Efficient Photocatalytic Activation of Peroxymonosulfate by Cobalt-Doped Oxygen-Vacancies-Rich BiVO4 for Rapid Tetracycline Degradation

In this work, cobalt-doped oxygen-vacancies-rich BiVO4 (Co/BiVO4-Vo) was successfully synthesized for the degradation of tetracycline (TC) by activated peroxymonosulfate (PMS) under visible light. The morphologies, microstructures, and optical properties of the photocatalysts were analyzed in detail. Co/BiVO4-Vo exhibited significantly enhanced degradation, removing 92.3% of TC within 10 min, which was greater than those of pure BiVO4 (62.2%) and oxygen-vacancies-rich BiVO4 (BiVO4-Vo) (72.0%), respectively. The photogenerated charge separation and transport properties were explored through surface photovoltage (SPV), photoluminescence spectrum (PL), and UV-vis diffuse reflectance spectroscopy (UV-vis DRS) measurements. Additionally, an in-depth investigation was conducted on the photocatalytically assisted advanced oxidation processes based on SO4•- (SR-AOPs) for the degradation of organic pollutants. The experimental results showed that the introduction of oxygen vacancies and Co doping achieved an effective separation of photogenerated carriers, which could accelerate the cycling between Co3+ and Co2+ and further activate PMS. The results of free radical capture experiments and electron spin resonance (ESR) experiments showed that reactive oxygen species (ROSs) such as 1O2, •O2-, and SO4•- played a dominant role in the removal of pollutants. This work provides a novel insight into the further development of efficient and rapid PMS photoactivators for environmental remediation of water bodies.

Insight into Potassium Vanadates as Visible-Light-Driven Photocatalysts: Synthesis of V(IV)-Rich Nano/Microstructures for the Photodegradation of Methylene Blue

Photocatalysis is regarded as a promising tool for wastewater remediation. In recent years, many studies have focused on investigating novel photocatalysts driven by visible light. In this study, K₂V₆O₁₆·nH₂O nanobelts and KV₃O₈ microplatelets were synthesized and investigated as photocatalysts. Samples were obtained via the facile method based on liquid-phase exfoliation with ion exchange. By changing the synthesis temperature (20–80 °C), different compositions, morphologies, and V⁴⁺/V⁵⁺ ratios were obtained and investigated as photocatalysts for organic dye degradation. Potassium vanadates’ structural, morphological, and optical properties were characterized using X-ray diffraction(XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Physical Property Measurement System (PPMS), thermogravimetric analysis (TGA) with mass spectrometry (MS), N₂ adsorption, scanning electron microscopy (SEM), photoluminescence (PL), and UV–vis diffuse reflectance spectroscopy (DRS). Synthesized K₂V₆O₁₆·nH₂O and KV₃O₈ showed an efficient absorption in the visible wavelength region with a narrow band gap energy of 1.80 and 1.91 eV, respectively. Their photocatalytic activity was evaluated by the degradation of methylene blue (MB) under simulated solar light illumination. The KV₃O₈ microplatelets exhibited the greatest photocatalytic activity, resulting in more than 90% degradation of the dye within the first 30 min. It is suggested that the observed excellent photocatalytic performance is attributed to the high content of V⁴⁺ species. Furthermore, the influence of active species was investigated, and the mechanism responsible for the photodegradation of the MB dye was discussed for the first time for potassium vanadates.

Potassium vanadates were synthesized via the facile method based on liquid-phase exfoliation with ion exchange. Different synthesis temperatures (20−80 °C) resulted in various phase compositions, morphologies, and V⁴⁺/V⁵⁺ ratios. The obtained samples were demonstrated as efficient visible-light driven photocatalysts, resulting in more than 90% degradation of methylene blue within the first 30−60 min. The enhanced photoactivity is attributed to the high content of V⁴⁺ species, which are beneficial for the separation of photogenerated electrons and holes and their lifetime.

Step-Scheme Heterojunction between CdS Nanowires and Facet-Selective Assembly of MnOx-BiVO4 for an Efficient Visible-Light-Driven Overall Water Splitting

The spatial separation and transport of photogenerated charge carriers is crucial in building an efficient photocatalyst for solar energy conversion into chemical energy. A step-scheme CdS/MnO_x-BiVO₄ photocatalyst was synthesized by spatial deposition of MnO_x and one-dimensional (1D) CdS nanowires on a three-dimensional (3D) decahedron BiVO₄ surface. The photocatalytic activity of CdS/MnO_x-BiVO₄ for the overall water-splitting reaction was investigated without sacrificial reagent under visible light irradiation. The synthesized photocatalysts were thoroughly analyzed using high-end characterization techniques. The 5CdS/MnO_x-BiVO₄ exhibited the highest H₂ and O₂ production rates of 1.01 and 0.51 mmol g^-1 h^-1, respectively, with an apparent quantum yield of 11.3% in the absence of any sacrificial reagent. The excellent photoactivity is due to the presence of oxygen vacancies along with effective charge separation/transfer properties and strong interaction of cocatalysts (MnO_x and Pt) with the photocatalysts (BiVO₄ and CdS) in the 5CdS/MnO_x-BiVO₄ heterojunction. The significance of the presence of MnO_x and Pt cocatalysts on the selective facets of BiVO₄ for efficient overall water splitting reaction is highlighted in this work.

