Simple fabrication of Z-scheme MgIn₂S₄/Bi₂WO₆ hierarchical heterostructures for enhancing photocatalytic reduction of Cr(vi)

Abstract

The direct Z-scheme MgIn2S4/Bi2WO6 hierarchical heterostructures were elegantly fabricated via immobilising MgIn2S4 nanoflakes onto the surface of Bi2WO6 hierarchical nanosheet-like structures towards photocatalytic reduction of Cr(VI). The analyses of the...

Simultaneously enhanced photocatalytic cleanup of Cr(vi) and tetracycline via a ZnIn2S4 nanoflake-decorated 24-faceted concave MIL-88B(Fe) polyhedron S-scheme system

“…These indicate its excellent stability towards treating Cr( vi ) and TC-polluted effluents. Additionally, the Cr 2p spectrum of the M88B@ZIS-10 sample after the 5 cycle experiment shows two peaks at 577.6 and 587.0 eV, being attributed to Cr 2p 3/2 and Cr 2p 1/2 of Cr 3+ , 41 respectively, which confirms the photoreduction of Cr( vi ) into Cr( iii ) in the hybrid solution of Cr( vi ) and TC (Fig. S6†).…”

Hierarchical S-Scheme Heterostructure of CdIn2S4@UiO-66-NH2 toward Synchronously Boosting Photocatalytic Removal of Cr(VI) and Tetracycline

“…In this context, the CIS and U66N layers are positively and negatively charged near their interface, respectively, resulting in the results that the internal electrical field (IEF) directing from CIS to U66N can be formed and that the band edge of CIS bends upward, while that of U66N bends downward (Figure b). Therefore, the staggered band structures, IEF, band bending at the interface, and Coulombic attraction between holes and electrons, collectively, urge the recombination of photogenerated electrons in the LUMO of U66N and holes in the VB of CIS at their interface region . Obviously, the migration of photogenerated charge carriers follows a slide-like route, indicating the successful construction of S-scheme heterostructures consisting of CIS and U66N …”

“…Therefore, the staggered band structures, IEF, band bending at the interface, and Coulombic attraction between holes and electrons, collectively, urge the recombination of photogenerated electrons in the LUMO of U66N and holes in the VB of CIS at their interface region. 28 Obviously, the migration of photogenerated charge carriers follows a slide-like route, indicating the successful construction of S-scheme heterostructures consisting of CIS and U66N. 28 Inversely, a traditional type II charge-transfer pathway requires more energy because of the band bending at the interface and IEF, which are unfavorable to sustaining charge migration in thermodynamics.…”

“…28 Obviously, the migration of photogenerated charge carriers follows a slide-like route, indicating the successful construction of S-scheme heterostructures consisting of CIS and U66N. 28 Inversely, a traditional type II charge-transfer pathway requires more energy because of the band bending at the interface and IEF, which are unfavorable to sustaining charge migration in thermodynamics. To further ascertain the proposed S-scheme mechanism above, the DMPO-ESR spintrapping tests, with DMPO as a radical trapping agent, were carried out to investigate the • O 2 − and • OH of CIS, U66N, and CIS@U66N-30 in methanol and aqueous solutions, respectively.…”

“…Morphology regulation and heterostructure construction are two typical means to conquer the above shortcomings. For morphology regulation, the construction of hierarchical structures (e.g., flower-like, dendritic, and branched structures and porous microsphere structures assembled with nanosheets) has garnered considerable attention thanks to their high surface area to accommodate more active sites, boosting the dynamics of surface reaction. , Moreover, CIS hierarchical structures as supports can be easily decorated by more co-catalysts or additional useful materials, leading to an intimate contact between the two components, in favor of the charge migration and their chemical stability. − On the other hand, the novel S-scheme heterostructure, composed of a reduction photocatalyst (RP) and an oxidation photocatalyst (OP) with staggered band structures, is verified to not only present more efficient separation and transfer of photoinduced charge carriers but also hold their stronger redox capability, thermodynamically benefiting photocatalytic reactions. , CIS can be as an RP due to its pretty negative CB potential. UiO-66-NH 2 (U66N), a metal–organic framework (MOF), has high thermal, chemical, and structural stability in aqueous environments and can absorb visible light because of NH 2 moieties attached to organic linkers. , It has been found that U66N displayed efficient photocatalytic activity toward the oxidation of volatile organic compounds (VOCs) and oxygen evolution reaction owing to its considerably positive potential of the valence band (VB) or the highest occupied molecular orbital (HOMO). , Moreover, U66N has been as one component to construct heterostructures, which effectively retard the recombination of photoinduced charge carriers so as to boost their separation efficiency, leading to good photocatalytic activities for the oxidation degradation of antibiotics like TC and ciprofloxacin. , More importantly, the energy band structure of U66N can well match with that of CIS .…”