Recombination Rate Of Carriers Research Articles

Solar light assisted enhanced photocatalytic activity of smart ternary ZnO:TiO2:SnO2 nanocomposites

In the present study, the smart combinations of metal oxide semiconductors (ZnO:TiO2)1-x(SnO2)x (ZTS) with different SnO2 loadings (as x = 0.0, 0.30, 0.25, 0.20, coded as ZTS0, ZTS1, ZTS2, and ZTS3) were synthesized by employing the simple sol-gel technique. The structural, morphological, optical properties and elemental composition were analyzed by using XRD, Raman spectroscopy, FE-SEM, BET, UV–Vis spectroscopy, IC-PMS, XPS and FTIR of ZTS nanocomposite and proved the formation of smart ternary combination of nanocomposites. Systematic investigation through the characterization emphasised that the acute interfacial combination was established between metal oxide semiconductors. The crystallite size was decreased on adding the amount of SnO2 in the pristine ZTS0 nanocomposites from 23.5 nm to 10.5 nm which was confirmed by Scherrer's equation. The optical energy band gap of the obtained ZTS nanocomposites was found to vary from 3.23 to 3.34 eV on adding the amount of SnO2. The performance of the ZTS nanocomposites as photocatalyst was examined towards organic dyes and the results shows highest degradation of MB and MO dyes with ZTS3 achieving 99 % and 97.3 % degradation efficiency with 1 g/L loading dose. The plausible mechanism was suggested considering the visible light absorption spectra and band diagram resulting in supressed of the recombination rate of charge carriers. The smart combination of ZTS nanocomposites makes it an ideal material for excellent photocatalytic activity for degrading organic contaminants in presence of solar light irradiation.

Remarkable improvement in photocatalytic activity of g-C3N4 for NO oxidation through surface hydroxylation

The nitrogen oxide emissions originating from combustion pose significant risks to the environment. Photocatalysis is considered an efficient and environmentally friendly strategy to alleviate this problem. Graphitic carbon nitride (g-C3N4) is regarded as one of the most promising organic photocatalytic materials for environmental purification. However, its small specific surface area, weak adsorption and high recombination rate of charge carriers result in low intrinsic photocatalytic activity. To overcome these obstacles, a hydrothermal treatment of dicyandiamide-derived g-C3N4 (DCN) at different temperatures (140–200 °C) was employed to enhance the photocatalytic activity for NO oxidation. The experimental results demonstrated a significant improvement in the photocatalytic oxidation removal rate of NO after a hydrothermal treatment. The optimal photocatalyst, DCN-180, treated at 180 °C, demonstrated the highest NO removal efficiency (65.0 %), which is twice the value of pristine DCN (32.5 %). Additionally, the formation of the toxic intermediate NO2 was effectively suppressed during the reaction. Photoelectrochemical tests revealed that DCN-180 exhibited higher photocurrent density and smaller impedance radius compared to the untreated g-C3N4 sample. Moreover, density functional theory (DFT) calculations confirmed that the DCN-180 sample showed a stronger ability to adsorb O2 and NO. The enhanced photocatalytic NO oxidation performance of DCN − 180 has been primarily attributed to its enlarged specific surface area (from 10.7 to 35.5 m2 g−1), local polarization effect, reduced interfacial charge transfer resistance, and improved adsorption abilities for NO and O2 molecules. This study provides valuable insights for designing and preparing highly efficient g-C3N4 based photocatalysts through surface modification for photocatalytic NO purification.

Optimizing inorganic SnS/ZrS2 heterojunction solar cells: Numerical analysis and performance insights

The SnS and ZrS2 have emerged as promising photovoltaic materials. This paper gives the first numerical analysis of inorganic SnS/ZrS2 heterojunction solar cells using SCAPS-1D. The study focuses on the effect of several parameters, such as thickness, doping charge carrier concentration, and energy bandgap, on fundamental solar cell properties in both the window and active layers. Our findings show that a variety of parameters influence solar cell performance, including built-in voltage, minority charge carrier lifetime, depletion breadth, charge carrier collection length, photogenerated current, and recombination rate. The maximum efficiency (η) attained in our simulated devices was 32.13 %, with FF of 84.51 % and Voc of 0.796 V. To achieve this efficiency, particular SnS parameters were used, such as a band gap of 1.00 eV, thickness of 5.0 μm, and doping charge carrier concentration of 1020 cm−3. In ZrS2, characteristics such as a band gap of 1.2 eV, thickness of 0.2 μm, and doping charge carrier content optimized 1020 cm−3 contribute to the observed efficiency. Our simulation results indicate that inorganic SnS/ZrS2 heterojunction devices have potential for solar device production that is cost-effective, large-scale, and high-efficiency. High performance enables a new path toward clean energy.

