Construction and photocatalytic properties of WS2/MoS2/BiOCl heterojunction

Construction of Hexagonal Prism-like Defective BiOCL Hierarchitecture for Photocatalytic Degradation of Tetracycline Hydrochloride

Oxygen vacancy manipulation and hierarchical morphology construction in oxygen-containing semiconductors have been demonstrated to be effective strategies for developing high efficiency photocatalysts. In most studies of bismuth-based photocatalysts, hierarchical morphology and crystal defects are achieved separately, so the catalysts are not able to benefit from both features. Herein, using boiling ethylene glycol as the treatment solution, we developed an etching-recrystallization method for the fabrication of 3D hierarchical defective BiOCl at ambient pressure. The target hierarchical 3D-BiOCl is composed of self-assembled BiOCl nanosheets, which exhibit a hexagonal prism-like morphology on a micron scale, while simultaneously containing numerous oxygen vacancies within the crystal structure. Consequently, the target catalyst was endowed with a higher specific surface area, greater light harvesting capability, as well as more efficient separation and transfer of photo-excited charges than pristine BiOCl. As a result, 3D-BiOCl presented an impressive photocatalytic activity for the degradation of tetracycline hydrochloride in both visible light and natural white light emitting diode (LED) irradiation. Moreover, an extraordinary recycling property was demonstrated for the target photocatalyst thanks to its hierarchical structure. This study outlines a simple and energy-efficient approach for producing high-performance hierarchically defective BiOCl, which may also open up new possibilities for the morphological and crystal structural defect regulation of other Bi-based photocatalysts.

Bismuth Oxyhalide-Based Materials (BiOX: X = Cl, Br, I) and Their Application in Photoelectrocatalytic Degradation of Organic Pollutants in Water: A Review

An important target of photoelectrocatalysis (PEC) technology is the development of semiconductor-based photoelectrodes capable of absorbing solar energy (visible light) and promoting oxidation and reduction reactions. Bismuth oxyhalide-based materials BiOX (X = Cl, Br, and I) meet these requirements. Their crystalline structure, optical and electronic properties, and photocatalytic activity under visible light mean that these materials can be coupled to other semiconductors to develop novel heterostructures for photoelectrochemical degradation systems. This review provides a general overview of controlled BiOX powder synthesis methods, and discusses the optical and structural features of BiOX-based materials, focusing on heterojunction photoanodes. In addition, it summarizes the most recent applications in this field, particularly photoelectrochemical performance, experimental conditions and degradation efficiencies reported for some organic pollutants (e.g., pharmaceuticals, organic dyes, phenolic derivatives, etc.). Finally, as this review seeks to serve as a guide for the characteristics and various properties of these interesting semiconductors, it discusses future PEC-related challenges to explore.

MoSe2-WS2 Nanostructure for an Efficient Hydrogen Generation under White Light LED Irradiation

In this work, MoSe2-WS2 nanocomposites consisting of WS2 nanoparticles covered with few MoSe2 nanosheets were successfully developed via an easy hydrothermal synthesis method. Their nanostructure and photocatalytic hydrogen evolution (PHE) performance are investigated by a series of characterization techniques. The PHE rate of MoSe2-WS2 is evaluated under the white light LED irradiation. Under LED illumination, the highest PHE of MoSe2-WS2 nanocomposite is 1600.2 µmol g-1 h-1. When compared with pristine WS2, the MoSe2-WS2 nanostructures demonstrated improved PHE rate, which is 10-fold higher than that of the pristine one. This work suggests that MoSe2-WS2 could be a promising photocatalyst candidate and might stimulate the further studies of other layered materials for energy conversion and storage.

Enhanced photocatalytic hydrogen production of MoS2 sheet/carbon nanofiber using rapid electron transport of Mo6+ and carbon nanofiber

Normal MoS₂ exhibits a low photocatalytic performance for H₂ production owing to the deficiency of the active sites and the poor electrical conductance. In this work, MoS₂ anchored on the surface of the carbon nanofibers was designed to enhance the activity of the exposed edge and the electrical conductivity at the same time. The oxidation of the surface Mo atoms increases the activity of the exposed edge of the MoS₂. The introduction of carbon nanofibers facilitates the effective transportation of the electron-hole pairs by enhancing the electrical conductivity. As a result, the introduction of carbon nanofibers and Mo⁶⁺ can facilitate the electron-hole pair separation to enhance the photocatalytic hydrogen evolution reaction (HER) performance (to eight fold more than normal MoS₂).

Recent developments on bismuth oxyhalides (BiOX; X = Cl, Br, I) based ternary nanocomposite photocatalysts for environmental applications

Photocatalytic treatment of organic pollutants present in wastewater using semiconductor nanomaterials under light irradiation is one of the efficient advanced oxidation processes. Stable metal oxide (e.g. TiO₂) based semiconductor photocatalytic systems have been mainly investigated for this purpose. Nevertheless, their large band gap (~3.2 eV) makes them inefficient in utilization of visible light portion of solar light leading to a lower degradation efficiency. Investigations have focused on the development of visible light responsive bismuth oxyhalides (BiOX; X = Cl, Br, I), one of the potential nanomaterials with unique layered structure, for efficient absorption of solar light for the degradation of pollutants. However, the rapid recombination rate of photogenerated charge carriers limits their practical applicability. To overcome such drawbacks, the development of BiOX based ternary nanocomposites received significant attention because of their unique structural and electronic properties, improved visible light response and increased separation and transfer rate of photogenerated charge carriers. This review aims to provide a comprehensive overview of the recent developments on bismuth oxyhalides-based ternary nanocomposites for enhanced environmental pollutants decomposition under visible light irradiation. The principles of photocatalysis, synthetic methodologies of bismuth oxyhalides and their characteristics such as heterojunctions formation, improved visible light response and separation rate of charge carriers and the mechanisms for enhanced visible light photocatalytic activity are discussed. In addition, the future prospects on the improvement in the photocatalytic activity of bismuth oxyhalides-based ternary nanocomposites are also discussed. This review could be beneficial for designing new ternary nanocomposites with superior visible light photocatalytic efficiency.