Recombination Of Electron-hole Pairs Research Articles

3D monolithic composites TiO2/HKUST-1/RGO@melamine foam with improved surface mass transfer for efficient photocatalytic degradation of toluene gas

Currently, photocatalytic technology mostly uses powdered TiO2 catalysts, which are not conducive to recycling, limit the contact between volatile organic compounds (VOCs) and the photocatalyst, and result in lower mass transfer efficiency in gas-solid reactions. Meanwhile, TiO2 catalysts including the electrospun TiO2 nanofibers with hydrophilic surfaces are not favorable for the infiltration and adsorption of non-polar VOCs. To solve these problems, in this work, the monolithic composites TiO2/HKUST-1/RGO@melamine foam (named MRTH) with improved surface mass transfer composed of metal-organic framework (HKUST-1), graphene oxide (GO) and electrospun TiO2 nanofibers was designed. The metal-organic framework HKUST-1 plays a role in promoting the adsorption of toluene, while the reduced graphene oxide (RGO) facilitates the infiltration of non-polar molecules on the surface of the composite and has better electron transport capability. A type II heterojunction between the electrospun TiO2 nanofibers and HKUST-1 formed in the monolithic composites suppresses the recombination of electron-hole pairs and extends their lifespan. Comparing with the bare electrospun TiO2 nanofibers, the MRTH foam composites exhibit a wider light absorption range, hydrophilic and oleophobic properties and a higher separation efficiency of photogenerated carriers. In 90 min of dark adsorption, the removal rate of toluene over MRTH-8 was 52.32 %, while under irradiation by xenon lamp for 150 min, the removal rate over MRTH-8 reached 90.15 %. The amount of monolithic foam composites can also be easily adjusted in the reactor to achieve the best possible removal of the contaminant. The prepared composite materials have been characterized in detail, and the possible mechanisms have also been discussed. The foam composites prepared in this work have high catalytic activity and gas-solid reaction mass transfer efficiency, so they have wide practical application prospects in the field of VOCs abatement.

Synthesis of a novel biomass waste-based photocatalyst for degradation of high concentration organic pollutants under visible light: Optimization of synthesis condition and operational parameters via RSM-CCD

Reducing electron-hole pair recombination rate under visible light and preventing α-Fe2O3/WO3 nanoparticle aggregation enhances the photocatalytic efficiency. Herein, a novel heterojunction-activated carbon-based photocatalyst (α-Fe2O3/WO3/AC) was successfully synthesized from Rosa Canina seeds and characterized by PL, EIS, Photocurrent, ESR, XPS, LC-MS, FTIR, XRD, SEM, EDS-map, TEM, and BET analyses. Investigating the influence of significant parameters, including impregnation ratio (1–5), activation temperature (400–600 °C), and α-Fe2O3/WO3 loading (10–90 wt.%) by RSM method resulted in optimal photocatalyst synthesis (50 wt.%: FeW/AC3–500) evidenced by its capability for doxycycline degradation. The maximum doxycycline degradation (98.01 %) was achieved under optimal conditions with a degradation rate constant of 0.03 min−1. Trapping experiments revealed that •OH and •O2− played crucial roles in photocatalysis. The possible doxycycline degradation pathway of (50 wt.%: FeW/AC3–500) photocatalyst is proposed. Based on the transient photocurrent measurements and EIS results, the 50 wt.% FeW/AC3–500 composite exhibited a significant enhancement in photocatalytic activity, which can be attributed to the efficient speed of electron-hole separation. Overall, an innovative approach was introduced to design an efficient AC-based photocatalytic process, which enhances the performance of wastewater treatment and environmental remediation.

A Novel Perspective on Enhancing Photocatalytic Performance through the Synergistic Effect of Nd Single Atoms and Heterostructures.

