Vacancy-Modified Porous g‑C3N4 Nanosheets Controlled by Physical Activation for Highly Efficient Visible-Light-Driven Hydrogen Evolution and Organics Degradation

As a promising photocatalyst material, g-C3N4 has great application potential in energy production and environmental improvement. In this work, surface-modified g-C3N4 nanosheets with excellent stability and high photocatalytic activity were successfully synthesized by physical steam activation. The charge transfer rate of carbon nitride was improved due to the synergistic effect of nitrogen defect and oxygen doping caused by steam activation. Meanwhile, the specific surface area and pore volume of the optimized sample reached 124.3 m2 g–1 and 0.42 cm3 g–1, respectively, which increased the exposed reaction sites of reactants, enhancing the photocatalytic activity of g-C3N4. In addition, this novel g-C3N4 displayed a great H2 evolution rate of 5889.39 μmol h–1 g–1 with a methylene blue degradation rate up to 6.52 × 10–3 min–1, which was 3.7 and 2.1 times of original g-C3N4, respectively. This study provided a simple and economical method to develop a highly efficient g-C3N4 photocatalyst for solar energy conversion.