Photoexcited Electron-hole Pairs Research Articles

Enhanced Photocatalytic Degradation by the Preparation of a Stable La-Doped FeTiO3 Photocatalyst: Experimental and DFT Study.

The rapid photocarrier recombination limits the photocatalytic activity of iron titanate (FeTiO3) to be further improved. Developing novel approaches to inhibit the rapid recombination rate of the FeTiO3 photocatalysts is crucial for efficiently degrading pollutants in wastewater. Rare earth ions, with unique electron dispositions and large ion radii, could effectively inhibit photocarrier recombination. Herein, novel lanthanum (La)-doped FeTiO3 photocatalysts were designed and successfully synthesized. The photocatalytic performance of the 12 mol % La/FeTiO3 photocatalyst was superior in degrading tetracycline hydrochloride (TCH), methylene blue (MB), and brilliant blue (BB). These degradation rate constants (k) were 0.12358, 0.01357, and 0.03064 L mg-1 min-1, respectively, which were 12.83, 1.61, and 7.78 times that of pure FeTiO3. The photoelectronic tests and density functional theory (DFT) calculations revealed that the La 4f orbital forms an impurity energy level in the conduction band of FeTiO3. This level narrows the bandgap and acts as an electron acceptor, capturing photoexcited electrons and inhibiting the rapid recombination of photoexcited electron-hole pairs in FeTiO3. This work enhances the potential of FeTiO3 in the photocatalysis field and provides important insights into the efficient degradation of organic pollutants in wastewater.

An efficient NiS-ReS2/CdS nanoparticles with dual cocatalysts for photocatalytic hydrogen production

The construction of heterojunctions is one of efficacious ways to improve the charge transfer and suppress the recombination of photoexcited electron-hole pairs for enhancing reactive activities of photocatalysts. Ternary NiS-ReS2/CdS composites are synthesized via a one-step hydrothermal method and the heterojunction nanostructures are achieved. The NiS-ReS2/CdS photocatalyst exhibits the superior photocatalytic activity with a hydrogen production rate up to 139 mmol g−1 h−1, which is much higher than binary composites and pure CdS. The contributions of the dual cocatalysts NiS and ReS2 are verified to narrower bandgaps, lower resistances and increase photocurrent density of NiS-ReS2/CdS, promoting the absorption of visible light and the migration of photoinduced electrons. The NiS-ReS2/CdS heterostructures provide a possible dual Z-scheme path for the rapid transfer of electrons. The tailoring of the dual cocatalysts is effective to improve the photocatalytic hydrogen production.

The Hydrothermal-Assisted Approach Improves the Photocatalytic and Energy Storage Performance of Novel CuSe-TiO2-GO Composite.

This study reports a novel CuSe-TiO2-GO composite, synthesized by a facile hydrothermal method at a controlled temperature, and investigates its electrochemical performance for supercapacitors (SCs) and photocatalytic behavior for degrading methylene blue (MB) dye. The compositional phase structure and chemical bond interaction were thoroughly investigated. The as-fabricated pristine, binary, and ternary composites underwent comprehensive characterization employing spectroscopic techniques and electrochemical analysis. Compared with pure and binary compounds (CuSe, TiO2, and binary CuSe-TiO2 composites), the ternary CuSe-TiO2-GO composites demonstrated a high degradation efficiency while degrading MB in less than just 80 min (240 min, 100 min, and 140 min, respectively). The photocatalytic activity of the ternary CuSe-TiO2-GO composites is enhanced due to the highly positive conduction band of CuSe, leading to the quick excitation of electrons to the conduction band of CuSe. Subsequently, graphene oxide (GO) left holes on the photocatalyst surface for MB, as GO assisted the photoexcited electron-hole pairs, resulting in enhanced photocatalytic performance. The CuSe-TiO2-GO electrode for the supercapacitor indicates a 310.6 F/g and 135.2 F/g capacitance when the discharge current upsurges from 1 to 12 A/g. The good photocatalytic and energy storage performance is due to the smaller charge transfer resistance, which promotes efficient separation of electron-hole pairs.

