Synthesis of cuprous oxide with morphological evolution from truncated octahedral to spherical structures and their size and shape-dependent photocatalytic activities.

In this study, a facile room-temperature solution-chemical route has been developed to synthesize Cu2O crystals with various sizes and morphologies. Adjustment of feeding speed of the aqueous mixture of polyvinyl pyrrolidone (PVP) and ascorbic acid (AA) enables the Cu2O crystal morphology and size evolution. It is also interesting to find that, simple alteration of the feeding speed of AA aqueous solution enables the size of Cu2O crystals evolved, while the morphology of Cu2O crystals keep unchanged. These Cu2O crystals samples were used as photocatalysts for the decomposition of methyl orange (MO) under visible light irradiation. The results show that Cu2O spiny spheres with hierarchical structure exhibited superior photocatalytic activity compared with truncated octahedrons and spheres. In addition, the photocatalytic activity of truncated octahedral Cu2O can be greatly improved by decreasing the size of Cu2O particles. The work demonstrated a novel strategy for the shape and size-controlled synthesis of Cu2O crystals with superior photocatalytic activities.

Two-Dimensional CaIn2S4/g-C3N4 Heterojunction Nanocomposite with Enhanced Visible-Light Photocatalytic Activities: Interfacial Engineering and Mechanism Insight.

Design and exploitation of efficient visible light photocatalytic systems for water splitting and degradation of organic dyes are of huge interest in the fields of energy conversion and environmental protection. Herein, two-dimensional CaIn2S4/g-C3N4 heterojunction nanocomposites with intimate interfacial contact have been synthesized by a facile two-step method. Compared with pristine g-C3N4 and CaIn2S4, the CaIn2S4/g-C3N4 heterojunction nanocomposites exhibited significantly enhanced H2 evolution and photocatalytic degradation of methyl orange (MO) activities under visible light irradiation. The optimal CaIn2S4/g-C3N4 nanocomposite shows a H2 evolution rate of 102 µmol g(-1) h(-1), which is more than 3 times that of pristine CaIn2S4. The mechanisms for improving the photocatalytic performance of the CaIn2S4/g-C3N4 nanocomposites were proposed by using the photoluminescence measurement and electrochemical analyses. It was demonstrated that the enhanced photocatalytic performance of CaIn2S4/g-C3N4 heterojunction nanocomposites mainly stems from the enhanced charge separation efficiency. In addition, a plausible mechanism for the degradation of MO dye over CaIn2S4/g-C3N4 nanocomposites is also elucidated using active species scavenger's studies.

Novel AgI-decorated ß-Bi2O3 nanosheet heterostructured Z-scheme photocatalysts for efficient degradation of organic pollutants with enhanced performance.

The low photocatalytic activity of single semiconductor photocatalysts mainly originates from their fast recombination of photogenerated electron-hole pairs. Constructing nanosheet-based composite photocatalysts is an effective way to enhance the charge separation efficiency of photogenerated electron-hole pairs. In this work, AgI-decorated ß-Bi2O3 nanosheet heterostructured photocatalysts were prepared by a facile method. The as-obtained AgI/ß-Bi2O3 heterostructures exhibited enhanced visible-light-driven photocatalytic activity towards the degradation of methyl orange (MO) and tetracycline hydrochloride (TC) in aqueous solution. The optimum photocatalytic activity of 20%-AgI/ß-Bi2O3 for the degradation of MO was about 4.1 and 6.2 times higher than that of AgI and ß-Bi2O3. The photocatalytic activity enhancement of AgI/ß-Bi2O3 heterostructures could be ascribed to the formation of a Z-scheme system, which results in the efficient space separation of photo-induced charge carriers.

Hydrothermal synthesis of In2S3/g-C3N4 heterojunctions with enhanced photocatalytic activity.

Graphitic carbon nitride (g-C3N4) was hybridized by In2S3 to form a novel In2S3/g-C3N4 heterojunction photocatalyst via a hydrothermal method. TEM and HRTEM results reveal that In2S3 nanoparticles and g-C3N4 closely contact with each other to form an intimate interface. The as-obtained In2S3/g-C3N4 heterojunctions exhibit higher photocatalytic activity than those of pure g-C3N4 and In2S3 for the photodegradation of rhodamine B (RhB) under visible light irradiation. The enhanced photocatalytic performance of In2S3/g-C3N4 heterojunctions could be attributed to its wide absorption in the visible region and efficient electron-hole separation. On the basis of radical scavenger experiments, superoxide radicals and holes are suggested to play a critical role in RhB degradation over In2S3/g-C3N4 heterojunctions.

Ion-exchange synthesis of Ag/Ag2S/Ag3CuS2 ternary hollow microspheres with efficient visible-light photocatalytic activity.

Ternary Ag/Ag2S/Ag3CuS2 hollow microspheres were synthesized via an in situ ion-exchange method using Cu7S4 hollow submicrospheres as the template. The as-obtained Ag/Ag2S/Ag3CuS2 composite exhibited a well-defined uniform hollow microsphere morphology with an average diameter of about 1.3 µm. The photocatalytic property of the as-prepared Ag/Ag2S/Ag3CuS2 hollow microsphere composite was investigated by the decomposition of methyl orange (MO) under visible light irradiation (λ > 420 nm). It was shown that the photocatalytic activity of the Ag/Ag2S/Ag3CuS2 hollow microsphere was higher than those of Ag/Ag2S, Cu2O, Cu7S4 and P25 for the photodegradation of MO under visible light irradiation. Radical scavenger experiments demonstrated that superoxide radicals and holes were the main reactive species for MO degradation.

Controlled synthesis of Bi2S3/ZnS microspheres by an in situ ion-exchange process with enhanced visible light photocatalytic activity.

A novel Bi2S3/ZnS heterostructure has been synthesized through an in situ cation-exchange method between ZnS and bismuth(III) chloride. The obtained samples were characterized by multiform techniques, such as X-ray diffraction, field emission scanning electron microscopy, high-resolution transmission microscopy, UV-visible diffuse-reflectance spectroscopy, and photoluminescence spectra. The photocatalytic activities of the obtained photocatalysts were measured by the degradation of rhodamine B (RhB) and refractory oxytetracycline (OTC) under visible-light irradiation (λ ≥ 400 nm). The as-prepared Bi2S3/ZnS photocatalysts exhibit wide absorption in the visible-light region and display superior visible-light-driven photocatalytic activities in degradation of RhB and OTC compared with pristine ZnS microspheres and Bi2S3 nanorods. The dramatic enhancement in the visible light photocatalytic performance of the Bi2S3/ZnS composites could be attributed to the effective electron-hole separations at the interfaces of the two semiconductors, which facilitate the transfer of the photoinduced carriers. The present study provides helpful insight into the design of novel and highly efficient sulfate heterostructure photocatalysts.