Synthesizing the High Surface Area g-C3N4 for Greatly Enhanced Hydrogen Production

Adjusting the structure of g-C₃N₄ to significantly enhance its photocatalytic activity has attracted considerable attention. Herein, a novel, sponge-like g-C₃N₄ with a porous structure is prepared from the annealing of protonated melamine under N2/H₂ atmosphere (PH-CN). Compared to bulk g-C₃N₄ via calcination of melamine under ambient atmosphere (B-CN), PH-CN displays thinner nanosheets and a higher surface area (150.1 m²/g), which is a benefit for shortening the diffusion distance of photoinduced carriers, providing more active sites, and finally favoring the enhancement of the photocatalytic activity. Moreover, it can be clearly observed from the UV-vis spectrum that PH-CN displays better performance for harvesting light compared to B-CN. Additionally, the PH-CN is prepared with a larger band gap of 2.88 eV with the Fermi level and conduction band potential increased and valence band potential decreased, which could promote the water redox reaction. The application experiment results show that the hydrogen evolution rate on PH-CN was nearly 10 times higher than that of B-CN, which was roughly 4104 μmol h⁻¹ g⁻¹. The method shown in this work provides an effective approach to adjust the structure of g-C₃N₄with considerable photocatalytic hydrogen evolution activity.