Sulfur promoted n-π* electron transitions in thiophene-doped g-C3N4 for enhanced photocatalytic activity

Expanding the optical absorption range of photocatalysts is still a key endeavor in graphitic carbon nitride (g-C3N4) studies. Here, we report on a novel thiophene group extending the optical property, which is assigned to n-π* electronic transitions involving the two lone pairs on sulfur (TLPS). The as-prepared samples, denoted as CN-ThAx (where x indicates the amount of ThA added, mg), showed an additional absorption above 500 nm as compared to pristine g-C3N4. Further, the thiophene group enhanced charge carrier separation to suppress e−/h+ pair recombination. The experimental results suggest that the thiophene group can obstruct the polymerization of melem to generate a large plane, thus exposing the lone electron pairs on the sulfur. The photocatalytic activity was evaluated in the decomposition of bisphenol A and H2 evolution. Compared with g-C3N4, the optimized CN-ThA30 sample led to a 6.6- and 2-fold enhancement of the degradation and H2 generation rates, respectively. The CN-ThA30 sample allowed for synchronous H2 production and BPA decomposition.