Field Of Photocatalysis Research Articles

Study on photocatalytic degradation and antibacterial properties of conjugated microporous polymers/TiO2 composite membranes

Conjugated microporous polymers (CMPs) are widely used in the field of photocatalysis due to their unique conjugated structures and various synthesis methods. Herein, we report the design and synthesis of conjugated microporous polymers hollow spheres (CMPs-HS) superhydrophilic modified by acetylcysteine (CMPs-HS-S) and compounded with the inorganic semiconductor material titanium dioxide (CMPs-HS-S/TiO2) for efficient photocatalytic degradation. To facilitate recycling, the composite membrane material was prepared by combining the materials mentioned above with PVDF membrane. The composite membrane materials had good hydrophilic and photocatalytic properties. Under visible light, the degradation rate of tetracycline (TC) (10 mg/L 180 min) reached 90 %, and the bactericidal rates for Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were 89 % and 99.99 %, respectively. The efficient photocatalytic performance of the composite membranes could be attributed to the hollow sphere structure of CMPs and the role of TiO2 as a photogenic electron transfer platform. Additionally, the hydrophilicity of the membrane also helped to accelerate the occurrence of photocatalytic reactions. After electron paramagnetic resonance (EPR) detection, h+, 1O2 and O2− were proved to be important reactive substances, which played a major role in degradation. These studies reflect the versatility of CMPs-based photocatalysts and provide a new idea for the future development of CMPs-based photocatalysts.

Green synthesis of ZnO, Fe3O4, and TiO2 nanoparticles: exploring enhanced bacterial inhibition, catalysis, and photocatalysis for sustainable environmental applications

ABSTRACT This study investigates the physicochemical and biological properties of metal oxide nanoparticles (TiO2, ZnO, and Fe3O4) synthesised via the phytosynthesis method using an extract from Boerhaavia diffusa leaves (BDL). The proteins and phenols present in the BDL extract played essential roles in reducing and stabilising TiO2, ZnO, and Fe3O4 nanoparticles. The study reveals size-dependent morphological, structural, and biological characteristics of the produced nanoparticles. FTIR spectra confirm the involvement of BDL extract in the synthesis process of TiO2, ZnO, and Fe3O4 nanoparticles. Transmission electron microscopy (TEM) analysis of TiO2 nanoparticles identified small, spherical particles (9 nm in diameter). BDL-derived TiO2, ZnO, and Fe3O4 demonstrated significant photocatalytic activity, achieving degradation rates of 98.96%, 96.26%, and 94.42%, respectively, in the decomposition of mono-azo dye after 40 minutes of UV irradiation. The reaction rates for BDL-derived TiO2, ZnO, and Fe3O4 were 0.367/min, 0.186/min, and 0.061/min, respectively, when catalysing the reduction of 4-Nitrophenol (4-NP) to 4-Aminophenol using NaBH4. BDL-derived TiO2 nanoparticles exhibited significant antibacterial effectiveness, showing a 23.6 mm zone of inhibition against Salmonella typhi. The BDL-derived TiO2, ZnO, and Fe3O4 nanoparticles exhibited remarkable cytotoxicity against lung cancer cell lines with IC50 values of 76.36 µg/mL, 90.21 µg/mL, and 94.61 µg/mL, respectively. This study reveals the potential of BDL-derived TiO2, ZnO, and Fe3O4 nanoparticles for applications in antibacterial, anticancer, catalytic, and photocatalytic fields, contributing to sustainable development of multifunctional nanomaterials for various technical and environmental advancements.

A Review on Bi2WO6-Based Materials for Photocatalytic CO2 Reduction.

