A piezo-self-Fenton system based on dual co-catalyst modified Bi4Ti3O12 with accelerated Fe3+/Fe2+ cycle and efficient in situ production of H2O2†

Abstract

Conventional Fenton technology has been suffering from the sluggish Fe³⁺/Fe²⁺ cycle, and it also heavily relies on the exogenous H₂O₂. Herein, Bi₄Ti₃O₁₂ (BTO) nanosheets modified with dual co-catalysts of Ag and CoO_x (Ag/BTO/CoO_x) were prepared and used as piezocatalysts, and it was observed that their yield of H₂O₂ in pure water was boosted to 0.18 mmol g⁻¹ h⁻¹ under ultrasound stimuli, which was 2.25 times higher than that of pristine Bi₄Ti₃O₁₂. Furthermore, a piezo-self-Fenton system (PEFS) was successfully constructed after introducing trace Fe²⁺ to activate the in situ generated H₂O₂. The PEFS exhibited high degradation performance towards various organic pollutants, and typically its RhB degradation rate was 3.45 times as high as the piezocatalytic degradation rate without Fe²⁺. The optimized charge carrier dynamics, as demonstrated by the electrochemical characterization and a higher piezoelectric response and as verified by PFM after co-catalyst modification, were the reason for the high-performance exhibited by Ag/BTO/CoO_x. More importantly, owing to the higher piezoelectric potential and charge carrier densities, the reduction of Fe³⁺ occurred in the Ag/BTO/CoO_x PEFS. It was further confirmed via monitoring the valence state of Fe ions and the accelerated Fe³⁺/Fe²⁺ cycle. The distinct active species trapping results before and after the addition of Fe²⁺ further supported the triggered Fenton reactions in the PEFS, and the dominant role of ˙OH and electrons in piezo-self-Fenton degradation was confirmed. Thus, this work provides a promising Ag/BTO/CoO_x-based piezo-self-Fenton system for wastewater treatment, and it is hoped to assist in gaining an in-depth understanding of PESF mechanisms.