Excellent Photocatalytic Performance For Degradation Research Articles

CsPbBr3-MoS2-GO nanocomposites for boosting photocatalytic degradation performance

In order to address the main challenge of weak photocatalytic performance of pure metal halide perovskite materials, we innovatively introduced MoS2-graphene oxide (GO) composite structure and synthesized CsPbBr3-MoS2-GO nanocomposites by a two-step method. XRD and Raman results show that the three components are well combined to form a new CsPbBr3-MoS2-GO nanocomposite. TEM results show that MoS2 nanoribbons and CsPbBr3 quantum dots (QDs) are uniformly dispersed on the GO sheet. The photocatalytic activity of nanocomposites was evaluated by studying the photodegradation of Sudan Red III under xenon lamp irradiation. Benefiting from abundant active interfaces, the nanocomposites show much excellent photocatalytic degradation performance compared with pure CsPbBr3 QDs. The degradation rate of Sudan Red III by CsPbBr3-MoS2-GO nanocomposites is 3.1 times of that of pure perovskite QDs. Sudan Red III was completely photocatalytic degraded in 100 min. We believe that GO, with suitable band structure, high conductivity and good dispersibility, can bridge well MoS2 and CsPbBr3, act as a good electron transport channel, reduce carrier recombination and ultimately boost photocatalytic performance.

AgCl/Au/g-C3N4 ternary composites: Efficient photocatalysts for degradation of anionic dyes

Ternary composites involved graphitic carbon nitride (g-C3N4) have gained scientific interest in recent years. Herein, we report a series of ternary composites containing AgCl nanoparticles, Au nanoparticles, and g-C3N4 (AgCl/Au/CN) via a two-step chemical deposition method. In this semiconductor−metal−semiconductor structure, AgCl nanoparticles can absorb organic anions, as well as form a Z-scheme heterojunction combined with g-C3N4; Au nanoparticles can play a role in the separation of photogenerated carriers. These features allow AgCl/Au/CN to exhibit excellent photocatalytic degradation performance for anionic dyes. When the molar ratios of AgCl and Au to g-C3N4 are 1% and 0.5%, respectively, the optimal AgCl/Au/CN sample can achieve effective degradation for Rhodamine B within 25 min under visible-light irradiation of relatively low intensity.

Z-scheme α-Fe2O3/g-C3N4 with the Fe[sbnd]OC[sbnd] bond toward enhanced photocatalytic degradation

The key to developing efficient Z-scheme photocatalysts is to improve the electron transport ability of the interface through structural design via the preparation method. In this work, a Z-scheme α-Fe2O3/g-C3N4 photocatalyst with a Fe-O-C bond providing bridge-mediated electron transfer was obtained through the genetic strategy. Utilizing the hydrogen bonds between Fe(OH)3 and dicyandiamide, the Fe-O-C bond formed at the interface between α-Fe2O3 and g-C3N4 during high-temperature polymerization. Moreover, the effects of the Fe-O-C bond on the photocatalytic performance of the Z-scheme photocatalyst were carefully investigated. It was found the α-Fe2O3/g-C3N4 photocatalyst with the Fe-O-C bond had an excellent photocatalytic degradation performance, structural stability and catalytic stability. The improvement of the photocatalytic efficiency is attributed to the expanded absorption of visible light by the semiconductor combination, the Fe-O-C bond acting as an efficient electron transfer channel and the Z-scheme structure retaining its strong redox ability. This work introduces a novel approach for the preparation of other effective Z-scheme photocatalysts.

Uncovering the origin of full-spectrum visible-light-responsive polypyrrole supramolecular photocatalysts

Environmentally friendly polypyrrole (PPy) catalysts with conjugated nanostructures for superior photophysical and photoelectric applications are developed. The high coplanar structure via α-α connection is benefit for the transferring of photo-induced electron and improving the life of the light generated carrier. Importantly, the energy level structure of conjugated polymers was obtained via theoretical calculation and the photocatalytic mechanism of PPy photocatalyst was illuminated in detail. O2− are the main radical responsible for the degradation of MO. Moreover, conjugated PPy photocatalysts are stable with cycling. Compared to P25 and g-C3N4, PPy showed excellent photocatalytic performance for degradation of organic pollutants in full spectrum and visible light, the reaction rate constants of PPy are 4.27 and 5.31 times as much as the P25, respectively. Furthermore, PPy also exhibited effective photocatalytic performance towards different organic pollutants. These results obviously open interesting perspectives of using conjugated polymer and provide theoretical guidance for designing new organic photocatalysts to solve the energy and environment issues.

