Synthesis of Fluoride-Substituted Layered Perovskites ZnMoO4 with an Enhanced Photocatalytic Activity.

Oxyfluorides possess considerable attention for their multiple excellent properties, but the conventional high-temperature solid-state syntheses have seen bottlenecks in the synthesis of new compounds. Herein, we report a novel layered oxyfluoride ZnMoO4:F, which is prepared by a facile hydrothermal method using ZnF2 as the fluoride source. The fluoride anions are successfully introduced into the oxygen sublattice, which is confirmed by a combined analysis using XRD, STEM, and TGA techniques. The as-synthesized ZnMoO4:F has an absorption edge at around 550 nm, indicating a red shift of Eg to the visible region compared to the oxide counterpart. The layered oxyfluoride exhibits an enhanced photocatalytic active for hydrogen evolution under simulated sunlight (λ > 350 nm), and the activity of ZnMoO4:F (651.9 µmol g-1) was 2 times higher than that of ZnMoO4 (309.7 µmol g-1). Further electrochemical analysis has shown that the conduction band position plays a critical role in the high performances of ZnMoO4:F. This work sheds new light on the future design and synthesis of novel fluoride-doped materials for photocatalysis applications.

Synthesis of ZnIn2S4@Co3S4 particles derived from ZIF-67 for photocatalytic hydrogen production.

In this work, ZIF-67 derivative Co3S4 with diamond dodecahedron structure was firstly synthesized via a series of reactions, and ZnIn2S4@Co3S4 heterostructures with adjustable band gaps were successfully obtained through a simple hydrothermal method. Consequently, ZnIn2S4@Co3S4 heterostructures have significantly enhanced visible light absorption and improved photocatalytic efficiency, among which the ZC-5 composite exhibits the highest photocatalytic hydrogen production rate up to 4261 µmol g-1 h-1 under simulated sunlight, to be approximately 4.8 times higher than that of pure ZnIn2S4. The enhanced photocatalytic activity can be attributed to faster electron transfer and more efficient electron-hole pairs separation derived from the heterostructures which form at the interface between Co3S4 and ZnIn2S4. Thus, this study provides a good strategy for photocatalytic hydrogen production without precious metals using heterostructures.