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.

Effect of layers on the photocatalytic hydrogen evolution in Dion-Jacobson layered-tantalum perovskites

Tantalum-based layered perovskites have always been an interesting topic in photocatalysis, but limited information has been reported in terms of their layer factor. In this work, we have synthesized Dion-Jacobson layered perovskites (A'[A_n-1Ta_nO_3n+1]) of LaTaO₄, KLaTa₂O₇, and KCa₂Ta₃O₁₀ with n = 1, 2, and 3, respectively. With the modification of 1 wt% Pt co-catalysts, the photocatalytic analysis showed that the performance order of these layered perovskites with different layers is KLaTa₂O₇ (n = 2) > KCa₂Ta₃O₁₀ (n = 3) ≫ LaTaO₄ (n = 1) with both methanol and NaI as the sacrificial agents. This suggested the importance of interlayer K⁺ for high photocatalytic performance. We further analyzed the layered perovskites in detail by BET, photoelectrochemical analysis, Mott-Schottky, and VB-XPS test. The combined results indicated that the positions of the conduction band are the dominant factors for the photocatalytic performance of tantalum-based Dion-Jacobson layered perovskites with n = 2 and 3. This work sheds new light on the field of layered perovskites as efficient photocatalysts.