Excellent Photocatalytic Activity Research Articles

Photocatalytic colorimetry and fluorescence dual-signal biosensor for instant determination of terminal deoxynucleotidyl transferase

Terminal deoxynucleotidyl transferase (TdT) is a crucial biomarker for diseases such as lymphoblastic leukemia. Herein, a photocatalytic colorimetry and fluorescence dual-signal biosensor (PhoCoF-sensor) for simple, low-cost and sensitive detection of TdT was developed, which integrated with the TdT-triggered polymerization reaction and the fluorescence-photocatalytic dual performance of double-strand DNA/SYBR Green-I (dsDNA/SG-I) complex. The target TdT catalyzed the elongation of single-stranded DNA in the dTTP substrate pool, and then hybridized with complementary DNA to form dsDNA/SG-I complex that exhibited obvious fluorescent and excellent photocatalytic activity. Reactive oxygen species were generated from photosensitization of the dsDNA/SG-I complex acted as the visual colorimetric readout. The PhoCoF-sensor was successfully used to detect TdT activity with a series of color and fluorescence changes in the concentration range from 0.5 U/mL to 20.0 U/mL. The PhoCoF-sensor further improves the assay simplicity and accuracy and reduces the time and cost, which overcomes the limitations of traditional detection TdT methods and single-signal sensors. Additionally, this PhoCoF-sensor can readily be integrated with centrifugal microfluidic device for one-step test and achieve quantitative determination without sophisticated instruments. Moreover, the PhoCoF-sensor has good sensitivity and good practical reliability and is suitable for instant determination in early disease diagnosis and drug discovery.

Layered double hydroxide (LDH)-derived zinc oxide (ZnO) nanorod on exfoliated graphene oxide (GO) nanosheet for photocatalytic dye degradation and hexavalent chromium reduction

A new low-temperature facile chemical decomposition of layered double hydroxide (LDH) has been developed for the large-scale controlled synthesis of zinc oxide (ZnO) nanorod on exfoliated graphene oxide (GO) nanosheet. ZnAl-LDH/GO composite precursor was prepared via in situ growth of the LDH on the exfoliated GO nanosheets. Thermo-chemical decomposition of ZnAl-LDH/GO composite at 80 °C produced highly dispersed ZnO nanorods on GO nanosheets. Although, neat ZnAl-LDH produces ZnO nanoparticle aggregates in the absence of GO. The morphology and properties of ZnO nanorods/GO nanocomposite was studied by X-ray diffraction analysis (XRD), transmission electron microscopy (TEM), UV–vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). The band gap engineering of the nanocomposite was evaluated by varying GO content. The ZnO/GO nanocomposites materials exhibited excellent photo-catalytic activity towards the degradation of methylene blue (MB) and Cr(VI) reduction under the irradiation of direct sunlight at ambient condition. GO plays a crucial role in the directional growth of nanorods and enhances the photocatalytic activity of ZnO nanorods via the synergistic hole formation and electron transfer effect for the potential remediation of waste water.

Localized surface-plasmon resonance effect as a new driver of Z-scheme electron transfer in cerium dioxide–graphitic carbon nitride heterojunctions

The intersecting interface between the two semiconductors of cerium dioxide (CeO2)–graphitic carbon nitride (g-C3N4) heterojunctions, which have demonstrated excellent photocatalytic activity, inhibits the rapid compounding of the photogenerated electron–hole pairs of g-C3N4. CeO2–g-C3N4 heterojunctions with Z-scheme and type-II electron-transfer routes were prepared via calcination in argon and air atmospheres, respectively. The built-in electric field theory cannot be used to explain the presence of a type-II electron-transfer route in CeO2–g-C3N4 heterojunctions. According the femtosecond transient absorption spectra, the localized surface-plasmon resonance (LSPR) effect of CeO2 drove the Z-scheme electron transfer in CeO2–g-C3N4 heterojunctions. The CeO2–g-C3N4 heterojunction exhibited a type-II electron-transfer route when the particle size of CeO2 increased, which attenuated the LSPR effect. The CeO2–g-C3N4 heterojunction with the Z-scheme electron-transfer route exhibited 4.4 times higher degradation efficiency for bamboo pulping wastewater than g-C3N4, and this result was attributed to the reduced complexation of photogenerated electron–hole pairs and extended photogenerated electron lifetime. Overall, this research provides a new idea for constructing Z-scheme electron-transfer heterojunctions.

