Polymeric triazine/heptazine imide heterostructures enable photocatalytic O2 reduction to H2O2

Heptazine-based carbon nitrides are a class of transition metal free semiconductors, which are extensively studied in various photocatalytic processes. The localized nature of the excitons, incomplete exciton conversion into the charge-separated state and the recombination of the charge carriers are the factors that limit performance of the pristine heptazine-based carbon nitrides. Herein, we design heterojunctions composed of poly (triazine imide) intercalated by LiCl and poly(heptazine imide) phases. The donor-acceptor character of the heterojunctions improves the charge separation yield. The heterojunction with the optimal composition of the phases shows an apparent quantum yield of H2O2 formation of 14 % at 365 nm and 7 % at 465 nm, while the H2O2 production rate reaches 7.8 mol L(-1)g(photocatalyst)(-1) h(-1) in flow using a packed-bed photoreactor. The heterojunction undergoes photocharging under anaerobic conditions. The charges stored in the material after irradiation enable O-2 reduction to H2O2 in the dark with the rate 367 mu mol kg(photocatalyst)(-1) h(-1) (1.8 mu mol h(-1) stored in 5 mg of photocatalyst).