Extension of π-conjugated aromatic structure in g-C₃N₄ nanosheets and their applications into bisphenol E decomposition

In the present study, multiple carbon-doped g-C₃N₄, consisting of urea and various carbon sources (trisodium citrate, citric acid, ethanol, and methanol), was fabricated through a two-step calcination process, and their activities of photocatalysts were compared for the degradation of bisphenol E (BPE). As a result, g-C₃N₄ (ethanol), which was secondly calcinated in ethanol, exhibited the maximum degradation efficiencies (C-C₀)/C of 94.7% after 20 min of irradiation. It was better than those obtained from both the addition of citric acid and ethanol, CCN (ethanol): 90.9%. It was revealed that ethanol was more advantageous relative to citric acid for extending the localized π-conjugated aromatic structure. It was confirmed from TEM analysis that the thinning of g-C₃N₄ through the two-step calcination and the formation of curl structures due to the carbon doping. BET analysis revealed an increase in specific surface area. The decrease in photoluminescence (PL) intensity gave the low electron and hole pair recombination owing to the localized π-conjugated aromatic structure with carbon doping. The present study provided a novel approach to optimize the precursor for the extension of the localized π-conjugated aromatic structure of carbon-doped g-C₃N₄, and simultaneously increase the specific surface area by a two-step calcination.