There are few reports on lanthanide single atom modified catalysts, as the role of the 4f levels in photocatalysis is difficult to explain clearly. Here, the synergistic effect of 4f levels of Nd and heterostructures is studied by combining steady-state, transient, and ultrafast spectral analysis techniques with DFT theoretical calculations based on the construction of Nd single atom modified black phosphorus/g-C3N4 (BP/CN) heterojunctions. As expected, the generation rates of CO and CH4 of the optimized heterostructure are 7.44 and 6.85 times higher than those of CN, and 8.43 and 9.65 times higher than those of BP, respectively. The Nd single atoms can not only cause surface reconstruction and regulate the active sites of BP, but also accelerate charge separation and transfer, further suppressing the recombination of electron-hole pairs. The electrons can transfer from g-C3N4:Nd to BP:Nd, with a transfer time of ≈11.4ps, while the radiation recombination time of electron-hole pairs of g-C3N4 is ≈26.13 µs, indicating that the construction of heterojunctions promotes charge transfer. The 2P1/2/2G9/2/4G7/2/2H11/2/4F7/2→4I9/2 emissions from Nd3+ can also be absorbed by heterostructures, which improves the utilization of light. The energy change of the key rate measurement step CO2 *→COOH* decreases through Nd single atom modification.

Enhanced photodegradation of methylene blue by Zr-doped TiO2:A combined DFT and experimental investigation

The effective mitigation of effluents in water has attracted researchers as a foremost task for addressing environmental concerns. To overcome these concerns, TiO2 (labeled as PCT-1) and Zr-doped TiO2 (labeled as PCT-2) nano catalysts are prepared by an efficient sol–gel protocol and their photocatalytic degradation performance of methylene blue (MB) is investigated. The structural integrity of nanostructures is determined by analytical tools. More than 96 % MB degradation is observed when PCT-2 is subjected to ultraviolet light for 180 min. Nanosized PCT-2 exhibits attractively advanced photocatalytic performance than PCT-1 owing to lower electron–hole pair recombination (3.02 eV) as well as superior photon capture via oxidation by photocatalytic response (confirmed through active species trapping scavenger tests). Furthermore, the results of bandgap are also confirmed by spin-polarized density functional theory (DFT) computations. The findings of this study indicate that band tuning is an attractive photocatalytic system for improving catalytic performance.

Review of the performance and energy requirements of metals modified TiO2 materials based photocatalysis for phenolic compounds degradation: A case of agro-industrial effluent

The waste effluent generated by agro-industries and oil refineries has a high level of phenolic compounds (PhCs) even after the secondary treatment, and is considered one of the major polluters of rivers and streams across the edible oil and petroleum producing countries. Photocatalytic technology based on TiO2 or modified TiO2 materials has proven to be both technically and economically feasible for the treatment of such effluents. It has a few significant, enduring problems that must be resolved first, such as inefficient use of visible light by TiO2, its broad bandgap, and its rapid electron-hole pair recombination. TiO2 photocatalyst-based photocatalysis has several advantages, such as the ability to fully mineralize organic pollutants into byproducts that are environmentally friendly, high reaction rates, operation at room temperature and pressure, low cost, and chemical and thermal stability of TiO2. However, to transfer this technology to industrial scale require a thorough analysis of its performance and energy requirements especially, when applied for photodegradation of PhCs from agro-industries. This review critically examined various methods for enhancing the degradation of PhCs using metal modified TiO2 materials based photocatalysis. It is also described how different strategies will impact the overall visible-light efficiency and energy requirements of the TiO2 photocatalyst. Furthermore, the most significant modifications to the TiO2 photocatalysts for enhancing the degradation of PhCs were identified. Finally, estimates and comparisons of each strategy's energy needs, energy savings and treatment costs for various modifications were carried out and presented. The industry should be encouraged to promote the advancement of TiO2-based photocatalysis by being aware of the technical challenges and energy demands during its development.

BNQDs and Fe2O3QDs co-doped in porous g-C3N4 for accelerating photogenerated electron migration and enhancing photo-Fenton catalysis efficiency

With the maturity of advanced oxidation processes, photo-Fenton synergistic catalytic technology, as one of them, has become an irreplaceable strategy in environmental treatment and other fields. However, this technology suffers from drawbacks such as facile recombination of electron-hole pairs (e-/h+), low conversion efficiency between Fe3+ and Fe2+, and limited active sites. To address these issues, this study constructs a photo-Fenton synergistic system based on porous g-C3N4 (FBNCN) modified with BNQDs and Fe2O3QDs. Among them, the porous g-C3N4 provides more active sites and larger quantum dot anchoring space for the catalytic reaction. The introduction of the BNQDs effectively traps the hole (h+), reduces e-/h+ recombination, facilitates the photo-generated electrons leap, and accelerates charge transfer, while the anchoring of Fe2O3QDs enables efficient the migration of active sites and charges. This results in improved conversion efficiency between Fe3+ and Fe2+, leading to enhanced generation of ·O2- and ·OH species that exhibit excellent visible-light-catalyzed oxidation ability. Moreover, remarkable degradation efficiency was achieved for antibiotic organic pollutants (tetracycline hydrochloride, chlortetracycline hydrochloride, norfloxacin, amoxicillin) per unit of time using this catalyst system, thus providing a new method for antibiotic organic pollutant degradation. In-situ XPS technique was used to analyze the movement direction of the photogenerated charges of the composite photocatalytic materials and reveal the degradation mechanism under the synergistic system.

