Atomic-scale understanding of a new electrocatalyst could lead to more affordable and efficient fuel cells

In a paper in the journal Nature Materials published in December, 2024,  Manos Mavrikakis, the Ernest Micek Distinguished Chair, James A. Dumesic Professor, and Vilas Distinguished Achievement Professor in the Department of Chemical and Biological Engineering at the University of Wisconsin-Madison, discusses the atomic-level basis for the enhanced oxygen reduction reaction activity of a class of electrocatalytic materials called transition metal nitrides.

In fuel cells and other energy storage devices, the oxygen reduction reaction at the cathode, in which oxygen is protonated or adds a proton, is key to completing a circuit and generating energy. This reaction, however, is often the bottleneck in the efficiency of electrochemical energy systems.

Researchers have found that using platinum as a catalyst can greatly improve the oxygen reduction reaction speed. However, platinum is one of the most expensive metals in the world. That’s why researchers are searching for non-precious metal catalysts that can do the job equally well.

A class of materials called transition metal nitrides are promising alternative catalysts which cost much less than platinum; however, a lack of fundamental understanding of the catalytic reaction mechanism that takes place on the surface of metal nitrides has limited the ability to design improved catalysts for the oxygen reduction reaction on these materials.

Through a combination of electrochemical experimentation and computational modeling, Mavrikakis and Dr. Lang Xu from UW-Madison and other team members, including researchers from Cornell University and Emory University, found that during oxygen reduction reactions on manganese nitride, an electrocatalytically active spinel manganese oxide shell grew over the core of the material. This thin oxide shell is stretched compared to the pure spinel oxide and its catalytic activity is 300 percent more active than that of the pure spinel oxide.

This atomic-level insight of the process provides a new understanding of how these materials function, and could lead to better, much more affordable transition metal nitride-based electrocatalysts and fuel cells.