A General Stepwise Confinement Strategy for Rapidly In Situ Precipitated Nanocatalysts within N-Doped Hollow Carbon Spheres Toward Efficient Thermal Decomposition of Ammonium Perchlorate

Nanoconfined composites exhibit outstanding catalytic performance for the thermal decomposition of ammonium perchlorate (AP). However, it remains a formidable challenge to construct nanoconfined catalysts when the restricted species are insoluble precipitates that form rapidly at room temperature. Herein, a general precursor-based stepwise confined strategy is proposed to encapsulate M 3 [Fe(CN) 6 ] 2 ·xH 2 O (M-Fe-PBA) (M = Fe, Co, Ni, Cu, Zn) within N-doped hollow carbon nanospheres (NHCs), resulting in yolk-shell structured composites, M-Fe-PBA@NHCs. Catalytic tests reveal that 5 wt.% Co-Fe-PBA@NHCs show the highest catalytic activity among the M-Fe-PBA@NHCs composites, significantly lowering the high-temperature decomposition peak of AP and increasing its heat release. Electrochemical analysis confirms that fast electron transfer of Co-Fe-PBA@NHCs facilitates AP combustion. TGA-FTIR-MS measurements further elucidate an accelerated decomposition pathway. Density functional theory calculations indicate that NH 3 and O 2 released during AP degradation are preferentially adsorbed on the in situ formed Co 3 O 4 /CoFe 2 O 4 , promoting O 2 reduction to O 2 − species and facilitating the deeper oxidation of NH 3 into higher-valence NO 2 . Crucially, this confinement strategy enables the efficient incorporation of instantly formed insoluble species into any hollow host material with accessible voids, providing a versatile platform for the development of multifunctional nanoconfined catalysts and the rational design of high-performance confined catalysts with potential applications.