Search

• CdS/KPW/meso-g-C 3 N 4 tandem heterojunction is fabricated for the first time. • It has good light response and narrow band gap. • It exhibits excellent visible light photocatalytic activity. • It can be due to the synergy between the Z-scheme and type-II heterojunction. • The tandem heterojunction favors the spatial charge carrier separation greatly. It is known that fabrication of tandem heterojunctions between different types of heterojunctions can promote the charge separation. Herein, novel cadmium sulfide quantum dots (CdS QDs)/dodecahedral phosphotungstic acid potassium K 3 PW 12 O 40 (KPW)/oxygen-doped mesoporous graphite carbon nitride (meso-g-C 3 N 4) nanosheets tandem heterojunctions are prepared by the hydrothermal method combined with direct template calcination and in-situ chemical sedimentation strategy. The results show that tandem heterojunctions formed by the Z-Scheme heterojunction between CdS QDs and KPW and the type-II heterojunction between CdS QDs and meso-g-C 3 N 4 can extend the optical response into visible light region. Importantly, under visible light irradiation, photocatalytic hydrogen production rate and photocatalytic Cr6+ removal rate over CdS/KPW/meso-g-C 3 N 4 is higher than that of KPW and CdS/KPW. This remarkable photocatalytic performance is due to the effective charge separation and transfer of the special tandem heterojunction structure. This novel tandem heterojunction will offer new insights for fabricating other high-performance photocatalytic systems. [ABSTRACT FROM AUTHOR]

[Display omitted] A hollow core–shell potassium phosphomolybdate (KMoP)@cadmium sulfide (CdS)@bismuth sulfide (Bi 2 S 3) Z-scheme tandem heterojunction is fabricated by a simple hydrothermal strategy and kept in a water bath to continue the reaction. At the same time, the ternary structure combined Keggin-type polyoxometalate with two photosensitive sulfide semiconductors to form a stable hollow core–shell heterojunction. KMoP@CdS@Bi 2 S 3 with a narrow band gap of ∼ 1.2 eV also has excellent photothermal performance, which may further promote photocatalytic efficiency. The hollow core–shell KMoP@CdS@Bi 2 S 3 tandem heterojunction shows excellent H 2 production performance, CrVI reduction ability and photocatalytic degradation performance of highly toxic tetracycline (TC). Under visible light irradiation, the photocatalytic H 2 generation rate of the KMoP@CdS@Bi 2 S 3 tandem heterojunction reaches 831 μmol h−1, which is 103 times higher than that of pristine KMoP. The photocatalytic reduction efficiency of CrVI and degradation efficiency of TC are as high as 95.5 and 97.51%, ∼4 times higher than that of KMoP. The boosted photocatalytic performance can be ascribed to the formation of core–shell Z-scheme tandem heterojunctions favoring spatial charge separation and the narrow band gap, which extends the photoresponse to visible light/NIR regions. When TC and CrVI exist at the same time, the reduction efficiency of CrVI can be as high as 99.64% because the intermediate of TC degradation can promote the reduction of CrVI. In addition, the photocatalytic performance of the KMoP@CdS@Bi 2 S 3 heterojunction remains nearly constant after 4 recycles, which indicates high stability. The design strategy may provide new insights for preparing other high-performance core–shell tandem heterojunction photocatalysts for solar energy conversion. [ABSTRACT FROM AUTHOR]