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

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.