Suppressing Cation Interdiffusion at CeO₂/ZrO₂ Heterointerfaces via Dopant Segregation

Cation interdiffusion as a result of a chemical-potential gradient occurring at heterointerfaces is often regarded as an unfavorable side reaction and is typically suppressed through the use of a diffusion barrier layer. In this study, we propose a straightforward method for suppressing interdiffusion that involves the creation of nanometer-thick diffusion barrier layers by means of dopant segregation. Using the CeO₂/ZrO₂ heterointerface in this study, we demonstrate that a Sc acceptor dopant tends to accumulate at the heterointerface during the sintering process, especially at the edge of the CeO₂ grain boundary, thereby effectively suppressing Ce-Zr interdiffusion. Defect formation energy calculations through density functional theory indicate that the presence of the Sc layer acts to impede the formation of vacancies in the neighboring Ce layer, thereby reducing the V_Ce^⁗ concentration, which is the source of interdiffusion. Furthermore, the implementation of the Sc segregation layer confers advantageous outcomes with respect to the full-cell operation, including lower levels of ohmic and polarization resistance, as well as enhanced long-term durability. The present study highlights the crucial role of selecting the proper dopant so as to impede interdiffusion and thereby achieve superior fuel cell performance in composite oxides.