Alkali-assisted engineering of ultrathin graphite phase carbon nitride nanosheets with carbon vacancy and cyano group for significantly promoting photocatalytic hydrogen peroxide generation under visible light: Fast electron transfer channel

Exfoliating bulk graphite phase carbon nitride (g-C3N4) into 2D nanosheets is considered to be an effective method to enhance its photocatalytic activity. However, optical absorption capacity of the exfoliated g-C3N4 nanosheets are lower than that of the original bulk g-C3N4 due to the quantum size effect. Here, the ultrathin graphite phase carbon nitride nanosheets containing both carbon vacancy and cyano group (UCNS580) were prepared by two-step calcination in air with the assistance of KOH. The formation and position of carbon vacancy and cyano group were first investigated and determined. The simultaneous introduction of carbon vacancy and cyano group not only improved light absorption range and intensity of g-C3N4 nanosheets, but also more importantly constructed a fast transfer channel for photogenerated electrons, further enhancing the separation efficiency and migration ability of photogenerated carriers. The cyano group as the accumulation center of photogenerated electrons and the oxygen adsorption center increased the proportion of one-step two-electrons reaction path to efficiently generate H2O2. As a result, UCNS580 exhibited highly boosted H2O2 generation activity, its H2O2 production yield for 6 h reached 939 µmol/L and the formation rate was up to 4167 µM h-1 g-1, which was in priority in the reported literature under the same conditions.