The mechanism of Co oxyhydroxide nano-islands deposited on a Pt surface to promote the oxygen reduction reaction at the cathode of fuel cells

With the rapid development of fuel cell technology, the low reduction rate of oxygen on Pt-based cathodes is generally considered the main obstacle. Pt/transition metal alloys (Pt-Ms) or Pt/transition metal oxides (Pt-MO _x ) can be formed by doping transition metal atoms into the lattice of the Pt layer or depositing onto the surface of the Pt layer to intensify the catalytic activity of the electrodes. In this work, a stepwise solution chemical reduction method for high dispersion of cobalt oxyhydroxide (-OCoOH) deposited onto the facet of Pt as nano-islands and the mechanism of promoting the oxygen reduction reaction (ORR) at the cathode have been investigated by density functional theory (DFT) calculation. As a result, the electrocatalytic activity of Pt with nano-island -OCoOH structure was 3.6 times that of the Pt/C catalyst, which indicated that promoting the desorption of the first O atom and weakening the adsorption capacity of the interfacial junction Pt for the second O atom from adsorbed oxygen attributed to the migration of d-band center in Pt and the existence of the Co hydroxyl group.

Synthesis of Pd-M@HCS(M = Co, Ni, Cu) Bimetallic Catalysts and Their Catalytic Performance for Direct Synthesis of H2O2

Hydrogen peroxide (H2O2), as a clean and green oxidant, is widely used in many fields. The direct synthesis of H2O2 (DSHP) from H2 and O2 has attracted most research interest because it relates to a facile, environmentally friendly, and economic process. Yolk–shell Pd-M@HCS (hollow carbon sphere) (M = Co, Ni, Cu) nanocatalysts, in which the bimetal nanoparticle is the core and porous carbon works as the shell layer, are reported in this work. It was found that catalytic activities were enhanced because of the introduced M metals. Additionally, the different mass ratios of Pd to Co (mPd/mCo) were further investigated to improve the catalytic performance for the DSHP. When mPd/mCo was 4.4, the prepared Pd-Co@HCS-(4.4) catalyst, with an average Pd nanoparticle size of 7.30 nm, provided the highest H2O2 selectivity of 87% and H2O2 productivity of 1996 mmolgPd−1·h−1, which were increased by 24% and 253%, respectively, compared to Pd@HCS.

A Co–Cu bimetallic magnetic nanocatalyst with synergistic and bifunctional performance for the base-free Suzuki, Sonogashira, and C–N cross-coupling reactions in water

A novel bimetallic catalytic system based on Cu/Co has been developed and used as an efficient, eco-friendly, and recyclable catalyst for base- and Pd-free Sonogashira, Suzuki and C–N cross-coupling reactions in mild reaction conditions.

An environmentally friendly one-pot synthesis method by the ultrasound assistance for the decoration of ultrasmall Pd-Ag NPs on graphene as high active anode catalyst towards ethanol oxidation

An environmentally friendly one-pot synthesis approach for the decoration of Pd-Ag nanoparticles with the ultrasmall size on graphene (Pd-Ag/G) by the assistance of ultrasound is proposed in this paper. This method offers exceptional advantages over other approaches such as environmentally friendly synthesis, being low temperature, reductant, surfactant free, simple, fast and one-pot synthesis. In this work, silver formate is added to the graphene suspension at 25 °C. Then, PdCl₂ is added to the suspension under stirring to fabricate Pd-Ag/G. The uniform dispersity of nanoparticles with an average size of about 2-3 nm is well confirmed by transmission electron microscopy micrographs. The resultant catalyst is applied as anode electrocatalyst towards electrooxidation reaction of ethanol. The Pd-Ag/G catalyst displays exceptional catalytic activity and durability towards electro-oxidation of ethanol. According to the obtained results, it be concluded that the combination of Ag and Pd, ultrasmall and uniform distribution of Pd-Ag nanoparticles led to the improvement of electrocatalytic activity of the Pd-Ag/G catalyst.

