A broom-like tube-in-tube bundle O-doped graphitic carbon nitride nanoreactor that promotes photocatalytic hydrogen evolution

Metal-free graphite carbon nitride (g-C₃N₄) is an ideal catalyst in the field of photocatalytic hydrogen evolution due to its visible light response, thermochemical stability and low cost. However, limited by the high photogenerated electron-hole recombination rate and poor light trapping ability of bulk g-C₃N₄ prepared by thermal condensation, it remains a great challenge in boosting the photocatalytic hydrogen (H₂) evolution performance. Herein, a broom-like O-doped g-C₃N₄ nanoreactor (O-CN-NTs) oriented by tube-in-tube was developed for the first time through the “calcination-hydrothermal-calcination” method. The tube-in-tube nanoreactor not only can facilitate the scattering of incident light inside the cavity to enhance the utilization of light, but also can reduce the transport distance of carriers from the bulk to the surface to facilitate electron-hole separation. The morphology design of the tube-in-tube nanoreactor plays a very important role in improving the performance of photocatalytic H₂ production. Furthermore, the density functional theory (DFT) calculation results manifest that the charge redistribution around the doped oxygen atoms accelerates the separation of electron-hole. The doping of oxygen atoms in g-C₃N₄ nanoreactor further enhanced the photocatalytic H₂ production performance. Attributed to above advantages, the visible-light-driven (≥420 nm) photocatalytic H₂ production rate of O-CN-NTs can achieve 13.61 mmol g^-1h⁻¹, which is approximately 71.63 times that of bulk g-C₃N₄ (CN₅₅₀).