Constructing interfacial P − N bonds Boosts charge transfer Crossing interfaces in redPhosphorus/Phosphorus doped graphitic carbon nitride heterojunction for Cr(Ⅵ) photoreduction

The construction of heterojunction is considered to be an effective way to promote the photocatalytic activity, while it is always challenging due to the mismatched lattices of heterojunctional materials and results in an unsatisfactory enhancement of charge carrier separation. It is critical to overcome that lattice mismatch and establish charge transfer channels in heterojunction for achieving high charge transfer and separation. In this study, a red phosphorus/phosphorus doped graphitic carbon nitride (RP/P-CN) type I heterojunction was constructed to boost interfacial charge transfer for Cr(Ⅵ) photoreduction through in situ growing RP on g-C 3 N 4 nanosheets. The formed P − N bonds around interfaces in the RP/P-CN allowed photoexcited charge to rapidly transfer from the conduction band of P-CN to that of RP, which contributed to the significant achievement of Cr(Ⅵ) reduction. The constructed interfacial charge transfer channels largely promoted the photoexcited charge carrier separation in the RP/P-CN. Additionally, the simultaneous RP formation and P doping significantly enhanced the visible light response and the adsorption efficiency of Cr(Ⅵ). As a result, RP/P-CN 1:5 could achieve 99.1 % removal of Cr(Ⅵ) after 20-min visible light irradiation with an achieved apparent kinetic rate constant (k app ) of 0.2289 min −1 , which were much better than the 19.2 % of Cr(Ⅵ) removal by pure g-C 3 N 4 and presented a 21-fold higher k app than pure g-C 3 N 4 (0.0108 min −1 ) achieved, respectively. This study provides a new strategy to design an efficient g-C 3 N 4 based metal-free heterojunction for Cr(Ⅵ) photoreduction.