Bismuth oxyhalide layered materials for energy and environmental applications

In the present work, an efficient composite photocatalyst composed of 2D BiOBr nanoplates and 2D La2Ti2O7 thin nanosheets was synthesized. The photocatalytic performance of the as-obtained samples was investigated by the degradation of dye Rhodamine B and phenol under both UV and visible light irradiation. The results demonstrated that the La2Ti2O7 modified with proper amount of BiOBr nanosheets exhibited high efficiency in the photocatalytic process, and the holes took part in the photo-decomposition reaction as the main radicals. The morphology, crystallization, photo-response and electrochemical properties of the obtained catalysts were characterized to understand the mechanism of high photocatalytic activity. The results illustrated that the high photocatalytic performance could be ascribed to the following reasons. First of all, the decoration of BiOBr enlarged the photoresponce of La2Ti2O7 to visible light region, thus the composite can be activated to generate more electron and hole pairs. Secondly, the formed BiOBr/La2Ti2O7 p-n heterojunction promoted the transfer rate of electrons through the interface and improved the separation efficiency of electron-hole pairs. It is expected that this novel 2D-2D p-n heterostructured photocatalyst would be a promising candidate for environmental remediation.

Synthesis of novel 2D-2D p-n heterojunction BiOBr/La2Ti2O7 composite photocatalyst with enhanced photocatalytic performance under both UV and visible light irradiation

Solar-driven molecular oxygen activation is a promising and low energy-cost way for environmental remediation. To fabricate semimetal/semiconductor composite photocatalyst is an effective strategy to accelerate the transfer and separation of photogenerated carriers for boosting molecular oxygen activation. Herein, we report a 0D Bi nanodots/2D Bi3NbO7 nanosheets heterostructured composite with enhanced molecular oxygen activation under visible light irradiation, which was synthesized by a two-step wet chemical method. Transmission electron microscopy (TEM) analysis shows that the Bi nanodots with diameters of 2–5 nm were uniformly distributed on the surface of Bi3NbO7 nanosheets. More importantly, both experiments and density functional theory (DFT) calculations confirm that a strong covalent interaction existed between the Bi atom of Bi nanodots and Bi O layer on the surface of the Bi3NbO7 nanosheets, which enhanced the visible light absorbability of the composite, fostered the transfer and separation of its interfacial photogenerated carriers, and promoted the activation of molecular oxygen into superoxide radicals (•O2−) and singlet oxygen (1O2) by the composite under visible light illumination for degradation of ciprofloxacin (CIP). The photocatalytic degradation rate of CIP by the Bi/Bi3NbO7 composites is 4.58 times higher than that by the pristine Bi3NbO7. The Bi/Bi3NbO7 photocatalyst still revealed high photocatalytic activity even after five cycles. This work elucidates the mechanism of molecular oxygen activation over 0D/2D semimetal-semiconductor system and provides a promising approach for designing high efficient 0D/2D photocatalysts toward sustainable environmental remediation.

0D Bi nanodots/2D Bi3NbO7 nanosheets heterojunctions for efficient visible light photocatalytic degradation of antibiotics: Enhanced molecular oxygen activation and mechanism insight

The availability of robust, versatile, and efficient photocatalysts is the main bottleneck in practical applications of photocatalytic degradation of organic pollutants. Herein, N‐WO3/Ce2S3 nanotube bundles (NBs) are synthesized and successfully immobilized on a carbon textile, resulting in a flexible and conducting photocatalyst. Due to the large interfacial area between N‐WO3 and Ce2S3, the interwoven 3D carbon architecture and, more importantly, the establishment of a heterojunction between N‐WO3 and Ce2S3, the resultant photocatalyst exhibits excellent light absorption capacity and superior ability to separate photoinduced electron–hole pairs for the photocatalytic degradation of organic compounds in air and water media. Theoretical calculations confirm that the strong electronic interaction between N‐WO3 and Ce2S3 can be beneficial to the enhancement of the charge carrier transfer dynamics of the as‐prepared photocatalyst. This work provides a new protocol for constructing efficient flexible photocatalysts for application in environmental remediation.

Heterojunction Architecture of N-Doped WO3 Nanobundles with Ce2S3 Nanodots Hybridized on a Carbon Textile Enables a Highly Efficient Flexible Photocatalyst

A novel 3D structure Ag/p-Ag2S/n-BiVO4 plasmonic p-n heterojunction photocatalyst was successfully fabricated via a depositing p-type Ag2S on n-type BiVO4, followed by light reduction. In this innovative plasmonic p-n heterojunction photocatalyst strcture, p-n heterojunction can play the role of suppression of charge recombination, and surface plasmon resonance of Ag can enhance the absorption of visible light confirmed by finite difference time domain (FDTD) simulations method. For the photocatalytic oxidation of oxytetracycline hydrochloride (OTH) and reduction of Cr6+, the Ag/p-Ag2S/n-BiVO4exhibits excellent photocatalytic performance, compared with BiVO4 and p-Ag2S/n-BiVO4. The results of active species detection reveal that h+ radical is the main reactive species in the photocatalytic oxidation of OTH. Moreover, 13 photocatalytic degradation intermediates and products of OTH were also identified by the gas chromatography-mass spectrometer (GC-MS). Finally, the photocatalytic oxidation and reduction mechanism over Ag/p-Ag2S/n-BiVO4 was discussed in detail. The present study will benefit the development of the new plasmonic p-n heterojunction photocatalysts and would be of great importance to meet ever-increasing environmental demands in the future.