Electrochemical sensor studies and optical analysis of developed clay based CoFe2O4 ferrite NPs

The Cobalt ferrite (CoFe2O4) and Clay/CoFe2O4 has been successfully synthesized via chemical method have been investigated. The structural properties of the produced powders were investigated using X-ray diffraction (XRD) and Field emission scanning electron microscopy (FE-SEM). XRD patterns confirms the spinel/cubic structure of the prepared Clay/CoFe2O4. FE-SEM micrographs showed uniform sphere-shaped CoFe2O4 when infused with the clay. In addition, Infrared spectroscopy has been used to verify cobalt ferrite formation and Clay/CoFe2O4 particles. The photocatalytic performance of Clay/CoFe2O4 was examined for their potential role in photo degradation of Indigo carmine dye under UV-light. The result shows that the composite is suitable for excellent photocatalytic degradation performance and degradation was found to be 98 %. Electrochemical analysis was conducted for the synthesized material with prepared Nickel mesh electrode in 0.1 M KOH electrolyte. It showed excellent performance in redox potential measured by cyclic voltammetry and extended their sensor activities towards chemical sensors (arsenic trioxide, lead acetate, mercuric acetate and stannous chloride). These studies showed new platform to use simple chemical method for the preparation of Clay/CoFe2O4 for their potential applications such as in detection of heavy metals, waste water treatment and electrochemical studies.

Fabrication of AgCl/Ag3PO4/graphitic carbon nitride heterojunctions for enhanced visible light photocatalytic decomposition of methylene blue, methylparaben and E. coli

Herein, a novel ternary nanocomposite AgCl/Ag3PO4/g-C3N4 was successfully synthesized via sedimentation precipitation and ion exchange method. The photocatalytic performance of the as-prepared AgCl/Ag3PO4/g-C3N4 nanocomposite was investigated via photocatalytic degradation of methylene blue (MB), methylparaben (MPB) and inactivation of E. coli under visible light irradiation. The AgCl/Ag3PO4/g-C3N4 composite presented the optimal photocatalytic performance, degrading almost 100% MB and 100% MPB, respectively. The excellent stability of AgCl/Ag3PO4/g-C3N4 was also verified in the cycle operations; the degradation efficiency of MPB could still be maintained at 85.3% after five cycles of experiments. Moreover, the AgCl/Ag3PO4/g-C3N4 composite displayed more superior photocatalytic inactivation efficiency with 100% removal of E. coli (7-log) in 20 min under visible light irradiation. The efficient photo-generated charge separation originated from a strong interaction in the intimate contact interface, which was confirmed by the results of photocurrent and EIS measurements. In addition, radical trapping experiments revealed that hole (h+) was the predominant active species in the photocatalytic system. Based on the experimental results, a photocatalytic mechanism for the degradation of parabens over AgCl/Ag3PO4/g-C3N4 was also proposed. We believe that this work provides new insights into the multifunctional composite materials for the applications in solar photocatalytic degradation of harmful organic compounds and common pathogenic bacteria in wastewater.

Fabrication of ZnO Nanocap-Ordered Arrays with Controllable Amount of Au Nanoparticles Decorated and Their Detection and Degradation Performance for Harmful Molecules.

This paper mainly presents a facile and cost-effective method to achieve large-scale ZnO nanocap (ZnO NC)-ordered arrays with a controllable amount of Au nanoparticles (Au NPs) decorated on their surface. The preparation process includes the construction of polystyrene nanosphere (PS) mask, metal deposition, and annealing process. The Au NPs/ZnO NCs have apparent hierarchical structure. Interestingly, the size and number of Au NPs can be controlled by changing the time of Au deposition and the diameter of PSs. Moreover, the Au NP/ZnO NC arrays can be used as a substrate to detect harmful dye molecules based on surface-enhanced Raman scattering (SERS) effect, and show ultrahigh sensitivity with a limit of detection (LoD) of 10–10 M for crystal violet (CV) molecules. In addition, the above substrate has achieved reusable detection due to their excellent photocatalytic degradation performance for harmful molecules. The finite difference time-domain (FDTD) simulation results have revealed that SERS “hot spots” are almost distributed at the junctions of Au NPs and ZnO NCs. The above results show that the composite substrates have a good prospect in practical applications in the future.

