Drastic Enhancement of Photocatalytic Activities over Phosphoric Acid Protonated Porous g-C3N4 Nanosheets under Visible Light

A simple method is developed to fabricate protonated porous graphitic carbon nitride nanosheets (P-PCNNS) by protonation–exfoliation of bulk graphitic carbon nitride (BCN) with phosphoric acid (H3PO4). The H3PO4 treatment not only helps to exfoliate the BCN into 2D ultrathin nanosheets with abundant micro- and mesopores, endowing P-PCNNS with more exposed active catalytic sites and cross-plane diffusion channels to facilitate the mass and charge transport, but also induces the protonation of carbon nitride polymer, leading to the moderate removal of the impurities of carbon species in BCN for the optimization of the aromatic π-conjugated system for better charge separation without changing its chemical structure. As a result, the P-PCNNS show much higher photocatalytic performance for hydrogen evolution and CO2 conversion than bare BCN and graphitic carbon nitride nanosheets.