Graphitic carbon nitride decorated with C-N compounds broken by s-triazine unit as homojunction for photocatalytic H₂ evolution

The gradual depletion of global fossil energy and environmental pollution make the development of hydrogen energy an imminent concern. Two-dimensional g-C₃N₄ (CN) based heterostructures have attracted considerable research interest in the photocatalytic H₂ evolution field, but the unsatisfactory interfacial contact between metal-free CN and other metal oxide/sulfide semiconductors usually results in a low transfer efficiency of charge carriers. Herein, we develop a new homojunction by in situ decoration of CN nanosheets with a C-N compound broken by s-triazine units (abbreviated to BST). The resultant CN/BST homojunction presents significantly enhanced photocatalytic H₂ generation (12.47 mmol g⁻¹ h⁻¹), which is about 4 and 33 times higher than that of pristine CN (3.086 mmol g⁻¹ h⁻¹) and BST (0.376 mmol g⁻¹ h⁻¹), respectively. It is revealed that the BST fragments tightly anchored on the CN nanosheets act as electron-trapping agents to rapidly transfer photogenerated electrons from the CN conduction band to generate hydrogen, effectively inhibiting the recombination of photogenerated electrons and holes. The work shows that the construction of a suitable homojunction is an effective way to obtain high photocatalytic activity.