Photocatalytic Reaction Mechanism Research Articles

Advances and challenges of photocatalytic technology for air purification

<p indent="0mm">With the acceleration of the urban industrialization process, air pollutant emission has increased sharply, which seriously endangers the ecological environment and human beings. Solar-driven photocatalysis has the broad-spectrum activity for various inorganic to organic pollutants at ambient temperature without harsh reaction conditions, which shows a very broad application prospect in air purification. However, the photocatalysis technology suffers from the unrevealed reaction mechanism and the deactivation of photocatalysts, which severely limits its practical application. Currently, there is still a huge gap between basic research and industrial application in the field of photocatalytic air purification. This review summarizes recent progress on photocatalytic degradation of air pollutants and categorizes them based on the types of photocatalytic materials and air pollutants, with a focus on photocatalytic reaction mechanisms and the application scenarios of photocatalytic air purification to identify this gap. We also critically discussed the major challenges for promoting applications of photocatalytic technology and put forward the development prospect.

Construction of ternary multifunctional Fe3O4/Cu2O/Au nanocomposites: SERS detection and visible light driven photocatalysis for organic dyes

The multifunctional ternary magnetic core/semiconductor/noble-metal nanocomposites have received considerable concerns because they can realize the integration of photocatalytic degradation, surface-enhanced Raman scattering (SERS) detection and magnetic separation to target organic waste water. Herein, the Fe 3 O 4 /Cu 2 O/Au nanocomposites were prepared through wet-chemical and in-situ reduction reactions. The influence of content of Au nanocrystals immobilized on the surfaces of Fe 3 O 4 /Cu 2 O on the photocatalytic and SERS performance of Fe 3 O 4 /Cu 2 O/Au nanocomposites was investigated. Photoluminescence (PL) results showed that Fe 3 O 4 /Cu 2 O/Au nanocomposites possessed higher photocurrent response compared with Fe 3 O 4 /Cu 2 O nanocomposites. And Fe 3 O 4 /Cu 2 O/Au nanocomposites exhibited stronger absorption of visible light owing to the localized surface plasmon resonance (LSPR) effect of Au nanocrystals. Methylene blue (MB) and malachite green (MG) were chosen as the photocatalytic degradation and detection targets to verify photocatalytic property and SERS characteristic of Fe 3 O 4 /Cu 2 O/Au nanocomposites. Results indicated that the photocatalytic efficiency and SERS signal intensity of Fe 3 O 4 /Cu 2 O/Au nanocomposites were improved significantly along with the increase of Au contents. The universal applicability of Fe 3 O 4 /Cu 2 O/Au nanocomposites was also evaluated by detecting SERS signals of residue of MB in fish. Our work offers exciting opportunities to acquire the multifunctional material for SERS trace detection and photocatalytic elimination to organic pollutants and will have more hopeful prospects in efficient catalytic and highly sensitive detection applications. • Fe 3 O 4 /Cu 2 O/Au nanocomposites (NCs) were prepared by wet chemistry reaction process. • Effect of Au content on catalytic activity of Fe 3 O 4 /Cu 2 O/Au NCs was studied. • Mechanism of photocatalytic reaction of dyes by Fe 3 O 4 /Cu 2 O/Au NCs was investigated. • Fe 3 O 4 /Cu 2 O/Au NCs achieved integration of photocatalysis and SERS detection. • Limit of detection of Fe 3 O 4 /Cu 2 O/Au NCs for MB and MG was as low as 10 −11 M.

Selective Photocatalytic Dehydrogenation of Formic Acid by an In Situ-Restructured Copper-Postmetalated Metal-Organic Framework under Visible Light.

