Fabrication of a high-efficiency hydrogen generation Pd/C3N5-K,I photocatalyst through synergistic effects of planar and spatial carrier separation†

Nitrogen-rich graphitic carbon nitride (g-C₃N₅) has garnered significant attention in photocatalytic hydrogen production due to its unique physicochemical properties. However, g-C₃N₅ faces persistent challenges stemming from rapid carrier recombination. In this study, we successfully synthesized a Pd/C₃N₅-K,I photocatalyst through sequential doping of non-metallic heteroatoms and metal nanoparticles. The Pd/C₃N₅-K,I photocatalyst demonstrates a remarkable enhancement in the photocatalytic H₂ evolution rate (2.9 mmol g⁻¹ h⁻¹), approximately 14 times higher than that of pure g-C₃N₅ (0.2 mmol g⁻¹ h⁻¹). Characterization and calculation analyses reveal that iodine doping into the g-C₃N₅ skeleton leads to the formation of planar C–I bonds, facilitating C₃N₅ layer electron–hole pair separation. The subsequent insertion of Pd nanoparticles between the layers leads to electron accumulation on C₃N₅-K,I, while resulting in hole concentration on Pd nanoparticles, thereby facilitating thorough spatial separation of electron–hole pairs. The strategic co-doping of iodine and palladium nanoparticles effectively restrains carrier recombination of g-C₃N₅ by connecting intra- and inter-layer interactions. This study constitutes a novel conceptual framework for CN-based photocatalysts, offering a promising approach to improve their performance in hydrogen production applications.