Non-covalent doping of carbon nitride with biochar: Boosted peroxymonosulfate activation performance and unexpected singlet oxygen evolution mechanism

A noncovalent functionalization approach was implemented using graphitic biochar (BC) as dopant to manipulate electronic properties of polymeric carbon nitride (PCN) while preserving its robust geometric skeleton. By fine-tuning the mass proportions of precursors during copolymerization, the carbonization of corncob was successfully confined in the PCN interlayers. An electron transport highway from PCN to BC was built owing to the pi-electron delocalization. As a result, the non-covalent assembled PCN/BC composite rivaled popular nitrogen-doped carbon materials in activating peroxymonosulfate (PMS), and meanwhile exhibited superior durability. Singlet oxygen (1O2) was identified as the primary reactive oxygen species. Combining theoretical calculations and in-situ detections, a novel 1O2 evolution route with respect to the dissociation of PMS at the S/O site and the formation of superoxide radical was decoded. This work offers a new idea for the synthesis of durable PMS activators and enriches mechanistic understanding of PMS decomposition over metal-free catalysts.