Photoresponse dependence of WS2/Pt Schottky junction on the features of Pt nanoparticles

In this study, we delve into the photoresponsive characteristics of Schottky junctions fabricated through the deposition of Pt nanoparticles (NPs) onto multilayer WS2 sheets grown via chemical vapor deposition. Our analysis encompasses a comprehensive examination of the junction's morphology, structural attributes, and photophysical behavior. Of particular interest is the intricate relationship between the efficiency of hot electron injection and the specific properties of the Pt NPs, namely their density and size. Our findings reveal that Pt NPs effectively extinguish the photoluminescence of WS2, an outcome attributed to the efficient separation of photo-generated electron-hole pairs facilitated by the WS2/Pt Schottky junction. This process, however, does not significantly alter the electronic configuration of WS2. The modulation of exciton radiative decay is shown to be contingent upon the size and density of the Pt NPs, with an average size of 1.27 nm and density of 0.82 /nm² yielding the most rapid exciton decay rate of 1.15 ns. This pronounced dependence of exciton dynamics on Pt NPs features can be attributed to the quenching effect exerted by densely packed Pt NPs, which also plays a pivotal role in the injection of hot electrons from Pt to WS2. The enhancement of internal photoemission is evidenced by a pronounced increase in near-infrared photoresponse within the 800-1000 nm range. Furthermore, the optimization of Pt NPs features leads to superior photoresponsive performance in the WS2/Pt Schottky junctions, manifesting as a responsivity of 280 A/W and a detectivity of 7.77 × 1012 Jones at a wavelength of 850 nm. This photoresponse's dependence on Pt NPs features underscores the dual mechanism governing photodetection in the WS2/Pt Schottky junction: a synergistic interplay between hot electron injection and the separation of photo-excited electron-hole pairs.

An innovative triple interface reinforced photocatalytic system based on BiOCl/BaTiO3@Co-BDC-MOF composite for the simultaneous detoxification of Cr(VI) and sulfamethoxazole

The development of effective photocatalysts for the reduction of Cr(VI) and the degradation of antibiotics remains a challenge. The present work reports the development of a novel heterojunction composite material, BiOCl/BaTiO3@Co-BDC-MOF (BOC/BTO@Co-MOF), based on solvothermal techniques. To characterize the surface and bulk features of the material, techniques such as FE-SEM, HR-TEM, BET/BJH, XPS, FT-IR, p-XRD, and UV–Vis-DRS were used. Based on the results, the BiOCl/BaTiO3 nanocomposites are uniformly dispersed on the rod-shaped Co-BDC MOF, resulting in a layered texture on the surface. A further advantage of the composite structure is the strong interfacial enhancement facilitating the separation of photoexcited electron-hole pairs. Also, compared to its pristine counterparts, the heterostructure material exhibited excellent surface area and pore properties. The photocatalytic efficiency towards reduction and degradation of Cr(VI)/SMX pollutants were evaluated by optimizing various analytical parameters, such as pH, catalytic loading concentrations, analyte concentration, and scavenger role. The specially designed BOC/BTO@Co-MOF composite achieved a 96.5% Cr(VI) reduction and 98.2% SMX degradation under 60.0–90.0 min of visible light illumination at pH 3.0. This material is highly reusable and has a six-time recycling potential. The findings of this study contribute to a better understanding of the efficient decontamination of inorganic and organic pollutants in water purification systems.

Bidirectional heterojunctions photocatalyst engineered with separated dual reduction sites for hydrogen evolution

Photocatalytic technology is identified as one of the most clean and sustainable routes for hydrogen generation. Nonetheless, inadequate photoinduced carrier separation limits photocatalytic performance. Rationally designing bidirectional heterojunctions that leverage single/two-photon co-excitation pathways and dual reduction sites, thereby inhibiting recombination of the photoinduced carriers and exposing active sites to increase photocatalytic activity. This study proposes bidirectional heterojunctions consisting of 0D carbon dots (CDs) and nickel phthalocyanines co-modified sulfur-doped multivesicular carbon nitride tubes (denoted as 7CDs/SMVCTs/Ni0.5 %). The as-prepared photocatalyst displays a remarkable yield of 16,363.62 μmol g−1 h−1, with a rate 23.2 times that of pristine carbon nitride (denoted as PCN, 704.23 μmol g−1 h−1). The improvement of photocatalytic performance is attributed to the efficient separation and transportation of photoexcited electron-hole pairs induced by the coexistence of single/two-photon excitation pathways and dual reduction sites. The efficient combination of lateral and vertical heterostructures plays an essential role in the photocatalytic process and is exhaustively studied using catalyst rational design and modification technology.

