Proton Exchange Membrane Fuel Cells--The Power Source For Transportation of the Future

Gang Wu Lab

An electron microscopy images showing atomically dispersed Co sites in carbon. The point spectrum taken on the bright atom shows both Co and N, indicating that Co is coordinated with N at an atomic scale.

The Wu research group developed a new class of high-performance nitrogen-coordinated single cobalt atom catalyst derived from Co-doped metal-organic frameworks (MOFs) through a one-step thermal activation for Proton Exchange Membrane Fuel Cells (PEMFCs).

Overview

Proton exchange membrane fuel cells (PEMFCs) have been widely considered the most promising power source for future transportation and other stationary applications by using hydrogen fuel instead of hydrocarbon-based ones. They are capable of providing an extraordinary practical energy conversion efficiency (50-60%) and omitting greenhouse emission via clean electrochemical reactions. The Gang Wu group has published a paper addressing this issue problem is that a significant amount of expensive and scarce platinum is necessary for catalyzing the electrochemical reactions, especially the sluggish oxygen reduction reaction (ORR), which prohibits large scale application of PEMFCs. Therefore, development of high-performance platinum-group-metal free (PGM-free) catalysts has become an ultimate solution to address the cost issue and implement PEFMC technologies for future transportation applications.

The Wu research group at the University at Buffalo developed a new class of high-performance nitrogen-coordinated single cobalt site catalysts derived from Co-doped metal-organic frameworks (MOFs) through a one-step thermal activation. Through carefully engineering Co doping contents and thermal activation conditions, an atomically Co site dispersed catalyst with optimal chemical and structural properties has achieved respectful activity and stability for the ORR, approaching Pt catalysts in challenging acidic media. Real fuel cell tests confirmed that catalyst activity and stability could translate to high-performance cathodes in PEMFCs. Importantly, for the first time, such nitrogen coordinated single atomic Co sites in catalysts were virtually observed by using advanced aberration-corrected electron microscopy coupled with electron energy loss spectroscopy, which provided an insightful understanding of active sites at the atomic scale.

This work addresses two grand challenges for ORR electrocatalysis in acidic PEMFCs: (i) replacing expensive platinum group metal (PGM) catalysts, and (ii) eliminating Fenton reagent degradation of membrane and ionomer caused by iron-based catalysts. It represents a promising step toward the development of advanced catalysts for future PEMFC technologies for transportation.

Resulting Publications

Wang, Xiao Xia, David A. Cullen, Yung-Tin Pan, Sooyeon Hwang, Maoyu Wang, Zhenxing Feng, Jingyun Wang, et al. "Nitrogen-Coordinated Single Cobalt Atom Catalysts for Oxygen Reduction in Proton Exchange Membrane Fuel Cells." Advanced Materials