Revealing the role of ionic liquids in promoting fuel cell catalysts reactivity and durability

Ionic liquids have shown to be promising additives to the
catalyst layer to enhance oxygen reduction reaction in polymer electrolyte
fuel cells. However, fundamental understanding of their role
in complex catalyst layers in practically relevant membrane
electrode assembly environment is needed for rational design of highly
durable and active platinum-based catalysts. Here
we explore three imidazolium-derived ionic liquids,
selected for their high proton conductivity and oxygen
solubility, and incorporate them into high surface area carbon
black support. Further, we establish a correlation between the physical
properties and electrochemical performance of the ionic
liquid-modified catalysts by providing direct evidence of ionic
liquids role in altering hydrophilic/hydrophobic interactions within the
catalyst layer
interface. The resulting catalyst with
optimized interface design achieved a high mass activity of 347 A
g-1Pt at 0.9 V H2/O2, power density of 0.909 W
cm-2 under H2/air and 1.5 bar and had only 0.11
V potential decay at 0.8 A cm-2 after 30 k
accelerated stress test cycles. This performance stems from substantial
enhancement in Pt utilization, which is buried inside the mesopores and is
now accessible due to ILs addition.