Tuning the Electronic Bandgap of Graphdiyne by H-Substitution to Promote Interfacial Charge Carrier Separation for Enhanced Photocatalytic Hydrogen Production

Graphdiyne (GDY), which features a highly pi-conjugated structure, direct bandgap, and high charge carrier mobility, presents the major requirements for photocatalysis. Up to now, all photocatalytic studies are performed without paying too much attention on the GDY bandgap (1.1 eV at the G(0)W(0) many-body theory level). Such a narrow bandgap is not suitable for the band alignment between GDY and other semiconductors, making it difficult to achieve efficient photogenerated charge carrier separation. Herein, for the first time, it is demonstrated that tuning the electronic bandgap of GDY via H-substitution (H-GDY) promotes interfacial charge separation and improves photocatalytic H-2 evolution. The H-GDY exhibits an increased bandgap energy (approximate to 2.5 eV) and exploitable conduction band minimum and valence band maximum edges. As a representative semiconductor, TiO2 is hybridized with both H-GDY and GDY to fabricate a heterojunction. Compared to the GDY/TiO2, the H-GDY/TiO2 heterojunction leads to a remarkable enhancement of the photocatalytic H-2 generation by 1.35 times under UV-visible illumination (6200 mu mol h(-1) g(-1)) and four times under visible light (670 mu mol h(-1) g(-1)). Such enhancement is attributed to the suitable band alignment between H-GDY and TiO2, which efficiently promotes the photogenerated electron and hole separation, as supported by density functional theory calculations.

Automated summary

Graphdiyne, with its high pi-conjugated structure and direct bandgap, meets the requirements for photocatalysis. By tuning the bandgap through H-substitution, the interfacial charge separation can be promoted and photocatalytic performance can be improved. Hybridizing GDY and H-GDY with TiO2 leads to enhanced H-2 generation due to efficient electron and hole separation.