Induction of a piezo-potential improves photocatalytic hydrogen production over ZnO/ZnS/MoS2 Heterostructures

In this study, we applied a piezo-potential to ZnO/ZnS/MoS2 heterostructures through ultrasonication to improve the separation of photoexcited electrons and holes and, thereby, increase their ability to mediate the production of H2. We prepared the ZnO/ZnS/MoS2 heterostructures through hydrothermal synthesis from MoS2 flakes and ZnO microrods, with the ZnS layer formed spontaneously between the ZnO and MoS2 structures. The production of H2 over these heterostructures irradiated with light varied with respect to the mixing ratio of ZnO and MoS2, with the MZ-0.5 heterostructure providing the best performance (4.45 mmol g-1 h-1). When introducing a piezopotential through ultrasonication during the photocatalytic reaction, the rate of H2 production increased dramatically to 10.42 mmol g-1 h-1-approximately 230% higher than that under light irradiation alone. The piezo-potential caused band tilting that facilitated charge transfer; accordingly, recombination was suppressed and the rate of H2 production increased. This combination of a novel multi-heterostructured photocatalyst and piezoelectricity is a cost-effective and non-toxic approach toward the production of H2 as a renewable energy source.