Bandgap engineering of polymetric carbon nitride copolymerized by 2,5,8-triamino-tri-s-triazine (melem) and barbituric acid for efficient nonsacrificial photocatalytic H2O2 production

Photocatalytic production of H2O2 from water and oxygen utilizing polymetric carbon nitride (PCN) is a promising alternative to the energy-consuming anthraquinone method. However, insufficient oxidation potential and limited light-absorption have restricted its further improvement. Herein, PCN with sufficient oxidation potential and improved visible-light usage (up to 550 nm) was prepared by co-polymerization of 2,5,8-triamino-tri-s-triazine (melem) and barbituric acid (BA). With the loading of Na2CoP2O7 as a water-oxidation co-catalyst, this novel PCN system showed a record-high apparent quantum efficiency (420 nm) of 8.0 % and a solar-to-chemical conversion efficiency of 0.30 % for H2O2 production. This improvement is attributed to the introduced O 2p states by CO groups remained in the PCN matrix, leading to a positive valence band maximum of 1.85 eV (vs. SHE). The co-polymerization of BA and melem combined with Na2CoP2O7 loading also suppressed the charge recombination, resulting in a rapid stepwise one-electron to one-electron reaction for efficient H2O2 production.