Published November 14, 2018
CBE PhD candidate Yanghua He has developed a cobalt catalyst for electrochemical energy technology that solves environmental concerns. Her research interest focuses on exploring advanced electrocatalyst designs and synthesis strategies using earth-abundant elements for energy conversion applications such as metal-air batteries and fuel cells.
Platinum-group-metal (PGM)-free catalysts have been considered as a long-term goal for advanced fuel cell technologies with recent investments from both The United States Department of Energy (DOE) and agencies from other nations. Currently, the primary issue of PGM-free catalysts is the catalysts' stability with H2O2 as by-products from potential Fenton reactions during the Oxygen Reduction Reaction (ORR) in acid media. Co-based catalysts emerge as ideal candidates for Pt-free and Fe-free catalysts in challenging acidic media.
Comparing with Fe-N-C catalysts, most Co-N-C catalysts still suffer from inactivity and high yields of H2O2 during the ORR in acid media. Yanghua's research focuses on improving these hindering characteristics of Co-N-C catalysts. With her collaborators, Yanghua and her team reported an efficient surfactant-assisted confinement pyrolysis strategy to effectively control the synthesis of CoN4 active sites with significantly increased in power density. As expected, the Co-N-C@F127 catalyst exhibits an unprecedented ORR activity with a half-wave potential (E1/2) of 0.84 V (vs. RHE) as well as enhanced stability in the corrosive acidic media. The catalyst also demonstrates high initial performance with a power density of 0.87 W cm-2 along with encouraging durability in H2-O2 fuel cells. The performance of the atomically dispersed Co site catalyst approaches that of the Fe-N-C catalysts. Unlike other Co catalysts, this new atomically dispersed Co-N-C@F127 catalyst is deemed to contain substantial CoN2+2 sites, which are active and thermodynamically favorable for the four-electron ORR pathway. At this moment, the catalyst invented by Yanghua and her collaborators exhibits the highest ORR performance reported for PGM-free and Fe-free catalysts.
This finding is published in Energy & Environmental Science, which is a monthly journal published by the Royal Society of Chemistry with an impact factor over 30. [Read the full paper]