Promoted photo-Fenton reactivity through electron transfer between non-contacted Au nanoparticles and Fe2O3 nanowires in a confined space

Abstract

The tubular one-dimensional nanoreactor with a unique confinement effect has captured great research interest but it is still challenging to realize the synergistic catalytic performance. In this work, a Fe₂O₃–Au@SiO₂ nanoreactor with a coaxial cable structure was prepared. Fe₂O₃ nanowires and Au nanoparticles were wrapped in a SiO₂ shell in a non-contact manner, and the relative positions of Fe₂O₃ and Au NPs were precisely controlled. As an efficient H₂O₂ activator toward catalytic oxidation of toxic organic contaminants, the Fe₂O₃–Au@SiO₂ nanoreactor presents high activity in the photo-Fenton degradation of 2-CP, 4-CP, ciprofloxacin, BPA and so on. The degradation rate of 2-CP reached 87% within 15 minutes with a reaction rate constant of 0.1029 min⁻¹. Compared with Fe₂O₃–Au@SiO₂ with intimate contact between Fe₂O₃ and Au, Fe₂O₃–Au@SiO₂ displayed a superior kinetic rate constant. The non-contacted Fe₂O₃ and Au nanoparticles not only avoided the possible negative strong metal–support interaction (SMSI) that affects the chemical states but also displayed an efficient synergistic effect and accelerated the catalytic reaction in the confined space. The LSPR effect of Au NPs generated hot electrons and produced ˙O²⁻ significantly. Meanwhile, the photogenerated electrons transferred to the conduction band (CB) of Fe₂O₃ and promoted Fe²⁺/Fe³⁺ cycling. The LSPR effect of Au NPs and scattering in the confined space increased the utilization efficiency of light. Among the homologous composites of Fe₂O₃–Au@SiO₂, the one with a void diameter of 10 nm represented the highest activity, revealing that the electron/mass transport route was also a key factor in the system. This work supplies a model for the uncontacted synergistic catalytic theory with confinement space and also opens up new horizons for the design of high-efficiency and stable catalysts for water treatment.