Insight into mechanism of excellent visible-light photocatalytic activity of CuO/MgO/ZnO nanocomposite for advanced solution of environmental remediation

Environmental remediation has sought several innovative ways for the treatment of wastewater and captivated researchers around the globe towards it. Through this study, we aim to proceed with the efforts to foster sustainable and feasible ways for the treatment of wastewater. In this work, we report the sol-gel synthesis of CuO/MgO/ZnO nanocomposite and carry out their systematic characterization with the help of state-of-the-art analytical techniques, such as FTIR, SEM, TEM, PL, XRD, Raman, and AFM. The SEM along with TEM and AFM provided useful insights into the surface morphology of the synthesized nanocomposite on both 2D and 3D surfaces and concluded the well-dispersed behavior of the nanocomposite. The characteristic functional groups responsible for carrying out the reaction of Cu–O, Mg–O, and Zn–O were identified by FTIR spectroscopy. On the other hand, crystal size, dislocation density, and microstrain of the nanocomposite were calculated by XRD. For optical studies, photoluminescence spectroscopy was performed. Once the characterization of the nanocomposite was done, they were eventually treated against the toxic organic dye, methylene blue. The calculated rate constant values of k for CuO was 2.48 × 10−3 min−1, for CuO/MgO (2.04 × 10−3 min−1), for CuO/ZnO (1.82 × 10−3 min−1) and CuO/MgO/ZnO was found to be 2.00 × 10−3 min−1. It has become increasingly evident that nanotechnology can be used in various facets of modern life, and its implementation in wastewater treatment has recently received much attention.

The construction of Cs3MoxSbyBr9/BiVO4 S-scheme heterojunction photocatalyst for efficient photocatalytic N2 fixation

Synergistic nitrogen (N2) reduction with water (H2O) oxidation is meaningful but challenging owing to the inertness of the N2 molecule and the sluggish kinetics of H2O oxidation. Herein, a simutaneous-promotion strategy of redox capacities is presented for constructing a lead-free Cs3Sb2Br9-based S-scheme heterojunction, by decorating Mo-functionalized Cs3Sb2Br9 nanocrystals (Cs3MoxSbyBr9) on BiVO4 nanosheet through an in-situ plane-to-point growth manner. The Mo-functionalization for Cs3Sb2Br9 enables the regulation of the d-band center position, greatly improving surface reaction kinetics for N2 reduction. Furthermore, the construction of the S-scheme heterojunction enhances the driving force for H2O oxidation and spatial charge separation of photocatalysts. As anticipated, the resultant Cs3MoxSbyBr9/BiVO4 exhibits an excellent photocatalytic N2 reduction activity under ambient atmosphere, achieving ammonia (NH3) production at a rate of 300 ± 5 μmol g−1 h−1 under simulated sunlight illumination (100 mW cm−2), which is nearly 20-fold higher than that of pristine Cs3Sb2Br9.

Green synthesis of Abutilon indicum (L) derived iron oxide (FeO) nanoparticles with excellent biological, anticancer and photocatalytic activities

Cancer is one of the most common causes of death all over the world. Although there are many treatments available none of them are without side-effect and most of them are very expensive. Similarly, Inflammation is one of another common medical worldwide but most of the therapies available are not environment and pocket friendly. Thus, the aim of our study was to synthesize environmentally friendly, cost-effective FeO NPs with significant anticancer, anti-inflammatory, antibacterial properties. The green synthesis of Iron Oxide Nanoparticles (FeO NPs) using plant extract is one of the environmentally friendly, cost-effective, and a secure alternative to physical or chemical synthesis methods. In the present study we used Abutilon indicum leaf extract to synthesize the Ai-FeO NPs and performed various experiments to confirm the therapeutic potential of green synthesized Ai-FeO nanoparticles. In this method, an aqueous plant leaf extract (A. indicum: Ai) was used as a reducing and stabilizing agent for the synthesis of FeO nanoparticles. The synthesized Ai-FeO NPs were characterized by the ultraviolet–visible (UV–Vis) absorbance of the surface at a resonance band 415 nm. Fourier transform infrared (FTIR) spectroscopy study confirmed the inherent bioactive functional groups as capping and stabilizing agents for Ai-FeO NPs. The X-ray powder diffraction (XRD) spectra revealed crystalline nature of the NPs. Further, the synthesized NPs have been isolated in highly stable, crystalline nature with spherical shape having size 10–95 nm. In addition, the green synthesized Ai-FeO-NPs demonstrated dose-dependent antimicrobial, antioxidant, anti-inflammatory, and anticancer properties. The findings of this study suggested that A. indicum leaf extract mediated FeO nanoparticles could be potentially used as a therapeutic agent for many human diseases and breast cancer.

