Molecularly Tunable Donor-Acceptor Integrated Carbon Nitride for Sunlight-Driven H₂O₂ Synthesis: Mechanism and...

Graphite phase carbon nitride (CN) emerges as a promising catalyst for sunlight-driven H₂O₂ synthesis owing to its merits of stable physicochemical properties, distinctive electronic structure, adjustable bandgap, etc., yet poor charge behavior, especially high carrier recombination and low charge migration rate, limit its photocatalytic activity. Herein, a molecularly tunable donor-acceptor (D-A) integrated CN is fabricated via cytosine doping combined with molten salt-assisted calcination. The catalyst is utilized for sunlight-driven H₂O₂ synthesis and achieves the highest H₂O₂ yield of 8.07 mmol g^-1 h^-1, which exceeds the initial CN by the factor of 40.4, surpassing numerous reported CN-based photocatalysts. Series characterizations/tests (e.g., transient absorption, steady-state SPV spectra, KPFM) and theoretical calculations (e.g., HOMO/LUMO, adsorption energy) confirm that the incorporation of K⁺, -C≡N and pyrimidine ring disrupts the symmetry of CN and establishes a molecularly tunable D-A integrated structure, significantly augmenting the separation and migration of photogenerated charges. The capture experiment and rotating disk electrode test affirm that a two-step single electron oxygen reduction pathway occurs in the process of sunlight-driven H₂O₂ synthesis. This work offers novel approaches and profound revelations for the development of sunlight-driven H₂O₂ synthesis.