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

Abstract

Early-late intermetallic phases have garnered increased attention recently for their catalytic properties. To achieve the high surface areas needed for industrially relevant applications, these phases must be synthesized as nanoparticles in a scalable fashion. Herein, Pt 3 Y-targeted as a prototypical example of an early-late intermetallic-has been synthesized as nanoparticles approximately 5-20 nm in diameter in a solution process and characterized by XRD, TEM, EDS and XPS. The key development is the use of a molten borohydride (MEt 3 BH, M= Na, K) as both the reducing agent and reaction medium. Readily available halide precursors of each metal are used. Accordingly, no organic ligands/surfactants are necessary as the resulting halide salt byproduct prevents sintering, which further permits dispersion of the nanoscale intermetallic onto a support. The versatility of this approach was validated by synthesis of other intermetallic phases such as Pt

Simple chemical synthesis of intermetallic Pt2Y bulk nanopowder

“…Still, the easy removal has been confirmed by acid treatments afterward to activate the surface for superior catalytic performances. 9,11 As for platinum 4f, a similar spectrum to a reference Pt/C was observed. Of note, two extra peaks appear in a lower binding energy region (70.2 eV for 4f 7/2 and 73.5 eV for 4f 5/2 ).…”

“…Kanady et al successfully prepared intermetallic Pt 3 Y nanoparticles of 5-20 nm by a molten salt reducing approach with molten borohydride (KEt 3 BH) both as a strong reducing agent and a reaction medium. 9 Roy et al synthesized carbon-supported Pt x Y nanoparticles by a hydrogen-reduction of YCl 3 at 600-800 1C, while keeping very low ppm-range concentrations of O 2 and H 2 O in the system. 10 Hu et al reported intermetallic Pt 3 Y nanoparticles prepared from the reduction of an oxygen-free yttrium carbodiimide precursor that is insensitive to O 2 and H 2 O.…”

“…[13][14][15][16] In the method, Pt/Y 2 O 3 precursor was totally reduced under argon flow in a physical mixture with LiCl and CaH 2 powders at 600 1C, at which temperature the mixed LiCl was in a molten salt form. Apart from the previous molten salt approach, 9 LiCl and CaH 2 are commonly approachable powder chemicals at room temperature and allow for easy handling without any special facilities, such as glove boxes and vacuum systems. CaH 2 was additionally mixed as a reducing agent to extract oxygen from yttrium oxides in the reduction process.…”

Scalable Synthesis of Carbon-Supported Platinum–Lanthanide and −Rare-Earth Alloys for Oxygen Reduction

“…Kanady et al are the first, to our knowledge, that showed clear formation of intermetallic Pt3Y nanoparticles. In that work, molten borohydride was both the reducing agent and reaction medium 35 . Unfortunately, the catalyst was not tested for the electrochemical reduction of oxygen, and the activity cannot be compared to the one reported by our model study.…”

Synthesis of rare-earth metal and rare-earth metal-fluoride nanoparticles in ionic liquids and propylene carbonate

“…Nevertheless, the high reduction potentials of rare-earth metal ions (typically below −2.0 V vs NHE) cause much difficulties regarding the chemical reduction of any chosen precursor and the prevention of post-synthesis oxidation or contamination of the RE-NPs. Recently, Alivisatos and co-authors reported on the synthesis of Pt 3 Y and other so-called early–late intermetallic nanoparticles by a solvent-free route employing a melt of the reducing agent (Na/K)BEt 3 H [ 26 ]. We like to put our results into this context.…”