Suppressing Defects-Induced Non-Radiative Recombination for Activating the Near-Infrared Photoactivity of Red Polymeric Carbon Nitride

Many cases of light absorption modification exceeding 700 nm or near-infrared (NIR) light are reported for capturing more than half of the solar energy, however, very few modifications can produce NIR photoactivity due to the inevitably introduced defects-induced non-radiative recombination. Here, taking four kinds of C/O co-doped red polymeric carbon nitride as examples, defect-repairing is carried out using alkali metal molten-salts (LiCl/NaCl and LiCl/KCl) or solid-salt (KCl) to activate their NIR photoactivity. The defect repair results from the passivation of alkali metal valence electron pairing and the formation of crystalline polyheptazine imide structure with more complete polymerization. More importantly, it sharply eliminates bulk defects (such as carbon vacancy and nitrogen vacancy) introduced by C/O co-doping. Since structural defects are inevitably introduced in most photocatalysts during expanding light absorption, this proposed strategy is bound to be universal in suppressing defects-induced non-radiative recombination to activate NIR photoactivity.