Formic acid is considered as one of the most promising liquid organic hydrogen carriers. Its catalytic dehydrogenation process generally suffers from low activity, low reaction selectivity, low stability of the catalysts, and/or the use of noble-metal-based catalysts. Herein we report a highly selective, efficient, and noble-metal-free photocatalyst for the dehydrogenation of formic acid. This catalyst, UiO-66(COOH)2-Cu, is built by postmetalation of a carboxylic-functionalized Zr-MOF with copper. The visible-light-driven photocatalytic dehydrogenation process through the release of hydrogen and carbon dioxide has been monitored in real-time viaoperando Fourier transform infrared spectroscopy, which revealed almost 100% selectivity with high stability (over 3 days) and a conversion yield exceeding 60% (around 5 mmol·gcat–1·h–1) under ambient conditions. These performance indicators make UiO-66(COOH)2-Cu among the top photocatalysts for formic acid dehydrogenation. Interestingly, the as-prepared UiO-66(COOH)2-Cu hetero-nanostructure was found to be moderately active under solar irradiation during an induction phase, whereupon it undergoes an in-situ restructuring process through intraframework cross-linking with the formation of the anhydride analogue structure UiO-66(COO)2-Cu and nanoclustering of highly active and stable copper sites, as evidenced by the operando studies coupled with steady-state isotopic transient kinetic experiments, transmission electron microscopy and X-ray photoelectron spectroscopy analyses, and Density Functional Theory calculations. Beyond revealing outstanding catalytic performance for UiO-66(COO)2-Cu, this work delivers an in-depth understanding of the photocatalytic reaction mechanism, which involves evolutive behavior of the postmetalated copper as well as the MOF framework over the reaction. These key findings pave the way toward the engineering of new and efficient catalysts for photocatalytic dehydrogenation of formic acid.

Outlook on bismuth-based photocatalysts for environmental applications: A specific emphasis on Z-scheme mechanisms.

Semiconductor photocatalysis is thought to be a viable solution for addressing the growing problem of environmental pollution. Bismuth (Bi) metal oxides can function as a direct plasmonic photocatalyst or cocatalyst to accelerate the photogenerated charge separation and thus improve their photocatalytic activity. Hence, Bi-based photocatalysts have received a lot of attention due to their extensive environmental applications, including pollutant remediation and energy concepts. Massive efforts have been undertaken in the recent decade to find superior Bi-metal oxides (Bi2XO6, X=MO, W, or Cr) and to uncover the corresponding photocatalytic reaction mechanism for the degradation of organic contaminants in water. Herein, the unique crystalline and electronic properties and main synthesis methods, as well as the major Bi-Based direct Z-scheme photocatalysts, are timely discussed and summarized in their usage in water treatment. Besides, the impact of Bi2XO6 in energy storage devices and solar energy conversion is reviewed as an energy application. Finally, the future development and challenges of Z-scheme-based Bi2XO6 photocatalysts are briefly explored, summarized, and forecasted.

Variable Temperature LED-NMR: Rapid Insights into a Photocatalytic Mechanism from Reaction Progress Kinetic Analysis.

A multitude of techniques are available to obtain a useful understanding of photocatalytic mechanisms. The combination of LED illumination with nuclear magnetic resonance spectroscopy (LED-NMR) provides a rapid, convenient means to directly monitor a photocatalytic reaction in situ. Herein, we describe a study of the mechanism of an enantioselective intermolecular [2 + 2] photocycloaddition catalyzed by a chiral Ir photocatalyst using LED-NMR. The data-rich output of this experiment is suitable for same-excess and variable time normalization analyses (VTNA). Together, these identified an unexpected change in mechanism between reactions conducted at ambient and cryogenic temperatures. At -78 °C, the kinetic data are consistent with the triplet rebound mechanism we previously proposed for this reaction, involving sensitization of maleimide and rapid reaction with a hydrogen-bound quinoline within the solvent cage. At room temperature, the cycloaddition instead proceeds through intracomplex energy transfer to the hydrogen-bound quinolone. These results highlight the potential sensitivity of photocatalytic reaction mechanisms to the precise reaction conditions and the further utility of LED-NMR as a fast, data-rich tool for their interrogation that compares favorably to conventional ex situ kinetic analyses.

