The aim of this study
was to clarify the effectiveness
and challenges
of applying mesoporous tin oxide (SnO2)-based supports
for Pt catalysts in the cathodes of polymer electrolyte fuel cells
(PEFCs) to simultaneously achieve high performance and high durability.
Recently, the focus of PEFC application in automobiles has shifted
to heavy-duty vehicles (HDVs), which require high durability, high
energy-conversion efficiency, and high power density. It has been
reported that employing mesoporous carbon supports improves the initial
performance by mitigating catalyst poisoning caused by sulfonic acid
groups of the ionomer as well as by reducing the oxygen transport
resistance through the Pt/ionomer interface. However, carbon materials
in the cathode can degrade oxidatively during long-term operation,
and more stable materials are desired. In this study, we synthesized
connected mesoporous Sb-doped tin oxides (CMSbTOs) with controlled
mesopore sizes in the range of 4–11 nm and tested their performance
and durability as cathode catalyst supports. The CMSbTO supports exhibited
higher fuel cell performance at a pore size of 7.3 nm than the solid-core
SnO2-based, solid-core carbon, and mesoporous carbon supports
under dry conditions, which can be attributed to the mitigation of
the formation of the Pt/ionomer interface and the better proton conductivity
within the mesopores even at the low-humidity conditions. In addition,
the CMSbTO supports exhibited high durability under oxidative conditions.
These results demonstrate the promising applicability of mesoporous
tin oxide supports in PEFCs for HDVs. The remaining challenges, including
the requirements for improving performance under wet conditions and
stability under reductive conditions, are also discussed.