Identifying N Coordination Types of Single-Atom Catalysts by Spin-Modulated Luminol Cathodic Electrochemiluminescence

The type of coordinated N atoms in the metal-N coordination structure is of paramount importance to the catalytic property of N-modified carbon-based single-atom catalysts (SACs). Extended X-ray absorption fine structure (EXAFS) spectroscopy is a powerful tool for analyzing the coordination environments of SACs. Despite its efficacy, the limited availability of synchrotron light sources and the complexity of data analysis have constrained its broader application in identifying metal-N coordination types within SACs. In this work, two kind of CoN₄ SACs, were prepared by varying the N source. Then their electrochemiluminescence (ECL) behavior in the luminol/dissolved oxygen system during cathodic scanning were investigated. In comparison to CoN_{4(pyridinic N)}, for which the spin density displays d_z2 orbital characteristics, CoN_{4(pyrrolic N)} exhibits d_xz orbital features, which was more conducive to the subsequent cleavage of the O-O bond in O₂⋅^- to ⋅OH, resulting in the generation of more active intermediates *OH and the promotion of cathodic ECL emission. This work demonstrates that the ECL technique provides a novel method for the rapid identification of Co-N coordination types and the spin nature of the metal center in CoN₄ SACs.