Efficient upconverting carbon nitride nanotubes for near-infrared-driven photocatalytic hydrogen production

We report a facile chemical technique for synthesizing nanotube-based hybrid materials for near-infrared-driven photocatalytic hydrogen (H₂) production. Upconversion nanoparticles (UCNPs), NaYF₄:Yb,Tm,Gd (NYFG) and NaYF₄:Yb,Tm (NYF), were engineered on C₃N₄ nanotubes (C₃N₄ NTs) separately to construct heterojunction structures. With a UCNP loading content of 15 wt%, the NYFG/C₃N₄ NT heterojunction exhibits the highest H₂ generation rate of 311.6 μmol g⁻¹ with an apparent quantum efficiency of 0.80 ‰, about 1.4 times higher than that of the NYF/C₃N₄ NT nanocomposite under 980 nm laser irradiation. Comprehensive characterization reveals that the enhanced photocatalytic performance of the Gd doped nanostructure is attributed to the synergistic effect, stronger interaction, higher emission intensities, and faster charge transfer between the UCNPs and C₃N₄ NTs. Moreover, the steady-state and dynamic fluorescence spectra indicate that the energy from NYFG NPs was transferred to C₃N₄ NTs via a fluorescence-resonance energy-transfer process. Our work demonstrates the potential of developing near-infrared-responsive photocatalysts for energy and environmental applications.