Photocatalytic Activity and Antibacterial Properties of ZnO/CNTs Composites

Photocatalytic technology is one of the promising technologies for wastewater treatment. Herein, zinc oxide/multi-walled carbon nanotubes (ZnO/CNTs) photocatalyst was successfully prepared by hydrothermal method with combining in-situ synthesis technology. The micro-morphology, crystalline structure, surface chemical elements, and optical properties were characterized by SEM, TEM, XRD, FTIR, UV-Vis, and DRS technologies. The ZnO/CNTs photo-catalyst exhibited enhancement photo activity for degradation of organic pollutants under simulated light irradiation. Specifically, the photo-catalytic activity of the ZnO/CNTs catalysts improved with the rise of CNTs content in the composites. Investigation on the photo-degradation mechanism verified that the presence of CNTs in the catalyst not only optimized the band structure of ZnO semiconductor but also contributed to the transfer of photo-generated electrons and reducing the recombination of electron-hole pairs due to its excellent conductivity. Moreover, the active radical groups such as superoxide radical (O-2), hole (h+), and hydroxyl radical (·OH) played the dominated role for the pollutants degradation under the simulated sunlight irradiation. In addition, ZCT20 catalysts and light irradiation had synergistic effects on antibacterial activity, whose antibacterial rates against E. coli and S. aureus were up to 99.96% and 99.94%, respectively. Investigation on antibacterial mechanisms revealed that the existence of ROS and the continuous release of Zn2+ played an important role for improving the antibacterial activity of the ZCT20 catalyst under the simulated sunlight irradiation.

Double S-scheme Cu2−xSe/twinned-Cd0.5Zn0.5S homo-heterojunctions with surface plasmon effects for efficient photocatalytic H2 evolution

The enhancement of charge separation and utilization efficiency in both the bulk phase and interface of semiconductor photocatalysts, as well as the expansion of light absorption range, are crucial research topics in the field of photocatalysis. To address this issue, twinned Cd0.5Zn0.5S (T-CZS) homojunctions consisting of wurtzite Cd0.5Zn0.5S (WZ-CZS) and zinc blende Cd0.5Zn0.5S (ZB-CZS) were synthesized via a hydrothermal method to facilitate the bulk-phase charge separation. Meanwhile, Cu2−xSe with localized surface plasmon resonance effect (LSPR) generated by Cu vacancies was also obtained through a hydrothermal process. Due to their opposite electronegativity, a solvent evaporation strategy was employed to combine Cu2−xSe and T-CZS by intermolecular electrostatic. After optimization, the photocatalytic hydrogen (H2) evolution rate of 5 wt% Cu2−xSe/T-CZS reached an impressive value of 60 mmol∙h−1∙g−1, which was 4.6 and 66.6 times higher than that of pure Cu2−xSe and T-CZS, respectively. Furthermore, this composites demonstrated a remarkable rate of 0.46 mmol∙h−1∙g−1 under near-infrared (NIR) wavelength (>800 nm). The enhanced performance observed in Cu2−xSe/T-CZS can be attributed to its unique and efficient double S-scheme charge transfer mechanism which effectively suppresses rapid recombination of electron-hole pairs both within the bulk phase and at the surface interfaces; this conclusion is supported by Density Functional Theory (DFT) calculations as well as electron paramagnetic resonance spectroscopy analysis. Moreover, incorporation of Cu2−xSe enables effective utilization ultraviolet visible-near infrared (UV–Vis-NIR) light by the composites while facilitating injection “hot electrons” into T-CZS for promoting photocatalytic reactions. This study provides a potential strategy for achieving efficient solar energy conversion through synergistic integration of non-stoichiometric plasmonic materials with photocatalysts with twinned-twinned structures.