Photocatalytic reduction of CO2 (PCR) technology offers the capacity to transmute solar energy into chemical energy through an eco-friendly and efficacious process, concurrently facilitating energy storage and carbon diminution, this innovation harbors significant potential for mitigating energy shortages and ameliorating environmental degradation. Bismuth tungstate (Bi2WO6) is distinguished by its robust visible light absorption and distinctive perovskite-type crystal architecture, rendering it highly efficiency in PCR. In recent years, numerous systematic strategies have been investigated for the synthesis and modification of Bi2WO6 to enhance its photocatalytic performance, aiming to achieve superior applications. This review provides a comprehensive review of the latest research progress on Bi2WO6 based materials in the field of photocatalysis. Firstly, outlining the fundamental principles, associated reaction mechanisms and reduction pathways of PCR. Then, the synthesis strategy of Bi2WO6-based materials is introduced for the regulation of its photocatalytic properties. Furthermore, accentuating the extant applications in CO2 reduction, including metal-Bi2WO6, semiconductor-Bi2WO6 and carbon-based Bi2WO6 composites etc. while concludes with an examination of the future landscape and challenges faced. This review hopes to serve as an effective reference for the continuous improvement and implementation of Bi2WO6-based photocatalysts in PCR.

Highly selective photocatalytic oxidation of CH4 to CH3OH: A theoretical study

Photooxidation of methane (CH4) in aqueous solution to generate high-value organic compounds is an effective way to replace traditional industrial methods. It is crucial to select catalysts that can avoid competitive reactions and achieve high selectivity. Using first principles calculations, a novel one-dimensional (1D) Ti3C2O2 nanoribbon (NR)/two-dimensional (2D) monolayer MoS2 (MS) heterojunction photocatalyst was ingenious designed in this work, which can achieve the oxidation of CH4 molecules and suppress the execution of competitive reactions. The results indicate that the constructed 1D NR exhibits semiconductor properties and its energy level position meet the requirements of photocatalytic oxidation for CH4. The heterojunction structure composed of NR and MS forms an efficient S-Scheme electron transfer mechanism under illumination, which not only provides sufficient internal driving force for CH4 oxidation, but also effectively avoids the competitive reaction between water molecules and photo-generated holes. Specifically, the photocatalysts exhibits high selectivity and low reaction overpotential for the generation of methanol (CH3OH). This study provides a new perspective for photocatalytic CH4 oxidation and demonstrates the potential application value of 1D MXene in the future field of photocatalysis.

H2O2-assisted room temperature preparation of crystalline TiO2 and Ti3C2Tx-derived C-doped amorphous TiOx homojunction for photocatalytic degradation of tetracycline

The light absorption, active sites, and charge carriers separation of photocatalysts are extremely important factors in the field of photocatalysis. Near-perfect lattice-matched homojunction constructed using disorder engineering and doping strategies is an effective strategy to improve photocatalytic activity. Herein, we developed crystalline TiO2 nanoparticles (NPs) and Ti3C2Tx MXene-derived C-doped amorphous TiOx homojunction (TCT) at room temperature. In this homojunction, TiO2 NPs are evenly distributed on the surface of the C-TiOx nanosheet to form a type-II structure, which promotes the separation of photogenerated carriers. The light absorption range of TCT extends to 550 nm due to the presence of intermediate energy levels in C-TiOx, which increases its photon absorption capacity. Moreover, TCT possesses a large number of oxygen vacancies, which are beneficial for improving the adsorption and degradation of pollutants. These characteristics of TCT could significantly improve its photodegradation performance for tetracycline. Interestingly, the precursor mass ratio of TCT with the best degradation efficiency is different under different illumination conditions, which is attributed to the different band gaps of C-TiOx and TiO2 NPs resulting in different light absorption ranges. This work provides a new approach to rationally designing crystalline and amorphous homojunction for photocatalytic applications.

Photocarrier behavior and photocatalytic H2O2 synthesis performance of amorphous/crystalline SrTiO3/BiVO4 layered heterostructures

BiVO4 (BVO), as a visible light responsive semiconductor material, has been widely employed in the field of photocatalysis. However, monoclinic BVO is afflicted by a high recombination rate of photogenerated charge carriers and poor charge transport capability, resulting in low charge utilization efficiency. Constructing heterostructures for interface modification of BVO is an effective strategy to improve photocatalytic performance. Herein, amorphous/crystalline SrTiO3/BiVO4 (STO/BVO) layered film nanoheterostructures have been successfully fabricated on the (001) yttrium stabilized zirconia substrate by magnetron sputtering. Under 440 nm monochromatic light irradiation, the H2O2 production rate of the composite film is increased by 1.2 times compared to pure BVO. The type II heterostructure composed of STO and BVO accomplishes selective interface hole transport from BVO to STO, promoting the separation of space charges. Additionally, the interaction between amorphous/crystalline interfaces effectively suppresses the photocorrosion of BVO and strengthens the stability of the film, which is of great significance for studying charge transport behavior and photocatalytic mechanisms.

