Bismuth ferrite: An abnormal perovskite with electrochemical extraction of ions from A site

Perovskite materials (ABX₃) are significant for energy storage and conversion, and most of the electrochemical processes are currently known to link with the reaction from the active B site. Here, a novel electrochemical active reaction is observed from the A site in perovskite bismuth ferrite (BiFeO₃) nanoparticles. With bismuth ion extraction from the A site, single-phase BiFeO₃ is found to convert into two phases, namely, Bi₂O₃ and residual Bi-deficient BiFeO₃, and these irreversible products undergo additional separate electrochemical processes in the subsequent cycles. The fundamental understanding suggests that the extracted Bi³⁺ ions play a dominant role in the electrochemical process via redox reactions of Bi³⁺ Bi²⁺ Bi⁰. Interestingly, such an electrochemical reaction involving the A site could also be suppressed via heteroatom doping at the A site (yttrium ions), which effectively supports the mechanism of ion extraction. The perspectives for the novel mechanism in electrochemical energy storage are further discussed.