Fabrication of MoS2/CdIn2S4 Z-scheme heterojunctions with fast interface electronic transfer for highly efficient photocatalytic degradations of multiple organic pollutants

In this work, a novel Z-scheme MoS2/CdIn2S4 (MS-CIS) face-to-face heterostructure with excellent photocatalytic activities for multiple organic pollutant degradation was designed and constructed by a green mild in-situ hydrothermal method, where CdIn2S4 nano-octahedra coated on the surfaces of ultra-thin MoS2 nanosheets to form a face-to-face interface contact. The photocatalytic performance was systematically evaluated by the degradation of Oxytetracycline (OTC) under simulated visible light condition. Compared to MoS2 and CdIn2S4, the as-obtained MS-CIS-3 sample showed significantly improved photocatalytic activities toward OTC degradation, and the rate constant of MS-CIS-3 was 1.29959 h−1, which was 2.31 and 34.16 times those of CdIn2S4 (0.56303 h−1) and MoS2 (0.03804 h−1). The reason for the improvement in photocatalytic performance was that the MS-CIS heterostructure possessed a larger face-to-face contact area which could provide more charge transfer nanochannels, effectively shorten the photogenerated electron transport path and increase the electron-hole separation efficiency. In addition, the possible reaction routes of OTC and the photocatalytic reaction mechanism of MS-CIS sample were also discussed in detail. Furthermore, the MS-CIS-3 heterostructure with excellent photostability and repeatability also possessed outstanding degradation activities for both tetracycline hydrochloride (TCH) and 2-Mercaptobenzothiazole (MBT). This work may provide a promising strategy to synthesize other Z-scheme face-to-face heterostructure photocatalysts with highly efficient photocatalytic activity to solve environmental pollution.

Facile fabrication of sulfuretted NiFe-layered double hydroxides/oxalic acid induced g-C3N4 Z-scheme heterojunction for enhanced photocatalytic removal of tetracycline and Cr(Ⅵ) under visible light irradiation

Novel sulfuretted NiFe-layered double hydroxides/oxalic acid induced g-C3N4 (NFS/OCN) heterostructures have been fabricated via a simple method and studied as photocatalysts for removal of tetracycline (TC) and Cr(Ⅵ) under visible light irradiation. Several advanced characterizations (XRD, SEM, TEM, XPS, PL, UV-Vis DRS, PL, etc.) were applied to identify its structure information of the as-obtained catalysts concerning the generation of the NFS sample, the presence of the heterojunction between NFS and OCN as well as triumphant incorporation of O into the structure of CN. In detailed, the photocatalytic removal efficiencies towards TC and Cr(Ⅵ) were 85.88 % and 93.69 % under the optimal conditions, which was ascribed to the enhanced light-harvesting ability, well transfer and separation efficiency of photo-generated carriers through the unique Z-scheme heterojunction structure. At last, the possible photocatalytic reaction mechanism is proposed.

Photo-induced absorption spectroscopy (PIAS) study of the kinetics of water oxidation by P25 TiO2 using periodate as an electron acceptor

Photoinduced absorption spectroscopy, PIAS, coupled with the measurement of dissolved O2, % O2, is used to probe the kinetics of water oxidation by periodate, photocatalysed by a P25 TiO2 film on glass. The rate of the photocatalysed oxidation of water by periodate, rO2, depends upon ρ0.9, where ρ is the UV irradiance. In contrast, PIAS reveals the steady-state change in the absorbance of the film, ΔAbsSS, is proportional to ρ0.22, where ΔAbsSS is a direct measure of the steady-state concentration of photogenerated holes on the surface of the photocatalyst particles, [h+]SS. The combination of this data reveals rO2 is proportional to [h+]SS4, which is rationalised in terms of an electrochemical oxide path reaction mechanism with the combination of two surface adsorbed O atoms as the rate determining step. The potential of PIAS to provide an invaluable direct insight into the mechanism of photocatalytic reactions by powders is discussed briefly.