Z-scheme InVO4/ZnFe2O4 heterojunction for efficient photocatalytic nitrogen fixation

Given outstanding light absorption and utilization capabilities, narrow-bandgap semiconductors receive intensive interests in the photocatalysis field. However, the narrow bandgap is a double-edged sword, with the non-negligible charge carrier recombination and hinderance of redox reactions due to the limited redox capability. The construction of Z-scheme heterojunctions could address the aforementioned issues. In this work, we selected two band-matched narrow-bandgap semiconductor catalysts (InVO4 and ZnFe2O4) for the construction of a Z-scheme heterojunction. Compared with pure InVO4 and pure ZnFe2O4, the as-obtained InVO4/ZnFe2O4 Z-scheme heterojunction exhibited improved light harvesting capability and enhanced photogenerated electron-hole pair separation rate. The regulated energy band structure of as-formed InVO4/ZnFe2O4 Z-scheme heterojunction could accelerate the spatial separation of photogenerated electrons and holes, reduce the recombination probability, and provide sufficient electrons to participate in the nitrogen reduction, ultimately significantly promoting photocatalytic activity. Benefiting from above improvements, the NH3 yield of InVO4/ZnFe2O4 for photocatalytic nitrogen fixation was up to 453.37 μmol/gcat/h, which was about 17.7 times and 62.9 times higher than that of pure InVO4 and ZnFe2O4 samples, respectively. This study gives a promising guidance to the facile design and utilization of Z-scheme heterojunction composed of narrow-bandgap semiconductors.

Efficient photocatalytic CO2 and Cr(VI) reduction on carbon quantum dots/carbon nitride heterojunctions

Carbon quantum dots (CQDs), known for their exceptional optical properties, hold the potential to enhance light absorption, charges separation and transfer in semiconductor materials. However, using cheap medicinal materials as precursors in the field of photocatalysis to obtain CQDs has seldom concerned. In this study, we utilized biomass-derived CQDs from carbon-rich licorice powder to improve photocatalytic CO2 and Cr(VI) reduction in polymer carbon nitride (PCN). The CQDs/g-C3N4 heterojunctions were synthesized via a hydrothermal method, and the successful fabrication and integration of CQDs on g-C3N4 surfaces were confirmed through detailed characterization. The optimal sample with a licorice powder to PCN mass ratio of 0.05:1 ((50CQDs/CN) demonstrates a tripling in CO2 conversion efficiency under simulated sunlight compared to the reference PCN. Under visible light irradiation, the 50CQDs/CN also performs superior photocatalytic Cr (VI) removal efficiency, which is 2.48 times of that of the reference PCN. This significant boost is attributable to the successful construction of the CQDs/CN heterojunction and the abundance of functional groups on the CQDs surface, which provide more active sites, improve light absorption and increase charges migration rates. The stability of these new photocatalysts was confirmed through repeated photocatalytic cycles, indicating their potential for practical applications. Mechanistic studies reveal insights into the enhanced photocatalytic pathways and intermediate conversion processes. Our findings present a novel, efficient and sustainable route to fabricate g-C3N4-based photocatalysts, offering a promising strategy for further mitigate the greenhouse gas crisis and environmental pollution.