Enhanced photocatalytic nitrogen fixation in BiVO4: constructing oxygen vacancies and promoting electron transfer through Ohmic contact

The Ag nanoparticles deposited on the surface of BiVO4 containing oxygen vacancies are employed in photocatalytic N2 fixation. The NH3 generation rate is enhanced by constructing abundant oxygen vacancies and promoting electron transfer by Ohmic contact.

Easy Synthesis of BiVO4 for Photocatalytic Overall Water Splitting

Developing a photocatalyst system to generate hydrogen from water is a topic of great interest for fundamental and practical importance. In this study, we develop a new Z-scheme photocatalytic system for overall water splitting that consists of Rh/K₄Nb₆O₈ for H₂ evolution, Pt/BiVO₄ for O₂ evolution, and I^-/IO₃ ^- for an electron mediator under UV light irradiation. The oxygen evolution photocatalyst BiVO₄ was prepared by the microwave-assisted hydrothermal method. The method is fast and simple, as compared to conventional hydrothermal synthesis. The catalysts were characterized by powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and UV-visible spectroscopy. The photocatalytic water splitting is investigated in (i) aqueous AgNO₃ as sacrificial electron scavengers and (ii) a Z-scheme photocatalytic water splitting system. The BiVO₄ photocatalysts prepared by the microwave-assisted hydrothermal method not only showed a very high oxygen evolution rate (2622 μmol g^-1 h^-1) of water splitting reaction in an aqueous AgNO₃ solution but also achieved a high H₂ evolution rate (340 μmol g^-1 h^-1) and O₂ evolution rate (172 μmol g^-1 h^-1) in a Z-scheme overall water splitting system.

Bismuth-rich bismuth oxyiodide microspheres with abundant oxygen vacancies as an efficient photocatalyst for nitrogen fixation

A combined bismuth-rich and defect introduction strategy was used to prepare the H-Bi₅O₇I with abundant oxygen vacancies, which can effectively yield ammonia under visible light without any organic scavengers or noble-metal cocatalysts.

Efficient solar-driven conversion of nitrogen to ammonia in pure waterviahydrogenated bismuth oxybromide

Solar-driven reduction of dinitrogen to ammonia under mild conditions has attracted widespread interest in recent years. In this study, we first report low-temperature hydrogenated BiOBr for the direct synthesis of ammonia from dinitrogen with high efficiency under solar-light irradiation. In a proof of concept, the hydrogenation treatment can lead to surface disorder due to the strong reducing capacity of hydrogen. Oxygen atoms can be activated, and they can escape from the surface structure to form oxygen vacancies. Then, defect engineering can broaden the photoelectricity absorption window and effectively trigger interfacial electron transfer from the semiconductor to the combined nitrogen. This method exhibits a satisfactory result for photocatalytic nitrogen fixation, yielding about 2.6 times more NH₃ than that obtained from the original sample. The corresponding apparent quantum efficiency can reach a significant value of 2.1% under 380 nm monochromatic light irradiation. These results may pave a new way for the synthesis of highly active photocatalysts for efficient nitrogen fixation under solar light irradiation.

Samples of H-BiOBr use water as reactant which demonstrates efficient nitrogen fixation under sunlight.

A novel supramolecular preorganization route for improving g-C3N4/g-C3N4 metal-free homojunction photocatalysis

Enhancing the novel g-C₃N₄/g-C₃N₄ metal-free homojunction photocatalysis: efficient solar energy harvesting and charge transfer.

The controllable fabrication of a novel hierarchical nanosheet-assembled Bi2MoO6 hollow micronbox with ultra-high surface area for excellent solar to chemical energy conversion

In this study, we demonstrated that a novel controllable nano-sheet assembled Bi₂MoO₆ micronbox had higher activity for nitrogen fixation and dye degradation.

An efficient strategy for full mineralization of an azo dye in wastewater: a synergistic combination of solar thermo- and electrochemistry plus photocatalysis

An efficient strategy for full mineralization of azo dye in wastewater.