Fabrication of Flower-Shaped Sb2S3/Fe2O3 Heterostructures for Enhanced Photoelectrochemical Performance.

Antimony sulfide (Sb2S3) has been recognized as a catalytic material for splitting water by solar energy because of its suitable narrow band gap, high absorption coefficient, and abundance of elements. However, many deep-level defects in Sb2S3 result in a significant recombination of photoexcited electron-hole pairs, weakening its photoelectrochemical performance. Here, by using a simple hydrothermal and spin-coating method, we fabricated a step-scheme heterojunction of Sb2S3/α-Fe2O3 to improve the photoelectrochemical performance of pure Sb2S3. Our Sb2S3/α-Fe2O3 photoanode has a photocurrent density of 1.18 mA/cm2 at 1.23 V vs reversible hydrogen electrode, 1.39 times higher than that of Sb2S3 (0.84 mA/cm2). In addition, our heterojunction has a lower onset potential, a higher absorbance intensity, a higher incident photon-to-current conversion efficiency, a higher applied bias photon-to-current efficiency, and a lower charge transfer resistance compared to pure Sb2S3. Based on ultraviolet photoelectron spectroscopy, we constructed a step-scheme band structure of Sb2S3/α-Fe2O3 to explain its photoelectrochemical enhancement. This work offers a promising strategy to optimize the performance of Sb2S3 photoelectrodes for solar-driven photoelectrochemical water splitting.

Tailored BiPO4/Bi‐MOF heterostructure photocatalysts with diverse morphologies for highly efficient organic pollutant degradation

Three distinct morphologies of Bi‐MOFs were innovatively employed as carriers, facilitating the formation of heterojunctions with BiPO4. Among these, the optimal photocatalytic performance was demonstrated by the type II heterojunction BiPO4/CAU‐17. Bi3+ competitively coordinated to crucially aid CAU‐17's transformation into a heterojunction, enhancing interfacial contact in BiPO4/CAU‐17. These photocatalysts effectively degraded dyes (RhB, MO, MB) and tetracycline (TC) under light exposure. RhB degradation was 3.33 times faster with BiPO4/CAU‐17 than BiPO4, 1.45 times faster than FCAU‐17, 1.36 times faster than FRCAU‐17, and 1.32 times faster than CAU‐17. Analyzing carrier density, Fermi level, and band structure through VB‐XPS, UV–VIS, and Mott–Schottky provided insights into enhanced separation of photoexcited electron–hole pairs. This study presents a novel approach to tackle the aggregation challenge of the wide‐bandgap material BiPO4 by using suitable MOFs as carriers. It offers valuable perspectives for the design and application of photocatalysts in environmental remediation.

Homogeneous distribution of highly dispersed Pt species over O and P co-doped g-C3N4 and its superior photocatalytic H2 evolution activity

In this study, we synthesized O and P co-doped graphitic C3N4 (OPCN) materials by a one-step calcination method and prepared Pt/OPCN photocatalysts for the photocatalytic H2 evolution reaction. Among the Pt/OPCN catalysts with various O and P contents, Pt/OPCN2 exhibited the highest H2 evolution rate of 2198 μmol·g−1 (AQE = 7.33 %), which was 1.65 times higher than that of Pt/CN (1330 μmol·g−1). Moreover, Pt/OPCN2 demonstrated excellent photocatalytic properties, such as suitable band gap (2.50 eV) for visible light and efficient charge separation of photoexcited electron–hole pairs, which was confirmed by ultraviolet-visible spectroscopy, electrochemical impedance spectroscopy, photoluminescence spectroscopy, and time-resolved photoluminescence measurements. Fundamentally, the Pt species effectively interacted with neighboring PO and CO functional groups that optimally located on defective OPCN2, resulting in a homogeneous formation of highly dispersed PtO evenly distributed over Pt/OPCN2, as confirmed by X-ray photoelectron spectroscopy, high-angle annular dark-field scanning transmission electron microscopy, and density functional theory calculations. However, excessive O and P contents of OPCN3 damaged the morphological structure of g-C3N4, inducing a poor interaction between the Pt species and OPCN3 and forming isolated Pt nanoparticles, resulting in the low photocatalytic activity of Pt/OPCN3.

