Search

The enhancement of electron-and-hole separation efficiency and facile generation of reactive oxygen species are significant factors for performance improvement of photocatalysts in selective toluen...

The introduction of oxygen vacancies (Ov) has been regarded as an effective method to enhance the catalytic performance of photoanodes in oxygen evolution reaction (OER). However, their stability under highly oxidizing environment is questionable but was rarely studied. Herein, NiFe-metal-organic framework (NiFe-MOFs) was conformally coated on oxygen-vacancy-rich BiVO4 (Ov-BiVO4 ) as the protective layer and cocatalyst, forming a core-shell structure with caffeic acid as bridging agent. The as-synthesized Ov-BiVO4 @NiFe-MOFs exhibits enhanced stability and a remarkable photocurrent density of 5.3±0.15 mA cm-2 at 1.23 V (vs. RHE). The reduced coordination number of Ni(Fe)-O and elevated valence state of Ni(Fe) in NiFe-MOFs layer greatly bolster OER, and the shifting of oxygen evolution sites from Ov-BiVO4 to NiFe-MOFs promotes Ov stabilization. Ovs can be effectively preserved by the coating of a thin NiFe-MOFs layer, leading to a photoanode of enhanced photocurrent and stability.

Selective photooxidation of toluene to benzaldehyde using O2 as an oxidant has the advantages of mild reaction conditions and excellent atomic economy, but it often suffers from low conversion effi...

Octahedral CdS–ZnS composites were synthesized using a simple method of cation exchange and hydrothermal treatment, using Cd3(C3N3S3)2 (denoted as Cd3(TMT)2) as a precursor and Zn2+ for ion exchang...

Bismuth oxyhalide (BiOX)-based heterostructures have attracted much attention due to their promotion effect on photocatalytic performance. Nonetheless, there is a lack of theoretical understanding on the relationship between the BiOX-induced interface and the enhancement of photocatalytic activity. In the present work, density functional theory (DFT) calculations were conducted to investigate the energy band structure, charge transfer and optic properties of layered MoS 2 /BiOX (X = Cl, Br, I) van der Waals (vdW) heterojunctions. All the MoS 2 /BiOX heterojunctions have lower band gaps, smaller effective mass and better light absorption ability than BiOX monolayers. Moreover, electrons transfer from MoS 2 to BiOX, and MoS 2 /BiOX heterojunctions show typical type-II band arrangement. Importantly, MoS 2 /BiOI presents significant performance in the carrier mobility and light absorption ability among the three heterostructures, which can facilitate effective separation of photo-generated electron-hole pairs and enhance photocatalytic activity. It is disclosed that the band edges MoS 2 /BiOX are suitable for the photocatalytic decomposition of water into oxygen. It is especially so for MoS 2 /BiOI which can affect full photocatalytic water splitting. The results clarify why the combination of MoS 2 and BiOX for the generation of MoS 2 /BiOX vdW heterojunctions could result in excellent photocatalytic activity, and disclose why MoS 2 /BiOI is the best among the three for photocatalytic water splitting.

Submicron-sized SAPO-34 zeolites were synthesized via nanosheet seed-assisted method using cheap diethylamine as the template. Only 2 wt % seeds are needed to obtain the submicron-sized SAPO-34 (ca. 700 nm). Further increase of seed dosage has little effect on reducing the crystal size but leads to an increase of acidity. Among the as-prepared samples, S-0.3-2% (SiO2/Al2O3 = 0.3, 2 wt % seed) shows the best catalytic performance (CH3Br conversion of up to 95%, ethylene and propylene selectivity of 94%, and a lifetime of over 125 min) ever reported in the studies of CH3Br conversion to light olefins. The results undoubtedly demonstrate that lifetime and olefin selectivity are highly dependent on the particle size and acidity of SAPO-34 zeolites. The decrease of particle size and acidity is beneficial to alleviating carbon deposition, resulting in enhanced catalyst lifetime. In addition, the decrease of particle size and lowering of acidity could diminish the second hydrogen transformation reactions of olef...

