One step method of structure engineering porous graphitic carbon nitride for efficient visible-light photocatalytic reduction of Cr(VI)

Porous g-C₃N₄ nanosheets (PCN) were prepared by the nickel-assisted one-step thermal polymerization method. Hydrogen (H₂) which was produced by the reaction between nickel (Ni) foam and ammonia (NH₃) defined the structure and properties of PCN. During the formation of PCN, the participation of H₂ not only enhanced the spacing between layers but also boosted the specific surface area that more active sites were exposed. Additionally, H₂ promoted pores formation in the nanosheets, which was beneficial to the transfer of photons through lamellar structure and improved the absorption efficiency of visible light. Remarkably, the obtained PCN possessed better Cr(VI) photocatalytic reduction efficiency than pure g-C₃N₄. The reaction rate constant (k) of PCN (0.013 min⁻¹) was approximately twice that of bare g-C₃N₄ (0.007 min⁻¹). Furthermore, the effects of original pH and concentration of Cr(VI)-containing solution on removal efficiency of Cr(VI) were explored. A possible photocatalytic mechanism was proposed based on the experiments of radical scavengers and photoelectrochemical characterizations.