Facile synthesis of CaWO4 nanoparticles incorporated on porous carbons with improved photocatalytic degradation of tetracycline

The construction of an efficient and recyclable photocatalyst for the degradation of antibiotics is still a challenge. In this work, we successfully synthesized porous carbon-supported CaWO4 nanoparticles (CaWO4 @C) by solidifying sodium alginate (SA) mixed with Na2WO4 by Ca2+ ions and subsequent high-temperature carbonization. The introduction of porous carbon significantly reduced the size of CaWO4 particles, increased the specific surface area for mass transport, and improved visible light utilization. The influence factors of photocatalytic activity were extensively explored through photocatalytic degradation of tetracycline (TC). As a result, the optimized CaWO4 @C exhibited excellent photocatalytic performance with the TC degradation rate of 94.56% after 60-min visible light irradiation. The TC photodegradation rate constant was calculated to be 0.051 min−1, which was 30.19-time higher than the pristine CaWO4. Besides, the photocatalytic reaction mechanism for degradation of TC was revealed in terms of free radical trapping experiments and electron spin resonance (ESR) techniques.

Machine Learning for Electrocatalyst and Photocatalyst Design and Discovery

Electrocatalysts and photocatalysts are key to a sustainable future, generating clean fuels, reducing the impact of global warming, and providing solutions to environmental pollution. Improved processes for catalyst design and a better understanding of electro/photocatalytic processes are essential for improving catalyst effectiveness. Recent advances in data science and artificial intelligence have great potential to accelerate electrocatalysis and photocatalysis research, particularly the rapid exploration of large materials chemistry spaces through machine learning. Here a comprehensive introduction to, and critical review of, machine learning techniques used in electrocatalysis and photocatalysis research are provided. Sources of electro/photocatalyst data and current approaches to representing these materials by mathematical features are described, the most commonly used machine learning methods summarized, and the quality and utility of electro/photocatalyst models evaluated. Illustrations of how machine learning models are applied to novel electro/photocatalyst discovery and used to elucidate electrocatalytic or photocatalytic reaction mechanisms are provided. The review offers a guide for materials scientists on the selection of machine learning methods for electrocatalysis and photocatalysis research. The application of machine learning to catalysis science represents a paradigm shift in the way advanced, next-generation catalysts will be designed and synthesized.

Magnetic cobalt ferrite/reduced graphene oxide (CF/rGO) porous balls for efficient photocatalytic degradation of oxytetracycline

Photocatalytic degradation is an effective technique for removing antibiotics from contaminated water. The kernel of photocatalytic degradation lies in the design and preparation of high-performance and recyclable catalysts. Herein, magnetic porous cobalt ferrite/reduced graphene oxide (CF/rGO) balls were prepared by calcination of spherical composites obtained via modified microfluidic method for effective photocatalytic degradation of oxytetracycline (OTC). The strong interfacial interaction between rGO and cobalt ferrite nanoparticles in porous balls enhanced electron transfer, charge separation and light absorption. Porous spherical structure was favorable for light harvesting. The catalyst could rapidly and efficiently absorb OTC. These characteristics were beneficial to the enhancement of photocatalytic efficiency. The optimized sample (CF/rGO-0.2) exhibited an excellent apparent rate constant (0.0410 min−1) for OTC degradation under visible light irradiation, which was 3.73 times that of CF/rGO-0 (0.0110 min−1). CF/rGO-0.2 had excellent stability in cycle experiments and could be quickly recovered by magnets. The trapping experiments showed that hole (h+) and superoxide radicals (·O2-) acted an extremely important role in degradation of OTC, thus suggesting a possible photocatalytic reaction mechanism. This work provides a potential photocatalyst for antibiotic removal from water.

In-situ construction of Bi2S3/Bi2MoO6 hollow microsphere with regulable oxygen vacancies for full-spectrum photocatalytic performance

Novel Bi2S3/Bi2MoO6 hollow microsphere composites with oxygen vacancies were successfully synthesized through in-situ anion exchange and hydrothermal method. After introducing sulfur into the Bi2MoO6 substrate with oxygen vacancies, Bi2S3 was close distributed on the surface of the Bi2MoO6 hollow microsphere to form Bi2S3/Bi2MoO6 heterojunctions and led to inducing the more oxygen vacancies. Compared to pristine Bi2MoO6 and Bi2S3, the Bi2S3/Bi2MoO6-0.03 exhibited higher photocatalytic efficiency toward Rhodamine B (RB) degradation under the full-spectrum (visible and near-infrared) light illumination. Meanwhile, it showed high near-infrared photocatalytic activity for antibiotics. The enhanced catalytic performance was attributed to the synergetic effect of heterojunction and the oxygen vacancies between Bi2MoO6 and Bi2S3. Meanwhile, the active species were carefully investigated by the active species capture tests and the electron spin resonance technique. Finally, the reasons for the improved photocatalytic performance and reaction mechanism were also uncovered in detail, and degradation products obtained by N-de-ethylation by the cleavage of CN of RB were demonstrated. The findings in this work provide insight into the potential applications in treating wastewater.