The activation of C–H bonds is an efficient approach for the production of value-added organics. The partial oxidation of hydrocarbons to oxygen-containing products at mild conditions is a profound...

An electrochemically mediated atom transfer radical polymerization (eATRP) of methyl acrylate (MA) in 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM-PF6) ionic liquid (IL) was reported. Remarkably, the kinetic results revealed an extremely fast and well controlled polymerization in the presence of tris(2-(dimethylamino)ethyl)amine (Me6TREN). The monomer conversion reached more than 90% within a period of 300 s. Computational and simulation results indicated that the IL induced acceleration of polymerization can be attributed to the increased value of k t / k p 2 compared to the associated literature value. Additionally, polymerizations under different conditions, including ligand types, monomer/IL ratios, catalyst loadings, and targeted degrees of polymerization were explored. All the kinetic plots suggested superfast polymerization rates with good control over molecular weight and dispersity. Furthermore, the livingness of MA polymerization was confirmed by chain extension experiment. This work provides a new insight into eATRP in IL through experimentation and simulation and thus enriches the knowledge of reaction features of eATRP.

Multishelled micro-/nanostructures have attracted much research attention because of their unique properties. It is a big challenge to fabricate multishelled hollow structures of complex nanoarchit...

Inert C–H bonds activation at room temperature has been regarded as the control step in photocatalytic generation of valuable products from hydrocarbons. Herein, lead-free perovskite Cs3Bi1.8Sb0.2Br9 nanosheets with a proper amount of Sb in Cs3Bi2Br9 not only improves optical absorption due to anomalous band gap behavior, but also promotes the generation of holes (h+). The convergence of h+ on the surface of Cs3Bi1.8Sb0.2Br9 is crucial for the dissociation of toluene C(sp3)–H bond, which was proved by the density functional theory calculation and isotopic labelling results. The excellent activity in photocatalytic selective oxidation of toluene with a conversion rate of 5.83 mmol g−1h−1 under visible light is the highest ever achieved. This work sheds light on the modification of halide perovskites through the regulation of B-site cations for photocatalytic applications.

Metal-free atom transfer radical polymerization (ATRP) was successfully achieved in aqueous media for the first time. Polymerization of poly(ethylene oxide) methyl ether acrylate (PEGA480) was well controlled (Đ < 1.40) under visible light irradiation using tetrabromofluorescein (Eosin Y) as catalyst and pentamethyldiethylenetriamine (PMDETA) as electron donor. A validated kinetic model was developed to investigate the process of photoredox catalytic cycle via reductive quenching pathway. Experimental and simulation results showed that electron donor not only had an important influence on the ATRP activation, but also participated in the ATRP deactivation. Furthermore, the effects of water content, catalyst concentration, and degree of polymerization on the polymerization were studied thoroughly by a series of experiments. Good controllability of the polymerization regulated by light on and off confirmed the high degree of temporal control. The livingness of the chains was proved by a successful chain ext...

A high efficient visible-light-region Cu 2 O/g-C 3 N 4 /RGO composite 3D aerogel photocatalyst was fabricated by a facile self-assemble method. The aerogel composite with various RGO and g-C 3 N 4 to Cu 2 O weight ratios was synthesized and characterized. The results showed that the Cu 2 O/g-C 3 N 4 heterojunction absorbed visible light region shifted to a lower energy. In order to improved photocatalytic activity, the Cu 2 O/g-C 3 N 4 heterojunction loaded on reduced graphene oxide sheets resulted in increasing absorption in the visible light range and improving photodegradation activity. The optimal content of Cu 2 O in the Cu 2 O/g-C 3 N 4 /RGO aerogel was 40%, which exhibited the effectively synthetized Cu 2 O/g-C 3 N 4 heterojunction, and greatly improved photocatalytic activity. Moreover, the ternary composite aerogel exhibited 96% (Methylene Blue) and 83% (Methyl Orange) degradation efficiency within 80 min. The combined heterojunction with synergistic effects of this novel composite aerogel account for the excellent photocatalytic efficiency.