Insights into the effect of Ni doping on In2S3 for enhanced activity and selectivity of photocatalytic CO2 reduction

The limited photocatalytic CO2 reduction performance mainly lies in the low utilization of photogenerated electrons during the reaction. In this work, we developed the defect level within the Ni-doped In2S3 nanotube photocatalysts via a simple solvothermal method to increase the available amount of photogenerated electrons for enhanced photocatalytic CO2 reduction performance than the pristine In2S3. The introduction of Ni element into the lattice of In2S3 could significantly improve the photocatalytic activity and selectivity without destruction of the nanotube structure of In2S3. The yield of CO reaches 243.2 μmol/g/h under visible light, which is the highest reported value among In2S3 photocatalysts, and is 8.2 times more than the pure In2S3. Moreover, by modulating the doping amount of Ni element, the selectivity of CO varied from 27.7% to 51.0%. Further characterizations suggest that the doping of Ni element altered the electronic bandgap arrangement of In2S3, where the position of the conduction band is conducive to the activation of CO2 molecules. Moreover, the defect level resulting from Ni-doping not only facilitates the separation of photoexcited electron-hole pairs but also suppresses the recombination of electrons and holes. This study provides an available and reliable strategy for enhancing the photocatalytic CO2 reduction performance of related sulfide photocatalytic materials in future studies.

The enhancement of photocatalytic hydrogen production over Ag2WO4 modified g-C3N4 with Pt as cocatalyst

ABSTRACT The construction of heterojunction photocatalyst is an effective mean to improve the photoexcited electron–hole pair separation. The Ag2WO4-doped graphitic carbon nitride (g-C3N4, C3N4 for short) composite photocatalysts were fabricated by a simple calcination and in-situ depositing strategy. The composites were characterized by different techniques. The effects of Ag2WO4 content, type of scavengers, pH value of reaction solution and dose of scavenger on photocatalytic hydrogen (H2) generation were studied. It was found that the Ag2WO4 micro-nano particles were highly dispersed on the C3N4 surface. After doping Ag2WO4, the light absorption range of Ag2WO4-C3N4 material was broadened effectively from 440 nm to 448 nm, and the BET surface area of C3N4 was increased from 35.63 to 40.73 cm2·g−1, indicating that Ag2WO4 loading could provide some new BET surface areas. The binding energy of all elements in Ag2WO4-4/C3N4 was clearly shifted due to the charge transfer from C3N4 to Ag2WO4, implying a strong interaction between C3N4 and Ag2WO4. The photocatalytic H2 production rate of the optimized Ag2WO4-4/C3N4 was 6047.4 μmol·g−1·h−1, which was 2.04 and 171.8 times that of C3N4 and Ag2WO4, respectively. While Ag2WO4-4/C3N4 exhibited a poor H2 production performance in the absence of Pt co-catalyst (309.3 μmol·g−1·h−1), indicating the formation of heterojunction among Ag2WO4, C3N4 and Pt.

Efficient degradation of organics by ultrasonic piezoelectric effect on CuO-BTO/AFC composite

The recombination of photoexcited electron–hole pairs greatly limits the degradation performance of photocatalysts. Ultrasonic cavitation and internal electric field induced by the piezoelectric effect are helpful for the separation of electron–hole pairs and degradation efficiency. The activated foam carbon (AFC) owing to its high surface area is often used as the substrate to grow catalysts to provide more reactive active sites. In this work, CuO@BaTiO3 (CuO@BTO) heterostructure is prepared by hydrothermal method on the surface of AFC to investigate the ultrasonic piezoelectric catalysis effect. X-ray diffraction (XRD), Raman spectroscopy, energy dispersive x-ray spectroscopy (EDS) and scanning electron microscopy (SEM) were used to analyze the structure and morphology of CuO-BTO/AFC composite. It is found that the CuO-BTO/AFC composite exhibits excellent piezo-catalytic performance for the degradation of organics promoted by ultrasonic vibration. The CuO-BTO/AFC composite can decompose methyl orange and methylene blue with degradation efficiency as high as 93.9% and 97.6% within 25 min, respectively. The mechanism of piezoelectricity enhanced ultrasound supported catalysis effect of system CuO-BTO/AFC is discussed. The formed heterojunction structure between BTO and CuO promotes the separation of positive and negative charges caused by the piezoelectric effect.

