Novel nanowires protection shell prepared for stable oxygen reduction reaction

(Nanowerk News) Chinese scientists have recently prepared stable face-centered tetragonal (fct)-phase platinum (Pt)-based intermetallics in nano-scaled size, which can be used as a protection shell for new PtFeIr nanowires preparation for stable oxygen reduction reaction (ORR).
This research, published in Angewandte Chemie International Edition ("Ordered PtFeIr intermetallic nanowires through a silica-protected strategy for oxygen reduction reaction"), was conducted by Prof. ZHANG Tierui and Dr. SHANG Lu from the Technical Institute of Physics and Chemistry (TIPC) of the Chinese Academy of Sciences (CAS).
Schematic Diagram of Preparation of fct-phase PtFeIr Nanowires for ORR
Schematic Diagram of Preparation of fct-phase PtFeIr Nanowires for ORR. (Image: ZHANG et. al.)
Pt-based alloy nanowires are considered as promising ORR catalysts. It is also widely accepted that intermetallic Pt-based alloys with face-centered tetragonal (fct) structure are more stable than corresponding disordered Pt-based alloys with fcc structure. However, nanowires are instable under high temperature. The synthesis of fct-phase Pt-based nanowires under the phase transformation process still remains a significant challenge.
Besides, the dissolution of transition metals during acidic conditions will result in their structural collapse and activity loss. Consequently, the improvement of the stability of nanowires is highly desirable.
In this work, for the first time, the researchers reported the synthesis of fct-phase PtFeIr ordered intermetallic nanowires with an average diameter of 2.6 nm for ORR.
Original fcc-PtFeIr catalyst is coated with silicon dioxide (SiO2) and become fct-phase PtFeIr nanowires. With the protection of SiO2 cover, it retards the aggregation and breakage of nanowires. Meanwhile, the existence of Ir has guaranteed the thermal stability of catalysts and promotes the phase transformation of nanowires.
Electrochemical test results indicate that the mass activity of PtFeIr nanowires has increased over 80% after phase transformation for ORR.
On the other hand, experiment has shown that "new" ordered structure in slowing down the dissolution of iron in ORR.
The researchers believed that the fct structure Pt-based alloy nanowires prepared in this study can be applied to more fields to ensure efficient and stable ORR.
Source: Chinese Academy of Sciences
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