Hierarchical TiO2/AgBr core/shell microspheres with enhanced visible light photocatalytic activity

TiO2/AgBr core/shell microspheres have been successfully synthesized via a two-step solvothermal process. The TiO2 core (1.5 µm in average diameter) is coated with a shell (100 nm in average thickness) consisting of AgBr nanoparticles of 6 nm in average size. The composite nanomaterials demonstrate much stronger light absorbance, narrower bandgap, and lower recombination rate of photogenerated electron–hole pairs than both bare TiO2 microspheres and pure AgBr nanoparticles, which endue it with much enhanced photocatalytic activity. The as-prepared TiO2/AgBr photocatalyst exhibits excellent photocatalytic degradation performance towards methylene blue (MB) under visible light irradiation, and 92% MB could be degraded in 90 min, which is much higher than that of bare TiO2 (11%) and pure AgBr (52%). TiO2/AgBr core/shell microsphere photocatalyst also demonstrates good reusability, and the photocatalytic activity has no obvious decrease after five cycles. This study may provide a new insight into the design and synthesis of visible light photocatalytic materials.

Rational construct CQDs/BiOCOOH/uCN photocatalyst with excellent photocatalytic performance for degradation of sulfathiazole

The novel heterojunction photocatalysts also known as carbon quantum dots-decorated BiOCOOH/ultrathin g-C3N4 nanosheets (CQDs/BiOCOOH/uCN) were designed, where carbon quantum dots (CQDs) acted as mediators to shuttle electrons between BiOCOOH and ultrathin g-C3N4 nanosheets (uCN). The physicochemical properties of as-obtained composites were systematically characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffractometry, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The 4-CQDs/BiOCOOH/uCN consisting of 50 wt% ultrathin g-C3N4 nanosheets (uCN) and 4 mL CQDs solution manifested the optimal photoactivity. After 90 min of LED lamp irradiation, the STZ degradation efficiency by 4-CQDs/BiOCOOH/uCN reached 99.28% ± 1.04, and the corresponding degree of mineralization was 49.58% ± 1.36. The enhanced photocatalytic performance of 4-CQDs/BiOCOOH/uCN was owing to the fast photogenerated charges transfer and separation revealed by photoluminescence (PL), transient photocurrent responses and electrochemical impedance spectra (EIS) measurements. By means of the radicals quenching experiments and electron spin resonance spectroscopy (ESR) analysis, it was demonstrated that •O2– and •OH were the dominant reactive species of STZ degradation. Besides, the effects of catalyst dosage (0.2–1.2 g/L), pH value (3.0–11.0), natural organic matter and different anions (Cl−, SO42−, NO3−) on the photocatalytic activity of 4-CQDs/BiOCOOH/uCN composite were systematically explored. 17 main intermediates were found based on high-resolution mass spectrometry (HRMS) detection. Eventually, the 4-CQDs/BiOCOOH/uCN composite showed favorable reusability in recycling experiments, and displayed satisfactory degradation abilities for STZ in deionized water (99.28% ± 1.04), tap water (97.15% ± 1.16), river water (96.44% ± 0.76), and wastewater treatment plant effluent (96.19% ± 1.20).

Novel p-n type porous Ag2O/Bi5O7I heterojunction for Uv–Vis-NIR activated high efficient photocatalytic degradation of bisphenol A: Photoelectric properties and degradation mechanism

