Boosting nanoconfined peroxymonosulfate activation in Fe2O3@carbon yolk-shell catalyst via cavity regulation for high-efficiency organic pollutant degradation

Abstract

Constructing yolk-shell structure that confines metal-based catalyst in nanoscale cavity could trigger nanoconfinement effect for highly efficient peroxymonosulfate (PMS) activation. However, the structure-activity relationship of yolk-shell catalysts and the intrinsic role of nanoconfinement effect remain underexploited. In this work, the hollow carbon sphere encapsulated Fe₂O₃ yolk-shell catalysts (Fe₂O₃@CS-5, Fe₂O₃@CS-10 and Fe₂O₃@CS-15) with varying cavity sizes (76, 37 and 20 nm) were designed and synthesized, and the correlation of cavity size with catalytic performance of Fe₂O₃@CS was deeply investigated. The result revealed the catalytic efficiency of Fe₂O₃@CS significantly improved with the decreasing cavity size. The Fe₂O₃@CS-15 with the smallest cavity size featured the best performance, whose kinetic constant for 4-chlorophenol (4-CP) degradation (0.044 min⁻¹) was 5.3, 5.2, and 4.4 times higher than that of pure Fe₂O₃ (0.0083 min⁻¹), Fe₂O₃@CS-5 (0.0085 min⁻¹), and Fe₂O₃@CS-10 (0.010 min⁻¹), respectively. Moreover, Fe₂O₃@CS-15 exhibited negligible Fe leaching, broad pH stability range (3.0–8.9) and high performance towards diverse organic pollutants. Experimental results and theoretical calculation corroborated the nanoconfinement effect in the cavity of Fe₂O₃@CS played critical role in enhancing its catalytic performance, which promoted reactants mass transfer and enhanced electron-donating capability of Fe₂O₃ for high-efficiency PMS reduction into surface-bound radicals (SO₄^•− and •OH) towards pollutant degradation.