Solvothermal synthesis of Bi12TiO20/Bi4Ti3O12 heterostructure with highly efficient photodegradation of MO under UV irradiation

The sillenite-structured bismuth titanate (Bi12TiO20) is thought to be a viable photocatalyst for environmental remediation. However, the performance of Bi12TiO20 as a photocatalyst is severely constrained by its limited range of light sensitivity and the rapid photoinduced electron-hole pair recombination. A practical and effective way to overcome these limitations is to combine Bi12TiO20 with adequate photocatalysts to create heterojunctions. Here, a one-step solvothermal technique is used to synthesize Bi12TiO20/Bi4Ti3O12 heterojunction (BTO). The electric field that exists between B12TiO20, Bi4Ti3O12 and the closed interfacial contacts had a synergistic effect on the constructed composites, which resulted in high charge transfer abilities. Therefore, the BTO heterojunction demonstrated increased photocatalytic efficacy in the presence of ultraviolet irradiation. The MO removal efficiency of optimal BTO was 97.15%, significantly higher than that of pure Bi2O3 (46.9%). Furthermore, the cycling experiment demonstrated that the BTO heterojunction is stable and reusable. The probable mechanism of photocatalytic MO oxidation over BTO heterojunction was studied by various scavengers. The •OH radicals and holes played essential roles in BTO system of photocatalytic oxidation process.

Boosting photocatalytic activity of β-PbO nanoparticles through metal doping

The current work focuses on the fabrication of pristine and metals (Co, Cu, Ni, Li, and Sn) doped β-PbO phase nanoparticles by cost-effective precipitation method. The properties of the produced nanoparticles were investigated using a variety of characterization techniques. The produced compound was a highly pure β-PbO phase, according to the XRD data. From the UV–vis DRS the obtained bandgap of pristine β-PbO, Co, Cu, Ni, Li, and Sn doped β-PbO was 2.68 eV, 1.88 eV, 2.01 eV, 2.65 eV, 2.64 eV, and 2.70 eV, respectively. The doped samples with the lowest photoluminescence (PL) intensities show the reduced photogenerated electron–hole pair recombination, which increased the photocatalytic activity of β-PbO nanoparticles. The study of the surface morphology by SEM reveals the irregular distribution of the particles. In both pristine and doped nanoparticles, EDX verifies the existence of the expected elements. In comparison to pristine β-PbO, all doped β-PbO nanoparticles have enhanced photocatalytic activity for the degradation of methylene blue (MB) dye under the irradiation of visible light. Among the doped nanoparticles, Cu and Co-doped β-PbO demonstrated particularly high performance. After 80 min of irradiation, Cu and Co-doped β-PbO showed 99.45% and 99.39% degradation rates of MB dye, compared to only 75.13% for pure β-PbO. Hence, the photocatalytic activity of pure β-PbO is boosted through metals doping due to bandgap narrowing, generation of impurity states, increased specific surface area, higher carrier concentration, reduced carriers recombination, the action of dopant ions, and microstructural changes.

Composite ZnFe2O4/SrWO4 hollow microspheres as catalyst for high-performance photo-Fenton degradation

Low degradation rate for a long degradation time and poor cycle stability caused by rapid recombination of generated electron-hole pairs are tough challenges for photo-Fenton degradation The unique microstructure catalyst can provide enough catalytic surface to prevent the recombination of electron-hole pairs and facilitate the barrier-free transport of active species. In addition, the special hollow microsphere structure can effectively accelerate the Rhodamine B (RhB) penetration and the photo-Fenton process. Introducing SrWO4 can increase oxygen vacancies and optimize the electronic structure of ZnFe2O4, thus enhancing electron transport and RhB degradation in the photo-Fenton process. This kind of catalytic material ZnFe2O4/SrWO4 (ZFO/SW) in the photo-Fenton process can effectively degrade the 99.18 % RhB dye only within 20 min with remarkable cycling stability. This work demonstrates the high efficiency of ZFO/SW as a photocatalyst and confirms the contribution of the current design concept to the development of photo-Fenton degradation materials.

