Microwave-Assisted Synthesis of Hydrangea-Like Graphitic Carbon Nitride as an Effective Photocatalyst in Dye Degradation and Hydrogen Generation

Photocatalysis is a process that has been extensively studied for its great potential in environmental remediation and energy production. In this study, a two-step microwave-assisted synthesis approach was employed to prepare graphitic carbon nitrides (GCNs) as an environmentally friendly metal-free photocatalyst. A porous, high surface area, graphitic carbon nitride (C2N3) photocatalyst with unique hydrangea-like morphology (CNUMW) was successfully synthesized with a yield 5 times greater than directly calcined GCN. The enhanced yield was attributed to the formation of polar functional groups containing a biuret and cyanuric acid mixture as the intermediate prior to microwave pretreatment, which effectively reduced the loss of decomposition gases during the thermochemical conversion process. The as-synthesized CNUMW has a smaller band gap, a larger surface area, and a higher light absorption capacity near the Urbach energies, which are responsible for its superior activity in photocatalytic dye degradation (k = 0.216 min–1) compared to non-microwave pretreated counterparts. Scavenging tests revealed that the CNUMW-catalyzed photocatalytic reaction undergoes a superoxide-mediated pathway, which can be increased with the addition of a hole scavenger. The resulting CNUMW can also catalyze hydrogen production at an enhanced rate of 1.93 mmol g–1 h–1. The novel urea-derived flower-like C2N3 demonstrates great potential in simultaneous wastewater treatment and energy production..