Ozone treatment of graphitic carbon nitride with enhanced photocatalytic activity under visible light irradiation

An efficient and stable catalyst with fragment-exfoliating structure was prepared by directly ozone treatment of bulk graphitic carbon nitride (g-C₃N₄). The photocatalytic performances of the as-prepared catalysts were evaluated by degradation of methylene blue (MB) and photocatalytic hydrogen evolution reaction under visible light irradiation. Compared with untreated g-C₃N₄, the ozone-treated g-C₃N₄ (OCN) exhibited almost 5 times higher photodegradation activity and 2 times H₂ evolution rate. The enhanced photocatalysis capability could be assigned to a narrowed band gap (2.62eV), the increased defects and active sites, and the reduced recombination efficiency of photoinduced carriers in OCN. Furthermore, the photocatalytic mechanism in degradation process of MB was discussed and the hydroxyl radical and superoxide radical have proven to be the predominant active species. It is reasonable to believe that chemical modifying of catalysts through ozone treatment could efficiently regulate its catalytic activity.