Microspectroscopy at a moving reduction front in zirconia solid electrolyte

Employing photoelectron emission microscopy (PEEM) and scanning photoelectron microscopy (SPEM) the surface reduction of zirconia solid electrolyte under cathodic polarisation has been observed in situ. A microstructured platinum film and a porous platinum paste have been used as electrodes. Starting from the three phase boundary (tpb) between platinum, solid electrolyte and the gas phase, a reduction front was detected in PEEM by a significant local work function decrease. Local XPS shows that zirconia has been reduced behind the front, resulting in the presence of Zr atoms in a low oxidation state and Zr0.