Surface modified FeCoZn-ZIF derived polyhedral electrocatalysts for ORR under alkaline and acidic conditions

Abstract

Electrocatalysts for catalyzing oxygen reduction reactions at variable pH conditions are essential for energy conversion and storage. Herein, Fe@FeCoZn–CN electrocatalysts were prepared with internal and external doping approach. The Fe@FeCoZn–CN electrocatalyst exhibits a desirable ORR performance in both acid and alkaline electrolytes. Specifically, the half-wave potential (E1/2) of Fe@FeCoZn–CN electrocatalyst is 0.890 V which far beyond Pt/C electrocatalyst (0.839 V) in alkaline electrolyte. In addition, Fe@FeCoZn–CN electrocatalyst also exhibits improved ORR activity (E1/2 = 0.801 V) compared to Pt/C (0.797 V) electrocatalysts in acidic electrolytes. What's exciting is that the rechargeable ZABs based on Fe@FeCoZn–CN electrocatalysts exhibit an impressive performance with a favorable open-circuit potential of 1.517 V and a promising specific capacity is 833.7 mA h gzn−1, good charge/discharge cycle stability. The remarkable ORR catalytic performance of Fe@FeCoZn–CN electrocatalysts can be traced to the internal doping of metals which prevent excessive metal aggregation and surface modified which can increase the metal loading to expose more active sites.