A green approach to synthesis of Ag-doped CeO2 nanorods embedded reduced graphene oxide nanocomposite for excellent photocatalytic and antimicrobial activity

In this paper, the Ag-doped cerium oxide nanorods embedded reduced graphene oxide (Ag@CeO2/rGO) nanocomposite was synthesized via Punica Granatum leaf extract for for photocatalytic degradation of methylene blue (MB) and 4-nitrophenol (4-NP). The microstructural results confirmed the successful decoration of Ag-doped CeO2 nanorods on rGO matrix. The photocatalytic properties, including photocatalytic degradation, charge transfer kinetics and photocurrent generation, are systematically investigated using electrochemical impedance spectroscopy (EIS), photocurrent transient response (PCTR) and open circuit voltage decay (OCVD). The results of photocatalytic dye degradation measurements indicated that Ag@CeO2/rGO nanocomposite is more effective than pristine CeO2 to degrade the MB dye, and the degradation rate reached 100 % in 60 min. The decomposition of MB with Ag@CeO2/rGO nanostructure followed first-order reaction kinetics with a reaction rate constant (Ka) of 0.0198 min−1. The EIS and OCVD measurements revealed that the Ag doping and incorporation of rGO could suppress the recombination probability in CeO2 by the separation of photo-generated electron–hole pairs, which leads to the enhanced photocurrent generation and photocatalytic activity. The photocurrent density of Ag@CeO2/rGO, CeO2/rGO and pristine CeO2 are 215, 167.4 and 98.8 mAcm−2, respectively.

Photo-induced in-situ synthesis of Cu2O@C nanocomposite for efficient photocatalytic evolution of hydrogen

Cuprous oxide (Cu2O) is an ideal visible light catalyst owing to its narrow band gap, environmental benignity and abundant storage; however, the fast recombination of photogenerated charge carriers and poor stability of Cu2O has impeded its application in photocatalysis. Herein, we demonstrate that Cu2O@C nanocomposite can spontaneously evolve from a methanol aqueous solution containing cupric ions under the induction of irradiation. Compared with the traditional carbon coating method, the Cu2O@C nanocomposite obtained by the photo-induced in-situ synthesis can reserve superior original characteristics of the semiconductor under mild reaction conditions, promote the charge transfer and enhance the separation efficiency of charge carriers; in addition, the carbon shells can also effectively prevent Cu2O from photo-corrosion. As a result, the Cu2O@C nanocomposite exhibits excellent photocatalytic activity in the hydrogen evolution in comparison with the Cu2O particles; the H2 evolution rate over the Cu2O@C nanocomposite reaches 1.28 mmol/(g·h) under visible light, compared with the value of 0.065 mmol/(g·h) over Cu2O. Moreover, the Cu2O@C nanocomposite displays good cycle stability, viz., without any deactivation in the catalytic activity after five cycles.

Enhancement photocatalytic activity of CeO2 infused CA@Gelatin nanocomposites for the degradation of organic dyes under UV-light irradiation

In the present study, facile 100% recoverable handpicked CeO2/CA@GEL (CA; Cellulose acetate, GEL; Gelatine) nanocomposite thin film photocatalyst were successfully synthesized by simple solution cast method. The efficacy of the CeO2/CA@GEL was tested against the photodegradation of organic dyes viz Crystal violet (CV) and Rhodamine-B (RhB) under visible light irradiation. The CeO2/CA@GEL exhibited excellent photocatalytic activity, durability and utmost 80.52% (CV) and 82.65% (RhB) degradation of the dye solution was achieved within 60 min. The CeO2/CA@GEL showed the excellent degradation efficiency compared to pure CeO2 Nanoparticles. The reactive oxidative species involved in the photocatalytic reaction is superoxide radical anion (O2 radical) and OH radical under visible light irradiation by trapping experiments. The 100% recovery of the photocatalyst was achieved by simple handpicking process and stable unto its 3rd usage.

