Targeting Synthesis of Diatomic Catalysts by Selective Etching and Sequential Adsorption of Metal Atom

Diatomic catalysts featuring a tunable structure and synergetic effects hold great promise for various reactions. However, their precise construction with specific configurations and diverse metal combinations is still challenging. Here, a selective etching and metal ion adsorption strategy is proposed to accurately assign a second metal atom (M²) geminal to the single atom site (M¹-N_x) for constructing diatomic sites (e.g., Fe-Pd, Fe-Pt, Fe-Ru, Fe-Zn, Co-Fe, Co-Ni, and Co-Cu). In this strategy, hydrogen peroxide selectively etches the positively charged carbon atoms near the M¹-N_x moiety (denoted as α-C) and produces vacancy, which could trap the M² at the subsequent adsorption step. These catalysts show optimized electronic structure and enhanced oxygen reduction activity compared to single-site counterparts, and the representative Fe-Pd-NC and Co-Fe-NC catalysts stand as the most active oxygen reduction reaction catalysts (half-wave potential of 0.92 and 0.91 V, respectively). The selective etching of α-C in single-atom catalysts reported here represents a new post-treatment strategy for the targeting synthesis of diatomic sites.