The Effect of Transition-Metal Doping on Chromium Deposition at Pt/YSZ Cathode Interfaces

Abstract

Understanding compositional effects, especially at solid oxide fuel cell operating conditions, is important for the selection of materials that minimize the impact of chromium deposition. In this study, the effect of yttria-stabilized zirconia (YSZ) doping on Cr deposition at a Pt electrode/YSZ electrolyte interface was investigated. A comparison between undoped and doped YSZ electrolyte surfaces after cathodic polarization in moist air at in the presence of chromia indicated that the presence of Mn, Co, or Fe in the electrolyte significantly promotes Cr deposition at the electrode/electrolyte interface. Electron microscopy of the Co-doped YSZ electrolyte surface after cathodic polarization for 10–45 h clearly showed that with Co doping, the deposition of Cr occurs preferentially at YSZ grain boundaries. Impedance spectroscopy results showed that chromium deposition led to a decrease in resistance with Mn- and Fe-doped YSZ electrolyte, which was attributed to the increase in the three-phase boundary length. However, this beneficial effect of Cr deposition was not observed with Co doping, which may be related to the preferential deposition of chromia at the YSZ grain boundary, resulting in fewer Cr deposits at the cathode/electrolyte interface.