Kamel Eid

One-step synthesis of trimetallic Pt–Pd–Ru nanodendrites as highly active electrocatalysts

Precise control over composition and structure is highly important for designing highly active nanostructured electrocatalysts. Herein, we report a one-step strategy to directly synthesize trimetallic Pt–Pd–Ru nanodendrites in an aqueous solution at room temperature. These newly designed nanodendrites exhibit superior catalytic activities for both methanol oxidation reaction (MOR) and oxygen reduction reaction (ORR) in comparison with bimetallic Pt–Pd nanoflowers and commercially available Pt/C catalysts.

Facile Synthesis of Porous Dendritic Bimetallic Platinum-Nickel Nanocrystals as Efficient Catalysts for the Oxygen Reduction Reaction.

Certain bimetallic nanocrystals (NCs) possess promising catalytic properties for electrochemical energy conversion. Herein, we report a facile method for the one-step synthesis of porous dendritic PtNi NCs in aqueous solution at room temperature that contrasts with the traditional multistep thermal decomposition approach. The dendritic PtNi NCs assembled by interconnected arms are efficient catalysts for the oxygen reduction reaction. This direct and efficient method is favorable for the up-scaled synthesis of active catalysts used in electrochemical applications.

Synthesis of Hollow Platinum-Palladium Nanospheres with a Dendritic Shell as Efficient Electrocatalysts for Methanol Oxidation.

Engineering the size, composition, and morphology of platinum-based nanomaterials can provide a great opportunity to improve the utilization efficiency of electrocatalysts and reinforce their electrochemical performances. Herein, three-dimensional platinum-palladium hollow nanospheres with a dendritic shell (PtPd-HNSs) are successfully fabricated through a facile and economic route, during which SiO2 microspheres act as the hard template for the globular cavity, whereas the triblock copolymer F127 contributes to the formation of the dendritic shell. In contrast with platinum hollow nanospheres (Pt-HNSs) and commercial platinum on carbon (Pt/C) catalyst, the novel architecture shows a remarkable activity and durability toward the methanol oxidation reaction (MOR) owing to the coupled merits of bimetallic nanodendrites and a hollow interior. As a proof of concept, this strategy is also extended to trimetallic gold-palladium-platinum hollow nanospheres (AuPdPt-HNSs), which paves the way towards the controlled synthesis of other bi- or multimetallic platinum-based hollow electrocatalysts.

Hydrogen gas-assisted synthesis of worm-like PtMo wavy nanowires as efficient catalysts for the methanol oxidation reaction

Bi-metallic Pt-based nanocrystals (NCs) with anisotropic structures are highly promising catalysts for electrochemical energy conversion technologies. Herein we provide a facile method for one-pot synthesis of worm-like PtMo wavy nanowires in oleylamine (OAm) under hydrogen pressure. This is based on a combination between the autocatalytic effect and oriented attachment growth mechanism. The particle size, morphology, and composition of the as-made NCs are tuned by adjusting appropriate reaction parameters and conditions. The as-made worm-like PtMo wavy nanowires composed of multiple crystalline domains exhibit superior catalytic activity and durability towards the methanol oxidation reaction (MOR) compared to commercial Pt/C. This is ascribed to the self-supported interconnected network structure and composition effect. The newly developed one-pot approach is feasible for the synthesis of worm-like Pt-based nanostructures with designed composition for various catalytic applications.

A Three-Dimensionally Structured Electrocatalyst: Cobalt-Embedded Nitrogen-Doped Carbon Nanotubes/Nitrogen-Doped Reduced Graphene Oxide Hybrid for Efficient Oxygen Reduction

To develop low-cost and efficient oxygen reduction reaction (ORR) catalysts, a novel hybrid comprising cobalt-embedded nitrogen-doped carbon nanotubes and nitrogen-doped reduced graphene oxide (Co-NCNT/NrGO-800) was simply prepared by pyrolysis. The combination of nanotubes and graphene, and the efficient doping with cobalt and nitrogen, greatly contribute to the excellent ORR performance. This optimized Co-NCNT/NrGO catalyst exhibits a positive onset potential of 0.91 V and a half-wave potential of 0.82 V, combined with a relatively low peroxide yield, better durability, and better methanol tolerance than commercially available Pt/C, which makes it a promising candidate as a low-cost and effective non-precious-metal ORR catalyst.

