0D/2D Z-scheme heterojunctions of Zn-AgIn5S8 QDs/α-Fe2O3 nanosheets for efficient visible-light-driven hydrogen production

Abstract

• Z-scheme mechanism was demonstrated by ESR characterizations. • The high photocatalytic activity is owing to the successful fabrication of Z-scheme heterojunction and efficient charge separation. • Direct Z-scheme system enhances the separation of photogenerated charge carriers. • 0D/2D Zn-AgIn 5 S 8 QDs/α-Fe 2 O 3 heterostructures exhibit the efficient photocatalytic H 2 generation. Multinary sulfide quantum dots (QDs) have exhibited outstanding advantages including large surface areas, unique optical properties and adjustable band gap, which are beneficial for visible-active photocatalysis. However, the use of QDs also brings about serious issues of charge recombination and particle agglomeration. Here, a rational design of direct 0D/2D Z-scheme heterojunction of Zn-AgIn 5 S 8 /α-Fe 2 O 3 is described. Appropriate band alignment is conducive to the construction of Z-scheme heterostructures, thus enhancing the redox ability of the semiconductors and inhibiting the charge recombination. Simultaneously, the zeta potential differences between the two semiconductors can make them achieve a close interface contact by electrostatic adsorption and then the 0D Zn-AgIn 5 S 8 (ZAIS) QDs can be dispersed uniformly on 2D α-Fe 2 O 3 nanosheets, which can reduce the agglomeration of QDs. At the same time, the advantages of large specific surface area and short electron transmission path of QDs can also be exerted. Meanwhile, α-Fe 2 O 3 nanosheets with high conductivity can rapidly lead out the photogenerated charge carriers and thus suppress the recombination of the electrons and holes in QDs. The optimum nanocomposites with 3 wt% α-Fe 2 O 3 nanosheets display a photocatalytic H 2 evolution rate of 1.7 mmol g −1 h −1 , 3.5 times to that of pure QDs, with an apparent quantum efficiency of 7.48% at 450 nm. Electrochemiluminescence spectra, time-resolved photoluminescence spectra and electron spin resonance spectra further testify the enhanced charge transfer and the direct Z-scheme mechanism of the 0D/2D heterojunction. This work emphasizes the suitable band matching to adjust the exciton properties and charge transfer characteristics of QDs by constructing Z-scheme heterojunction for efficient utilization of visible light.