Proton exchange membrane fuel cells (PEMFCs) are considered to be an important low-carbon energy conversion technology, which has shown impressive performance improvement in the past decades. However, the sluggish kinetics of the oxygen reduction reaction (ORR) at the cathode has been an impediment to the successful commercialization of the technology. Novel highly active electrocatalysts for the ORR are highly desired to meet the US DOE performance targets. In recent years, polyhedron-engineered Pt-alloy nanocrystals have demonstrated unprecedented electrocatalytic activity. Different from previous reviews on shape-manipulated Pt-based ORR catalysts, this review focuses on 3D polyhedron-engineered Pt-based nanocrystal electrocatalysts with an in-depth comparison of different active facet-tailored geometric configurations and their advanced electrocatalytic properties. The review carefully examines and criticizes the aggregated data in this area, and provides an important overview as well as a critical insight into the topic. Understanding the catalytic mechanism taking place with polyhedron-designed Pt-based nanocrystals helps to unlock the door to highly active ORR electrocatalysts for PEMFC applications.