High-efficiency photocatalytic CO2 reduction enabled by interfacial Ov and isolated Ti3+ of g-C3N4/TiO2 Z-scheme heterojunction

Exploring the real force that drives the separation of Coulomb-bound electron-hole pairs in the interface of heterojunction photocatalysts can establish a clear mechanism for efficient solar energy conversion efficiency. Herein, the formation of oxygen vacancy (Ov) and isolated Ti3+ was precisely regulated at the interface of g-C3N4/TiO2 Z-scheme heterojunction (g-C3N4/Ov-Ti3+-TiO2) by optimizing the opening degree of the calcination system, showing excellent production rate of CO and CH4 from CO2 photoreduction under visible light. This photocatalytic system also exhibited prominent stability. Combining theoretical calculation and characterization, the introduction of Ov and isolated Ti3+ on the interface could construct a charge transfer channel to break the forbidden transition of n → π*, improving the separation process of photoexcited electron-hole pairs. The photoexcited electrons weakened the covalent interaction of CO bonds to promote the activation of adsorbed inert CO2 molecules, significantly reducing the energy barrier of the rate-limiting step during CO2 reduction. This work demonstrates the great application potential of reasonably regulating heterojunction interface for efficient photocatalytic CO2 reduction.

Rational construction of MOF-on-MOF heterojunction with an array of flexible two-dimensional microsheets for efficient CO2 photoreduction

MOF-on-MOF composites are deemed promising candidates to accomplish synergistic CO2 capture and photoreduction thanks to their plentiful active sites, extended light response range, timely separation of photoexcited electron-hole pairs, and large CO2 adsorption capacities. Unfortunately, the controllable growth of the designed MOF-on-MOF heterostructure is challenging. Deficient interphase contact and the consequent mass transfer deprivation is one of the primary obstacles severely impairing the catalytic efficiency. Herein, the contact between two widely-employed MOFs of Ni-BDC and NH2-MIL-125 was significantly strengthened by exploiting a self-assembled array of Ni-BDC microsheets. In contrast to the spontaneously formed spheroidal aggregate, the loosely-packed array exhibits amplified accessible surfaces to interact with NH2-MIL-125, contributing to a radically improved interfacial built-in electric field and 7∼9 times rises in the product yields. Moreover, the preferably thin thickness of Ni-BDC microsheets prompts its macroscopic flexibility, permitting intensified deformation for enhanced interphase contact. Coupled with the additional contribution from its copious Lewis acid sites, the developed NH2-MIL-125@Ni-BDC array simultaneously converted CO2 into CO and CH4 at rates that cannot be matched by its isostructural Co counterpart with declined acidity and flexibility. This work innovatively reveals the immense importance of morphology tailoring and assembly tactic to interphase contact modulation and the upgrade of catalyst performances.

Controllable Modulation of the Electronic Properties of a Two-Dimensional Ambipolar Semiconductor by Interface Ferroelectric Polarization.

Precise control of charge carrier type and density of two-dimensional (2D) ambipolar semiconductors is the prerequisite for their applications in next-generation integrated circuits and electronic devices. Here, by fabricating a heterointerface between a 2D ambipolar semiconductor (hydrogenated germanene, GeH) and a ferroelectric substrate (PbMg1/3Nb2/3O3-PbTiO3, PMN-PT), fine-tuning of charge carrier type and density of GeH is achieved. Due to ambipolar properties, proper band gap, and high carrier mobility of GeH, by applying the opposite local bias (±8 V), a lateral polarization in GeH is constructed with a change of work function by 0.6 eV. Besides, the built-in polarization in GeH nanoflake could promote the separation of photoexcited electron-hole pairs, which lead to 4 times enhancement of the photoconductivity after poling by 200 V. In addition, a gradient regulation of the work function of GeH from 4.94 to 5.21 eV by adjusting the local substrate polarization is demonstrated, which could be used for data storage at the micrometer size by forming p-n homojunctions. This work of constructing such heterointerfaces provides a pathway for applying 2D ambipolar semiconductors in nonvolatile memory devices, photoelectronic devices, and next-generation integrated circuit.

