Zn3[Fe(CN)6]2 derived Fe/Fe5C2@N-doped carbon as a highly effective oxygen reduction reaction catalyst for zinc-air battery

We fabricated a highly effective oxygen reduction reaction (ORR) catalyst consisting of Fe/Fe5C2 species wrapped in N-doped carbon (Fe/Fe5C2@N-C), derived from annealing decomposition of a zinciferous Prussian blue analogue Zn-3[Fe(CN)(6)](2), which can be prepared through a facile precipitation reaction. The rationally designed carbon layer-encapsulated structure with iron/iron carbide encased inside the N-doped graphitic carbon shells is favorable for ORR, wherein the iron species not only facilitate the graphitization process but also improve the ORR activity together with outside N-doped graphic carbon. The resultant catalyst demonstrates a positive half-wave potential (E-1/2) of 0.85 V (vs. RHE) and a nearly four-electron pathway in 0.1 M KOH solution, comparable to that of the commercial Pt/C. With superior stability to that of Pt/C, Fe/Fe5C2@N-C suffers almost no performance attenuation after 5000 potential cycles. The zinc-air battery using Fe/Fe5C2@N-C catalyst exhibits high power density and capacity, holding great promise for the practical application of metal-air batteries.