Enhanced Photocatalytic Hydrogen Production Over G-C₃N₄-Based Composites

The acceleration of industrialization underscores the critical necessity for new energy technologies that are safe,environmentally friendly,user-friendly,and long-lasting.Hydrogen is now widely recognized as one of the world’s cleanest sources of energy,and photocatalytic technology based on semiconductors can produce hydrogen gas（H₂）.Among the extensively researched semiconductors,such as titanium dioxide（Ti O₂）,many only respond to ultraviolet（UV）light.Therefore,there is a pressing need to explore photocatalysts that can harness visible light from the sun.Graphitic carbon nitride（g-C₃N₄）has emerged as the most investigated photocatalyst due to its cost-effectiveness,responsiveness to visible light,and impressive physical and chemical properties.However,the photocatalytic capabilities of g-C₃N₄ are constrained by rapid charge carrier recombination.Combining g-C₃N₄ with co-catalysts or other semiconductors can significantly enhance carrier separation and improve its overall performance.This study includes:（1）Dual plasmonic Au and TiN cocatalysts were incorporated into g-C₃N₄ nanotubes to create a ternary LSPR-enhanced 0D/0D/1D Au/TiN/g-C₃N₄ composite.This was achieved through in-situ coupling followed by thermal polycondensation and chemical reduction.The plasmonic cocatalysts composed of Au and TiN nanoparticles enhanced light absorption and promoted the separation of charge carriers.Multiple interfaces and dual-junctions were formed between the Au and TiN nanoparticles and g-C₃N₄ nanotubes,including an Au/g-C₃N₄ Schottky-junction and a TiN/g-C₃N₄ ohmic-junction.These structures provided multiple routes for multi-electron transfer,facilitating the separation of carriers and enhancing photocatalytic performance.（2）A porous 2D/2D boron-doped g-C₃N₄（BCN）/Ni-MOF-74 heterojunction was successfully prepared through high thermal polymerization,hydrothermal routes,and a simple solution mixing way.The porous surface and carrier transfer mode created additional reactive sites for H₂generation and facilitated mass transfer at the contact inter-phase between BCN and Ni-MOF-74.This enhanced light trapping ability,improved the spectral absorbance range,and extended the lifespan of photoinduced carriers.The optimal BCN/Ni-MOF-74 composite demonstrated outstanding H₂ generation,achieving up to 2190μmol g^-1h^-1,which was nearly 11 times higher than that of BCN alone.（3）A novel Z-scheme photocatalyst,comprising AgVO₃/g-C₃N₄（CN）,was prepared with the mediation of Pt quantum dots（QDs）,and it demonstrated effective hydrogen generation under sunlight.The resulting 1D/0D/2D composite of AgVO₃/Pt/CN（referred to as Av PCN）exhibited significantly improved charge separation capabilities and a notably reduced onset potential for hydrogen production.Notably,the plasmonic Pt QDs offer electron transfer pathways,potentially enhancing carrier separation and extending the lifespan of photoinduced carriers.Compared to the binary composite,the Av Pt CN composite achieved an impressive hydrogen production rate of up to 10444 mol g^-1h^-1.These findings contribute to a deeper understanding of the photocatalytic hydrogen production mechanism using new graphitic carbon nitride.Key factors,such as the incorporation of dual cocatalysts and the formation of heterojunctions with other semiconductors and metal-organic frameworks,create additional active sites and enhance stability,thereby playing pivotal roles in the photocatalytic and photo-electrocatalytic hydrogen evolution reactions.