Two-dimensional Janus SnS/MoSi2N4 structure for high-efficiency photocatalytic splitting

Energy consumption and environmental pollution need us to explore new and sustainable energy sources. Photocatalytic water splitting for hydrogen production offers one of the most effective solutions to this problem. Identifying an advanced photocatalyst is essential to achieve high-efficiency photocatalytic water splitting. We observed that the SnS/MoSi2N4 van der Waals heterostructure (vdWH) is a viable candidate for photocatalytic water splitting using density functional theory (DFT). Our investigation has revealed that the SnS/MoSi2N4 vdWH exhibits type-II band alignment, which is highly advantageous for spatially separating photoexcited electron-hole pairs. Remarkably, this type-II band arrangement remains stable across different stacking forms of the vdWH. Meanwhile, SnS/MoSi2N4 vdWH exhibits high light absorption ability. After considering the Janus effect, we have ascertained that SnS/MoSi2N4 vdWH likely possesses appropriate band edge positions for facilitating water splitting. Moreover, we revealed that bandgap and light absorption of SnS/MoSi2N4 vdWH could be further improved by applying the strain while SnS/MoSi2N4 vdWH still maintains the appropriate band edge positions. The results suggest that SnS/MoSi2N4 vdWH is an ideal photocatalyst for water splitting.

Organic cations promote exciton dissociation in Ruddlesden-Popper lead iodide perovskites: a theoretical study.

Two-dimensional (2D) Ruddlesden-Popper perovskites (RPPs) are a class of quantum well (QW) materials showing large exciton binding energy owing to quantum confinement. The existence of localized edge states was proposed to accelerate exciton dissociation into long-lived charge carriers in 2D RPPs, but recent experimental reports suggested that highly efficient internal exciton dissociation is achievable in 2D RPPs despite the absence of edge states. Herein, we adopt first-principles calculations to unveil the physical origin of the high internal quantum efficiency in the bulk region of widely familiar (BA)2(MA)n-1PbnI3n+1 (BA = butylammonium; MA = methylammonium) materials. We discover that the dipolar nature of MA cations provides the driving force for the separation of photoexcited electron-hole pairs inside QWs as the inorganic layer thickens from n = 1 to n = 3. Concurrently, electronic coupling between organic spacer layers and QWs is enhanced in the energetically favorable configurations where MA cations orient with their CH3 groups towards the exterior PbI2 layers of QWs in the n = 3 structure. Consequently, hole delocalization is promoted along the out-of-plane direction of QWs, which in turn facilitates exciton dissociation into free charge carriers despite large exciton binding energy. Our simulations reveal that the hydrogen bonding between organic species (including both MA and BA cations) and iodine atoms, which is subtly interconnected, engineers the response of morphology in QWs and electronic interactions at organic-inorganic interfaces, providing novel insights for the exciton-free carrier behavior in the bulk area of 2D RPPs.

Self-powered dual-mode UV detector based on GaN/(BA)<sub>2</sub>PbI<sub>4</sub> heterojunction

