New catalyst enables fuel cell and battery to be combined in one device

A single device that generates both fuel and oxidizer from water and, when a switch is flipped, converts fuel and oxygen to electricity and water, has many application benefits land, space and military. From low environmental impact to high energy density, the development of efficient unitized regenerative fuel cells, or CFUs as they are called, has been in the sights of researchers for years.

But to be truly effective, a CFRU needs bifunctional catalysts. This means that in electrolyser mode, the catalysts should facilitate the decomposition of water into hydrogen and oxygen and, in fuel cell mode, facilitate their recombination into water. Today, working in the laboratory of Vijay Ramani, professor emeritus of the University Roma B. & Raymond H. Wittcoff, a team of researchers have found an excellent bifunctional catalyst for the oxygen electrode.

Their work has been published in the journal Proceedings of the National Academy of Sciences.

“Unlike the hydrogen electrode, in which platinum is an efficient bifunctional catalyst, it is very difficult to identify a suitable catalyst for the oxygen electrode due to the slow kinetics of oxygen reduction and of its evolution, “said Pralay Gayen, who currently works at Intel, who was a postdoctoral research associate in Ramani’s lab at the McKelvey School of Engineering at Washington University in St. Louis and was the first author. of the article.

Sulay Saha, a postdoctoral research associate in Ramani’s lab, and Gayen’s research were guided by first principles: taking into account the fundamental properties of different substances before going to the lab to test for potential catalysts.

Together with former undergraduate researcher and co-author Xinquan Liu, the team eventually identified and developed Pt-Pyrochlore, a composite of platinum and lead ruthenate pyrochlore, which gave high bifunctionality.

The “bifunctionality index” is a measure of the catalyst’s ability to facilitate both the forward and reverse direction of a reaction. “We want the index to be low,” said Kritika Sharma, doctoral student. engineering student. “Zero, ideally.” This new catalyst has a bifunctionality index of 0.56 volts, which is very low compared to the other catalysts reported. When used in a laboratory-developed URFC device, the catalyst provided a round-trip energy efficiency (RTE) of 75%, the highest round-trip efficiency reported in this type of CFRU.

With such high efficiency, the developed URFCs are well suited for applications such as submersibles, drones, spacecraft and space stations, as well as for off-grid energy storage.