In
protonic ceramic fuel cells (PCFCs), oxygen reduction reaction
activity is governed by the oxygen adsorption/dissociation, proton
conduction, and electron transfer kinetics. Although various strategies
have been explored to enhance the proton and electron conductivity
via tuning the oxygen vacancy concentration in the electrode materials
and introducing electronic conducting agents, there are few studies
on improving oxygen adsorption/dissociation (surface-exchange reaction)
kinetics in PCFCs. In this study, we report uniformly distributed
thermodynamically stable nickel oxide (NiO) nanoparticles as a catalyst
to enhance the electrochemical performance of the BaCo0.4Fe0.4Zr0.1Y0.1O3‑δ (BCFZY) cathode, which is a promising cathode material because of
its triple (oxygen ion, proton, and electron) conductivity in PCFCs,
by improving surface-exchange reaction kinetics. The 0D NiO nanoparticles
with high adsorption and fast dissociation ability of oxygen could
enlarge the active sites for surface-exchange reactions without fading
the BCFZY surface and triple-phase boundaries where the H2O formation reaction occurs. The cathode employing NiO nanoparticles
exhibits largely reduced polarization resistance and a superior power
density of 780 mW/cm2 at 600 °C. This improvement
is attributed to the enhanced surface-exchange reaction kinetics.