Defect as the essential factor in engineering carbon-nitride-based visible-light-driven Z-scheme photocatalyst

[Display omitted] •Defect-rich carbon nitride was utilized in Z-scheme systems for the first time.•The proposed mechanism doubles the activity of traditional Z-scheme photocatalysts.•The promoted Z-scheme mechanism was verified to have an excellent universality.•The dye-photosensitization effect and dye decomposition mechanism were investigated. In designing of carbon nitride-based Z-scheme systems, band structure engineering of graphitic carbon nitride (g-C3N4) is unquestionably a crucial demand but paid rare attention to. Here, the broadened light absorption and charge transfer on sub gaps induced by thermal defects in defect-rich carbon nitride (d-C3N4) are simultaneously utilized to engineer a novel and more efficient Z-scheme system. The as-prepared α-Fe2O3/d-C3N4-1 exhibits dramatically improved photocatalytic degradation rate for tetracycline compared withα-Fe2O3/g-C3N4-1 under visible light. Dye photosensitization effect on photocatalytic reaction was ruled out, and the tetracycline decomposition mechanism was proposed. The efficiently restrained charge recombination and broadened light absorption in this Z-scheme system are key parameters of the outstanding photocatalytic activity. This proposed mechanism has the potential to push the limit of traditional carbon-nitride-based Z-scheme photocatalysts and can also shed substantial light on the engineering strategies for other polymeric Z-scheme photocatalysts.