A novel red phosphorus/perylene diimide metal-free photocatalyst with p-n heterojunctions for efficient photoreduction of bromate under visible light

Using solar energy to reduce bromate in drinking water is promising. Unfortunately, most effective photocatalysts for bromate conversion are metal-based semiconductors. Here, for the first time, metal-free hybrid composites made of red phosphorus and perylene diimide (RP/PDI) were successfully designed and constructed, and their excellent catalytic performance for removing bromate under visible light was demonstrated. Characterizations such as XRD, FTIR, Raman, SEM and XPS confirmed the successful preparation of the hybrid catalyst, and the impact of water matrices suggests that it can be used for the actual treatment of bromate. The bromate reduction rate of the prepared RP/PDI-2 was 4.2 times and 7.0 times faster than pure RP and PDI, respectively. As evidenced by EIS and EPR results, this improvement is mainly due to the formation of p-n heterojunctions, which enhanced the separation of charge carriers and inhibited the production of active species (O-center dot(2)- and (OH)-O-center dot) with strong oxidative capabilities. Considered holistically, the current study provides not only a metal-free photocatalyst with good photoreduction performance, but also some guidance for the rational design of hybrid photocatalyst in the treatment of aqueous bromate.