Fluorination inductive effect enables rapid bulk proton diffusion in BaCo0.4Fe0.4Zr0.1Y0.1O3-δ perovskite oxide for high-activity protonic ceramic fuel cell cathode

Protonic ceramic fuel cells (PCFCs) have generated significant interest due to their weak temperature dependence and efficient energy conversion. However, traditional cathode materials show poor electrocatalytic activity at a low operating temperature due to their intrinsically slow proton diffusion, which is a long-standing issue that limits the output performance of PCFCs. Herein, the strategy of fluorinating a perovskite cathode is proposed for promoting proton transfer within the bulk of the cathode. This strategy is demonstrated in a fluorinated BaCo0.4Fe0.4Zr0.1Y0.1O3−δ (BCFZY) perovskite, which reveals a reduced polarization resistance and enhanced PCFC output performance, superior to those of newly reported PCFCs. Combing the experimental characterization and theoretical calculations, we found that the performance improvement was ascribed to the strong inductive effect of F−, which can increase the polarity the M−O bonding and decrease the O···H interaction, thus boosting the production of protonic defects and increasing the protonic diffusion coefficient.