Strained Lattice with Persistent Atomic Order in Pt₃Fe₂ Intermetallic Core–Shell Nanocatalysts

Abstract

Fine-tuning nanocatalysts to enhance their catalytic activity and durability is crucial to commercialize proton exchange membrane fuel cells. The structural ordering and time evolution of ordered Pt3Fe2 intermetallic core-shell nanocatalysts for the oxygen reduction reaction that exhibit increased mass activity (228%) and an enhanced catalytic activity (155%) compared to Pt/C has been quantified using aberration-corrected scanning transmission electron microscopy. These catalysts were found to exhibit a static core-dynamic shell regime wherein, despite treating over 10,000 cycles, there is negligible decrease (9%) in catalytic activity and the ordered Pt3Fe2 core remained virtually intact while the Pt shell suffered a continuous enrichment. The existence of this regime was further confirmed by X-ray diffraction and the compositional analyses using energy-dispersive spectroscopy. With atomic-scale two-dimensional (2-D) surface relaxation mapping, we demonstrate that the Pt atoms on the surface are slightly relaxed with respect to bulk. The cycled nanocatalysts were found to exhibit a greater surface relaxation compared to noncycled catalysts. With 2-D lattice strain mapping, we show that the particle was about -3% strained with respect to pure Pt. While the observed enhancement in their activity is ascribed to such a strained lattice, our findings on the degradation kinetics establish that their extended catalytic durability is attributable to a sustained atomic order.

Core–shell nanoparticles: synthesis and applications in catalysis and electrocatalysis

“…[287][288][289][290][291][292][293][294][295][296][297] In this section, various catalytic reactions by CSNs 298 are described, such as hydrogenation reactions, oxidation reactions, cross-coupling reactions, tandem deprotection-Knoevenagel and Henry reactions, aerobic oxidative esterifications and synthesis of bulk chemicals (e.g., adipic acid), etc. [287][288][289][290][291][292][293][294][295][296][297] In this section, various catalytic reactions by CSNs 298 are described, such as hydrogenation reactions, oxidation reactions, cross-coupling reactions, tandem deprotection-Knoevenagel and Henry reactions, aerobic oxidative esterifications and synthesis of bulk chemicals (e.g., adipic acid), etc.…”

Organic Phase Syntheses of Magnetic Nanoparticles and Their Applications

“…However, the stability and activity of the MPt catalysts can be dramatically improved once the M and Pt are in an ordered intermetallic L1 0 structure. 168,192,411,412 Taking the FePt NPs as an example, the L1 0 -FePt is chemically more stable and catalytically more active for the ORR than the A1-FePt in acidic environment due to the unique intermetallic structure. 168 The key here is to obtain fully ordered L1 0 -FePt NPs.…”

Elemental Anisotropic Growth and Atomic-Scale Structure of Shape-Controlled Octahedral Pt–Ni–Co Alloy Nanocatalysts

“…Oxygen reduction electrocatalysts are known to play a crucial role on fuel cells performance, being the fundamental studies on the subject still required to overcome these barriers 3,4 . By alloying Pt with other non-noble metals, it is possible to produce cheaper electrocatalysts with novel properties for the oxygen reduction reaction (ORR) due to lattice compression 5,6 and/or modified electronic properties 7,8 . Thus, several studies have shown that binary Pt-M (M=Cr, Mn, Fe, Co, Ni, Cu, V, Ti) nanocrystals (NCs) greatly enhanced the kinetics of the ORR in comparison with standard Pt catalysts [9][10][11] .…”