Photolysis and photocatalysis of methylene blue by graphene oxide nanoparticle under sunlight irradiation

The Hummer technique was utilised to produce graphene oxide (GO), for this research. X-ray diffraction (XRD), energy dispersive X-ray (EDX), and a field emission scanning electron microscope (FESEM) were used to examine the structural properties of GO nanoparticles.By boosting adsorption, expanding the light absorption range, and blocking electron-hole pair recombination, GO enhances the photocatalytic efficiency. The GO have enormous potential uses in the degradation of organic contaminants from wastewater, and their manufacturing is expected to be scalable using this simple process. The improved catalytic activity of GO nanoparticle has been linked to the greater adsorption susceptibility of dye molecules, high charge separation, and suppressed recombination of photogenerated electron-hole pairs brought about by the presence of GO. These results demonstrated the promising prospects for future use of graphene-based semiconductor nanocomposites as visible-light photocatalysts in the field of water purification.

Adjustable n→π* electronic transition by sulfonated benzene functionalized g-C3N4 for enhanced photocatalytic H2 generation

The photocatalytic efficiency of graphitic carbon nitride (g-C3N4) in hydrogen production is primarily hindered by its poor absorption of visible light, rapid recombination of electron-hole pairs, and the absence of hydroxyl radical formation. Herein, a novel g-C3N4 nanosheets functionalized with sulfonic acid groups were effectively produced through thermal polymerization of melamine and 2, 4-diamino-6-phenyl-1, 3, 5-triazine (DPT), followed by sulfonation treatment. The introduction of the phenyl group brings about alterations to the initial symmetrical arrangement of g-C3N4, leading to the disruption of certain hydrogen bonds. This, in turn, facilitates the movement of electrons from the n to π* orbitals, resulting in enhanced light absorption and improved efficiency in charge separation. Moreover, it induces modifications to the band structure and amplifies the production of hydroxyl radicals. Additionally, the introduction of sulfonic acid enhances the water affinity and the ability of dispersing graphitic carbon nitride in water. The optimized sulfonated benzene-substituted g-C3N4 (1000-BCN-SO3H) with a melamine to DPT ratio of 4:1 exhibits a maximum hydrogen production rate of 6.52 mmol·h−1·g−1 under simulated sunlight irradiation with good cycling stability, which is 3.93 times higher than that of g-C3N4 nanosheets. This research offers a promising opportunity for a novel approach in advancing carbon nitride materials for effective photocatalytic processes.

Polyoxometalates electron acceptor-intercalated In2O3@SnO2 nanofibers for chemiresistive ethanol gas sensors

Polyoxometalates (POMs), as a kind of electron acceptors, comes into sight in gas sensing field. Here, we in situ construct a group of polyoxomethoate/semiconductor one-dimensional tandem heterojunction materials using convenient one-step coaxial electrospinning method. A polyoxometalates electron acceptor layer was intercalated into In2O3@SnO2 nanofibers (NFs), forming In2O3@PW12@SnO2 coaxial core-middle-shell NFs. Gas sensing performances of the one-dimensional In2O3@PW12@SnO2 tandem heterojunctions were investigated for the first time. The fabricated NFs exhibited excellent detection performances for ethanol gas. The optimal sensitivity response to 100 ppm ethanol can reach 22.6, which is about 4 times that of POMs-free samples. Other gas sensing parameters were also comprehensively studied. The significant enhancement can be attributed to the addition of appropriate amount of PW12 electron acceptor which accelerate electrons transfer and reduce the recombination of electron-hole pairs. This work provides a novel strategy for developing high performance gas sensors by constructing tandem heterojunctions as well as introducing POMs electron acceptor, and offers new insight into the development of POMs-based gas sensors.

Facile construction of MoS2 decorated CdS hybrid heterojunction with enhanced hydrogen generation performance