One-pot synthesis of PtIr tripods with a dendritic surface as an efficient catalyst for the oxygen reduction reaction

Pt-based nanocrystals with a dendritic structure are highly attractive materials for various electrocatalytic applications owing to their high surface area. Herein, a facile one-pot method is presented for the controlled synthesis of PtIr tripods with a dendritic surface (PtIr DTPs), which is achieved by the reduction of Pt and Ir metallic precursors in oleylamine and NH4F with H2. The unique PtIr DTPs exhibited superior catalytic activity and durability towards the oxygen reduction reaction (ORR). The newly developed one-pot approach is feasible for the synthesis of dendritic tripod Pt-based NCs with a designed composition for various catalytic applications.

Shape-controlled synthesis of porous AuPt nanoparticles and their superior electrocatalytic activity for oxygen reduction reaction

Abstract Control of structure and morphology of Pt-based nanomaterials is of great importance for electrochemical energy conversions. In this work, we report an efficient one-step synthesis of bimetallic porous AuPt nanoparticles (PAuPt NPs) in an aqueous solution. The proposed synthesis is performed by a simple stirring treatment of an aqueous reactive mixture including K2PtCl4, HAuCl4, Pluronic F127 and ascorbic acid at a pH value of 1 without organic solvent or high temperature. Due to their porous structure and bimetallic composition, as-made PAuPt NPs exhibit excellent electrocatalytic activity for oxygen reduction reaction.

Gaseous NH3 Confers Porous Pt Nanodendrites Assisted by Halides

Tailoring the morphology of Pt nanocrystals (NCs) is of great concern for their enhancement in catalytic activity and durability. In this article, a novel synthetic strategy is developed to selectively prepare porous dendritic Pt NCs with different structures for oxygen reduction reaction (ORR) assisted by NH3 gas and halides (F−, Cl−, Br−). The NH3 gas plays critical roles on tuning the morphology. Previously, H2 and CO gas are reported to assist the shape control of metallic nanocrystals. This is the first demonstration that NH3 gas assists the Pt anisotropic growth. The halides also play important role in the synthetic strategy to regulate the formation of Pt NCs. As-made porous dendritic Pt NCs, especially when NH4F is used as a regulating reagent, show superior catalytic activity for ORR compared with commercial Pt/C catalyst and other previously reported Pt-based NCs.

One-pot synthesis of bimetallic PdCu nanoframes as an efficient catalyst for the methanol oxidation reaction

We propose a one-pot solvothermal method for the synthesis of unique porous PdCu nanoframes (NFs). This is achieved by the simultaneous co-reduction of Pd and Cu precursors in oleylamine with NH3. The as-made PdCu NFs showed a superior electrocatalytic performance towards the methanol oxidation reaction, ascribed to their nanoporous morphology and bimetallic composition.

Chapter 6 – Nanoarchitectonic Metals

Controlling the size, morphology, and composition of nanoarchitectonic metals is very important for tailoring their properties for various applications. These can be achieved through different chemical, biological, and physical methods. Solution-based synthetic routes are some of the most robust approaches for fabrication of metal nanocrystals (NCs) with desired morphologies, compositions, and functions, which can be achieved by adjusting reaction parameters such as reactant concentrations, reduction kinetics, capping agents, precursor species, and solvents. This chapter gives a brief introduction to the solution-based chemical routes for the controllable fabrication of metal NCs with various morphologies and compositions as well as their catalytic applications.