Microwave-Assisted\nSynthesis of Hydrangea-Like Graphitic\nCarbon Nitride as an Effective Photocatalyst in Dye Degradation and\nHydrogen Generation

Photocatalysis is\na process that has been extensively studied for\nits great potential in environmental remediation and energy production.\nIn this study, a two-step microwave-assisted synthesis approach was\nemployed to prepare graphitic carbon nitrides (GCNs) as an environmentally\nfriendly metal-free photocatalyst. A porous, high surface area, graphitic\ncarbon nitride (C<sub>2</sub>N<sub>3</sub>) photocatalyst with unique\nhydrangea-like morphology (CNUMW) was successfully synthesized with\na yield 5 times greater than directly calcined GCN. The enhanced yield\nwas attributed to the formation of polar functional groups containing\na biuret and cyanuric acid mixture as the intermediate prior to microwave\npretreatment, which effectively reduced the loss of decomposition\ngases during the thermochemical conversion process. The as-synthesized\nCNUMW has a smaller band gap, a larger surface area, and a higher\nlight absorption capacity near the Urbach energies, which are responsible\nfor its superior activity in photocatalytic dye degradation (<i>k</i> = 0.216 min<sup>–1</sup>) compared to non-microwave\npretreated counterparts. Scavenging tests revealed that the CNUMW-catalyzed\nphotocatalytic reaction undergoes a superoxide-mediated pathway, which\ncan be increased with the addition of a hole scavenger. The resulting\nCNUMW can also catalyze hydrogen production at an enhanced rate of\n1.93 mmol g<sup>–1</sup> h<sup>–1</sup>. The novel urea-derived\nflower-like C<sub>2</sub>N<sub>3</sub> demonstrates great potential\nin simultaneous wastewater treatment and energy production..