A low-ppm-level iron (Fe)-based photoinduced atom-transfer-radical polymerization (ATRP) under visible-light irradiation was developed. Various ligands, tris(4-methoxyphenyl)phosphine (TMPP), 4,4′-dinonyl-2,2′-dipyridyl (dNbpy), and tris[2-(dimethylamino)ethyl]amine (Me6TREN), were used to enhance the catalytic activity of Fe complexes. Activator FeII complexes were formed by the reduction of FeIII complexes with a monomer under visible-light irradiation. Linear semilogarithmic plots and low polydispersities (Mw/Mn dNbpy > Me6TREN. Additionally, this polymerization could be ceased and restarted, responding to light off and light on. Retention of the chain-end functionality was anal...

Photoinduced atom transfer radical polymerization with an Fe catalyst was successfully performed in aqueous media for the first time. Three water-soluble ligands [i.e., tetrabutylammonium bromide (TBABr), tris[2-(2-methoxyethoxy)ethyl]amine (TDA), and triphenylphosphine-3,3′,3′′-trisulfonic acid trisodium (TPPSA)] were screened for polymerization in aqueous media. Linear semilogarithmic plots, increasing molecular weights (Mn) with conversion, and low dispersity (Đ < 1.40) were achieved by using a new water-soluble phosphine ligand TPPSA, indicating a well-controlled polymerization. Subsequently, the polymerization kinetics of different catalyst concentrations and the targeted degree of polymerizations were investigated. The applicability of this system to the polymerization of different water-soluble monomers was examined. Furthermore, the polymerization can be regulated by switching the light on and off, which further confirmed its controlled and “living” nature. A successful experiment of chain extension suggested the retention of chain-end functionality. A study of the mechanism showed that the activator (FeIIX2/L) and the additional initiator were generated by the photochemical reduction of FeIIIX3/L in the presence of a monomer. This work provides an environmentally benign ATRP to synthesize well-defined water-soluble materials.

In this work, a photoinduced iron(III)-based atom transfer radical polymerization (ATRP) without any reducing agents and additional initiators was suggested. In addition, detailed kinetic studies, including the effects of ligand and catalyst concentrations on polymerization kinetics, and the polymerization behaviors using various solvents and monomer types were evaluated for this new polymerization technique. Results showed that photoinduced iron(III)-mediated ATRP using 5000 ppm catalyst loading with 1 equiv of ligand in N,N-dimethylformamide (DMF) produced poly(methyl methacrylate) with low molecular weight distribution (Mw/Mn < 1.45) and that the evolution of molecular weight (Mn) was linearly related to monomer conversion. 1H NMR analysis confirmed that the resulting polymer prepared through photoinduced ATRP in the present work was initiated by methyl 2,3-dichloroisobutyrate. Facile temporal control and the successful chain extension highlighted the good chain-end functionality of the resulting polym...

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.

An iron- and methyl methacrylate (MMA)-based electrochemically mediated atom transfer radical polymerization (eATRP) system was developed for the first time. Kinetic behaviors, including the effect of applied potential and catalyst loading, were systematically investigated. Results indicated that with more negative electrode potential, the polymerization rate increased until the mass transport limitation was reached. However, reduction of the catalyst loading had adverse effects on polymerization behaviors, such as decreased polymerization rate and increased molecular weight distributions (Mw/Mn). In addition, a kinetic model based on the method of moments was also constructed to explain the mismatch in Mn and Mn,theo. Simulation results showed that slow initiation significantly influenced on the kinetic behaviors in this system. Iron(II) bromide-catalyzed normal ATRP, iron(III) bromide-catalyzed eATRP, and copper(II) bromide-catalyzed eATRP were conducted to compare and elucidate their respective polymer...

Aims Iron plaques can prevent the uptake of heavy metals on the root surface of wetland plants. The Fe and Mn oxides produced by microorganisms are major Fe/Mn-oxidizing agents in the environment. This study is the first to investigate the influence of Fe/Mn-oxidizing bacteria on Fe/Mn plaque formation and the uptake of Cd and As on rice tissues.