Localized surface plasmon resonance-enhanced photoelectrochemical immunoassay based on high-entropy yolk-shell Au@(ZnCdMnGaCu)xS

The yolk-shell structure has become a research hotspot in the field of photocatalysis in recent years due to its stability, movable yolk, and internal voids. However, yolk-shell has not been fully explored and applied in photoelectrochemical (PEC) immunoassays. In this work, a smartphone-based portable PEC immunoassay was constructed by using high-entropy yolk-shell Au@(ZnCdMnGaCu)xS as a photosensitive material, showing satisfactory detection with the assistance of localized surface plasmon resonance (LSPR). Specifically, a typical sandwich reaction introduces a detection antibody modified and labeled with gold nanoparticles (Au NPs) of alkaline phosphatase (ALP) into the system with the presence of prostate-specific antigen (PSA). Ascorbic acid (AA) content increased with increasing PSA and showed a linear enhancement of photocurrent at PSA concentrations of 0.01–50 ng mL−1 with a limit of detection of 8.94 pg mL−1. Additionally, the proposed assay technology not only provides a portable detection system for the immediate detection of tumor markers, but also offers a promising paradigm for the development of high-entropy materials.

Recent Developments in Immobilized Photocatalyst for Hydrogen Production

AbstractSolar‐driven water splitting for hydrogen production has emerged as one of the most promising methods for addressing environmental and energy crises. The utilization of immobilized photocatalyst for hydrogen production has attracted significant attention in recent years due to its excellent stability, high photocatalytic efficiency, and ease of recovery and reuse. Hence, a comprehensive review of the development of immobilized photocatalyst appears exceedingly significant. Herein, we initially analyze the advantages of the immobilized photocatalytic system in aspects such as light absorption, photon utilization, and charge separation. Subsequently, we introduce various assembly techniques for immobilized photocatalyst and elaborate on some representative characteristics of this immobilized system. Furthermore, we cite the examples of the application of immobilized photocatalyst in large‐scale hydrogen production to envision its future prospects. Finally, we discuss the remaining issues in this field and outline future directions of development and challenges therein. This review holds great promise for prompting the advancement of immobilized photocatalyst in the field of photocatalysis.

Photothermal-assisted magnetic recoverable Cd0.9Zn0.1S/NiCoB heterojunction with extraordinary photocatalytic hydrogen evolution

Easily recyclable photocatalysts hold great potential in the field of photocatalysis. Guided by rational theoretical predictions, this study designs a novel tetrapod-like Cd0.9Zn0.1S/NiCoB (CZS/NCB) Schottky heterojunction with magnetic and photothermal properties, and demonstrates its excellent photocatalytic hydrogen evolution performance. Under the combined effects of the photothermal properties and the Schottky heterojunction, the photocatalytic hydrogen evolution rate extraordinarily reaches 108.39 mmol g−1 h−1 after 3 h of visible light irradiation, which is 4.69 times that of pure CZS. Additionally, photocatalytic hydrogen evolution tests conducted using infrared thermography and alternating visible and visible plus infrared light irradiation have confirmed the material’s outstanding photothermal properties. In-depth density functional theory (DFT) calculations reveal potential charge transfer pathways and confirm the formation of the Schottky heterojunction. This work provides guidance for the rational construction of magnetic recoverable photocatalysts with practical application.

Recent Advances in Piezoelectric Coupled with Photocatalytic Reaction System: Synergistic Mechanism, Enhancement Factors, and Application.

The field of photocatalysis has demonstrated numerous advantages in the domains of environmental protection, energy, and materials science. However, conventional modification methods fail to simultaneously enhance carrier separation efficiency, redox capacity, and visible light absorption solely through light activation due to the intrinsic band structure limitations of photocatalysts. In addition to modification methods, the introduction of an external field, such as a piezoelectric field, can effectively address deficiencies in each step of the photocatalytic process and enhance the overall performance. The assistance of a piezoelectric field overcomes the limitations inherent in traditional photocatalytic systems. Hence, this review provides a comprehensive overview of recent advancements in piezoelectric-assisted photocatalysis and thoroughly investigates the interaction between the alternating piezoelectric field and photocatalytic processes. Various ideas for synergistic enhancement of the piezoelectric and photocatalytic properties are also explored. This multifield catalytic system shows remarkable performance in stability, pollutant degradation, and energy conversion, distinguishing it from single catalytic systems. Finally, an in-depth analysis is conducted to address the challenges and prospects associated with piezoelectric photocatalysis technology.

