One-step scalable synthesis of honeycomb-like g-C 3 N 4 with broad sub-bandgap absorption for superior visible-light-driven photocatalytic hydrogen evolution.

Integration of a nanostructure design with a sub-bandgap has shown great promise in enhancing the photocatalytic H 2 production activity of g-C 3 N 4 via facilitating the separation of photogenerated charges while simultaneously increasing the active sites and light harvesting ability. However, the development of a synthetic route to generate an ordered g-C 3 N 4 structure with remarkable sub-bandgap absorption via a scalable and economic approach is challenging. Herein, we report the preparation of a honeycomb-like structured g-C 3 N 4 with broad oxygen sub-bandgap absorption (denoted as HOCN) via a scalable one-pot copolymerization process using oxamide as the modelling agent and oxygen doping source. The morphology and sub-bandgap position can be tailored by controlling the oxamide to dicyandiamide ratio. All HOCN samples exhibit remarkable enhancement of photocatalytic H 2 production activity due to the synergistic effect between the sub-bandgap and honeycomb structure, which results in strong light absorption extending up to 1000 nm, fast separation of photogenerated charge carriers, and rich photocatalytic reaction sites. In particular, HOCN4 exhibits a remarkable photocatalytic H 2 production rate of 1140 μmol h -1 g -1 under visible light irradiation (>420 nm), which is more than 13.9 times faster than the production rate of pristine g-C 3 N 4 . Moreover, even under longer wavelength light irradiation ( i.e. , >500 and >800 nm), HOCN4 still exhibits a high H 2 production rate of 477 and 91 μmol h -1 g -1 , respectively. In addition, HOCN4 possesses an apparent quantum yield (AQY) of 4.32% at 420 nm and 0.12% at 800 nm. These results confirm that the proposed synthesis strategy allow for scalable production of g-C 3 N 4 with an ordered nanostructure via electronic modulation, which is beneficial for its practical application in photocatalytic H 2 production.