Janus-Faced SiO2: Activation and Passivation in the Electrode System Platinum/Yttria-Stabilized Zirconia

Small amounts of impurities cart strongly impact the electrode kinetics of electrochemical cells and devices, leading to an improved or declined performance. This study shows that one material, silica, can influence the electrochemical behavior of the basic solid-state electrode system Pt(O-2)/YSZ (yttria-stabilized zirconia) in opposite directions, depending on its local distribution in the system. Compared to a silica-free electrode as the reference, SiO2 located at the interface Pt/YSZ caused a reduced performance, while SiO2 on the surface of the Pt electrode caused a small enhancement. The passivation can be explained by blocking of active three-phase boundary sites (tpb, Pt/YSZ/O-2), while silica surface doping is hypothesized to influence the oxygen adsorption/desorption and surface diffusion.