Multi-regulation of charge separation and band structure by a novel O-doped g-C3N4 nanosheets homojunction for enhanced photodegradation performance

Using melamine-cyanuric acid (MCA) supramolecular, urea (U) and oxalic acid as the precursors, a novel O-doped g-C3N4 nanosheets (coiled/stacked) homojunction (O-g-C3N4-MCAU) was constructed and exhibited significantly enhanced photodegradation performance towards 2,4-dichlorophenol (2,4-DCP) under visible light. The optical and photo-electrochemical studies and density functional theory (DFT) calculations were carried out and revealed that the product can promote the photogenerated charge separation and transfer efficiency and adjust energy band structure in different ways. The homojunction enhanced charge separation efficiency on the surface. O doping changed the charge arrangement in the homojunction and formed an internal electric field, which enhanced the charge separation efficiency in the bulk phase. Meanwhile, O doping also regulated the band structure by substituting the N atoms, thereby expanding the photo-response range. Furthermore, the nanosheets structure shortened the transfer distance of photogenerated charges from bulk phase to surface. Combined the multi-regulation behavior with active species analysis, the enhanced photocatalytic mechanism was proposed. Under the coaction of the O2- and h+, 2,4-DCP was decomposed with intermediates of smaller organic acid molecules.