Exploration for high performance g-C3N4 photocatalyst from different precursors

High performance g-C3N4 photocatalysts were synthesized via a facile calcining process after mixing dual precursors with different mass ratios, including melamine/thiourea, melamine/urea and urea/thiourea. The g-C3N4 samples were systematically characterized and their photocatalytic performances were evaluated by photocatalytic degrading rhodamine B (RhB). g-C3N4 prepared from two precursors exhibited better degrading performance than g-C3N4 synthesized from single precursor, and the degradation rate constant of g-C3N4 prepared from urea and thiourea with mole ratio of 3:1(CN-UT-3) was the largest one, which was about 21.6 times that of g-C3N4 prepared from melamine alone. The enhanced specific surface area as well as the accelerated separation and transportation of photogenerated carriers were the main reasons for the improvement of photocatalytic performance. In addition, UV–vis and Mott-Schottky plots showed that an energy band structure like type Ⅱ heterojunction were constructed in as-synthesized g-C3N4 samples from dual precursors, whose internal electric field provided the power for the migration of photo-generated carriers. The scavenger experiments revealed that h+ and •O2− were the active groups taking part in the photocatalytic reaction. Moreover, CN-UT-3 exhibited excellent recyclability and stability during the cycle experiments. This work provides a facile way to synthesize g-C3N4 with high photocatalytic performance, and reveals the effects of the precursor types and their mole ratios on the structure and photocatalytic performance of the as-synthesized g-C3N4 photocatalyst.