Chemical design and synthesis of superior single-atom electrocatalysts via in situ polymerization

Abstract

Molecule-like electrocatalysts with FeN₄ motifs have been demonstrated to be excellent candidates for various renewable energy conversions. The ability to further tune the electronic properties of molecular FeN₄ motifs and integrate them onto conductive supports represents a key step towards the synthesis of highly robust and efficient single-atom catalysts (SACs) for practical applications. Here, we developed a new route for the synthesis of a well-defined single-atom FeN₄ electrocatalyst via in situ polymerization of four amino groups functionalized iron phthalocyanine (NH₂-FePc) molecules on conductive carbon nanotubes. The intermolecular oxidative dimerization between the amino groups of NH₂-FePc creates the desired electron-withdrawing pyrazine linker between FeN₄ motifs, which can significantly optimize their electrocatalytic performances. As a result, the FeN₄-SAC exhibits both outstanding ORR activity (a half-wave potential of 0.88 V vs. RHE) and excellent performance in Zn–oxygen batteries, outperforming the commercial Pt/C and pristine iron phthalocyanine (FePc) catalysts. Our theoretical calculations reveal that the presence of electron-withdrawing linkers shifts the occupied antibonding states towards lower energies and thus weakens the Fe–O bond, which is primarily responsible for the enhancement of ORR activity.