Engineers develop new fuel cells with twice the operating voltage as
hydrogen

Date:
June 18, 2020
Source:
Washington University in St. Louis
Summary:
Engineers have developed high-power, direct borohydride fuel
cells that operate at double the voltage of conventional hydrogen
fuel cells.



FULL STORY ========================================================================== Electrification of the transportation sector -- one of the largest
consumers of energy in the world -- is critical to future energy and environmental resilience. Electrification of this sector will require high-power fuel cells (either stand alone or in conjunction with
batteries) to facilitate the transition to electric vehicles, from cars
and trucks to boats and airplanes.


========================================================================== Liquid-fueled fuel cells are an attractive alternative to traditional
hydrogen fuel cells because they eliminate the need to transport and
store hydrogen.

They can help to power unmanned underwater vehicles, drones and,
eventually, electric aircraft -- all at significantly lower cost. These
fuel cells could also serve as range-extenders for current battery-powered electric vehicles, thus advancing their adoption.

Now, engineers at the McKelvey School of Engineering at Washington
University in St. Louis have developed high-power direct borohydride
fuel cells (DBFC) that operate at double the voltage of conventional
hydrogen fuel cells. Their research was published June 17 in the journal
Cell Reports Physical Science.

The research team, led by Vijay Ramani, the Roma B. and Raymond
H. Wittcoff Distinguished University Professor, has pioneered a reactant: identifying an optimal range of flow rates, flow field architectures and residence times that enable high power operation. This approach addresses
key challenges in DBFCs, namely proper fuel and oxidant distribution
and the mitigation of parasitic reactions.

Importantly, the team has demonstrated a single-cell operating voltage
of 1.4 or greater, double that obtained in conventional hydrogen fuel
cells, with peak powers approaching 1 watt/cm2. Doubling the voltage
would allow for a smaller, lighter, more efficient fuel cell design,
which translates to significant gravimetric and volumetric advantages when assembling multiple cells into a stack for commercial use. Their approach
is broadly applicable to other classes of liquid/liquid fuel cells.

"The reactant-transport engineering approach provides an elegant and
facile way to significantly boost the performance of these fuel cells
while still using existing components," Ramani said. "By following our guidelines, even current, commercially deployed liquid fuel cells can
see gains in performance." The key to improving any existing fuel cell technology is reducing or eliminating side reactions. The majority of
efforts to achieve this goal involve developing new catalysts that face significant hurdles in terms of adoption and field deployment.

"Fuel cell manufacturers are typically reluctant to spend
significant capital or effort to adopt a new material," said Shrihari Sankarasubramanian, a senior staff research scientist on Ramani's
team. "But achieving the same or better improvement with their existing hardware and components is a game changer." "Hydrogen bubbles formed on
the surface of the catalyst have long been a problem for direct sodium borohydride fuel cells, and it can be minimized by the rational design
of the flow field," said Zhongyang Wang, a former member of Ramani's
lab who earned his PhD from WashU in 2019 and is now at the Pritzker
School of Molecular Engineering at the University of Chicago. "With
the development of this reactant-transport approach, we are on the path
to scale-up and deployment." Ramani added: "This promising technology
has been developed with the continuous support of the Office of Naval
Research, which I acknowledge with gratitude. We are at the stage of
scaling up our cells into stacks for applications in both submersibles
and drones." The technology and its underpinnings are the subject of
patent filing and are available for licensing.


========================================================================== Story Source: Materials provided by
Washington_University_in_St._Louis. Original written by Shrihari Sankarasubramanian. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Zhongyang Wang, Shrihari Sankarasubramanian, Vijay Ramani. Reactant-
Transport Engineering Approach to High-Power Direct Borohydride
Fuel Cells. Cell Reports Physical Science, 2020; 100084 DOI:
10.1016/ j.xcrp.2020.100084 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/06/200618092445.htm

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