In the drive to achieve economically viable solid oxide fuel cells, efforts have been directed towards substantially decreasing their operating temperature. Unfortunately, these efforts have been hindered by extremely sluggish electrode kinetics at reduced temperatures. In this report, we show that silicon impurities on the surface of the electrolyte play a critical role in influencing electrode kinetics. More specifically, improvements by as much as three orders of magnitude are reported for the performance of platinum electrodes on yttria-stabilized zirconia electrolytes prepared as high purity thin films with a largely Si-free surface. These improvements in performance are estimated to enable operation of a solid oxide fuel cell down to approximately 400 °C.