Promoting the charge separation to improve photocatalytic performance of semiconductor photocatalysts is very important in the field of artificial photosynthesis. Here, a novel MoS2/CdS 2D–2D ultrathin nanosheet heterostructure was fabricated via a one-pot solvothermal route. The obtained 2D–2D MoS2/CdS nanojunction has not only provided large contact areas, but also shortened the charge transport distance, resulting in significantly enhanced photocatalytic H2 evolution property. The composites that were synthesized were examined using X-ray diffraction (XRD), Field emission scanning electron microscope (FESEM), Transmission electron microscope (TEM), UV-vis diffuse reflectance spectra (DRS), Photoluminescence (PL) and X-ray photoelectron spectra (XPS) analysis. By optimizing the 2D MoS2 amounts in the heterojunction, the 5 wt.% 2D/2D MoS2/CdS heterojunction displayed the maximal photocatalytic H2 evolution rate of 4449 μmolh−1g−1 under visible light irradiation in the presence of lactic acid as the sacrificial reagent, which was 6 times higher than that of pristine 2D CdS. Based on the photoelectrochemical and photoluminescence spectra tests, it could be deduced that the charge separation and transfer of 2D/2D MoS2/CdS heterojunction was tremendously improved, and the recombination of photoinduced electron-hole pairs was effectively impeded. Moreover, the 2D MoS2 was used as a cocatalyst to provide the abundant active sites and lower the overpotential for H2 generation reaction. The current work would offer an insight to fabricate the 2D/2D heterojunction photocatalysts for splitting H2O into H2.

Combating infections from drug-resistant bacteria: Unleashing synergistic broad-spectrum antibacterial power with high-entropy MXene/CDs

The growing resistance of bacteria to antibiotics has posed challenges in treating associated bacterial infections, while the development of multi-model antibacterial strategies could efficient sterilization to prevent drug resistance. High-entropy MXene has emerged as a promising candidate for antibacterial synergy with inherent photothermal and photodynamic properties. Herein, a high-entropy nanomaterial of MXene/CDs was synthesized to amplify oxidative stress under near-infrared laser irradiation. Well-exfoliated MXene nanosheets have proven to show an excellent photothermal effect for sterilization. The incorporation of CDs could provide photo-generated electrons for MXene nanosheets to generate ROS, meanwhile reducing the recombination of electron-hole pairs to further accelerate the generation of photo-generated electrons. The MXene/CDs material demonstrates outstanding synergistic photothermal and photodynamic effects, possesses excellent biocompatibility and successfully eliminates drug-resistant bacteria as well as inhibits biofilm formation. While attaining a remarkable killing efficiency of up to 99.99% against drug-resistant Escherichia coli and Staphylococcus aureus, it also demonstrates outstanding antibacterial effects against four additional bacterial strains. This work not only establishes a synthesis precedent for preparing high-entropy MXene materials with CDs but also provides a potential approach for addressing the issue of drug-resistant bacterial infections.

Inhibition photooxidation of pyrite under illumination via altering photogenerated carrier migration pathways: Role of DTC-TETA surface passivation

The oxidation of pyrite is the main cause of acidic mine drainage (AMD), which is a very serious environmental problem in numerous mining areas around the world. Previous studies have shown that passivation agents create a hydrophobic film on the surface of pyrite, effectively isolating oxygen and water. However, the presence of abundant sulfide minerals in tailings ponds may exacerbate AMD when exposed to solar radiation, due to the semiconductor properties of pyrite. It remains uncertain whether the current surface passivation coating can effectively prevent the oxidation of pyrite under light conditions. This paper is the first to investigate the passivation effect as well as the mechanism of surface passivation coating on pyrite under illumination from the perspective of materials science. The results demonstrated that the triethylenetetramine-bisdithiocarbamate (DTC-TETA) passivation coating on pyrite almost completely suppressed the photooxidation of pyrite under illumination by changing the migration path of photogenerated charge carriers. The formation of NC(S)2-Fe chelating groups provides atomic-level interface channels for DTC-TETA to transfer electrons to pyrite and creates a favorable reduction environment for pyrite. Besides, DTC-TETA coating greatly improves the electron-hole pairs recombination efficiency of pyrite, which significantly inhibits the photogenerated electron reduction of oxygen to generate reactive oxygen species (ROS). Moreover, DTC-TETA coating captures the photogenerated holes, avoiding direct oxidation of pyrite by holes. Density functional theory (DFT) calculations revealed that the DTC-TETA coating increases the adsorption energy barrier for oxygen and water. The results extend the existing knowledge on passivation mechanisms on pyrite and hold significant implications for the future screening, evaluation, and practical application of surface passivating agents.