Direct Z-scheme heterojunction rutile-TiO2/g-C3N4 catalyst constructed by solid grinding method for photocatalysis degradation

Schematic illustration of RhB photocatalytic reaction mechanism over the rutile-TiO 2 /g-C 3 N 4 photocatalyst. • The rutile-TiO 2 /g-C 3 N 4 photocatalyst is constructed by a simple solid grinding method. • The optimized rutile-TiO 2 /g-C 3 N 4 photocatalyst has more excellent photocatalytic performance than the pure rutile-TiO 2 and g-C 3 N 4 . • The direct Z-scheme heterojunction mechanism is proposed over the rutile-TiO 2 /g-C 3 N 4 photocatalyst. Constructing a direct Z-scheme heterojunction is an effective method to improve the catalytic performance of photocatalyst. Here, the direct Z-scheme heterojunction rutile-TiO 2 /g-C 3 N 4 photocatalyst was constructed by a simple solid grinding method. This method can not only avoid the weak activity of rutile-TiO 2 in high synthesized temperature condition, but also precisely control the amount of g-C 3 N 4 . The evaluation of photodegradation reaction suggests that the rutile-TiO 2 /g-C 3 N 4 photocatalyst exhibits higher photodegradation efficiency than the pure rutile-TiO 2 and the pure g-C 3 N 4 under simulated sunlight irradiation, and the optimal photocatalytic performance is achieved when the mass ratio of rutile-TiO 2 to g-C 3 N 4 is 2:5. The experimental results prove that a direct Z-scheme heterojunction is formed over the rutile-TiO 2 /g-C 3 N 4 photocatalyst, which promotes the effective electron-hole separation and the higher redox potential over the rutile-TiO 2 /g-C 3 N 4 photocatalyst. This work provides an attractive strategy to construct the direct Z-scheme photocatalyst consisted of rutile-TiO 2 and g-C 3 N 4 .

Facile sonochemical preparation of La2Cu2O5 nanostructures, characterization, the evaluation of performance, mechanism, and kinetics of photocatalytic reactions for the removal of toxic pollutants

Designing and simulating an effective photocatalytic material having a suitable bandgap to degrade organic pollutants is essential for environmental remediation. This paper describes the development of a class of nanostructure, La2Cu2O5, for photocatalytic decomposition of various types of organic pollutants under UV and visible lights. La2Cu2O5 nanostructures were synthesized by a rapid and environmentally friendly sonochemical technique for the first time. The impacts of molar ratio of precursors, calcination temperature, power, and time of sonication were scrutinized for the synthesis of La2Cu2O5 nanostructures with relevant attributes in terms of purity, particle size, and morphology. The bandgap of these nanostructures was calculated at 3.25 eV, making them profitable for contaminant degradation in the UV region. The photocatalytic activity of the desired La2Cu2O5 was examined for photodegradation of multiple pollutants, such as thymol blue, acid black, methyl violet, rhodamine B, phenol red, malachite green, acid Yellow, and erythrosine for the first time. The La2Cu2O5 nanocatalyst revealed premium performance over the degradation of the mentioned pollutants. La2Cu2O5 was capable of degrading the acid black contaminant better (80.1%). The highest photocatalytic efficiency was obtained at a greater rate constant reaction (k = 0.01332 min−1).

