2D Nanomaterials, with unique structural and electronic features, have shown enormous potential toward photocatalysis fields. However, the photocatalytic behavior of pristine 2D photocatalysts are ...still unsatisfactory, and far below the requirements of practical applications. In this regard, surface defect engineering can serve as an effective means to tune photoelectric parameters of 2D photocatalysts through tailoring the local surface microstructure, electronic structure, and carrier concentration. In this review, recent progress in the design of surface defects with the classified anion vacancy, cation vacancy, vacancy associates, pits, distortions, and disorder on 2D photocatalysts to boost the photocatalytic performance is summarized. The strategies for controlling defects formation and technique to distinguish various surface defects are presented. The crucial roles of surface defects for photocatalysis performance optimization are proposed and advancement of defective 2D photocatalysts toward versatile applications such as water oxidation, hydrogen production, CO2 reduction, nitrogen fixation, organic synthesis, and pollutants removal are discussed. Surface defect modulated 2D photocatalysts thus represent a powerful configuration for further development toward photocatalysis.
Recent progress in the design of surface defects on 2D photocatalysts to boost the photocatalytic performance is summarized. The strategies for controlling defects formation and technique to distinguish various surface defects are presented. The crucial roles of surface defects for photocatalysis performance optimization and advancement of defective 2D photocatalysts toward versatile applications are discussed.
Atomically-thin two-dimensional materials can afford promising opportunities for various photocatalytic applications thanks to its unique structure and fascinating properties. However, the ...understanding of their clear relationship between structure and activity is difficult and insufficient. In this review, various strategies for preparation of atomically-thin 2D materials have been surveyed. Then, the structure-activity relationship insights have been highlighted from three crucial factors of photocatalysis namely light harvesting, charge separation and interfacial reactions, by surveying the recent developed freestanding atomically-thin photocatalysts. Various activity improvement strategies for atomically-thin 2D materials, such as element doping, defect engineering, active sites enlarging, etc. have been proposed. Finally, the opportunities and challenges of atomically-thin two-dimensional materials for photocatalysis has been presented to satisfy people's requirement of potential applications.
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•Strategies for preparation of atomically-thin 2D materials have been surveyed.•Insight the structure-activity relationship from light harvesting, charge separation and interfacial reactions.•Various activity improvement strategies for atomically-thin 2D materials have been proposed.
Cobalt sulfide materials have attracted enormous interest as low‐cost alternatives to noble‐metal catalysts capable of catalyzing both oxygen reduction and oxygen evolution reactions. Although recent ...advances have been achieved in the development of various cobalt sulfide composites to expedite their oxygen reduction reaction properties, to improve their poor oxygen evolution reaction (OER) activity is still challenging, which significantly limits their utilization. Here, the synthesis of Fe3O4‐decorated Co9S8 nanoparticles in situ grown on a reduced graphene oxide surface (Fe3O4@Co9S8/rGO) and the use of it as a remarkably active and stable OER catalyst are first reported. Loading of Fe3O4 on cobalt sulfide induces the formation of pure phase Co9S8 and highly improves the catalytic activity for OER. The composite exhibits superior OER performance with a small overpotential of 0.34 V at the current density of 10 mA cm−2 and high stability. It is believed that the electron transfer trend from Fe species to Co9S8 promotes the breaking of the Co–O bond in the stable configuration (Co–O–O superoxo group), attributing to the excellent catalytic activity. This development offers a new and effective cobalt sulfide‐based oxygen evolution electrocatalysts to replace the expensive commercial catalysts such as RuO2 or IrO2.
A new Fe3O4@Co9S8/rGO composite is developed as a high‐performance oxygen evolution catalyst, which provides a small overpotential of 0.34 V for 10 mA cm−2 current density. It is proposed that the electron transfer trend from Fe species to Co9S8 promotes the breaking of the CoO bond in the stable configuration (CoOO superoxo group), attributing to the excellent catalytic activity.
