A review on experimental and theoretical studies of perovskite barium zirconate proton conductors

Highly stable proton conductive oxide materials with improved electrochemical and thermochemical properties are in great demand in numerous fields such as portable electronics and transport systems, energy storage, fuel cells, etc. BaZrO3 (BZO)-based perovskite oxides, due to excellent proton conduction at intermediate temperatures and diversified structural properties with good chemical stability have obtained distinguished attention in recent years. This review principally focuses on recent development in the proton-conducting performance of BZO as perspective energy materials. The main aim of this effort is to integrate the fundamental knowledge of proton conducting BZO perovskites studied from the point of view of material science and computational engineering. Therefore, in the first half of this review, the fundamentals of BZO perovskites are discussed with the experimental studies describing particular parameters such as grain size, effect on sintering aid, material stability, hydrogen solubility, hydrogen diffusivity, proton conductivity, electrolyte fabrication, and performance properties. The second part emphasizes the theoretical studies conducted using density functional theory (DFT)-based first-principle calculation or molecular dynamics (MD) simulation to provide a deeper insight into structural, thermodynamic, and proton conduction parameters, especially for doping mechanism, proton trapping, and proton diffusion properties of BZO perovskite. In the end, the prominent applications of BZO materials in low-temperature solid oxide fuel cells are discussed. Therefore, the comprehensive information provided in this paper about the physical properties of barium zirconate from experimental and theoretical studies will guide aspirants to easily understand the trend and continuing research on the development of BZO materials.