Recent advancements in Pt-nanostructure-based electrocatalysts for the oxygen reduction reaction

Developing highly efficient and durable electrocatalysts for the oxygen reduction reaction (ORR) is the key to improving the performance of proton exchange membrane fuel cells (PEMFCs) for future energy applications. Pt-Based electrocatalysts show the greatest promise for this reaction, among which nanostructure-based catalysts have been identified as potential candidates owing to their morphology, geometry, and size-dependent activities which were revealed from experimental and theoretical studies. The fundamental aspects of the origin of activity enhancement of nanostructure-based catalysts are manifested in the finest form in recent advancements in ORR catalyst design processes. Also, it is one of the areas of research where theoretical studies have contributed to a significant extent to developing tools and techniques which are currently applied in a wide range in the electrocatalysis scenario beyond fuel cell catalysis. This review covers the recent progress in Pt-based nanostructure catalysts for the ORR. This review delves into a comprehensive analysis of effective utilization of theoretically obtained insights into the experimental design of efficient Pt-nanostructure ORR catalysts as well as identifying the origin of their activities. A detailed discussion of the ORR mechanism on low and high-index facets, nanostructure morphologies, and composition, shape and size dependent activities of Pt-based catalysts is included as emphasized from theoretical perspectives. The underlying factors behind the experimentally reported excellent ORR activities of nanostructure-based catalysts are analysed by a detailed investigation of theoretically important factors such as binding energy, reaction barrier, overpotential and strain effects. Finally, challenges and future research directions towards experimental design of efficient ORR catalysts by using the knowledge gained from theory are also addressed.