Controlled Construction of Core-Shell Structured Prussian Blue Analogues towards Enhanced Oxygen Reduction

Metal-organic frameworks-based electrocatalysts have been developed as highly desirable and promising candidates for catalyzing oxygen reduction reaction (ORR), which, however, usually need to be prepared at elevated temperatures and may suffer from the framework collapse in water environments, largely preventing its industrial application. Herein, this work demonstrates a facile low-temperature ion exchange method to synthesize Mn and Fe co-loaded Prussian blue analogues possessing core-shell structured frameworks and favorable water-tolerance. Among the catalysts prepared, the optimal HMPB-2.6Mn shows a high ORR electrocatalytic performance featuring a half-wave potential of 0.86 V and zinc-air battery power density of 119 mW cm-2, as well as negligible degradation up to 60 h, which are comparable to commercial Pt/C. Such an excellent electrocatalytic performance is attributed to the special core-shell-like structure with Mn concentrated in outer shell, and the synergetic interactions between Mn and Fe, endowing HMPB-Mn with outstanding ORR activity and good stability. A HMPB-Mn structure with water-tolerant character that shows core-shell-like composition distribution where Mn and Fe are simultaneously located in the outer layer of HMPB-Mn and the inner layer is mainly composed of Fe is reported in this work, as well as the synergetic interactions between Mn and Fe, endowing HMPB-Mn outstanding ORR activity and good stability concurrently.image