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.