Bi3TaO7 film: a promising photoelectrode for photoelectrochemical water splitting

Facile construction of Z-scheme AgCl/Bi3TaO7 photocatalysts for effective removal of tetracycline under visible-light irradiation

A string of AgCl/Bi₃TaO₇ two-component composite was synthesized by hydrothermal and deposition-precipitation process initially. The photocatalytic activities of mixed-phase AgCl/Bi₃TaO₇ were evaluated toward the decomposition of tetracycline (TC). Among these as-prepared materials, AgCl/Bi₃TaO₇ nanocomposites when the molar ratio of baked materials between AgCl and Bi₃TaO₇ was 1:5 presented the optimal photocatalytic quantum efficiency for TC dissociation (86.82%) with visible-light exposure, which was 1.69 and 2.38 folders higher than that of single Bi₃TaO₇ and AgCl, respectively. What is more, it illustrated that the photo-generated carriers were markedly isolated on account of the formation of heterojunction confirmed by EIS analysis. Meanwhile, radical trapping experiments implied that the photo-induced holes (h⁺), hydroxyl radical (·OH), and superoxide radical (·O₂^-) were the major active species. The escalated photocatalytic activity could be ascribed to the unique construction of Z-scheme AgCl/Bi₃TaO₇ heterojunction, which could expedite charge separation and transmission, cement light absorption capability and retain the strong redox ability of photo-generated electrons and holes. Our finding suggests that AgCl/Bi₃TaO₇ nanocomposites possess great potential for photocatalytic oxidation of residual TC in the wastewater effluents and the reported strategy can contribute to the development of novel high-performance photocatalyst.

Construction of Z-scheme Bi3TaO7/Zn0.5Cd0.5S composites with high efficiency for levofloxacin degradation under visible light irradiation

Direct Z-scheme Bi₃TaO₇/Zn_0.5Cd_0.5S composite photocatalysts were successfully prepared via an in situ growth hydrothermal method. The photocatalytic activities of composites were investigated by the degradation of levofloxacin under visible light. All composites exhibited enhanced photocatalytic activities compared with Bi₃TaO₇ and Zn_0.5Cd_0.5S. The structure composition and photoelectric performance of the photocatalysts were investigated by related experiments. The dominant active species (h⁺ and ˙O₂^-) during levofloxacin degradation were identified through capture experiments. Meanwhile, the stability and cyclicity of the optimal photocatalyst (BZCS-2) were studied by cycling experiments. Finally, we proposed a possible direct Z-scheme charge-migration mechanism for levofloxacin degradation. This work would provide a feasible idea and theoretical support for the in-depth research of direct Z-scheme photocatalysts and Zn_xCd_1-xS-based semiconductor materials in the future.

Visible-light responsive BiNbO4 nanosheet photoanodes for stable and efficient solar-driven water oxidation

Herein, we report bismuth niobate (BiNbO4), which is regarded as an emerging photoanode material for sustainable photoelectrochemical (PEC) solar energy conversion. BiNbO4 possesses a direct bandgap (Eg) of ∼2.6 eV, and shows an appropriate band alignment for the water oxidation/reduction reaction. In this study, a simple sol-gel route followed by a spin coating method was applied to develop BiNbO4 nanosheets under the optimum annealing conditions. It is known that the annealing temperatures of 500 and 550 °C influence the crystallinity and PEC properties of BiNbO4 films. In particular, the 550 °C annealed film exhibited sharply improved crystalline properties, and rapidly enhanced PEC performance, which were accompanied by a photocurrent density of 0.45 mA cm-2 at 1.23 V vs. the reversible hydrogen electrode (RHE) (briefly abbreviated as 1.23 VRHE) in a strong alkaline solution of 1 M NaOH, compared with 0.26 mA cm-2 at 1.23 VRHE of the 500 °C annealed film. This may be attributed to the main increase of the crystallinity, as well as the improvement of the electronic properties. In addition, the BiNbO4 (550 °C) film showed an incident photon-to-current efficiency of 20% at 425 nm, and produced a stable photoresponse under light illumination in a strong alkaline solution over 5 h, compared with a BiVO4 electrode.