral Conformation of Subnanometric Materials

Subnanometric materials (SNMs) refer to nanomaterials with sizes comparable to the diameter of common linear polymers or confined at the level of a single unit cell in at least one dimension, usually <1 nm. Conventional inorganic nanoparticles are usually deemed to be rigid, lacking self-adjustable conformation. In contrast, the size at subnanometric scale endows SNMs with flexibility analogous to polymers, resulting in their abundant self-adjustable conformation. It is noteworthy that some highly flexible SNMs can adjust their shape automatically to form chiral conformation, which is rare in conventional inorganic nanoparticles. Herein, we summarize the chiral conformation of SNMs and clarify the driving force behind their formation, in an attempt to establish a better understanding for the origin of flexibility and chirality at subnanometric scale. In addition, the general strategies for controlling the conformation of SNMs are elaborated, which might shed light on the efficient fabrications of chiral inorganic materials. Finally, the challenges facing this area as well as some unexplored topics are discussed.

Enhanced Electrocatalytic Activity of Alloyed Palladium-Lead Nanoparticles toward Electrooxidation of Ethanol

Although many researchers have made great efforts to pursue promising high-efficiency electrocatalysts, a formidable challenge remains for designing excellent palladium-based electrocatalysts for commercializing direct liquid fuel cells. This study reports the synthesis of bimetallic PdPb nanoparticles (NPs) via a mixed solution containing cetyl trimethyl ammonium bromide as the capping agent. Alloyed PdPb NPs are formed, where the size of the NPs increases as Pb atoms are introduced gradually. However, Pd₃Pb NPs are obtained with the same molar ratio of Pd and Pb in the raw systems. Among all of the as-made NPs, Pd₉Pb₁ NPs exhibit superior catalytic activity (2620 mA mg^-1) toward ethanol electrooxidation, 4.3 times higher than commercial Pd/C catalysts (613 mA mg^-1). The overall rate of the EOR for PdPb NPs is determined, demonstrating that the electrocatalytic activity of the PdPb NPs increases at high catalytic temperatures, in high pH environments, and/or at high ethanol concentrations.