Inverted F-scheme heterojunction: Introduction and experimental validation using CdS/Co3O4 nanocage photocatalytic composite

Abstract

In the regime of augmenting photo-activity over semiconductor-semiconductor heterojunction, composite with Type-I-like band alignment is allegedly inferior to Type-II, Z-scheme, and S-scheme heterojunctions due to its incapability in separating photo-charges. While disagreeing this ‘dogma’, we demonstrated a composite with Type-I-like band structure but improved activity herein, alongside its electron mechanism that challenges general beliefs. Our synthesized CdS/Co3O4 composite is named ‘Inverted F-Scheme’ heterojunction, where the Fermi level-variation between both constituents induces edge-bending effects in such a way that the electrons and holes tend to reside at Co3O4 and CdS, respectively. This explains the outstanding performance of CdS/Co3O4 nanocage in photo-degrading tetracycline, with CdS/Co3O4-1.75 enabling removal kinetic of 71.4×10−4 min−1, comparing to 20.2×10−4 min−1 of pure CdS and 2.75×10−4 min−1 of Co3O4 nanocage. This work justifies the possibility of securing enhanced photo-activity even with Type-I-like composite, thereby opening up another interesting horizon for future investigation in related field.