One-step microwave method realizes two-step strategy to enhance the photocatalytic performance of fly ash: Enhance the carrier transfer efficiency and inhibit the carrier recombination

To address the negative impacts of fly ash (FA), its potential applications in various fields, including photocatalysis, should be investigated. In this study, a photocatalyst (P–C-dots@FA/P–C) with phosphorized carbon-dots (C-dots) and carbon layer on FA was synthesized by a one-step microwave method. To obtain the optimal catalytic activity, the synthesis conditions of different phosphoric acid contents and microwave times were tested. The addition of 18% phosphoric acid yielded the highest catalytic activity under a microwave of 700 W for 4 min. In addition, the photocatalytic activity of P–C-dots@FA/P–C for Rhodamine B was 238 times higher than that of FA alone. Furthermore, the doping of phosphorus resulted in the formation of C-dots on the FA surface, thereby obtaining the P–C-dots@FA material with enhanced photocatalytic activity of P–C. This material enhanced the transfer of photogenerated carriers, was further carbonized to form a carbon layer, and weakened the recombination of photogenerated carriers. The stability experiment of the material proves that the material has good reproducibility, stability and recyclability. • FA was modified by a one-step method for improved photocatalytic activity. • The possible degradation mechanism of the photocatalysts were determined. • The FA with carbon layer improved the photoelectric separation efficiency. • The resulting porous carbon layer was conducive to the adsorption of Rh B. • Rh B degradation was ascribed to the holes, and superoxide, and hydroxyl radicals.