Low-crystalline FeOx on carboxylic CNTs as high-performance Fenton-like catalysts: Influence of crystallinity and carbon matrix

A facile method to prepare the ultra-dispersed low-crystalline FeOx (2-5 nm) particles anchored on the carboxylic carbon nanotubes (CCNTs) was reported in this paper. The low-crystalline FeOx/CCNTs (LC-FeOx/ CCNTs) system features excellent Fenton-like performance which is 24.3 times larger than that of conventional crystalline Fe2O3/CCNTs (C-Fe2O3/CCNTs). It also exhibits outstanding stability and versatility in the catalytic degradation of different types of (cationic and anionic) compounds. Through comprehensive mechanistic investigations, it's confirmed that crystallinity of iron oxide played a vital role in catalytic performance. Specifically, singlet oxygen (1O2) was detected as the main reactive intermediate by introducing surface oxygen vacancy (SOV) and Fe2+ as "Fenton-catalytic" dual reaction center to promote H2O2 decomposition, which was distinct from the common Fenton-like reaction path with HO center dot as the main reactive oxygen species. Furthermore, the carboxylic groups on the surface of carbon nanotubes (CNTs) complexed with metastable FeOx can accelerate the transformation of Fe(III)/Fe(II) so as to adjust the utilization of H2O2 via donor-acceptor coupling. This work addresses an imaginative leap forward the understanding of the role of crystallinity and matrix coupling in the design of Fenton-like catalyst.