Donor-acceptor type conjugated porous polymers based on benzotrithiophen and triazine derivatives: Effect of linkage unit on photocatalytic water splitting

Donor-acceptor conjugated polymers have received significant attention as the most promising photocatalysts for efficient photocatalytic hydrogen production (PHP). Nonetheless, achieving high photocatalytic PHP performance relies on molecular framework design and the judicious selection of different structural units. Herein, benzotrithiophene (BTT) and triazine derivatives were used as the basic units of organic polymers, and two conjugated porous polymers (CPPs) named as CP1 and CP2 were successfully synthesized by Stille coupling reaction. Compared with benzene as the linkage unit of triazine, it is evident that the incorporation of the thiophene unit in CP2 broadens its light response range, and promotes the generation of electrons/holes induced by light. Density functional theory (DFT) calculations and femtosecond transient absorption(fs-TA) spectroscopy reveal that CP2 effectively inhibits the photogenerated electron-hole pair recombination and promotes carrier transport. Remarkably, CP2 with Pt co-catalyst exhibited a notably superior PHP performance compared with that of CP1 polymer, which achieved an impressive hydrogen evolution rate (HER) of 21702.4 μmol/g/h, surpassing CP1 by approximately 3.7 times. This work provides a new tactic for enhancing the intrinsic PHP activity and reveals the underlying mechanism for the enhanced photocatalytic activity by regulating the different structural units of the donor-acceptor conjugated polymers.

PtCu Alloy-Modified Triptycene-Based Polymer with Charge Separation for Photocatalytic Hydrogen Evolution from Water/Seawater.

Direct photocatalytic hydrogen from earth-abundant seawater is a great potential way to achieve sustainable and clean energy, yet unsatisfactory decomposition and rapid electron-hole pair recombination of catalysts hinder the solar-driven H2 conversion efficiency. Herein, we designed a series of PtCu alloy nanoparticle-modified porous triptycene-based polymers (PtxCu1-TCP) to construct the heterostructure for highly efficient hydrogen generation from photocatalytic water/seawater splitting. Characterizations displayed that TCP with an ultrahigh surface area can confine the agglomeration of PtCu alloy; meanwhile, the PtCu alloy can facilitate the rapid electron transfer from TCP. In addition, TCP with a stable covalent bond structure can resist the corrosion of seawater. Benefiting from these two advantages, Pt7Cu1-TCP showed a remarkably enhanced photocatalytic performance with a maximum H2 evolution rate of 3255 μmol g-1 h-1 in natural seawater with triethanolamine, which is 2.69, 116.25, and 1.08 times that of Pt-TCP, Cu-TCP, and optimal catalyst in pure water, respectively. This study provides an idea for the development of a novel catalytic system for hydrogen production from solar-driven water/seawater splitting.

Preparation and Properties of Cotton Fabric Photocatalyzed by Ag-Doped Madder-Sensitized TiO2

In this study silver nanoparticles (NP) were grown in-situ on the surface of madder-sensitized TiO2 by an in-situ reduction method using silver nitrate as a silver source and a honeysuckle extract as a reducing agent. Silver doped madder-sensitized TiO2 nanoparticles were then prepared, supported on the surface of cotton fabrics to prepare photocatalytic cotton fabrics with high-efficiency self-cleaning properties and excellent antibacterial properties. transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) analyses showed that elemental Ag NPs were deposited on the surface of the madder-sensitized TiO2, and that Ag-doped madder-sensitized TiO2 NPs were successfully loaded on the cotton fabric surface. The results of UV-Visible diffuse reflectance spectroscopy (UV-Vis-DRS) and Photoluminescence Spectroscopy (PL) showed that Ag-doping could further reduce the band gap of madder-sensitized TiO2 than pure TiO2. The absorption of light in the photocatalytic system was increased, and the recombination of electron-hole pairs was effectively inhibited. Compared with madder-sensitized TiO2 photocatalyzed cotton fabric, the degradation rate of nano-Ag-doped madder-sensitized TiO2 photocatalytic cotton fabric for methylene blue (MB) was increased by 10.66% within 2 h, and the degradation process was in line with the first-order reaction kinetic model. After 5 times of washing, the photocatalytic cotton fabric still had excellent photocatalytic performance. Its antibacterial rates against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) reached 100 and 99.99%, respectively. In addition, it had good wrinkle resistance and UV protection properties, but the cross-linking modification reduced the breaking strength by about 14%.