Porous size dependent g-C3N4 for efficient photocatalysts: Regulation synthesizes and physical mechanism

We propose a new template-free approach for the synthesis of porous graphitic carbon nitride (g-C3N4) nanosheets as efficient photocatalysts. This new template-free method includes a one-step hydrothermal treatment and a sequential two-step thermal treatment. This method can provide massively porous g-C3N4 nanosheets without external physical defects (such as atom doping and/or atom vacancies) in the g-C3N4 nanosheets. The Brunauer-Emmett-Teller (BET) surface areas and pore volumes of the porous g-C3N4 nanosheets can reach 125 m2 g-1 and 1.2 cm3 g-1, respectively, thereby showing significant increases of 22 and 15 times, respectively, compared with those of the pristine g-C3N4 nanosheets. The synthesized porous g-C3N4 nanosheets have large specific surface areas and exhibit high photocatalytic activities that are enhanced by as much as 8 times compared to those of the pristine g-C3N4 for the photodegradation of gas pollutants (using the photocatalysis of 2-propanol to acetone as an example) under visible light (λ > 420 nm). Experimental and theoretical results reveal the suitable porous size of porous g-C3N4 plays essential role for the efficient photocatalysis. Our multistep template-free approach can provide a new method for the preparation of porous g-C3N4 nanosheets as efficient photocatalysts that are better than those obtained by destroying the physical structures of the pristine g-C3N4 nanosheets.