Prussian Blue analogue supported on sulfur-doped carbon nitride as an enhanced heterogeneous catalyst for activating peroxymonosulfate.

While Prussian Blue (PB) analogues are attractive catalysts for activating peroxymonosulfate (PMS), PB analogues are very small and thus difficult for recovery. Immobilizing PB particles onto graphene is a useful technique which facilitates recovery and also enhances catalytic activities. As doping graphene with sulfur/nitrogen (S/N) increases its electro-conductivity and active sites, the composite of PB and S/N-doped graphene should enhance PMS activation. Thus, this study aims to fabricate such a composite. Unlike conventional S/N-doped graphene prepared via post-modifications, trithiocyanuric acid is used as a precursor, which is converted to S-doped graphitic carbon nitride (SCN). The composite of PB and SCN (PBSCN) is then fabricated by growing a cobalt-based PB analogue on SCN. The resulting PBSCN preserves the crystalline structures, textural properties and catalytic sites of PB and SCN. As degradation of Acid Red 27 (AR) is used as a model reaction, PBSCN exhibits a higher catalytic activity than PB and SCN individually, as well as CoO to activate PMS for AR degradation possibly because SCN may facilitate electron transfer and enhance catalytic activities of PB. PBSCN also remains effective and re-usable over several cycles for AR degradation. These features indicate that PBSCN is a promising catalyst for activating PMS and the fabrication technique demonstrated here can be employed to prepare composites of various PB analogues and carbon nitride to exhibit enhanced catalytic activities.