Heterojunction CuO thin coated CaO drived from eggshell waste for fast removal of organic pollutants from water under visible light

AbstractThe conversion of food and agro-industrial wastes to produce useful products is one of the goals of economic and sustainable development, as also evidenced in the 2030 Agenda for Sustainable Development, adopted by all United Nations Member States in 2015. This work aims to study the transformation of CaCO3 based eggshell waste (ES) into a face centered cubic oxide form (namely, CaO), followed by CuO coating to be used as photocatalytic material (ES@CuO) for fast removal of basic fuchsin (BF) dye from water under visible light. Different ES@CuO samples with different CuO amounts (2.5, 5 and 10%, respectively) and calcined at different temperatures (600, 800, and 1000 °C) were prepared by hydrothermal method. Samples with CuO from medium to high amounts (5 and 10%) demonstrated excellent photocatalytic activity, as compared to low CuO amount (2.5%). In addition, the samples calcined at higher temperature (800 and 1000 °C) exhibited superior degradation rates, reaching 88.11% and 88.33%, respectively. The effect of operating parameters was investigated to understand the behavior of ES@CuO under different conditions. ES@CuO shows rapid removal of BF which combines adsorption and photooxidation, wherein the removal rate reaches up 99% for a BF dye concentration of 100 ppm within 30 min using 75 mg/L of ES@CuO5%. ES@CuO exhibits superior adsorption ability and excellent photoproduced charges transfer which provide synergistic effects to boost the quick removal of dye from water. The finding of this investigation encourages valorizing food wastes into sustainable materials for water remediation. Graphical abstract

The photocatalytic potential of single-atom Ag with tungsten-based two-dimensional transition metal dichalcogenides substrate for harmful gas removal

Tungsten-based two-dimensional transition metal dichalcogenides (TMDs) is a promising non-precious metal catalyst that can be applied to drive photocatalytic removal of harmful gases. However, the photocatalytic performance of these promising tungsten-based TMDs is limited by low carrier separation efficiency. In order to promote the separation efficiency of photogenerated carriers, it is a useful strategy to introduce a trace amount of precious metal Ag into tungsten-based TMDs. Due to the presence of precious metal Ag, the separation efficiency of photogenerated carrier is significantly improved. The photocatalytic removal potential of single-atom Ag with tungsten-based TMDs substrate for harmful gases was demonstrated in this work. Specifically, the effects of trace Ag atom and its load on the light absorption spectra, work function, band structure and density of states of tungsten-based TMDs were discussed by first principles calculations, among which tungsten-based TMDs substrate included 2 H-WS2, 2 H-WSe2 and 2 H-WTe2. It was found that Ag@2 H-WS2 and Ag@2 H-WSe2 possess strong light absorption capacity, low electron escape work and suitable band structure for photocatalysis. Through cohesive energy, formation energy and molecular dynamics, it was found that Ag@2 H-WSe2 possesses excellent stability, while Ag@2 H-WS2 may be unstable. Thus, Ag@2 H-WSe2 was identified as a new photocatalyst with broad application prospects. Finally, taking NH3, H2S, NO2 and SO2 as model harmful gases, it was proved that Ag@2 H-WSe2 can effectively photocatalyze the removal of harmful gases by differential charge density, projected density of states and energy barrier calculations. The above calculations indicates that Ag@2 H-WSe2 exhibits excellent photocatalytic activity and stability, and is a promising photocatalyst.

