(581e) Advanced Catalysts for Fuel-Flexible Fuel Cells

Advanced
Catalysts for Fuel-Flexible Fuel Cells

Su Ha^a,
Byeong Wan Kwon^a, Christian Martin Cuba Torres^a, Shreya
Shah^a, Kale Warren Herrison^b, Qian He^b, M. Grant Norton^b

^a The Gene and Linda Voiland School of
Chemical Engineering and Bioengineering, Washington State University, Pullman,
WA 99164

^bSchool of Mechanical and
Materials Engineering, Washington State University Pullman, WA, 99164-2920

Fuel cells offer a number of advantages as
an alternative energy production technology for both stationary and mobile
applications. In commercial aviation, a concept called
the more electric airplane (MEA) will allow greater fuel efficiency by
substituting hydraulically and pneumatically driven systems by those based on
electrical energy. The increased electrical power demand in a MEA can be met by
decentralizing the power-producing units using small individual devices such as
fuel cells. Furthermore, existing commercial aircraft use a low efficiency gas
turbine auxiliary power unit (APU) to provide electrical power for operating
navigation systems and various other electronic devices. By replacing the
conventional APU with a solid oxide fuel cell (SOFC) APU improvements can be
made in providing a means to obtain auxiliary power without consuming excessive
amounts of fuel when the airplane is on the ground or when the load is increased
on the main engines during flight. Thus, fuel cells may become the primary
electrical power source with engine-driven generators serving a backup role on
future airplanes.

An important practical requirement for the
use of fuel cells on commercial and military airplanes is that they must
operate using kerosene-based aviation fuels (such as Jet-A and JP-8), which are
already on board. The existing approach for fuel cell systems operating on
Jet-A fuel (the standard kerosene-based commercial aviation fuel) requires a
fuel reformation process in which the Jet-A is mostly converted to hydrogen and
carbon monoxide. This syngas mixture is fed into SOFCs where it is
electrochemically converted to H₂O and CO₂, and produces
electrical power. To develop a high performance fuel reforming system that can operate
with Jet-A fuel, a catalyst with the following attributes is required: (1) High
oxidation activity toward Jet-A fuel; (2) High resistance to coking; (3)
Stability at high operating temperatures (i.e., higher than 700^oC);
(4) High sulfur tolerance (e.g., aviation fuels typically contain 500 ppm of
sulfur).

Conventional nickel-based catalysts
quickly deactivate under reforming environments due to coke formation and
sulfur poisoning. However, we have developed a fuel-flexible molybdenum dioxide
(MoO₂) based catalyst that has been shown to display high catalytic
activity for various processes involving long-chain hydrocarbons and bio-based
aviation fuels. In this presentation, we will discuss the performance of MoO₂
based catalysts in a number of reforming environments and also the potential to
incorporate MoO₂ into an active anode for a SOFC that can operate
directly on a range of hydrocarbon fuels from both fossil and bio-based
sources. Although on-board applications for fuel cells may be some way off,
there are near term applications for this technology including alternative-fuel
fuel cells as range extenders or battery powered airport ground support
equipment (GSE). The airport GSE market includes various types of specialty
vehicles used to service aircraft during ground operations and fuel cells have
the potential to provide significant lifecycle cost savings over lead acid
battery and combustion engine systems.