Fabrication of CsPbBr3 nanocrystals/Bi2MoO6 nanosheets composites with S-scheme heterojunction for enhanced photodegradation of organic pollutants under visible light irradiation

Semiconductor photocatalysts can eliminate environmental pollution, especially water pollution. In this study, novel CsPbBr3 nanocrystals/Bi2MoO6 nanosheet composites were successfully fabricated via hydrothermal method together with electrostatic self-assemble process. The formation of S-scheme heterojunction, migration of photogenerated carriers and photocatalytic reaction mechanism were elaborated by means of density functional theory (DFT) calculation, In-situ irradiated X-ray photoelectron spectroscopy (XPS) and other characterization techniques. This scheme not only solved the problem of poor photogenerated carrier migration and separation efficiency of Bi2MoO6 based photocatalyst, but also broadened the photo-response range. For the emerging photocatalyst CsPbBr3, the surface morphology of the synthesized composite was also conducive to improve its’ chemical stability. Compared to other specimens, the CsPbBr3/Bi2MoO6 5 wt% (BC5%) composite sample showed the optimal photocatalytic activity and the Rhodamine B (RhB) degradation over it attained 95.8% under visible light irradiation for 90 mins. Additionally, the degradation performances of RhB in different solution environments such as catalyst dosage, pollution concentration, pH, and reaction temperature were thoroughly investigated. Especially, the photocatalytic activity of BC5% composite sample was also evaluated via biotoxicity experiments. This work would provide a successful experience for devising and realizing highly efficient photocatalysts in the future.

Hollow Nanospheres Organized by Ultra-Small CuFe2O4/C Subunits with Efficient Photo-Fenton-like Performance for Antibiotic Degradation and Cr(VI) Reduction

Hollow transition metal oxides have important applications in the degradation of organic pollutants by a photo-Fenton-like process. Herein, uniform, highly dispersible hollow CuFe2O4/C nanospheres (denoted as CFO/C-PNSs) were prepared by a one-pot approach. Scanning electron microscope (SEM) and transmission electron microscope (TEM) images verified that the CFO/C-PNS catalyst mainly presents hollow nanosphere morphology with a diameter of 250 ± 30 nm. Surprisingly, the photodegradation test results revealed that CFO/C-PNSs had an excellent photocatalytic performance in the elimination of various organic contaminants under visible light through the efficient Fenton catalytic process. Due to the unique hollow structure formed by the assembly of ultra-small CFO/C subunits, the catalyst exposes more reaction sites, improving its photocatalytic activity. More importantly, the resulting magnetically separable CFO/C-PNSs exhibited excellent stability. Finally, the possible photocatalytic reaction mechanism of the CFO/C-PNSs was proposed, which enables us to have a clearer understanding of the photo-Fenton mechanism. Through a series of characterization and analysis of degradation behavior of CFO/C-PNS samples over antibiotic degradation and Cr(VI) reduction, •OH radicals generated from H2O2 decomposition played an essential role in enhancing the reaction efficiency. The present work offered a convenient method to fabricate hollow transition metal oxides, which provided impetus for further development in environmental and energy applications. Highlights: Novel hollow CuFe2O4/C nanospheres were prepared by a facile and cost-effective method. CuFe2O4/C exhibited excellent photo-Fenton-like performance for antibiotic degradation. Outstanding photocatalytic performance was attributed to the specific hollow cavity-porous structure. A possible mechanism for H2O2 activation over hollow CuFe2O4/C nanospheres was detailed and discussed.

Photocatalytic Methane Conversion: Insight into the Mechanism of C(sp 3 )–H Bond Activation

Photocatalytic Methane Conversion: Insight into the Mechanism of C(sp ³ )–H Bond Activation

Excellent photocatalytic performance and dual-band degradation of organic pollutants through Z-scheme photocatalysts

