Abstract The non-precious materials with iron-pyrrolic nitrogen-carbon (Fe–N–C) moiety have attracted an increasing attention on the CO2 reduction reaction (CO2RR). However, the influence of iron valence state and environmental synergy is not still clear. Here, iron phthalocyanine (FePc) molecule with an intrinsic Fe–N4–C moiety is enough dispersed on graphene as the single-atom iron catalyst through a facile chemical method. The FePc-graphene composites with different FePc content and iron valence state are synthesized to investigate their catalysis for the CO2RR to CO. The onset overpotential of 190 mV and Faradaic efficiency of >90% may be achieved in the optimal composites. Experimental and calculational results prove the positive role and synergy of Fe(II)Pc with Fe(III)Pc and graphene. The formation of ∗COOH intermediate is confirmed to be the rate-limiting step. The theoretical calculation reveals that Fe(II)Pc should have higher activity than Fe(III)Pc, and Fe(II)Pc/FePc(III) dimer may be better than individual one. This work clearly exhibits the effect of Fe2+/3+- pyrrolic N4–C on the CO2RR.

中文翻译：

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铁酞菁修饰石墨烯纳米复合材料电催化 CO2 还原为 CO

摘要 具有铁-吡咯氮-碳 (Fe-N-C) 部分的非贵重材料在 CO2 还原反应 (CO2RR) 方面引起了越来越多的关注。然而，铁价态和环境协同作用的影响尚不清楚。在这里，具有固有 Fe-N4-C 部分的铁酞菁 (FePc) 分子通过简单的化学方法足以作为单原子铁催化剂分散在石墨烯上。合成了具有不同 FePc 含量和铁价态的 FePc-石墨烯复合材料，以研究它们对 CO2RR 转化为 CO 的催化作用。在最佳复合材料中可以实现 190 mV 的起始过电位和 >90% 的法拉第效率。实验和计算结果证明了 Fe(II)Pc 与 Fe(III)Pc 和石墨烯的积极作用和协同作用。∗COOH 中间体的形成被证实是限速步骤。理论计算表明，Fe(II)Pc 应该比 Fe(III)Pc 具有更高的活性，并且 Fe(II)Pc/FePc(III) 二聚体可能比单独的一个更好。这项工作清楚地展示了 Fe2+/3+- 吡咯 N4–C 对 CO2RR 的影响。