Acetamide‐ or Formamide‐Assisted In Situ Approach to Carbon‐Rich or Nitrogen‐Deficient Graphitic Carbon Nitride for Notably Enhanced Visible‐Light Photocatalytic Redox Performance

Acetamide- or formamide-assisted in situ strategy is designed to synthesize carbon atom self-doped g-C3 N4 (AHCNx ) or nitrogen vacancy-modified g-C3 N4 (FHCNx ). Different from the direct copolymerization route that suffers from the problem of mismatched physical properties of acetamide (or formamide) with urea, the synthesis of AHCNx (or FHCNx ) starts from a crucial preorganization step of acetamide (or formamide) with urea via freeze drying-hydrothermal treatment so that the chemical structures as well as C-doping level in AHCNx and N-vacancy concentration in FHCNx can be precisely regulated. By using various structural characterization methods, well-defined AHCNx and FHCNx structures are proposed. At the optimal C-doping level in AHCNx or N-vacancy concentration in FHCNx , both AHCNx and FHCNx exhibit remarkably improved visible-light photocatalytic performance in oxidation of emerging organic pollutants (acetaminophen and methylparaben) and reduction of proton to H2 in comparison of unmodified g-C3 N4 . Combination of the experimental results with theoretical calculations, it is confirmed that AHCNx and FHCNx show different charge separation and transfer mechanisms, while the enhanced visible-light harvesting capacity and the localized charge distributions on HOMO and LUMO are responsible for this excellent photocatalytic redox performance of AHCNx and FHCNx .