Degradation study of a reversible solid oxide cell (rSOC) short stack using distribution of relaxation times (DRT) analysis

Abstract

Reversible solid oxide cells (rSOC) can convert excess electricity to valuable fuels in electrolysis cell mode (SOEC) and reverse the reaction in fuel cell mode (SOFC). In this work, a five – cell rSOC short stack, integrating fuel electrode (Ni-YSZ) supported solid oxide cells (Ni-YSZ || YSZ | CGO || LSC-CGO) with an active area of 100 cm2, is tested for cyclic durability. The fuel electrode gases of H2/N2:50/50 and H2/H2O:20/80 in SOFC and SOEC mode, respectively, are used during the 35 reversible operations. The voltage degradation of the rSOC is 1.64% kh−1 and 0.65% kh−1 in SOFC and SOEC mode, respectively, with fuel and steam utilisation of 52%. The post-cycle steady-state SOEC degradation of 0.74% kh−1 suggests improved lifetime during rSOC conditions. The distribution of relaxation times (DRT) analysis suggests charge transfer through the fuel electrode is responsible for the observed degradation.