A detailed kinetic model was constructed using the method of moments to elucidate the electrochemically mediated atom transfer radical polymerization (eATRP). Combined with electrochemical theory, the reducing rate coefficient relevant to the overpotential in eATRP was coupled into the kinetic model. The rate coefficients for eATRP equilibrium and the reducing rate coefficient were fitted to match the experimental data. The effects of catalyst loading, overpotential, and application of programmable electrolysis on the eATRP behavior were investigated based on the tested kinetic model. Results showed that the apparent polymerization rate exhibited a square root dependence on catalyst loading. In addition, a more negative potential accelerated the polymerization rate before the mass transport limitation was reached. This phenomenon indicated that the polymerization rate could be artificially controlled by the designed program (i.e., stepwise and intermittent electrolysis programs). What is more, the normal ATRP, photo-ATRP, and eATRP were compared to obtain a deeper understanding of these ATRP systems. © 2015 American Institute of Chemical Engineers AIChE J, 61: 4347–4357, 2015

Among MOFs, the Fe-based ones (such as MIL-53(Fe)) show impressive visible light response due to the extensive presence of Fe-O clusters, but their photo-activities are often restrained by severe recombination of electron-hole pairs. To circumvent this limitation, we developed an in-situ etching-and-regrowth strategy for the fabrication of heterojunctions. Through the partial destruction of the external surface of a 3D MIL-53(Fe) bipyramid, we generated bismuth ferrite (BFO) nanosheets on its surface. The rough surface of the as-fabricated composite is beneficial for light absorption as well as enlargement of specific surface area and exposure of active sites. Furthermore, the interfaces between MIL-53(Fe) and BFO accelerate the separation and transfer of charge carriers owing to the co-presence of Fe O bonds in both components. The obtained composites show outstanding catalytic activity as well as excellent stability for the selective oxidation of benzyl alcohols to the corresponding aldehydes under visible light irradiation.

Herein, we report the use of cobalt sulfide (CoS2) as efficient and inexpensive co-catalyst of CdS nanorods for photocatalytic water splitting. The aim is to explore the use of earth-abundant cobalt species to replace precious metals for the photocatalytic reactions. The results of first-principles DFT simulation and planar-averaged differential charge density calculation reveal that at the CoS2/CdS interface, CoS2 has zero band gap which is a class nature of precious metals, and functions as electron trap to enhance the transfer of hot electrons from CdS to CoS2. Owing to the merits of efficient charge separation, high exposure of active sites as well as large surface area, the CoS2/CdS composites exhibit outstanding photocatalytic activity in H2 production under visible light (˜58 mmol·g−1 h−1), which is about 19 times that of CdS nanorods alone and 3 times that of 1 wt%Pt/CdS under the same conditions.

Different distributed residual stresses were introduced by quenching and two shot-peening treatments on 7075 aluminum alloy. The residual stress distributions and micro-hardness profiles in surface layers were measured. Pre-stress coefficient characterizing contribution of local residual stresses to local yield strength is introduced to analyze residual stress relaxation under cyclic loading. Load testing shows that re-distribution of residual stresses and proportional decrease of the pre-stress coefficient would occur in the non-uniform structural residual stresses introduced by quenching, while great stress relaxation and non-linear decrease of the pre-stress coefficient would occur in the uniform surface residual stresses introduced by shot-peening. Additionally, advantages of surface compressive residual stress and micro yield strength on anti-fatigue property and on restraining initiation and propagation of surface micro cracks should be considered in the usually conservative engineering design.

