Recent advances in electrocatalysts toward the oxygen reduction reaction: The case of PtNi octahedra

Designing highly efficient and durable electrocatalysts for the oxygen reduction reaction (ORR), the key step for the operation of polymer electrolyte membrane fuel cells (PEMFCs), is of a pivotal importance for advancing PEMFC technology. Since the most significant progress has been made on Pt₃Ni(111) alloy surfaces, nanoscale PtNi alloy octahedra enclosed by (111) facets have emerged as promising electrocatalysts toward the ORR. However, because their practical uses have been hampered by the cost, sluggish reaction kinetics, and poor durability, recent advances have engendered a wide variety of structure-, size-, and composition-controlled bimetallic PtNi octahedra. Herein, we therefore review the important recent developments of PtNi octahedral electrocatalysts point by point to give an overview of the most promising strategies. Specifically, the present review article focuses on the synthetic methods for the PtNi octahedra, the core-shell and multi-metallic strategies for performance improvement, and their structure-, size-, and composition-control-based ORR activity. By considering the results achieved in this field, a prospect for this alloy nanocatalysts system for future sustainable energy applications is also proposed.