Abstract
Metal sulfide semiconductors, such as molybdenum disulfide (MoS2) and bismuth trisulphide (Bi2S3), are of considerable interest for their excellent applications in photocatalysis and in many other fields. However, the controllable synthesis of MoS2/Bi2S3 hybrid nanostructures remains a challenge. In this study, we report a unique sacrificial templating strategy for preparing layer-controlled MoS2 on three-dimensional (3D) Bi2S3 micro-flowers. For this approach, Bi2S3 was utilized as a sacrificial template to regulate the ion exchange, and the dosage of molybdenum was adjusted to tune the dynamic formation, thus converting the MoS2 nanosheets on the Bi2S3 micro-flowers from monolayer to multilayer. Such a 3D flower-like hybrid nanostructure enables MoS2/Bi2S3 to exhibit adsorption-promoted photocatalysis under visible light irradiation, especially for the excellent photodegradation of low-concentration organic pollutants, for example, azo dye and atrazine. The observed superiority of the 3D MoS2/Bi2S3 was mainly attributed to the increased mass transfer, robust light-harvesting capacity, improved charge separation, lower oxygen-activation barrier and enhanced active oxygen yield. Our findings are of interest for the development of novel S-based photocatalysts and provide a new opportunity to efficiently remove low-concentration refractory pollutants. Researchers have combined inorganic ‘microflowers’ and metallic nanosheets to help remove persistent organic pollutants with sunlight. Bismuth trisulphide (Bi2S3) is a promising environmental photocatalyst because of its low toxicity and direct bandgap, but suffers from lower-than-expected chemical activity due to charge recombination. To better separate photogenerated charges, Han-Qing Yu and co-workers from the University of Science and Technology of China developed a one-pot, hydrothermal synthesis that transforms bismuth precursors into three-dimensional (3D) microstructures with petal-like shapes. The Bi2S3 microflowers then act as a template, growing multilayers of MoS2 onto the hybrid framework. The large, charge-stabilizing surface area of 3D MoS2/Bi2S3 had promising photocatalytic activity. For example, concentrations of atrazine — a common weed-killer difficult to remove from water runoff streams — were 89% lower after 4 hours of exposure to light and 3D MoS2/Bi2S3. A sacrificial strategy is developed for preparing layer-controlled MoS2 on three-dimensional Bi2S3 micro-flowers using a facile method. The nanostructured hybrid enables adsorption-promoted photocatalysis under visible light irradiation for excellent degradation of low-concentration organic pollutants, because of the increased mass transfer, robust light-harvesting capacity, improved charge separation, reduced oxygen-activation barrier and enhanced active oxygen yield.
Highlights
In recent years, metal sulfide semiconductors have been developed for environmental photocatalysis because of their narrow bandgaps, high sunlight absorption and satisfactory catalytic activity.[1,2,3,4] Among them, Bi2S3 is a promising visible light-driven photocatalyst owing to its low toxicity and narrow direct band gap of ~ 1.3 eV.[5]
Morphology and structure of 3D MoS2/Bi2S3 The prepared Bi2S3 with the micro-flower morphology was self-assembled from micro-rods with a length of 2–3 μm and a width of 200–400 nm (Supplementary Figure S1a)
A large number of MoS2 nanosheets were directly grown on each micro-rod of the Bi2S3 micro-flowers, forming the 3D flower-like heterostructure (Figure 1d)
Summary
Metal sulfide semiconductors have been developed for environmental photocatalysis because of their narrow bandgaps, high sunlight absorption and satisfactory catalytic activity.[1,2,3,4] Among them, Bi2S3 is a promising visible light-driven photocatalyst owing to its low toxicity and narrow direct band gap of ~ 1.3 eV.[5]. The semiconductor that is incorporated as a cocatalyst to construct such a self-established heterojunction should possess good electric conductivity, a suitable energy structure and excellent electrochemical activity.[7,8,9,10,11]
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