As an important part of an intelligent photoelectric system, ultraviolet detector has been widely used in many fields in recent years. The research on self-powered heterojunction photodiode is particularly important. In this work, a dual-mode self-powered GaN/(BA)<sub>2</sub>PbI<sub>4</sub> heterojunction ultraviolet photodiode is prepared and discussed. The GaN film is deposited on sapphire by metal-organic chemical vapor deposition, and then the (BA)<sub>2</sub>PbI<sub>4</sub> film is spin-coated onto the surface of the GaN film to construct a planar heterojunction detector. The X-ray diffraction, energy-dispersive X-ray spectroscopy mapping and scanning electron microscope measurements are used to determine the quality of GaN and (BA)<sub>2</sub>PbI<sub>4</sub> thin films. When the film is illuminated by 365 nm light with a power density of 421 μW/cm<sup>2</sup> at 5 V bias, the responsiveness (<i>R</i>) and external quantum efficiency (EQE) are 60 mA/W and 20%, respectively. In self-powered mode, the rise time (<i>τ</i><sub>r</sub>) and decay time (<i>τ</i><sub>d</sub>) are 0.12 s and 0.13 s, respectively, illustrating the fast photogeneration process and recombination process for photo-excited electron-hole pairs. And, the <i>R</i> is 1.96×10<sup>–4</sup> mA/W, owing to the development of space charge region across the interface of GaN thin film and (BA)<sub>2</sub>PbI<sub>4</sub> thin film. The outcomes of this study unequivocally demonstrate the extensive potential and wide-ranging applicability of self-powered UV photodiodes based on the GaN/(BA)<sub>2</sub>PbI<sub>4</sub> heterojunction configuration. Moreover, this research presents a new concept that provides a novel avenue to the ongoing development of intelligent optoelectronic systems.

Strategies for Enhancing the Photocatalytic and Electrocatalytic Efficiency of Covalent Triazine Frameworks for CO2 Reduction.

Converting carbon dioxide (CO2) into fuel and high-value-added chemicals is considered a green and effective way to solve global energy and environmental problems. Covalent triazine frameworks (CTFs) are extensively utilized as an emerging catalyst for photo/electrocatalytic CO2 reduction reaction (CO2RR) recently recognized for their distinctive qualities, including excellent thermal and chemical stability, π-conjugated structure, rich nitrogen content, and a strong affinity for CO2, etc. Nevertheless, single-component CTFs have the problems of accelerated recombination of photoexcited electron-hole pairs and restricted conductivity, which limit their application for photo/electrocatalytic CO2RR. Therefore, emphasis will then summarize the strategies for enhancing the photocatalytic and electrocatalytic efficiency of CTFs for CO2RR in this paper, including atom doping, constructing a heterojunction structure, etc. This review first illustrates the synthesis strategies of CTFs and the advantages of CTFs in the field of photo/electrocatalytic CO2RR. Subsequently, the mechanism of CTF-based materials in photo/electrocatalytic CO2RR is described. Lastly, the challenges and future prospects of CTFs in photo/electrocatalytic CO2RR are addressed, which offers a fresh perspective for the future development of CTFs in photo/electrocatalytic CO2RR.

Controllable lignin valorization to value-added aromatic chemicals by a UV-assisted ternary heterogeneous photo-fenton catalytic system

Photocatalysis, which leverages sustainable solar energy to facilitate the conversion of lignin under mild conditions, has gained considerable research interest. Therefore, our study introduces a novel heterogeneous photo-Fenton reagent, Fe3O4@GO@TiO2, designed to selectively depolymerize lignin into aromatic chemicals using ultraviolet light as the energy source. This ternary photo-Fenton catalyst could effectively depolymerize approximately 90% of lignin model compounds. The model compounds without or with phenolic OH blocking yield guaiacol exclusively and predominantly guaiacol with aromatic aldehydes, respectively. The lignin degradation mechanism using the photo-Fenton catalyst (Fe3O4@GO@TiO2) involves the formation of an enol ether intermediate, followed by the cleavage of lignin β-O-4 bonds, facilitated by a mild photon-stimulated reduction–oxidation Fenton process. Notably, the reduced GO plays a crucial role in two aspects. Firstly, it transfers and stabilizes the photoexcited electron-hole pairs. Secondly, it promotes the generation of radicals (•OH, •OOH) essential for selective degradation of the lignin side chains. Consequently, the average molecular weight of the lignin depolymerized product is half of that of the original lignin. Furthermore, this photocatalyst demonstrates recyclability, retaining 85% of its initial activity after five-time recycling. This tertiary Fenton-photocatalyst provides a novel approach for the selective depolymerization of lignin interunit bonds into valuable phenolic monomers under ambient conditions.