Exploring effective strategies to strengthen the photoresponse and charge separation efficiency is crucial for the preparation of photocatalysts with superior-performance. Herein, series of 0D-2D Ag2O/Bi5O7I heterojunctions with UV–Vis-NIR spectrum response were prepared by modifying Ag2O on the surface of porous Bi5O7I nanosheets to boost the photocatalytic degradation of bisphenol A. The modified p-type Ag2O semiconductor not only extends the optical absorbance range of the prepared p-n heterojunction but also improves the separation efficiency of photoinduced charge carriers by the internal electric field. Moreover, the unique porous thin-layer structure can further shorten the transport distance of bulk charges to the surface. In addition, uniformly distributed holes are able to provide more active sites to accelerate charge depletion on Bi5O7I substrate. As a result, the interfacial coulomb electrostatic repulsive force was greatly weakened, making it easier for the charge transferences from Ag2O to Bi5O7I under the internal electric field. Therefore, the prepared p-n heterojunction exhibited excellent performance in photocatalytic degradation of bisphenol A. In particular, 25% Ag2O/Bi5O7I showed the best bisphenol A degradation performance, which was 7.23 and 4.39 times than that of pristine Ag2O and Bi5O7I, respectively. In addition, the prepared samples showed excellent photocorrosion resistance, due to the rapid consumption of enriched electrons by the porous structure. Furthermore, intermediates of bisphenol A degradation reaction were characterized by liquid mass method, and then the degradation pathway was deduced. This work is of significance to the construction and design of efficient photocatalysts with full spectral response and high photoelectric conversion efficiency.

Construction and visible-light-photocatalysis of a novel ternary heterostructure BiOI/(001)TiO2/Ti3C2

Constructing effective heterojunctions between semiconductors and appropriate cocatalysts and exposing highly active crystal facets have been considered an effective approach to obtain efficient photocatalysts. Herein, a novel BiOI/(001)TiO2/Ti3C2 (BTT) hybrid was for the first time synthesized by in situ growing (001)TiO2 nanosheets on a 2D MXene nanomaterial (Ti3C2) and subsequent deposition of flower-like nanoflake BiOI on the obtained (001)TiO2/Ti3C2 hybrid. The BTT hybrid exhibited excellent photocatalytic performance for degradation of Rhodamine B under visible light irradiation, with the highest degradation rate being 6.26, 1.72, and 1.35 times of that of a pure BiOI, BiOI/TiO2 hybrid, and BiOI/Ti3C2 hybrid, respectively. The staggeringly enhanced photoactivity of BTT was attributed to the separation of photogenerated carriers by a multiple charge transfer channels because of the formed p-n and Schottky double junctions. This study demonstrates that (001)TiO2/Ti3C2 obtained by simple hydrothermal oxidation of Ti3C2 can be a good cocatalyst for fabricating excellent visible-light-driven photocatalyst.

Fabrication of Ag3PO4/Ag/MoO3-x Z-scheme system with excellent photocatalytic degradation performance under visible light irradiation

Z-scheme Ag3PO4/Ag/MoO3-x photocatalyst was prepared by deposition of Ag and Ag3PO4 nanoparticles on the surface of MoO3-x nanosheets. With Ag mediation between Ag3PO4 and MoO3-x, there is efficient separation and utilization of photogenerated charge carriers. Owing to the rich presence of oxygen vacancies on the surface of MoO3-x, oxygen adsorption on the surface is enhanced. The as-prepared Ag3PO4/Ag/MoO3-x Z-scheme system shows outstanding photocatalytic activity and stability for the degradation of dyes (rhodamine B, methylene blue, as well as their mixture) and ciprofloxacin under visible light irradiation, displaying degradation rate that is 15.9, 3.4, 14.9 and 3.0 times that of MoO3-x, Ag3PO4, Ag/MoO3-x and Ag3PO4/MoO3-x, respectively. According to the results of trapping experiments, ·OH and ·O2− are the main active species, and a possible reaction mechanism has been proposed.

Co-monomer engineering optimized electron delocalization system in carbon-bridging modified g-C3N4 nanosheets with efficient visible-light photocatalytic performance

The bridged nitrogen that linked each melem unit in g-C3N4 is considered to be sp3 hybridization with a high electronegativity, which confines the original conjugate system of melon networks. Herein, the carbon-bridging modified g-C3N4 nanosheet (CBCN) is prepared by a one-pot copolymerization for the first time through employing malondiamide (MLDD) as a novel polymerized small molecule to urea. Experimental and DFT computation identify that substituting parts of bridged nitrogen in melon units with carbon not only improves the original conjugate system and optimizes the band structure of g-C3N4, but also induces the charges redistribution, leading to an enhanced charges separation and visible light utilization. Moreover, the MLDD co-monomer can act as a blocking agent to generate structure edge defects, which results in numerous in-plane holes and increases the specific surface area greatly. As a result, the CBCN samples show an excellent photocatalytic performance in degradation of pollutants and H2 generation.