Novel carbon quantum dot (CQD) modified Bi2MoO6 photocatalysts were prepared via a facile hydrothermal process. The CQD modified Bi2MoO6 materials were characterized by multiple techniques. The CQDs ...with the average size of about 7 nm were distributed on the surface of Bi2MoO6 nanosheets. The photocatalytic activity of as-prepared CQD modified Bi2MoO6 materials was investigated sufficiently by the photodegradation of four different kinds of pollutants, such as ciprofloxacin (CIP), bisphenol A (BPA), tetracycline hydrochloride (TC), and methylene blue (MB). The improved photocatalytic activity was observed for CQD modified Bi2MoO6 samples compared with pure Bi2MoO6 under visible light irradiation. The CQD modified Bi2MoO6 photocatalysts with a CQD content of 2 wt% exhibited the optimum photocatalytic activity, which was found to increase by about 5 times than that of the pure Bi2MoO6 for the photodegradation of CIP. This improvement was attributed to the crucial role of CQDs, which acted as a photocenter for absorbing solar light, a charge separation center for suppressing charge recombination, and a catalytic center for pollutant photo-degradation. The main active species were determined to be ˙OH and O˙-(2) by the ESR technique and analyzed by calculations as well as XPS valence spectra, and a possible photocatalytic mechanism was also proposed.
The porous ultrathin graphitic carbon nitride (g-C3N4) with confined surface carbon defects was obtained via the twice thermal treatment of bulk g-C3N4. The as-prepared porous ultrathin g-C3N4 sample ...displayed the average thickness of about 0.9 nm. The porous ultrathin g-C3N4 with confined surface carbon defects was designed to bidirectional acceleration of carrier separation for both the bulk and the surface. Multiple characterizations have been employed to determine the structure, morphology, surface feature, defect, and electronic structure of the obtained samples. The photocatalytic activity of the obtained porous ultrathin g-C3N4 materials was evaluated for the degradation of rhodamine B under the visible light irradiation. The structure-activity relationship of the porous ultrathin g-C3N4 materials was studied in details. The free radicals during the photocatalysis process was determined and analyzed by electron spin resonance and X-ray photoelectron spectroscopy valence band spectra technique, in which the main free radicals would be changed from superoxide radical for bulk g-C3N4 to both superoxide radical and hydroxyl radical for porous ultrathin g-C3N4. This ideal material model disclosing atomic-level insights into the role of porous ultrathin structure with confined carbon defects in the enhanced photocatalytic activity.
Solar‐driven reduction of CO2, which converts inexhaustible solar energy into value‐added fuels, has been recognized as a promising sustainable energy conversion technology. However, the overall ...conversion efficiency is significantly limited by the inefficient charge separation and sluggish interfacial reaction dynamics, which resulted from a lack of sufficient active sites. Herein, Bi12O17Cl2 superfine nanotubes with a bilayer thickness of the tube wall are designed to achieve structural distortion for the creation of surface oxygen defects, thus accelerating the carrier migration and facilitating CO2 activation. Without cocatalyst and sacrificing reagent, Bi12O17Cl2 nanotubes deliver high selectivity CO evolution rate of 48.6 μmol g−1 h−1 in water (16.8 times than of bulk Bi12O17Cl2), while maintaining stability even after 12 h of testing. This paves the way to design efficient photocatalysts with collaborative optimizing charge separation and CO2 activation towards CO2 photoreduction.
Defect‐rich Bi12O17Cl2 superfine nanotubes were prepared for the photocatalytic reduction of CO2. Benefiting from the superfine nanotube structure to accelerate charge separation and oxygen defects to facilitate CO2 activation, the Bi12O17Cl2 nanotubes displayed a CO formation rate of 48.6 μmol g−1 h−1 in water without cocatalyst and sacrificial reagent, which is roughly 16.8 times that of bulk Bi12O17Cl2.
