High-power fuel cell enables more electric vehicle types

Researchers from Washington University in St. Louis have developed a fuel cell with the capacity to power electric vehicles such as planes, ships and submarines which have much higher energy requirements than electric cars.

Described in the journal Nature Energy, the device is a direct borohydride fuel cell that utilises a pH-gradient-enabled microscale bipolar interface (PMBI), which is thinner than a human fair. Research leader Professor Vijay Ramani said the PMBI is “at the heart of this technology”, enabling the researchers to run the fuel cell “with liquid reactants and products in submersibles, in which neutral buoyancy is critical, while also letting us apply it in higher-power applications such as drone flight”.

The fuel cell features an acidic electrolyte at one electrode and an alkaline electrolyte at the other electrode. Typically, the acid and alkali will quickly react when brought in contact with each other. Using membrane technology developed at Washington’s McKelvey Engineering School, the PMBI can keep the acid and alkali from mixing, forming a sharp pH gradient and enabling the successful operation of this system.

“Previous attempts to achieve this kind of acid–alkali separation were not able to synthesise and fully characterise the pH gradient across the PMBI,” said Shrihari Sankarasubramanian, a research scientist on Prof Ramani’s team. “Using a novel electrode design in conjunction with electroanalytical techniques, we were able to unequivocally show that the acid and alkali remain separated.”

Lead author Zhongyang Wang, a doctoral candidate in Prof Ramani’s lab, added, “Once the PBMI synthesised using our novel membranes was proven to work effectively, we optimised the fuel cell device and identified the best operating conditions to achieve a high-performance fuel cell. It has been a tremendously challenging and rewarding pathway to developing the new ion-exchange membranes that has enabled the PMBI.”

With the fuel cell said to operate at double the voltage of today’s commercial fuel cells, the researchers believe it could be used to power a variety of transportation modes — including unmanned underwater vehicles, drones and eventually electric aircraft — at significantly lower cost than current methods.

“This is a very promising technology,” Prof Ramani said, “and we are now ready to move on to scaling it up for applications in both submersibles and drones.”

Image caption: An artistic representation of the pH-gradient enabled microscale bipolar interface (PMBI) created by Vijay Ramani and his lab.

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