Silver‐Loaded Bio‐Structured Carbon/Cadmium Sulfide Lamellar Composites with Enhanced Photocatalysis under Visible Light

A silver (Ag)‐loaded biostructured carbon/cadmium sulfide (CdS) lamellar composite photocatalyst was synthesized using a hydrothermal and photodeposition method. Camellia petals functioned both as a biological layered template and as a source of carbon. The prepared composite photocatalyst demonstrated good absorption under visible light and exhibited excellent photocatalytic degradation performance. The photocatalytic degradation efficiency of the obtained composites substantially improved compared with pure CdS. The 5 wt.‐% Ag‐loaded C/CdS sample exhibited the highest photocatalytic activity, reaching 96.5 % after 180 min, which was 8.7 times that of pure CdS. Specifically, the biocarbon sheet enhanced the absorption of visible light. Furthermore, the high electrical conductivity of Ag can effectively transfer and separate photogenerated electrons and holes, thus enhancing both photocatalytic performance and stability.

Influences of silver halides AgX (X = Cl, Br, and I) on magnesium bismuth oxide photocatalyst in methylene blue degradation under visible light irradiation

AgX/MgBi2O6 composites (X = Cl, Br, and I), prepared from the hydrothermal procedure combined with a co-precipitation method, display unique visible light responsive photocatalytic activity. The catalytic performance of the AgX/MgBi2O6 composites were evaluated through the photodegradation of methylene blue (MB, 15 ppm) under white-light light-emitting diode irradiation (2.5 W, power density: 0.38 Wcm−2). Among the AgX/MgBi2O6 composites, the AgI/MgBi2O6 composite, with molar ratio of AgI to MgBi2O6 as 3:1, exhibited the highest photocatalytic performance within 20 min (degradation efficiency: 99.5 %) while MgBi2O6, AgCl/MgBi2O6, and AgBr/MgBi2O6 composites achieved degradation efficiency of 14.9 %, 24.9 % and 56.1 % respectively. The main reason of superior photocatalytic activity in AgI/MgBi2O6 composite attributes to the pn junction between AgI nanoparticles and MgBi2O6 effectively enhancing the charge separation efficiency and reducing the recombination rate of electron–hole pairs. This study revealed that hydroxyl and oxygen radicals are the major species involved in the degradation of MB from the photoactivated AgI/MgBi2O6 composite. To develop a practical application of this new material, the samples of AgI/MgBi2O6 composite have demonstrated excellent photocatalytic performance in degradation of various dyestuffs (92.3 %–99.5 % degradation within 10 min) under visible light irradiation and 99.8 % MB degradation under sunlight irradiation within 6 min.

Enhanced photocatalytic activity over g-C3N4/(BiO)2(OH)xCl2−x Z-scheme heterojunction

Photocatalytic degradation has been regarded as a promising method for environmental remediation. In this work, layered g-C3N4/(BiO)2(OH)xCl2−x (NBHC) heterojunction composites were synthesized by a hydrothermal method. The two-dimensional (2D)/2D porous layered Z-scheme heterojunction leaded to the suppressed recombination and the efficient separation of photogenerated electron-hole pairs. Meanwhile, NBHC composites exhibited a high specific surface area and rich mesopores for more reactive active sites. Thus, NBHC had an excellent photocatalytic degradation performance of pollutant trypan blue (TB). Furthermore, we found that the active species of superoxide radical (O2−) played a more important role, while hydroxyl radical (OH) contributed to a lesser extent in photocatalytic degradation of TB based on the active species capture experiment and electron spin resonance (ESR) spectra. A Z-scheme photocatalytic mechanism was proposed to understand the photodegradation of TB. This study may provide a new horizon for constructing novel Z-scheme heterostructure photocatalysts with an excellent performance.

