Encapsulation of metal precursor within ZIFs for bimetallic N-doped carbon electrocatalyst with enhanced oxygen reduction

Abstract High-performance non-precious metal-doped carbon catalysts for oxygen reduction reactions (ORR) are viable candidates in lieu of platinum-based catalysts. It has been universally reported that active Co–N sites combined with Fe–N sites embedded in carbon matrix represent the most promising active sites for ORR process. Benefiting from the cage-encapsulated-precursor pyrolysis strategy, herein, we fabricated a Fe–N and Co–N homogeneously doped carbon framework by one step. TEM demonstrated the ultimate product had well-defined morphology with Fe (0.54 at%), Co (0.31 at%) and N (2.94 at%) uniformly distributed into the carbon skeleton. The N 2 absorption-desorption isotherms indicated the MOF-derived catalyst had a high specific surface area of 647.6 m 2  g −1 and inherit hierarchical porosity. Significantly, such FeCo–NC catalyst outperformed a current density (5.6 mA cm −2 ) at 0.70 V (vs reversible hydrogen electrode) 1.18 times higher than that of a commercial 20 wt% Pt/C (5 mA cm −2 ) catalyst in alkaline medium, and more positive peak potential of 0.63 V than its counterparts. Its high cycling stability and immunity towards methanol crossover in a wide range pH value showed good potential to be used as cathodes in proton exchange membrane fuel cells (PEMFCs) for long term operation. This simple synthesis strategy would to some degree leverage a cage-encapsulated-precursor for tailored utility of active sites for ORR in a porous carbon framework.