RE ON EB RO GT IYC S
HIGH-POWERED FUEL CELL
BOOSTS ELECTRIC-POWERED SUBMERSIBLES, DRONES
A team of engineers in the McKelvey
School of Engineering at Washington
University in St Louis has developed
a high-power fuel cell that advances
technology in this area. Led by Vijay Ramani the
team has developed a direct borohydride fuel cell
that operates at double the voltage of today's
commercial fuel cells.
This advancement using a unique pH-gradientenabled
microscale bipolar interface (PMBI),
reported in Nature Energy Feb 25, could power
a variety of transportation modes - including
unmanned underwater vehicles, drones and
eventually electric aircraft - at significantly lower
cost.
"The pH-gradient-enabled microscale bipolar
interface is at the heart of this technology," says
Ramani, also professor of energy, environmental
& chemical engineering. "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."
The fuel cell developed at Washington University
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.
Ramani says 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.
"Previous attempts to achieve this kind of acidalkali
separation were not able to synthesize
and fully characterize the pH gradient across
the PMBI," says Shrihari Sankarasubramanian,
a research scientist on 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 Ramani's lab, adds: "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 ionexchange
membranes that has enabled the PMBI."
"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,"
Ramani says.
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
commercialisation opportunities.
An artistic representation of the pH-gradient
enabled microscale bipolar interface (PMBI)
created by Vijay Ramani and his lab. The
two layers that make up the interface are
covering the third bottom layer, which is
the electrode with palladium particles on it.
The submarine and drones are envisioned
applications of the direct borohydride
fuel cell which incorporates the PMBI.
Photocredit: McKelvey School of Engineering
42 April 2019