Photocatalytic Activity of Nonprecious Metal WSe2/g-C3N4 Composite Under Visible Light Irradiation

The WSe2/g-C3N4 (graphite carbon nitride) composite with photocatalytic properties was synthesized using a hydrothermal method. This synthesis pathway can be characterized by being simple, inexpensive and nonpolluting, integrating the concept of green chemistry. The WSe2/g-C3N4 composite could effectively degrade methyl orange solution under visible light irradiation. The decolorization experiment of methyl orange solution shows that the degradation rate of the 30[Formula: see text]wt.% WSe2/g-C3N4 composite can reach 98.7% after 100[Formula: see text]min of illumination, while the degradation rate of pure g-C3N4 was only 87.6% under the same conditions. This can be attributed to the fact that the combination of WSe2 and g-C3N4 nanosheets can increase the number of active binding sites, increasing the rate of charge separation and transport ability, decreasing the recombination rate of the photogenerated electron–hole pairs. Therefore, the WSe2/g-C3N4 composite will have potential development as a new material with low cost, easy synthesis and excellent performance in photocatalytic degradation of water pollution.

Fundamental properties of delafossite CuFeO2 as photocatalyst for solar energy conversion

Photocatalysis technology can meet the two global issues of energy shortage and environmental pollution at the same time. Due to the unique layered quasi-two-dimensional superlattice structure, and the specific functions of structural motifs, delafossite compounds have become a popular candidate family for photoelectric conversion applications. In this article, 3R-delafossite CuFeO2 microcrystals with complete stoichiometry, high crystallinity and purity, uniform composition, cubic size of ∼1.47 μm, single crystal phase were obtain by the optimized hydrothermal process. Combined with optical measurement and density functional theory calculation, the electron transition mechanism of CuFeO2 was analyzed in depth and systematically. CuFeO2 has obvious multi-band spectral absorption characteristics, which are helpful to clarify the controversy about band gap values of CuFeO2. CuFeO2 microcrystals exhibit potential hydrogen production from photocatalytic water-splitting to and photocatalytic degradation of pollutants. Tetracycline hydrochloride degradation testing was adopted to further verify the potential of CuFeO2 microcrystals for wastewater purification. CuFeO2 microcrystals not only exhibit excellent photocatalytic degradation performance, but also present Fenton reaction activity in dark conditions after adding H2O2. It is particularly important that the removal rate of tetracycline hydrochloride was significantly enhanced by the coupling of photocatalytic reaction and Fenton reaction, suggesting that CuFeO2 emerges excellent Photo-Fenton reaction activity. Finally, this article not only provides the fundamental physical chemical properties of CuFeO2 for solar energy conversion, but also points out the development direction of further improving the efficiency.

Synthesis visible photocatalyst carbon/BiOI and its photocatalytic degradation activity

The carbon/BiOI composite photocatalysts were synthesis by hydrothermal reaction and characterized by various methods. The as-prepared photocatalysts were used to remove organic pollutants in aqueous solution under visible light irradiation. The C/BiOI samples demonstrated excellent photocatalytic performance for degradation of methyl orange (MO), which is about 4 times higher than that of BiOI. Furthermore, C/BiOI also displayed good stability after 5 cycles testing. Such superior performance was attributed to the enhanced absorption ability and increased separation of photogenerated electrons and holes.

Characterization and photocatalytic activity of nanoparticulate PrVO4 prepared by hydrothermal method

Using praseodymium nitrate (III) hexahydrate (Pr(NO3)3·6H2O), ammonium metavanadate (NH4VO3) and hexadecyl trimethyl ammonium bromide (CTAB) as raw materials, PrVO4 samples were successfully prepared by hydrothermal method. The resulting samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric and differential scanning calorimetry (TG-DSC), UV–visible diffuse reflectance spectroscopy (DRS) and Fourier transform infrared spectroscopy (FT-IR). The effect of different synthesis temperature and illumination time on the ultraviolet photocatalytic activity of PrVO4 samples was studied with methyl orange solution as simulated sewage. The results show that the pure tetrahedral zircon structure of the PrVO4 sample can be obtained at a hydrothermal temperature of 100–180 °C. The sample of PrVO4 prepared by hydrothermal temperature at 140 °C was uniform, with an average particle diameter of 50–60 nm and a band gap width of 3.1 eV. The photocatalytic experiment demonstrates that the degradation rate of 100 mg/L methyl orange is nearly 92.4% in the presence of PrVO4 sample prepared at 140 °C after UV irradiation at 30 min. The PrVO4 samples show excellent photocatalytic performance for degradation of methyl orange.