Fluorine Doping Mediated Epitaxial Growth of NaREF4 on TiO2 for Boosting NIR Light Utilization in Bioimaging and Photodynamic Therapy

AbstractBy integrating TiO2 with rare earth upconversion nanocrystals (NaREF4), efficient energy transfer can be achieved between the two subunits under near‐infrared (NIR) excitation, which hold tremendous potential in the fields of photocatalysis, photodynamic therapy (PDT), etc. However, in the previous studies, the combination of TiO2 with NaREF4 is a non‐epitaxial random blending mode, resulting in a diminished energy transfer efficiency between the NaREF4 and TiO2. Herein, we present a fluorine doping‐mediated epitaxial growth strategy for the synthesis of TiO2‐NaREF4 heteronanocrystals (HNCs). Due to the epitaxial growth connection, NaREF4 can transfer energy through phonon‐assisted pathway to TiO2, which is more efficient than the traditional indirect secondary photon excitation. Additionally, F doping brings oxygen vacancies in the TiO2 subunit, which further introduces new impurity energy levels in the intrinsic band gap of TiO2 subunit, and facilitates the energy transfer through phonon‐assisted method from NaREF4 to TiO2. As a proof of concept, TiO2‐NaGdF4 : Yb,Tm@NaYF4@NaGdF4 : Nd@NaYF4 HNCs were rationally constructed. Taking advantage of the dual‐model up‐ and downconversion luminescence of the delicately designed multi‐shell structured NaREF4 subunit, highly efficient photo‐response capability of the F‐doped TiO2 subunit and the efficient phonon‐assisted energy transfer between them, the prepared HNCs provide a distinctive nanoplatform for bioimaging‐guided NIR‐triggered PDT.

Anchoring gadolinium oxide nanoparticles onto CuInZnS: Efficient photocatalytic tetracycline degradation and mechanism analysis

Photocatalysis technology is one of the potential methods to remit the growing issues of environmental pollution. It is of great significance to rationally design high performance antibiotic wastewater degradation catalysts in the whole pH range. In this experiment, Gd2O3 nanoparticles (GdO NPs) were successfully grown onto CuInZnS (CIZS) by a simple hydrothermal method. The introduction of GdO has obvious effects on the nanosheet thickness of CIZS, which reduces carrier transport distances and improves the active sites number of CIZS. What’s more, the SO4•- absorption and electron transfer ability are also greatly optimized. Under 300 W Xe light, tetracycline can be efficient degraded more than 93 % in the whole pH range, which presents absolute advantage compared to CIZS and GdO. Based on the combination of experimental characterization and density functional theory calculations, the proposed photocatalytic tetracycline degradation pathway and mechanism have been given. Moreover, the results of toxicity analysis proved that the CIZS-GdO catalyst could successfully reduce the toxicity of tetracycline wastewater. This work has reference value for the application of rare earth oxides in the field of photocatalysis at full pH range.

Fluorine Doping Mediated Epitaxial Growth of NaREF4 on TiO2 for Boosting NIR Light Utilization in Bioimaging and Photodynamic Therapy.

By integrating TiO2 with rare earth upconversion nanocrystals (NaREF4), efficient energy transfer can be achieved between the two subunits under near-infrared (NIR) excitation, which hold tremendous potential in the fields of photocatalysis, photodynamic therapy (PDT), etc. However, in the previous studies, the combination of TiO2 with NaREF4 is a non-epitaxial random blending mode, resulting in a diminished energy transfer efficiency between the NaREF4 and TiO2. Herein, we present a fluorine doping-mediated epitaxial growth strategy for the synthesis of TiO2-NaREF4 heteronanocrystals (HNCs). Due to the epitaxial growth connection, NaREF4 can transfer energy through phonon-assisted pathway to TiO2, which is more efficient than the traditional indirect secondary photon excitation. Additionally, F doping brings oxygen vacancies in the TiO2 subunit, which further introduces new impurity energy levels in the intrinsic band gap of TiO2 subunit, and facilitates the energy transfer through phonon-assisted method from NaREF4 to TiO2. As a proof of concept, TiO2-NaGdF4 : Yb,Tm@NaYF4@NaGdF4 : Nd@NaYF4 HNCs were rationally constructed. Taking advantage of the dual-model up- and downconversion luminescence of the delicately designed multi-shell structured NaREF4 subunit, highly efficient photo-response capability of the F-doped TiO2 subunit and the efficient phonon-assisted energy transfer between them, the prepared HNCs provide a distinctive nanoplatform for bioimaging-guided NIR-triggered PDT.