Enhanced Photocatalytic Degradation of Organic Matter In Nuclear Waste Liquid Under Visible Light by a Ternary Thin Layer System Based on g-C3N4

Graphitic carbon nitride (g-C3N4)-based materials are considered promising catalysts for organic waste photodegradation due to their excellent photocatalytic activity and stability. Herein, a ternary thin layer system based on g-C3N4 was prepared by hexagonal boron nitride (h-BN) deposition followed by liquid phase ultrasonic stripping and Ag deposition (marked as Ag-BCN), which increased the specific surface area of g-C3N4, expanded the corresponding range of the visible-near-infrared spectrum of g-C3N4 and promoted the photo-generated electron–hole pair separation in g-C3N4 to improve the photocatalytic efficiency of pure g-C3N4. The results showed that after deposition of h-BN and Ag into bulk g-C3N4 and liquid phase ultrasonic stripping, the efficiency of photocatalytic degradation of tannic acid (TA) was enhanced. The efficiency of photocatalytic degradation of TA by Ag-BCN-2 was 84.3% at 90 min, which was 1.6 times the efficiency of bulk g-C3N4.

Achieving water-floatable photocatalyst on recycled bamboo chopsticks

Disposable bamboo chopsticks (DBCs) are difficult to recycle, which inevitably cause secondary pollution. Based on energy and environmental issues, we propose a facile strategy to fabricate floatable photocatalyst (fPC) coated onto DBCs, which can be flexibly used in water purification. The photocatalyst of titania and titanium carbide on bamboo (TiO2/TiC@b) was successfully constructed from TiC-Ti powders and DBCs using a coating technique followed heat treatment in carbon powder, and the fPC exhibited excellent photocatalytic activity under visible light irradation. The analysis results indicate that rutile TiO2 forms on TiC during heat treatment, achieving a low-density material with an average value of approximately 0.5233 g/cm3. The coatings of TiO2/TiC on the bamboo are firm and uniform, with a particle size of about 20–50 nm. XPS results show that a large amount of oxygen vacancies is generated, due to the reaction atmosphere of more carbon and less oxygen, further favoring to narrowing the band gap of TiO2. Furthermore, TiO2 formed on residual TiC would induce the formation of a heterojunction, which effectively inhibits the photogenerated electron–hole recombination via the charge transfer effect. Notably, the degradation of dye Rhodamine B (Rh.B) is 62.4% within 3 h, while a previous adsorption of 36.0% for 1 h. The excellent photocatalytic performance of TiO2/TiC@b can be attributed to the enhanced reaction at the water/air interface due to the reduced light loss in water, improved visible-light response, increased accessible area and charge transfer effect. Our findings show that the proposed strategy achieves a simple, low-cost, and mass-producible method to fabricate fPC onto the used DBCs, which is expected to applied in multiple fields, especially in waste recycling and water treatment.

Constructing Interfacial Charge Transfer Channels and Electric Field in Violet Phosphorus-Based van der Waals Heterojunction for Phototherapy of Periodontitis.

Periodontitis, a chronic oral disease instigated by bacteria, severely compromises human oral health. The prevailing clinical treatment for periodontitis involves mechanical scraping in conjunction with antibiotics. Phototherapy is employed to rapidly remove the bacteria and achieve periodontitis treatment, effectively circumventing the adverse effects associated with traditional therapies. Constructing 2D/2D van der Waals (VDW) heterojunctions is a key strategy for obtaining excellent photocatalytic activity. Herein, a 2D/2D violet phosphorus (VP)/Ti3C2 VDW heterojunction is designed using an interfacial engineering strategy. By constructing an electron transport "bridge" (P-Ti bond) at the heterogeneous interface as an effective transfer channel for photogenerated carriers, a compact monolithic structure between the VP and Ti3C2 phases is formed, and the spatial barrier for electron transfer at the interface is eliminated. Meanwhile, the strong directional built-in electric field induced by the intensive electron-coupling effect at the heterogeneous interface served as an internal driving force, which greatly accelerates the exciton dissociation and charge transfer in the photocatalytic process. These excited photogenerated electrons and holes are trapped by O2 and H2O on the surfaces of Ti3C2 and VP, respectively, and are subsequently catalytically converted to antibacterial reactive oxygen species (ROS). The VP/Ti3C2 VDW heterojunction eradicated 97.5% and 98.48% of Staphylococcus aureus and Escherichia coli, respectively, by photocatalytic and photothermal effects under visible light for 10 min. The VP/Ti3C2 nanoperiodontal dressing ointment effectively attenuated inflammatory response, reduced alveolar bone resorption, and promoted periodontal soft and hard tissue repair. Its periodontitis therapeutic effect outperforms the clinically used Periocline.

