The synergistic effect in metal-free graphene oxide coupled graphitic carbon nitride/light/peroxymonosulfate system: Photothermal effect and catalyst stability

The combination of sulfate radical-mediated advanced oxidation process (SA-AOP) and photocatalysis is researched as a highly efficient strategy for pollutant degradation in recent decades. To systematically study the synergistic effect between photocatalysis and peroxymonosulfate (PMS) induced SA-AOP, graphene oxide (GO) coupled graphitic carbon nitride (CN) composites were synthesized as catalyst. About 98% of bisphenol A was decomposed in CNGO/PMS/light system, which was significantly higher than that in CNGO/PMS or CNGO/light system, demonstrating the strong synergistic effect between photocatalysis and SA-AOP. CNGO was deactivated in catalyst/PMS system, but not in catalyst/PMS/light system, showing that the deactivation of CNGO in the presence of sulfate radicals was inhibited by the photocatalysis. The photogenerated electrons may directly reduce the oxidized GO, or react with the oxidative species which may oxidize GO, and thus maintain the activity of CNGO. In addition, the system temperature was elevated due to the light-to-heat conversion on GO. The increased reaction temperature accelerated the degradation reaction due to the improved the charge separation and molecular collision. This work explains the synergy effect between photocatalysis and SA-AOP from different perspectives, and provides a new idea to improve the reusability of carbonaceous catalyst.