Laser-assisted synthesis of Z-scheme TiO₂/rGO/g-C₃N₄ nanocomposites for highly enhanced photocatalytic hydrogen evolution

Constructing nanocomposite structures with favorable charge transfer routes is an effective way to obtain highly efficient photocatalysts. Herein, fabrication of indirect and noble metal-free Z-scheme photocatalytic architecture is demonstrated using pulsed laser ablation in liquids (PLAL) technique for the first time. The as-prepared ternary photocatalyst (denoted as TiO₂/rGO/g-C₃N₄) comprises titanium dioxide (TiO₂) nanotubes, reduced graphene oxide (rGO) nanosheets, and graphitic carbon nitride (g-C₃N₄) nanosheets. The photocatalytic activity of the as-synthesized composite is evaluated by monitoring water splitting. Various analytical techniques were employed to investigate the compositional, morphological, structural, and optical properties of the photocatalysts. The system of TiO₂/rGO/g-C₃N₄ with the weight ratio of TiO₂ to g-C₃N₄ of 2:4 and 1% rGO exhibited the highest hydrogen production rate of 32 ± 1 mmol g⁻¹h⁻¹, which is about 93, 3.8 and 2.6 times higher than those of pure g-C₃N₄, TiO_2, and TiO₂/rGO, respectively. This enhanced performance can be ascribed to the strong interfacial bonding (TiO₂-rGO-g-C₃N₄), extended visible light absorption capacity due to higher photo-responsiveness of rGO and g-C₃N₄, the synergetic effect between TiO₂ and g-C₃N₄ and direct contact between TiO₂ and rGO which facilitated efficient separation and transfer of photogenerated charges. This study opens opportunities for the fabrications of different Z-scheme systems for various applications.