A Surfactant-Free Strategy for Synthesizing and Processing Intermetallic Platinum-Based Nanoparticle Catalysts

Abstract

Using Pt(3)Fe nanoparticles as an example, a surfactant-free Np-KCl matrix method (Np stands for nanoparticle) is developed for the synthesis of nanoparticles with controlled size and structure. In this method, the Np-KCl assembly is formed in a one-pot reduction in THF at room temperature. KCl is an insoluble byproduct of the reaction and serves as a matrix that traps the nanoparticles to avoid particle agglomeration and to control the coalescence of nanoparticles during thermal annealing up to 600 °C. By varying the molar ratio of metal precursors and KCl, as well as the time and temperature of annealing, the final particle sizes and crystalline order can be independently controlled. After thermal processing, nanoparticles were released from the KCl matrix and transferred in an ethylene glycol-water solution to support materials forming a uniform Np-support assembly. A detailed study of the synthesis of ordered intermetallic Pt(3)Fe nanoparticles with an average diameter of 4 nm, using this Np-KCl method, is provided as an example of a generally applicable method. This surfactant-free strategy has been extended to the synthesis of other bi- and trimetallic nanoparticles of Pt-transition metals.

Synthesis of Pt3Y and Other Early–Late Intermetallic Nanoparticles by Way of a Molten Reducing Agent

“…11,13,16 In our hands, YCl 3 could not be reduced with KEt 3 BH at room temperature in THF, and if PtCl 4 was included in the reaction, only pure Pt was observed. This is consistent with literature: an Y 3+ complex with two Et 3 BH -anions coordinated has been characterized.…”

“…Salt 13 and oxide 14 matrices have been used to great effect to prevent sintering and control particle size during annealing steps.…”

Bimetallic organic frameworks derived CuNi/carbon nanocomposites as efficient electrocatalysts for oxygen reduction reaction

“…The temperature was selected to both completely decompose the MOF framework [43] and avoid further agglomeration or particle size growth [44]. The SEM images of CuNi/C-80 (Fig.…”

Synthesis of Metastable Au-Fe Alloy Using Ordered Nanoporous Silica as a Hard Template

“…The wet chemistry synthesized alloy nanomaterials are prone to phase segregation especially when the constituent metals are much different in reduction potentials: one of the metal precursors with a low reduction potential readily forms a core, on which the other metal precursor with a high reduction potential precipitates to develop core-shell structures [6]. Post-annealing of such as-prepared alloy nanomaterials can improve the compositional uniformity because of promoted atomic interdiffusion but often lead to uncontrollable broadening in the particle/pore-size distribution due to particle agglomeration [7,8]. Moreover, nanomaterials of thermodynamically unstable (metastable) alloys are hardly materialized by post-annealing because phase separations can be promoted more than atomic interdiffusion at elevated temperatures.…”

“…The nanoporous template is finally dissolved in solution to yield the desired alloy with a skeletal porous structure replicated from the template. annealing of such as-prepared alloy nanomaterials can improve the compositional uniformity because of promoted atomic interdiffusion but often lead to uncontrollable broadening in the particle/pore-size distribution due to particle agglomeration [7,8]. Moreover, nanomaterials of thermodynamically unstable (metastable) alloys are hardly materialized by post-annealing because phase separations can be promoted more than atomic interdiffusion at elevated temperatures.…”