Construction of two-dimensional heterojunctions based on metal-free semiconductor materials and Covalent Organic Frameworks for exceptional solar energy catalysis

Covalent organic frameworks (COFs) are newly developed crystalline substances that are garnering growing interest because of their ultra-high porosity, crystalline nature, and easy modified architecture, showing promise in the field of photocatalysis. However, it is difficult for pure COFs materials to achieve excellent photocatalytic hydrogen production due to their severe carrier recombination problems. To mitigate this crucial issue, establishing heterojunction is deemed an effective approach. Nonetheless, many of the metal-containing materials that have been used to construct heterojunctions with COFs own a number of drawbacks, including small specific surface area and rare active sites (for inorganic semiconductor materials), wider bandgaps and higher preparation costs (for MOFs). Therefore, it is necessary to choose metal-free materials that are easy to prepare. Red phosphorus (RP), as a semiconductor material without metal components, with suitable bandgap, moderate redox potential, relatively minimal toxicity, is affordable and readily available. Herein, a range of RP/TpPa-1-COF (RP/TP1C) composites have been successfully prepared through solvothermal method. The two-dimensional structure of the two materials causes strong interactions between the materials, and the construction of heterojunctions effectively inhibits the recombination of photogenic charge carrier. As a consequence, the 9% RP/TP1C composite, with the optimal photocatalytic ability, achieves a photocatalytic H2 evolution rate of 6.93 mmol g−1 h−1, demonstrating a 10.19-fold increase compared to that of bare RP and a 4.08-fold improvement over that of pure TP1C. This article offers a novel and innovative method for the advancement of efficient COFs-based photocatalysts.

Europium (III)-modified sunflower-derived carbon dots for fluorescent anti-counterfeiting inks and photocatalysis.

A highly water-soluble and fluorescent N,S-doped carbon dots/europium (N,S-CDs/Eu) was successfully synthesized via a secondary hydrothermal method. This involved surface modification of N,S-CDs derived from sunflower stem pith (SSP) with europium ions (Eu3+) doping. When excited within the range of 400-470 nm, N,S-CDs/Eu exhibited a stable and broad optimal emission wavelength ranging from 505 to 540 nm. Notably, the photoluminescence quantum yield (PLQY) of N,S-CDs/Eu is 31.4%, significantly higher than the 19.5% observed for N,S-CDs. Additionally, by dissolving N,S-CDs/Eu into polyvinyl alcohol (PVA), a uniform fluorescent anti-counterfeiting ink can be prepared. The N,S-CDs/Eu/TiO2 composite demonstrates excellent photocatalytic degradation ability towards the organic dye methylene blue (MB). N,S-CDs/Eu has potential in the field of fluorescent inks and photocatalysis due to its simple and efficient preparation and excellent properties.

Scavenger-free solar photocatalytic degradation of Textile Dyes and Antibiotics using magnetically separable bi-junctional photocatalyst

