The Reduction Step and Mechanism Analysis of the NiO-8YSZ Anode Affected by the Hydrogen Concentration

Abstract

Hydrogen of different concentrations humidified by the water vapour were used to reduce the NiO-8YSZ anodes of the solid oxide fuel cells (SOFCs) at 700℃ and 720℃. The experimental results suggested that four periods of the open circuit voltage, namely rapid increase period, temporary stasis period, slow increase period and final stable period exist successively during the reduction, the characteristics of which were closely related to the hydrogen concentration of the reduction. After the reduction, the polarization resistance on open circuit and on load showed different correlation with the hydrogen concentration of the reduction. The variation trend of the initial performances of the SOFCs corresponded highly to the polarization resistance on load. The shrinking core model of the reduction of the NiO suggested that the further reduction of the unreacted NiO core would most likely cause the activation of the SOFC.