Enhancing Protonic Conductivity in Ba(Zr0.4Ce0.4Y0.1Yb0.1)O3 Electrolyte for Solid Oxide Electrolysis Cells through Sintering Aids and Single-Grain Layer Design

One of the formidable challenges is to reduce the reliance on fossil fuels and the greenhouse effect. Therefore, the development of storable and transportable chemical fuels by employing electricity and water vapor to drive an endothermic chemical reaction is the key. The electrolyte in solid oxide electrolysis cells serves a critical role in facilitating ionic conductivity. Among various investigated compositions, this project aims to develop a Ba(Zr_0.4Ce_0.4Y_0.1Yb_0.1)O₃ electrolyte with high protonic conductivity for proton-conducting solid oxide electrolysis cells. It is known that at 1500°C, the high-temperature densification process leads to Ba evaporation, Ni diffusion from other components, and phase segregation of Y₂O₃ and Yb₂O₃, all of which contribute to a reduction in the proton conductivity of this material. Sintering aids along with other additives have been investigated to achieve a single-grain layer electrolyte structure, thus avoiding the issues associated with high-temperature densification and high resistance from grain boundaries. Appropriate amounts of ZnO in addition to Ba, Y, and Yb oxides are introduced as sintering aids to improve the ionic conductivity and lower the electronic conductivity of the material with better Ni electrode performance. The effect of Ni diffusion from the substrate to the electrolyte and its coarsening is reduced due to lower electrolyte densification temperature. The electrolyte's phase purity, microstructure, and proton conductivity are further measured and analyzed.