Pt-based alloy nanowires are considered as promising oxygen reduction reaction (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 face-centered cubic (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.
Chinese scientists have recently prepared stable fct-phase Pt-based intermetallics in nano-scaled size.
This research, published online in Angewandte Chemie International Edition, was directed by Prof. ZHANG Tierui and Dr. SHANG Lu from Technical Institute of Physics and Chemistry (TIPC) of the Chinese Academy of Sciences.
In this work, researchers report the synthesis of fct-phase PtFeIr ordered intermetallic nanowires with an average diameter of 2.6 nm for ORR for the first time.
Original fcc-PtFeIr catalyst is coated with 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.
By taking electrochemical tests, the 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 Fe in ORR.
Researchers suggest that fct structure Pt-based alloy nanowires prepared in this study can be applied in more applications to ensure an efficient and stable ORR.
This work was supported by the International Partnership Program of Chinese Academy of Sciences (GJHZ201974).
Schematic Diagram of Preparation of fct-phase PtFeIr Nanowires for ORR (Image by ZHANG et. al.)