Active species trapping test for the mechanism study of photocatalytic dye degradation: A critical examination

In recent years, active species trapping technique was widely employed to identify the dominant reactive species involved in photocatalytic processes. Although well recognized by most researchers, the reliability, validity, and accuracy of this technique have never undergone systematic investigation. In this study, a series of experiments were conducted to examine the application of active species trapping technique in photocatalytic dye degradation. Control experiments were performed to study the direct reactions between dyes and quenchers. Active species trapping tests were carried out to compare the trapping effect of different quenchers in various photodegradation reactions. Benzoquinone (BQ) was chosen as the model quencher to understand the interactions between quenchers and photocatalysts. The etching characteristics of titanium dioxide and graphitic carbon nitride were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET) method, Fourier transform-infrared (FTIR) spectroscopy, and Electron spin resonance spectroscopy (ESR). The experimental findings indicated that active species trapping is a complex process involving several major participants, including light, photocatalyst, contaminant (or product), and quencher, rather than a simple interaction between quenchers and the photo-induced active species.