A novel 3D plasmonic p-n heterojunction photocatalyst: Ag nanoparticles on flower-like p-Ag2S/n-BiVO4 and its excellent photocatalytic reduction and oxidation activities

The hybrid Ag/TiO 2 -N photocatalyst was prepared via a supercritical solvothermal process in ethanol fluid. The simultaneous achievement of reduction of Ag + ions and N-doping in silver-ammonia complex solution led to the uniform distribution of Ag nanoparticles stably combined with the surface of TiO 2 -N substrate. As a result, the visible-light photocatalytic inactivation of Acinetobacter baumannii was facilitated via the enhanced visible light harvesting and the high separation efficiency of photo-induced charge carriers. By means of the main active species of O 2 − radical, the synergistic effect of Ag nanoparticles and TiO 2 -N could induce the structure change of bacteria with the leakage of K + ions as well as the mineralization of cell membrane with the elimination of self-repair function, leading to the final cell death. In comparison, the bactericidal activity of Ag nanoparticles and TiO 2 -N under UV light irradiation was due to the intrinsic efficiency and the high light harvesting, respectively. The photothermal effect of Ag nanoparticles in the near-IR light region could be possibly remained by TiO 2 -N substrate to achieve the antibacterial activity. Furthermore, Ag/TiO 2 -N photocatalyst played great bactericidal effect for kinds of bacteria, implying the applicable future to the medical disinfection.

Synergistic Ag/TiO2-N photocatalytic system and its enhanced antibacterial activity towards Acinetobacter baumannii

The electrochemical nitrate reduction reaction (NITRR) provides a promising solution for restoring the imbalance in the global nitrogen cycle while enabling a sustainable and decentralized route to source ammonia. Here, we demonstrate a novel electrocatalyst for NITRR consisting of Rh clusters and single-atoms dispersed onto Cu nanowires (NWs), which delivers a partial current density of 162 mA cm-2 for NH3 production and a Faradaic efficiency (FE) of 93% at -0.2 V vs. RHE. The highest ammonia yield rate reached a record value of 1.27 mmol h-1 cm-2. Detailed investigations by electron spin resonance, in-situ infrared spectroscopy, differential electrochemical mass spectrometry and density functional theory modeling suggest that the high activity originates from the synergistic catalytic cooperation between Rh and Cu sites, whereby adsorbed hydrogen on Rh sites transfer to vicinal *NO intermediate species adsorbed on Cu promoting the hydrogenation and ammonia formation.

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Efficient Electrochemical Nitrate Reduction to Ammonia with Copper Supported Rhodium Cluster and Single-Atom Catalysts.

Ag/BiOBr film coated on the glass substrate was synthesized by a solvothermal method and a subsequent photoreduction process. Such a Ag/BiOBr film was then adhered to a hollow rotating disk filled with long-afterglow phosphor inside the chamber. The Ag/BiOBr film exhibited high photocatalytic activity for organic pollutant degradation owing to the improved visible-light harvesting and the separation of photoinduced charges. The long-afterglow phosphor could absorb the excessive daylight and emit light around 488 nm, activating the Ag/BiOBr film to realize round-the-clock photocatalysis. Because the Ag nanoparticles could extend the light absorbance of the Ag/BiOBr film to wavelengths of around 500 nm via a surface plasma resonance effect, they played a key role in realizing photocatalysis induced by long-afterglow phosphor.

Ag/BiOBr Film in a Rotating-Disk Reactor Containing Long-Afterglow Phosphor for Round-the-Clock Photocatalysis

A ternary ZnxCd1−xS solid solution was prepared using a supercritical solvothermal route and was used as a photocatalyst without further thermal treatments. The ZnxCd1−xS exhibited high activity in the photocatalytic degradation of rhodamine B and p-chlorophenol under visible light irradiation owing to its uniform crystal growth with well-distributed crystallite size, high specific surface area with large pore volume, and low recombination rate of photo-induced electrons and holes. Moreover, the ZnxCd1−xS solid solution displayed strong stability against either structural damage or oxidation, leading to its excellent durability in photocatalysis.

Supercritical solvothermal preparation of a ZnxCd1−xS visible photocatalyst with enhanced activity

A facile solvothermal approach assisted with a [C16mim]Br ionic liquid for the preparation of BiOBr visible-light photocatalytic films was developed. A BiOBr film with uniformly assembled nanosheets was stably grown on the pretreated soda glass substrate via the Bi–O–Si bond. A rotating disk reactor coated with the BiOBr film was designed to effectively avoid the light shielding from color solution. The BiOBr film obtained with the [C16mim]Br ionic liquid presented an improved visible-light photcatalytic degradation rate of organics in wastewater, especially at a high concentration of organic dyes with deep color. A stable combination of BiOBr films with the substrate, the enhanced light harvesting owing to multiple reflections within the network of BiOBr nanosheets, the high separation efficiency of photo-induced charge carriers, the fast adsorption rate and the efficient utilization of light in the rotating disk reactor simultaneously played important roles in the degradation process, leading to the applicable future for the practical wastewater treatment.

Haibo Yin

Papers

Synergistic Ag/TiO2-N photocatalytic system and its enhanced antibacterial activity towards Acinetobacter baumannii

Efficient Electrochemical Nitrate Reduction to Ammonia with Copper Supported Rhodium Cluster and Single-Atom Catalysts.

Ag/BiOBr Film in a Rotating-Disk Reactor Containing Long-Afterglow Phosphor for Round-the-Clock Photocatalysis

Supercritical solvothermal preparation of a ZnxCd1−xS visible photocatalyst with enhanced activity

BiOBr visible-light photocatalytic films in a rotating disk reactor for the degradation of organics