Unraveling the pivotal role of heterointerfaces on oxide ion transport in solid oxide fuel cells

Overcoming fundamental key issues affecting performance and stability has been recognized as the most important challenge for the commercialization of solid oxide fuel cells (SOFCs). Here, we employed a multipronged approach based on advanced nanoscale analyses coupled with electrochemical evaluation to elucidate the interrelation among ohmic resistance, oxide ion transport, and cation interdiffusion mainly occurring at the interlayer-electrolyte heterointerfaces. The presence of an interdiffusion layer (IDL), formed from the interdiffusion of Ce, Gd, and Zr during high-temperature sintering of conventional screen-printed gadolinia-doped ceria (GDC) interlayer on yttria-stabilized zirconia (YSZ) electrolyte, inadvertently acts as a major barrier to oxide ion transport and results in a significant increase of the ohmic resistance. An effective way to suppress the IDL formation and its oxide ion blocking effect is by alternatively fabricating the GDC interlayer using pulsed laser deposition (PLD), whereby dense layers prepared at a relatively lower deposition temperature without post growth sintering can be obtained. Consequently, the cell's ohmic resistance is drastically lowered and a significant improvement in cell performance is achieved. These results have major implications for the selection and optimization of cell fabrication processes to mitigate degradation issues associated to heterointerfaces.