There is a remarkable difference in stress distribution between a specimen and a plate removed from the specimen. The plate presents a uniform stress distribution whereas the specimen presents a non-uniform stress distribution. Firstly, the real stress distributions in plates with thickness of 30, 40 and 50 mm and then in the specimens were obtained through simulation and X-ray surface stress measurement. Secondly, in order to study the impact of specimens shapes and processing ways on the results accuracy, two irregular shapes (parallelogram and trapezoid) and two processing ways (saw and electron discharge machining (EDM)) were compared and analyzed by simulation and experiment using layer removal method, then the specimen effects on measurement results were evaluated. The results show that: 1) the non-uniform stress distribution characteristics of the specimen near the surface of the cut is significant, the range of non-uniform stress distribution is approximately one-thickness distance away from the cut, and it decreases gradually along the depth; 2) In order to ensure the stability in the results, it is suitable to take the specimen plane size 2-3 times of its thickness; 3) Conventional processing methods have little effect on experimental results and the average deviation is less than 5%.

A comprehensive kinetic model based on the method of moments is developed for understanding the kinetics of activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP) under microwave irradiation. Both the experimental data and the simulation results show that the polymerization under microwave irradiation is much faster than the thermal polymerization. Simulation results indicate that the acceleration of polymerization can be attributed to the increase of propagation rate coefficient and the radical generation by microwave irradiation. Kinetic behaviors, such as the effect of catalyst concentration and initial initiator, are investigated in detail. Results show that the catalyst concentration has negligible influence on polymerization rate while the initiator concentration can affect both the molecular weight and the reaction rate. In conclusion, this work thoroughly investigates the kinetic mechanism of ARGET ATRP under microwave irradiation, providing both theoretic and experimental supports to improve the product property of polymer materials.

A metal-resistant and phosphate-solubilising bacterium, designated as strain D414(T), was isolated from heavy metal (Pb, Cd, Cu and Zn)-polluted paddy soils at the surrounding area of Dabao Mountain Mine in Southeast China. The minimum inhibitory concentrations of heavy metals for strain D414(T) were 2000 mg L(-1) (Cd), 800 mg L(-1) (Pb), 150 mg L(-1) (Cu) and 2500 mg L(-1) (Zn). The strain possessed plant growth-promoting properties, such as 1-aminocyclopropane-1-carboxylate assimilation, indole production and phosphate solubilisation. Analysis of 16S rRNA gene sequence indicated that the isolate is a member of the genus Burkholderia where strain D414(T) formed a distinct phyletic line with validly described Burkholderia species. Strain D414(T) is closely related to Burkholderia tropica DSM 15359(T), B. bannensis NBRC E25(T) and B. unamae DSM 17197(T), with 98.5, 98.3 and 98.3 % sequence similarities, respectively. Furthermore, less than 34 % DNA-DNA relatedness was detected between strain D414(T) and the type strains of the phylogenetically closest species of Burkholderia. The dominant fatty acids of strain D414(T) were C14:0, C16:0, C17:0 cyclo and C18:1 ω7c. The DNA G+C content was 62.3 ± 0.5 mol%. On the basis of genotypic, phenotypic and phylogenetic data, strain D414(T) represents a novel species, for which the name Burkholderia metalliresistens sp. nov. is proposed, with D414(T) (=CICC 10561(T) = DSM 26823(T)) as the type strain.

The taxonomic position of an actinomycete isolated from a lead-polluted soil in Gansu province, north-west China, was determined by using a polyphasic approach. Chemical and morphological properties of the isolate, designated strain CCNWHX 13-160(T), were similar to those of streptomycetes. Analysis of the almost complete 16S rRNA gene sequence placed strain CCNWHX 13-160(T) in the genus Streptomyces where it formed a distinct phyletic line with recognized Streptomyces species. The strain was most similar to Streptomyces pseudovenezuelae NBRC 12904(T) (98.9 %) and Streptomyces resistomycificus NBRC 12814(T) (98.8 %). Furthermore, DNA-DNA hybridization studies between the novel isolate and these two strains showed relatedness values of 49.7+/-0.8 and 43.2+/-1.1 %, respectively. It is proposed that strain CCNWHX 13-160(T) (=ACCC 41207(T)=HAMBI 2991(T)) be classified as the type strain of a novel species in the genus Streptomyces, Streptomyces plumbiresistens sp. nov. The MIC of Pb(2+) for growth of strain CCNWHX 13-160(T) was 4.0 mM.