Investigation of the Bifunctional Oxygen Electrocatalytic Performance of Atomically Dispersed Fe anchored on N doped Graphene

With the growing demand for efficient and environmentally friendly energy storage systems, zinc-air batteries have emerged as highly promising energy storage devices due to their high energy density, low cost, and environmental benignity. The oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), which suffer from sluggish kinetics, are critical factors limiting battery performance. Therefore, the development of high-performance and low-cost bifunctional oxygen electrocatalysts is of great significance. In this work, Fe single atoms / clusters anchored graphene hybrid catalysts (Fe-N/Gra) were prepared via a ball-milling assisted pyrolysis method. A series of Fe-N/Gra catalysts were obtained by adjusting the mass ratio of the metal phthalocyanine precursor to graphene, and their bifunctional oxygen electrocatalytic performances were systematically investigated. The results show that the amount of metal phthalocyanine precursor has a significant impact on the catalytic performance of the catalysts. Among them, Fe-N/Gra exhibits the optimal ORR and OER catalytic activity at a loading of 0.02 g, with an ORR half-wave potential as high as 0.911 V. A rechargeable zinc-air battery was assembled using the as-prepared catalyst as the air electrode catalyst. The as-prepared Fe-N/Gra delivers a maximum power density of 315 mW cm-2 at a loading of 0.02 g and maintains excellent stability for 220 h at a current density of 10 mA cm-2 during discharge. The superior bifunctional oxygen catalytic activity of Fe-N/Gra-0.02 is mainly attributed to the atomically dispersed FeNₓ active sites and the high electrical conductivity of the graphene support. Meanwhile, the agglomeration of active sites in the catalyst with a high precursor loading is unfavorable for exerting efficient catalytic activity.