Multi-sites synergistic modulation in oxygen reduction electrocatalysis
2023
Chen, Menghui | Chen, Yongting | Cai, Jialin | Yang, Zhili | Tang, Meihua | Chung-Yen Jung, Joey | Chen, Shengli | Zhang, Jiujun | Zhang, Shiming
Revealing the types of and interplays among multiple active-sites in iron-nitrogen-carbon (FeNC) materials is of great significance for developing high-performance, Fe-based non-precious metal catalysts for oxygen reduction reaction (ORR). In this paper, a single-atom FeNC catalyst is prepared through high-temperature pyrolyzing of melamine foam (MF), iron phthalocyanine (FePc), phthalocyanine (Pc), and zinc (Zn)-salts composite. The catalyst is found to contain a variety of active-sites, including carbon atom next to pyridinic-N (pyridinicNC), Fe-N₄ and pore defect. It is shown that MF with high N-content is responsible for the formation of the main pyridinicNC sites and in the meantime acts as the self-sacrificed template for framework of the catalyst. The presence of Pc can facilitate the formation of the predominant Fe-N₄ sites, since the interplay between Pc and FePc results in a confinement of Fe-N₄. Zn-salts serve as the pore-forming additives to create sufficient pore defects which can also anchor pyridinicNC and Fe-N₄ structures. The results of density functional theory (DFT) calculations suggest that the multiple active-sites function synergistically to enable high-efficiency ORR electrocatalysis. The optimal FeNC catalyst shows superior ORR activity with a half-wave potential of ∼0.88 V (vs. RHE), as well as high methanol tolerance and electrochemical stability compared to the commercial carbon-supported platinum (Pt/C) catalyst.
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