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 CoOx (Ag/BTO/CoOx) 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/CoOx. More importantly, owing to the higher piezoelectric potential and charge carrier densities, the reduction of Fe3+ occurred in the Ag/BTO/CoOx 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/CoOx-based piezo-self-Fenton system for wastewater treatment, and it is hoped to assist in gaining an in-depth understanding of PESF mechanisms.