The field of solar photocatalysis has been plagued by photocatalysts with low photon-to-electron conversion efficiency, resulting in poor photocatalytic degradation rates of water pollutants. With a keen idea to improve the existing photocatalysts, we developed a scavenger-free, magnetically separable, bi-junctional solar photocatalyst. The photocatalyst comprises Fe2+ doped zinc ferrite as core, ZnO as shell, and irregular CuO nanoparticles in conjunction with the surface of core-shell nanoparticles prepared using a combination of microwave-assisted solvothermal technique and microwave-assisted reflux method. The photocatalytic degradation properties of the solar photocatalyst were modelled and optimized with the help of Methyl Orange under direct sunlight. This novel composite degrades Methyl Orange roughly four times faster than core-shell nanoparticles. The photocatalyst meets most of the criteria for working of a promising solar photocatalyst, such as 1) excellent absorption of sunlight, 2) two physically distinct heterojunction and absorbing regions for efficient charge carrier generation and separation, 3) scavenger-free degradation of textile dyes and antibiotics, 4) High surface area (39 m2g −1), 5) good stability, 6) excellent reusability, 7) and easy separation of nanoparticles for reuse with the help of a magnet. The prepared photocatalyst efficiently degrades fluoroquinolone antibiotics such as Ciprofloxacin Hydrochloride, Norfloxacin, and Ofloxacin. The photocatalyst demonstrates the capability to efficiently degrade textile dyes such as Methyl Orange, Methylene Blue, Orange G, Fluorescein sodium salt, Rhodamine B, and Crystal Violet. Additionally, the bi-junctional photocatalyst can be coated with a thin layer of silver to achieve twice the degradation rate. This enhancement is attributed to the Localized Surface Plasmon Resonance (LSPR) effect. The current work presents an effective and economical option for removing dyes and antibiotics in wastewater, marking a significant stride towards sustainable industrial practices.

Tuning (Photo)Electronic Properties of an Electron Deficient Porous Polymer via n-Doping with Tetrathiafulvalene.

Charge-transfer complex formation within the pores of porous polymers is an efficient way to tune their electronical properties. Introduction of electron accepting guests to the electron donating hosts to conduct their p-doping is intensively studied in this context. However, the vice versa scenario, n-doping by treating the electron deficient (i.e., n-type) porous polymers with electron donating dopants, is rare. In this work, synthesis of an n-type phenazine based conjugated microporous polymer and its exposure to strong electron donating tetrathiafulvalene (TTF) dopants are presented. The fundamental physical characterizations (e.g., elemental analysis, gas sorption) showed that the vacuum impregnation technique is a good approach to load the guest molecules inside the pores. Moreover, the formation of charge-transfer complexes between the phenazine building blocks of the polymeric network and TTF dopants are confirmed via spectral techniques such Fourier transform infra-red, UV-vis, steady-state/time-resolved photoluminescence, and transient absorbance spectroscopies. Effect of the doping to the electronical properties is monitored by employing photoelectrochemical measurements, which showed lower charge-transfer resistivity and nearly doubled photocurrents after the doping. The study is, therefore, an important advancement for the applicability of (n-type) porous polymeric materials in the field of photo(electro)catalysis and organic electronics.

Modulation of π-Electron Density in Ultrathin 2D Layers of Graphite Carbon Nitride for Efficient Photocatalytic Hydrogen Production.

The rational design and synthesis of novel semiconductor nano-/quantum materials have been ambitiously pursued in the field of photocatalysis as the technology is promising and critical for attaining future energy and environmental sustainability. Herein, the integrity of aromatic carbon into graphitic carbon nitride (CN) at the same molecular plane with a few 2D layers is achieved by using modulated precursors of CN, forming carbon regulated ultrathin CN (CUCN) with improved charge transfer kinetics and photocatalytic hydrogen production. The grafted graphite rings adjacent to carbon nitride frameworks induce a significant rearrangement and relocalization of the overall framework, and form conjugated sp2 hybridized interfaces and internal electric fields that drive the separation and directional transfer of photogenerated electrons from CN sheets towards intralayer graphite regions, where the photocatalytic hydrogen evolution reaction occurs extensively, yielding largely increased HER rate of 2231.8 µmol g-1 h-1 by 8.2 times relative to CN, as well as a remarkable apparent quantum yield of 2.93% under monochromatic light at 420 nm. The high physicochemical stability and low synthesis cost of CUCN make it a potential benchmark photocatalyst that can be readily modified via element doping, heterojunction introduction, defect engineering, and so on, to further enhance its HER performance.