【摘 要】
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Due to the high specific surface area,abundant nitrogen and micropores,ZIF-8 is a commonly used precursor for preparing high performance Fe-N-C catalysts.Howeve
【机 构】
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School of Materials Science and Engineering,Beihang University,Beijing,100191,China;Department of Ph
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Due to the high specific surface area,abundant nitrogen and micropores,ZIF-8 is a commonly used precursor for preparing high performance Fe-N-C catalysts.However,the Zn element is inevitably remained in the prepared Fe-N-C catalyst.Whether the residual Zn element affects the catalytic activity and active site canter of the Fe-N-C catalyst caused widespread curiosity,but has not been studied yet.Herein,we built several Fe,Zn,and N co-doped graphene models to investigate the effect of Zn atoms on the electrocatalytic performance of Fe-N-C catalysts by using density functional theory method.The calculation results show that all the calculated Fe-Zn-Nx structures are thermodynamically stable due to the negative formation energies and relative stabilities.The active sites around Fe and Zn atoms in the structure of Fe-Zn-N6(lll) show the lowest oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) overpotentials of 0.38 and 0.43 V,respectively.The bridge site of Fe-Zn in Fe-Zn-Ns shows the lowest ηHER of-0.26 V.A few structures with a better activity than that of FeN4 or ZnN4 are attributed to the synergistic effects between Fe and Zn atoms.The calculated ORR reaction pathways on Fe-Zn-N6(lll) show that H2O is the final product and the ORR mechanism on the catalyst would be a four-electron process,and the existence of Zn element in the Fe-N-C catalysts plays a key role in reducing the ORR activation energy barrier.The results are helpful for the deep understand of high-performance Fe-N-C catalysts.
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