Protonated graphitic carbon nitride/polypyrrole/reduced graphene oxide composites as efficient visible light driven photocatalysts for dye degradation and E. coli disinfection

A novel ternary PPy/P-C 3 N 4 /r-GO visible light-driven photocatalyst was fabricated via chemical polymerization of pyrrole in the presence of protonated-C 3 N 4 /reduced graphene oxide (P-C 3 N 4 /r-GO). The resulting PPy/P-C 3 N 4 /r-GO composite showed excellent photocatalytic performance under visible light for brilliant red dye (X3B) degradation and E. coli inactivation. An X3B degradation efficiency of 98% was achieved in 60 min, and an E. coli removal efficiency of 100% achieved in 90 min. Moreover, PPy/P-C 3 N 4 /r-GO displayed good recycling performance, with 90% efficiency retained over 5×3B photodegradation cycles. A plausible photocatalytic mechanism for the PPy/P-C 3 N 4 /r-GO composites was proposed, where p-n heterojunctions formed between P-C 3 N 4 and PPy effective separate charges (photoexcited electrons accumulating in the conduction band of P-C 3 N 4 , holes accumulating in the valence band of PPy), with r-GO acting as an electron acceptor and trap. The valence band holes in P-C 3 N 4 directly oxidize X3B, whereas conduction band electrons react with O 2 to generate reactive oxygen species (superoxide and hydroxide radicals) which also degrade X3B and can inactivate E. coli . This work thus introduces an efficient metal-free ternary photocatalyst system for environmental applications.