One pot synthesis of donor-acceptor carbon nitride with distinct thiophene rings accelerate photocatalytic hydrogen evolution

Graphitic carbon nitride (g-CN) with a donor-acceptor structure was synthesized by urea and cross-linking thiophene precursors at the terminal sites, achieved through calcination of urea with four different thiophene-based precursors under atmospheric conditions. Among these, UDB-2-1, which incorporates dibenzothiophene-2-carboxyaldehyde (DB-2) 1 mg, demonstrated a hydrogen evolution activity of 650 μmol/g·h, approximately six times higher than pristine graphitic carbon nitride (U). The apparent quantum yield (AQY) was measured to be 4.01 %, 4.89 %, and 3.72 % at 400 nm, 420 nm, and 450 nm, respectively, in the presence of potassium hydrogen phosphate (KPH). This enhanced performance is attributed to increased visible light absorption from the n-π∗ transition introduced by the thiophene ring and enhanced charge separation due to the donor-acceptor (DA) structure, with DB-2 acting as an electron donor. Prepared photocatalysts were characterized by XRD, XPS, FTIR, SEM, TEM, BET, ESR, EIS, Mott-Schottky, DRS, PL, and TRPL measurement. This study provides a simple and effective strategy to improve carbon nitride performance and underscores the importance of functional group positioning and structural isomers in molecular design for solar-energy applications.