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 FeO x (2–5 nm) particles anchored on the carboxylic carbon nanotubes (CCNTs) was reported in this paper. The low-crystalline FeO x /CCNTs (LC-FeO x /CCNTs) system features excellent Fenton-like performance which is 24.3 times larger than that of conventional crystalline Fe 2 O 3 /CCNTs (C–Fe 2 O 3 /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 (1O 2) was detected as the main reactive intermediate by introducing surface oxygen vacancy (SOV) and Fe2+ as "Fenton-catalytic" dual reaction center to promote H 2 O 2 decomposition, which was distinct from the common Fenton-like reaction path with HO• as the main reactive oxygen species. Furthermore, the carboxylic groups on the surface of carbon nanotubes (CNTs) complexed with metastable FeO x can accelerate the transformation of Fe(III)/Fe(II) so as to adjust the utilization of H 2 O 2 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. [Display omitted] • A delicate Fenton-like catalyst at low-crystalline state with exceptional activity was designed. • Oxygen vacancy and Fe2+ were introduced as the "Fenton-catalytic" dual center influenced by crystallinity of Fe 2 O 3. • The carboxylic groups on the surface of CNT can form CNT–COOH–Fe bonds with iron oxide. • 1O 2 was detected as the main reactive intermediate in low-crystalline FeOx/H 2 O 2 system. [ABSTRACT FROM AUTHOR]