High-efficiency photocatalyst based on Au nanoparticles loaded on defective ZnO nanorods

Optimizing the semiconductor-metal interaction is the key to developing metal single-atom cocatalysts with 100 % metal atom utilization and unique electronic properties. Metal atom sites are exclusively coordinated with semiconductor, featuring a chemical-bond-driven tunable interaction. Here vacancy defect-rich ZnO nanorods (NRs) are fabricated by a facile hydrothermal approach. Au nanoparticles (NPs) are preferentially anchored on surface zinc vacancy sites of ZnO NRs in an ultra-low concentration (10−4 mol/L) of HAuCL4 solution. The Au/ZnO nanohybrids exhibit an excellent photocatalytic activity toward removal of Rhodamine B and levofloxacin. Combining ferromagnetism and valence-band XPS spectra analysis, it is demonstrated that the strong interaction of surface vacancy defects in ZnO and Au generates a distinct upshift of the valence band edge, resulting from the antibonding interaction between O 2p and Au 5d orbitals which significantly weakens the Au–O bonds. This facilitates the release of the lattice oxygen and thus generates more oxygen vacancies. The remarkable photoactivity of defective Au/ZnO is due to the synergistic interaction between the intrinsic oxygen vacancy and Au. Optimizing the hybridization of transition metal d and O 2p states at the atomic scale can induce more active-sites, improve atomic utilization efficiency and thus provide a new approach for enhancing photoactivity.

Role of metal (Fe(III), Zn(II), and Co(III)) and porphyrin in enhancing photocatalytic performance of MTCPP/TiO2 photocatalysts

Metal-porphyrin complexes modified TiO2 photocatalyst, called MTCPP@P25, shows excellent photocatalytic activity under visible light irradiation. Metal-porphyrin is successfully utilized to broaden the photo response range of TiO2 from ultraviolet (3.2 eV) to visible light (2.43 eV to 2.65 eV) resulting in significant enhancement of photocatalytic efficiency. MTCPP@P25 exhibited the higher photocatalytic activity than bare TiO2. Additionally, introduction of different metals, like Fe, Zn, and Co into porphyrin ring can effectively adjust the photocatalytic activity of MTCPP@P25 due to the increasing the electron density of porphyrin rings. The degradation order for MB followed as FeTCPP@P25≧ZnTCPP@P25 > CoTCPP@P25. This finding demonstrated that FeTCPP@P25 and ZnTCPP@P25 possess higher photo-excited electrons under visible irradiation resulting in higher photocatalytic performance. Based on the PL and EIS analysis, FeTCPP@P25 exhibited longest lifetime and fast electron transition compared to ZnTCPP@P25. The spent FeTCPP@P25 were reusable after three cycles, the efficiency remained at approximately 80 %.

Construction of freestanding BiOBr/CCFs composites: Enhanced carrier separation achieving efficient photocatalytic performance

The recycling efficiency of the photocatalyst is an important factor in practical application, which is one of the problems that most powder catalysts need to solve urgently. Herein, the freestanding photocatalyst that BiOBr nanosheets anchored on coal-based carbon fibers (CCFs) has been prepared. Integrating BiOBr to CCFs nanosheets can enlarge the specific surface area of materials, broaden the light absorption range, and increase the carrier transport rate. The optimum BiOBr/CCFs-2 sample exhibits excellent photocatalytic degrade Rhodamine B (RhB) efficiency of 92 % within 20 min under visible light, and the kinetic constant is 2.6 times higher than that of BiOBr. The photogenerated carriers generated by BiOBr nanosheets transfer to CCFs with excellent electrical conductivity and then synergistically improving the photocatalytic performance of BiOBr/CCFs-2. The BiOBr/CCFs-2 still remain excellent photocatalytic activity and cycling stability after five cycles, and the composite will be expected to be widely applied in other fields.

