High-powered fuel cell boosts electric-powered submersibles, drones

A high-power fuel cell that advances technology in the Transportation area.

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

The transportation sector is a major segment of the US economy: about 1 in 5 dollars in the US is spent annually on transportation products and services. While more people are using electric cars, designing electric-powered planes, ships and submarines are much harder due to power and energy requirements.

Now, a team of engineers may have found a solution for this. Engineers at the McKelvey School of Engineering at Washington University in St. Louis have developed a new fuel cell that can potentially advance the technology in this transportation sector.

They have come up with a direct borohydride fuel cell that operates at double the voltage of today’s commercial fuel cells. For this work, engineers used unique pH-gradient-enabled microscale bipolar interface (PMBI) that facilitates sharply different local pH environments at the anode and cathode of a direct borohydride fuel cell.

According to the team, the cell could power a variety of transportation modes — including unmanned underwater vehicles, drones and eventually electric aircraft — at a significantly lower cost.

Originally, this newly developed fuel uses 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.

Vijay Ramani, the Roma B. and Raymond H. Wittcoff Distinguished University Professor said, “The pH-gradient-enabled microscale bipolar interface is at the heart of this technology. It allows us to run this 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.”

Ramani said the key breakthrough is the PMBI, which is thinner than a strand of human hair. Using membrane technology developed at the 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.

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

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

Ramani
Ramani

Lead author Zhongyang Wang, a doctoral candidate in Ramani’s lab, added: “Once the PBMI synthesized using our novel membranes was proven to work effectively, we optimized 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 have enabled the PMBI.”

The study is published in the journal Nature Energy.

Other participants in this work include Cheng He, a doctoral candidate, and Javier Parrondo, a former research scientist in Ramani’s lab. The team is working with the university’s Office of Technology Management to explore commercialization opportunities.