Organic pollutants, particularly nitrogen-rich explosives and carbon-rich dyes are generally degraded by different photocatalysts under either visible or ultraviolet light, leading to substantial waste and cost. Three photocatalysts with Z-scheme structures, Ag@AgBr/Cu2O-1, Ag@AgBr/Cu2O-2, and Ag@AgBr/Cu2O-3, are designed and synthesized employing a simple solvothermal and photoreduction technique to develop advanced photocatalyst materials that can degrade nitro substances under ultraviolet (UV) irradiation and organic dyes under visible-light irradiation. The structural characterization of Ag@AgBr/Cu2O-2 as determined through various spectroscopic techniques (e.g. XPS, XRD and TEM) reveal that the Z-scheme photocatalysts are composed of Ag, Cu2O and AgBr nanospheres with particle size less than 100 ​nm, while nano-Ag and nano-AgBr coupled to the surface of the Cu2O microspheres. Further investigations demonstrate that these photocatalysts exhibit a good UV–visible absorption range (200–800 ​nm) and outstanding photocatalytic degradation activity for two typical organic pollutants. Among them, Ag@AgBr/Cu2O-2 achieve a 100% degradation of trinitrotoluene (a common explosive) in 30 ​min under UV radiation, and a 99.2% degradation of rhodamine B (a typical dye) in 60 ​min under visible-light irradiation in the absence of UV light, demonstrating remarkable dual-band adaptability. Moreover, Ag@AgBr/Cu2O-2 displays superior stability, with a degradation rate of up to 85% after four cycles. The putative photocatalytic reaction mechanism is proposed based on the radical trapping experiment.

Multi-functional well-dispersed pomegranate-like nanospheres organized by ultrafine ZnFe2O4 nanocrystals for high-efficiency visible-light-Fenton catalytic activities

The Photo-Fenton-like reaction has gained widespread attention, as an effective method in wastewater treatment. Herein, uniformly highly dispersible pomegranate-like ZnFe2O4 nanospheres (ZFO-PNSs) was prepared through a novel, facile, straightforward and general approach. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images are employed to verify that ZFO-PNSs mainly presents pomegranate-like nanospheres morphology with diameter of 210 ± 20 nm in size. Interestingly, the results of photodegradation test indicated that ZFO-PNSs was an excellent photo-Fenton catalyst which could degraded the oxytetracycline, norfloxacin, tetracycline, rhodamine B, methyl orange and Cr(Ⅵ) in solution under visible light irradiation. The unusual structure, which consists of ultra-small ZFO, is responsible for the excellent photocatalytic activity. Furthermore, the reaction parameters influenced the degradation performance was investigated, such as the calcination temperature, the catalyst dosage, the pH of solution and H2O2 volume used. The probable photocatalytic degradation pathways of OTC were analyzed by LC-MS. Finally, the possible photocatalytic reaction mechanism of ZFO-PNSs were tentatively proposed, which may help with the further understanding of the photo-Fenton mechanism. This work affords a novel and simple method to construct pomegranate-like transition metal oxides nanostructures, which provides impetus for further development in environmental and energy applications.

Hierarchical Sb2S3/ZnIn2S4 core–shell heterostructure for highly efficient photocatalytic hydrogen production and pollutant degradation

In this work, a novel hierarchical 1D/2D core/shell Sb2S3-ZnIn2S4 (SB-ZIS) heterostructure with highly efficient photocatalytic activities for both hydrogen production from water and organic pollutant degradation was designed and fabricated via a simple one-step hydrothermal method. The as-prepared SB-ZIS heterostructure, where ZnIn2S4 nanosheets uniformly grew onto Sb2S3 nanorod to form a tight and large intimate contacted interface, was conducive to improve the absorption capacity of light, increase the surface area, shorten the distance of electronic transmission channels and accelerate the separation and migration of photogenerated carriers. As a result, the presented SB-ZIS composites demonstrated significantly enhanced photocatalytic performances for H2 generation and Tetracycline Hydrochloride (TCH) photodegradation. The photocatalytic H2 production rate of optimal SB-ZIS-2 sample (1685.14 μmol·g−1·h−1) was about 12.24 times as large as that of pure ZnIn2S4 (137.63 μmol·g−1·h−1). The apparent quantum efficiency (AQE) at 420 nm was up to 3.8%. In addition, the highest rate constant for TCH removal (0.514 h−1) was 20.3 and 2.89 times larger than those of pure Sb2S3 and Znln2S4, respectively. The possible reaction routes of TCH and the photocatalytic reaction mechanism of SB-ZIS sample were also discussed in detail. This work will provide some useful information for the development of dual-functional Sb2S3-based type I core–shell heterostructure with an efficient photocatalytic activity for solving environmental pollution and producing clean hydrogen energy.