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

Abstract 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-AgIn5S8/α-Fe2O3 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-AgIn5S8 (ZAIS) QDs can be dispersed uniformly on 2D α-Fe2O3 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-Fe2O3 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-Fe2O3 nanosheets display a photocatalytic H2 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.