Graphene oxide modulated dual S-scheme ultrathin heterojunctions with iron phthalocyanine and phase-mixed bismuth molybdate as wide visible-light catalysts

Abstract

Herein, a phase-mixed Bi_3.2Mo_0.8O_7.5–Bi₂MoO₆ (2.7BMO) S-scheme nanosheet heterojunction (∼4 nm) is successfully synthesized using a microwave-assisted hydrothermal method firstly and then coupled with two-layered iron phthalocyanine (FePc) (∼1 nm) via a hydroxyl-induced assembly prior to graphene oxide (G) modification for fabricating an interface-modulated dual S-scheme ultrathin heterojunction (FePc/G/2.7BMO), in which the used G with abundant hydroxyl groups greatly improves the dispersion of FePc on 2.7BMO nanosheets to increase the optimized loading amount from 0.5 to 0.8 wt% with more exposed Fe–N₄ sites. The amount-optimized heterojunction displays greatly improved visible-light activity for tetracycline (TC) degradation, which is 8.5 and 4.3 times higher than those of bare Bi_3.2Mo_0.8O_7.5 and Bi₂MoO₆ nanosheets, respectively. The exceptional visible-light activity can be attributed to the enhanced charge separation due to the formed interface-modulated dual S-scheme heterojunction, and the extended wide visible-light response and the promoted O₂ activation via the Fe–N₄ sites from the assembled FePc.