Acceleration of the electron transfer for efficient photocatalytic hydrogen evolution via regulating the surfactant around the active center in 2D MOFs

Although surfactants have been proved to be effective in controlling the size and morphology to prepare high-quality two-dimensional (2D) MOF nanosheets, the impact of surfactants remaining on the 2D MOF nanosheets on their microenvironment is rarely reported. In this paper, polyvinylpyrrolidone (PVP) was used as surfactant to synthesize Co-TCPP(Pd) (abbreviated as Co-Pd) nanosheets, and the content of PVP attached to Co-Pd nanosheets was controlled by ethanol treatment, to regulate the microenvironment around Co-Pd nanosheets. The XRD, FT-IR, XPS, TEM, and TG were used to confirm that after ethanol ultrasonic treatment, the PVP content on Co-Pd nanosheets was gradually reduced without damaging the original structure and morphology of Co-Pd nanosheets. PVP attached to Co-Pd nanosheets will slow down the electron migration rate, affecting the microenvironment around co-catalyst Pd, which has been confirmed by EIS, PL and DFT etc. The results exhibited that the Co-Pd-6 obtained by ethanol ultrasonic treatment 6 times showed the more excellent photocatalytic hydrogen evolution activity (8284.25 umol·g−1·h−1), which was 4.02 times as that of Co-Pd-0 (2059.59 umol·g−1·h−1) without ethanol ultrasonic treatment), indicating that PVP will have a negative impact on the microenvironment around the co-catalyst, thereby affecting the photocatalytic hydrogen evolution performance. This study indicates that efficient photocatalytic hydrogen evolution can be achieved via adjusting the microenvironment around the co-catalyst to promote electron transfer.

Facile synthesis of bulk Au-Co-CoOx-CeOx@iron ball and its photocatalytic application in 4-nitrophenol degradation

Bulk noble metal–semiconductor composites can be chosen as photocatalysts to carry out the flow degradation of 4-nitrophenol (4-NP) whereas their preparation is complex and uncontrollable. Here, bulk Au-Co-CoOx-CeOx@iron ball (Au/Co-CC@iron ball) is designed and prepared by a facile and controllable route without any toxic chemical. The bulk Au/Co-CC@iron ball shows excellent photocatalytic activity and reusability for the 4-NP degradation, which can be ascribed to the synergistic action of active components and foliated iron ball surface. Furthermore, the highly active Au/Co-CC@iron ball is used as packing material to construct a new-type of packed reactor, by which the flow degradation of 4-NP is successfully achieved. As-fabricated packed reactor and its tandem module exhibit superior photocatalytic performance for the flow degradation of 4-NP. Noteworthy, based on the tandem module with six reactors, the removal rate of 4-NP can reach up to 2750 µmol/h. Meanwhile, the reactor and its module display satisfactory operational stability and reusability in the flow degradation of 4-NP. Clearly, the provided route is effective for the preparation of bulk noble metal–semiconductor composites with exceptional performance, which can also be a prospective strategy to obtain bulk packing materials to serve for the flow degradation.

Efficient separation of photo-generated carriers for in-situ induction of PDI cation radicals to enhance the photocatalytic performance of PDI supramolecules

In order to investigate whether the formation of hydrogen bonds can affect the degradation products of pollutants, a photocatalyst PDI-SE was obtained by end substituting perylene tetracarboxylic dianhydride with serine (SE) in this paper. As a reference, PDI-IS with isopropylamine (IS) terminal alkyl substitution was synthesized simultaneously. Their photocatalytic performance to decompose phenol and tetrabromobisphenol A (TBBPA) were investigated. PDI-SE could degrade 79.3% of phenol or 68.4% of TBBPA within 4 h under visible light. The degradation products of TBBPA were tracked using high-resolution mass spectrometry. The morphology, composition, structure, and optoelectronic properties of two photocatalysts, particularly their transient absorption spectra and fluorescence lifetime were studied. We also conducted theoretical calculations on their binding energy with phenol or TBBPA, distribution and separation of electron and hole of excited state PDI-SE and PDI-IS supramolecules. Due to the formation of hydrogen bonds the binding energy of PDI-SE with phenol or TBBPA is 1.24 eV or 1.99 eV, which is stronger than that of PDI-IS (0.85 eV or 1.66 eV). Although both PDI-SE and PDI-IS can form free radical cations in excited states, the high separation of electrons and holes of PDI-SE leads to a longer lifetime of free radical cations, so caused its excellent photocatalytic activity compared to PDI-IS. This article proposes a new strategy based on molecular design to promote efficient separation of photogenerated electrons and holes, thereby forming stronger oxidizing PDI cationic radicals in situ to enhance the photocatalytic performance of PDI supramolecules.