Stable ceria-based electrolytes for intermediate temperature-solid oxide fuel cells via hafnium oxide blocking layer

The electronic loss of ceria-based electrolytes is caused by the reduction of ceria at low oxygen partial pressure for intermediate temperature-solid oxide fuel cells. To address this issue, a thin hafnium oxide layer is deposited at the interface between the anode and electrolyte using a magnetron sputtering system, based on the hypothesis that the stability of ceria electrolytes in the anode side can be controlled as a function of the reducibility of the ceria surface. The performance of ceria-based cells (Nd0.1Ce0.9O2-delta; NDC, Sm0.2Ce0.8O2-delta; SDC) is investigated by varying the Hf0 2 film thickness on the same ceria-based substrate. The range of thickness of the HfO2 film is 121-686 angstrom for 6-30 min with the deposition rate of 0.38 angstrom.S-1. The open-circuit voltages and power densities of NDC- and SDC-based cells are measured at 600-700 degrees C as a function of HfO2 film thickness. It is clearly observed that open-circuit voltages and the maximum power densities of both cells increase with the increasing of thickness of HfO2 film until a film thickness of 600 A is reached. This indicates that the HfO2 layer effectively prevents the electron transfer through the electrolytes by the reduction of ceria. Furthermore, the NDC-cell with the HfO2 film shows a stable performance under a constant current density operation of 130 hat 650 degrees C. (C) 2018 Elsevier B.V. All rights reserved.