As a broad-spectrum antibiotic, tetracycline (TC) is widely used in agricultural purposes and human therapy. More attention is paid to TC as a serious threat to human health, including the fast ...spreading of antibiotic resistance gene and the serious toxicity to aquatic organisms. Therefore, the timely and accurate determination of TC residues is an urgent task to protect the safety of human. Herein, an effective and facile photoelectrochemical sensor platform based on carbon nitride/bismuth oxyhalide (CN/BiOBr) composites can be constructed for monitoring TC. The flower-like CN/BiOBr composites are prepared via a simple one-pot ethylene glycol-assisted solvothermal process with the addition of ionic liquid 1-hexadecyl-3-methylimidazolium bromide (C16mimBr). In view of matched energy band positions of CN and BiOBr, the addition of CN can reduce the recombination of photogenerated electron-hole pairs and improve the efficiency of visible light utilization, leading to enhancing photoelectrochemical response of BiOBr. Under light excitation, the photocurrent of CN/BiOBr composites is drastically improved, which is 6 times as much as that of pure BiOBr. Considering the superior photoelectrochemical performance, a photoelectrochemical sensor for monitoring TC has been developed, displaying linearly enhanced photocurrent with increasing the TC concentration. Two linear relationships received are from 8.0 to 4.0 × 102 ng mL−1, and 4.0 × 102 to 5.2 × 103 ng mL−1, respectively. The detection limit is 3.8 ng mL−1. The photoelectrochemical sensor exhibits a series of benefits including excellent stability, a wide linear range, a low detection limit and good anti-interference ability. Therefore, this work may offer great promises in providing a universal and efficient photoelectrochemical sensor for the tetracycline detection, and pave the way of constructing more materials used in photoelectrochemical detection field.
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•A photoelectrochemical sensing platform is fabricated for tetracycline detection.•The photoelectrochemical sensor is based on the flower-like CN/BiOBr composites.•The CN/BiOBr has been prepared by ionic liquid-associated solvothermal method.•The photoelectrochemical sensor shows wide detectable range and low detection limit.
Abstract
The design of efficient and stable photocatalysts for robust CO
2
reduction without sacrifice reagent or extra photosensitizer is still challenging. Herein, a single-atom catalyst of ...isolated single atom cobalt incorporated into Bi
3
O
4
Br atomic layers is successfully prepared. The cobalt single atoms in the Bi
3
O
4
Br favors the charge transition, carrier separation, CO
2
adsorption and activation. It can lower the CO
2
activation energy barrier through stabilizing the COOH* intermediates and tune the rate-limiting step from the formation of adsorbed intermediate COOH* to be CO* desorption. Taking advantage of cobalt single atoms and two-dimensional ultrathin Bi
3
O
4
Br atomic layers, the optimized catalyst can perform light-driven CO
2
reduction with a selective CO formation rate of 107.1 µmol g
−1
h
−1
, roughly 4 and 32 times higher than that of atomic layer Bi
3
O
4
Br and bulk Bi
3
O
4
Br, respectively.
The CoFe2O4/g-C3N4 composite could enhance the absorbtion of visibe-light and promote the separation of photogenerated electron–hole pairs. These electrons will activate H2O2 to degrade MB.
•There ...was no report to investigate the photocatalytic activities of CoFe2O4/g-C3N4.•The CoFe2O4/g-C3N4 composites are magnetic and stable.•Combination of CoFe2O4 and g-C3N4 could enhance the activity of activating H2O2.•The possible photocatalytic mechanism was discussed in detail.
A magnetic photocatalytic CoFe2O4/g-C3N4 composite was successfully synthesized by a simple calcination method. Powder X-ray diffraction (XRD), transmission electron microscopy (TEM), infrared (IR) spectra, UV–Vis diffuse reflection spectroscopy (DRS) and X-ray photoelectron spectroscopy (XPS) were applied to characterize the as-prepared samples. The magnetic properties of CoFe2O4 and CoFe2O4/g-C3N4 composites were measured by using a vibrating sample magnetometer (VSM) at room temperature. Photocatalytic property of the CoFe2O4/g-C3N4 composite was assessed by degrading methylene blue (MB) in aqueous medium under visible light irradiation. The results showed that the composite of 41.4% CoFe2O4/g-C3N4 exhibited the highest photocatalytic activity. It could activate H2O2 to degrade MB up to 97.3% in 3h under the visible light irradiation. This enhancement could be attributed to the synergistic effect between CoFe2O4 and g-C3N4, which could enhance their activity of activating H2O2 to degrade MB under visible light. The CoFe2O4/g-C3N4 composites also have a strong magnetic ability. After the photocatalytic reaction, it can be quickly separated from the water by an extra magnetic field. Moreover, a possible photocatalytic mechanism was proposed.
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