An in-situ etching strategy toward fully exposed Fe-N₅ active sites for boosted nitroaromatic reduction

Single-atom catalysts (SACs) hold considerable potential within the domain of heterogeneous catalysis, but the facile and meticulous synthesis of SACs with high activity and efficient utilization remains challenging. In this study, we present a straightforward in-situ etching strategy for the fabrication of a single-atom catalyst (NH₃-Fe₁/C) featuring fully exposed Fe-N₅ active sites toward boosted nitroaromatic reduction. By harnessing the activation and doping effects of NH₃, highly efficient Fe-N₅ active centers are in-situ generated and precisely anchored to carbon nanoshells. The distinctive etching action of NH₃ significantly elevates the specific surface area (S_BET = 1197 m²/g) of the catalyst, the hierarchical porous structure of which not only promotes the adsorption of reactants but also ensures the complete exposure of the Fe-N₅ active centers. Owing to the advantageous structural characteristics and effective active sites, the NH₃-Fe₁/C catalyst with extremely low Fe contents (0.23 wt%) demonstrates exceptional catalytic performance, achieving an impressive overall turnover frequency (TOF) of 18750 h⁻¹ and a rate constant of 1.01 min⁻¹ for the rapid conversion of highly concentrated nitroaromatics (5 mM) into amines at minimal reductant dosage (n_NaBH4/n_4-NP=12.5). This work explores the precise construction and efficient utilization of single-atom active sites, offering new insights into the application of SACs.