Pt Alloy Nanocrystal Catalysts: Diminishing Sizes and Improving Stability

Polymer electrolyte membrane fuel cells (PEMFCs) areone of themost promising energy conversion devices with the advantages of cleanand efficient, low-temperature operation, abundant fuel sources, andportability. Due to limited availability and high cost, the use ofnoble metal Pt catalysts in oxygen reduction reaction (ORR) must bereduced in order to achieve large-scale commercial application ofPEMFCs. Alloying with transition metals to reduce the Pt usage andincrease the utilization of Pt is by far the main way to develop ORRcatalysts with high activity and superior stability. Particularly,diminishing the sizes can increase the Pt atom utilization as wellas the Pt mass activity, but the smaller nanocrystals with highersurface energy are typically thermodynamically and electrochemicallyunstable. How to acquire smaller and even ultrafine Pt alloy nanocrystalswith high stability is thus especially important. Herein, we reviewthe research progress in this field in the very recent years. A fundamentalunderstanding of the size-activity and the size-durabilityrelationship is first introduced. Then the discussions focused onthe synthetic strategies and design concepts for reducing nanocrystalsize and simultaneously enhancing their stability. Finally, the challengesand future perspectives on the research directions of Pt-based alloynanocrystal catalysts are briefly summarized.

Automated summary

Polymer electrolyte membrane fuel cells (PEMFCs) are promising energy conversion devices with advantages of cleanliness, efficiency, low-temperature operation, abundant fuel sources, and portability. The use of noble metal Pt catalysts in the oxygen reduction reaction (ORR) needs to be reduced for large-scale commercial application of PEMFCs. Alloying with transition metals to develop ORR catalysts with high activity and stability by reducing Pt usage and increasing Pt utilization is the main research focus in recent years.