Bimetallic Nanoparticle Oxidation in Three Dimensions by Chemically Sensitive Electron Tomography and in Situ Transmission Electron Microscopy

The formation of hollow-structured oxide nanoparticles is primarily governed by the Kirkendall effect. However, the degree of complexity of the oxidation process multiplies in the bimetallic system because of the incorporation of more than one element. Spatially dependent oxidation kinetics controls the final morphology of the hollow nanoparticles, and the process is highly dependent on the elemental composition. Currently, a theoretical framework that can predict how different metal elements result in different oxide morphologies remains elusive. In this work, utilizing a combination of state-of-the-art in situ environmental transmission electron microscopy and three-dimensional (3D) chemically sensitive electron tomography, we provide an in situ and 3D investigation of the oxidation mechanism of the Ni-Fe nanoparticles. The direct measurements allow us to correlate the 3D elemental segregation in the particles with the oxidation morphologies, that is, single-cavity or dual-cavity hollow structure, and multicavity porous structures. Our findings in conjunction with theoretical calculations show that metal concentration, diffusivity, and particle size are important parameters that dictate the mechanical and phase stabilities of the hollow oxide shell, which in turn determine its barrier properties and the final hollow oxide morphology. It sheds light on how to use multielemental oxidation to control morphology in nanomaterials and demonstrates the power of 3D chemical imaging.

Nanowire networks and hollow nanospheres of Ag-Au bimetallic alloys at room temperature

Due to their physicochemical properties, metallic nanoalloys have potential applications in biomedicine, electrocatalysis and electrochemical sensors, among many other fields. New alternative procedures have emerged in order to reduce production costs and the use of toxic substances. In this study we present a novel low-toxicity synthesis method for the fabrication of nanowire networks (NWNs) and Ag-Au hollow nanospheres. The synthesis process is performed at room temperature without any sophisticated equipment, such as special cameras or furnaces, etc. Transmission electron microscopy showed that the NWNs contain random alloys with a diameter of between 10-13 nm. The radius for the hollow nanospheres is approximately located between 70-130 nm. The absorption bands in the UV-vis spectrum associated with the surface plasmon in Ag-Au bimetallic nanoparticles are highlighted at 385 nm for the NWNs and 643 nm for the hollow nanospheres. The study was performed with low-toxicity substances, such as rongalite, ascorbic acid and sucrose, and showed high efficiency for the fabrication of these types of nanostructures, as well as good stability for long periods of time.

Mechanistic insights into the activation process in electrocatalytic ethanol oxidation by phosphomolybdic acid-stabilised palladium(0) nanoparticles (PdNPs@PMo12)

A Keggin type polyoxometalate (POM), phosphomolybdic acid (PMo₁₂), has been employed to encapsulate and stabilise pseudo-spherical Pd(0) nanoparticles (PdNPs).

Activated nanostructured bimetallic catalysts for C–C coupling reactions: recent progress

This minireview highlights the recent progress made in the last decade towards the development of activated bimetallic alloy nanoparticle catalysts for C–C coupling reactions, including asymmetric C–C bond coupling reactions.

Highly dispersed palladium nanoparticles on poly(N1,N3-dimethylbenzimidazolium)iodide-functionalized multiwalled carbon nanotubes for ethanol oxidation in alkaline solution

Multi-walled carbon nanotubes (MWCNTs) have been considered as good catalyst supporting materials, and their dispersion and functionalization are important, challenging problems for high-performance composite catalysts.

Nickel core–palladium shell nanoparticles grown on nitrogen-doped graphene with enhanced electrocatalytic performance for ethanol oxidation

Herein, we report a facile two-step strategy for green synthesis of nickel core–palladium shell nanoclusters on nitrogen-doped graphene (Ni@Pd/NG) without any surfactant and additional reducing agent.

Growth Control of MoS2 Nanosheets on Carbon Cloth for Maximum Active Edges Exposed: An Excellent Hydrogen Evolution 3D Cathode

To greatly improve the hydrogen evolution reaction (HER) performance, it is the key approach to expose as many active edges of MoS2 as possible. This target is the research hotspot and difficulty of MoS2 which is a promising HER catalyst. In this work, we realized the active-edges control of MoS2 nanosheets on carbon cloth (CC) by growth control during the synthesis procedure. Moreover, MoS2 nanosheets vertically grown on carbon cloth (MoS2⊥CC) was confirmed to be the best morphology with maximum active edges exposed. Multifactors structure control resulted in abundant active-edges exposure and effective electron delivery, thus excellent HER activity. This three-dimensional cathode, MoS2⊥CC, can reach a great current density of 200 mA/cm(2) at a small overpotential of 205 mV. The preeminent HER performance can rival the best MoS2-based catalyst ever reported.