In-situ ionothermal synthesis of amorphous poly (heptazine imide) for the photoredox conversion of water

Abstract

In this study, in-situ ionothermal one-step synthesis was chosen to prepare amorphous potassium poly (heptazine imide) (APHI). The synthetic by-product potassium chloride (KCl) is critical in the thermal polymerisation procedure, which can effectively control the precursor conversion, optimise the structure and obtain amorphous APHI. Compared with the traditional highly crystalline poly (heptazine imide) (PHI), APHI maintains the chemical structure of PHI while introducing cyano groups and adjusting the bandgap. resulting in a higher photogenerated charge transfer rate and improved photocatalytic activity. The hydrogen production rate of APHI reaches 67 μmol h⁻¹, and its apparent quantum yield (AQY) is 4 % at 420 nm. It's worth mentioning that APHI also achieved remarkable results in the H₂O₂ generation reaction, with a generation rate of 382 μmol h⁻¹. This rate surpasses that of highly crystalline PHI and other carbon-nitride-based catalysts such as PTI, CN. The improvement is likely attributed to its amorphous structure and the incorporation of cyano groups. The in-situ ionothermal one-step synthesis method introduced in this study not only offers a new way to prepare APHI but also provides valuable insights for designing highly efficient photocatalysts.