Supramolecular self-assembly coupled with alkali metal molten salts to construct Nv-carbon nitride for efficient photocatalytic H₂O₂ production

H₂O₂ production over carbon nitride photocatalyst is an emerging alternative and ecological solar-driven application. However, bulk carbon nitride (BCN) has stubbornly weak visible light absorption and easy recombination of carriers. Here, a sodium/potassium co-doped N vacancy (Nv) rich carbon nitride was synthesized by a one-step melamine and cyanuric acid self-assembly coupled with alkali metal molten salts. The hybridization of sodium is found to locate on edge site of CN layers, which introduces Nv structure and cyano structure on CN layers, hence modulates the migration of in-plane electrons. The potassium is found to intercalate between CN layers, which promotes carrier transportation between the interlayers. Both effects induce higher carrier transfer efficiency of catalysts and the co-doping of Na and K bring us the optimal sample (CNNK) with an ultra-high production rate (6289.6 μmol/g/h) and apparent quantum yield (44.70 %, 380 nm), which is 124.5 and 10.4 times higher than BCN during the hydrogen peroxide process, respectively. Mechanistic analysis confirms the two-step single-electron oxygen reduction reaction pathway of H₂O₂ production. This strategy provides an achievable coupling strategy idea to design photocatalysts with elaborate structures for energy conservation.