An Efficient p-n Heterojunction Copper Tin Sulfide/g-C3N4 Nanocomposite for Methyl Orange Photodegradation.

The discharge of toxic dye effluents from industry is a major concern for environmental pollution and toxicity. These toxic dyes can be efficiently removed from waste streams using a photocatalysis process involving visible light. Due to its simple synthesis procedure, inexpensive precursor, and robust stability, graphitic carbon nitride (g-C3N4, or CN) has been used as a visible light responsive catalyst for the degradation of dyes with mediocre performance because it is limited by its low visible light harvesting capability due to its wide bandgap and fast carrier recombination rate. To overcome these limitations and enhance the performance of g-C3N4, it was coupled with a narrow bandgap copper tin sulfide (CTS) semiconductor to form a p-n heterojunction. CTS and g-C3N4 were selected due to their good stability, low toxicity, ease of synthesis, layered sheet/plate-like morphology, and relatively abundant precursors. Accordingly, a series of copper tin sulfide/graphitic carbon nitride nanocomposites (CTS/g-C3N4) with varying CTS contents were successfully synthesized via a simple two-step process involving thermal pyrolysis and coprecipitation for visible-light-induced photocatalytic degradation of methyl orange (MO) dye. The photocatalytic activity results showed that the 50%(wt/wt) CTS/g-C3N4 composite displayed a remarkable degradation efficiency of 95.6% for MO dye under visible light illumination for 120 min, which is higher than that of either pristine CTS or g-C3N4. The improved performance is attributed to the extended light absorption range (due to the optimized bandgap), effective suppression of photoinduced electron-hole recombination, and improved charge transfer that arose from the formation of a p-n heterojunction, as evidenced by electrochemical impedance spectroscopy (EIS), photocurrent, and photoluminescence results. Moreover, the results of the reusability study showed that the composite has excellent stability, indicating its potential for the degradation of MO and other toxic organic dyes from waste streams.

Enhancement of electrical properties by CuS–PVP nanocomposite on the ZnO/polymer heterojunction

AbstractA nanocomposite matrix of covellite–polyvinylpyrrolidone (CuS–PVP) was synthesized through a solution processing method and applied via spin coating onto hydrothermally grown zinc oxide (ZnO) nanorods. Characterization techniques, including X‐ray powder diffraction and scanning electron microscopy, confirmed the successful decoration of chain‐like CuS–PVP polymer composites onto hexagonal ZnO nanorods. The UV‐vis spectroscopy revealed an absorption peak at 372 nm, indicating excitonic absorption of ZnO, and a reduction in the band gap from 3.11 to 2.59 eV upon CuS–PVP polymer decoration, enhancing light harvesting efficiency. Photoluminescence spectra demonstrated the lowest charge carrier recombination rate in the ZnO/CuS–PVP sample, promoting efficient charge separation and transportation, supported by Fourier‐transform infrared analysis indicating chemical bonding. Subsequently, the impact of CuS–PVP as an insertion layer in the ZnO/poly(3,4‐ethylenedioxythiophene)‐poly(styrenesulfonate) (PEDOT:PSS) inorganic–organic heterojunction was investigated. Favorable band alignment between ZnO, CuS–PVP, and PEDOT:PSS improved conduction, increasing current from 0.3394 to 1.14 mA for D2 (poly‐ethyleneterephthalate/Indium tin oxide/ZnO/PEDOT:PSS/Al) and D1 (poly‐ethyleneterephthalate/Indium tin oxide/ZnO/CuS–PVP/PEDOT:PSS/Al) at a +2 V bias. Transient photo‐responses (J–t) at 0 V bias revealed decreased rise and fall times from 0.382 and 1.154 s to 0.301 and 0.229 s for D2 and D1 devices, respectively. This novel approach provides control over charge carrier transport characteristics at the interface, potentially benefiting self‐powered photo‐detection in optoelectronic devices.

Circumventing bottlenecks in H2O2 photosynthesis over carbon nitride with iodine redox chemistry and electric field effects

Artificial photosynthesis using carbon nitride (g-C3N4) holds a great promise for sustainable and cost-effective H2O2 production, but the high carrier recombination rate impedes its efficiency. To tackle this challenge, we propose an innovative method involving multispecies iodine mediators (I−/I3−) intercalation through a pre-photo-oxidation process using potassium iodide (suspected deteriorated “KI”) within the g-C3N4 framework. Moreover, we introduce an external electric field by incorporating cationic methyl viologen ions to establish an auxiliary electron transfer channel. Such a unique design drastically improves the separation of photo-generated carriers, achieving an impressive H2O2 production rate of 46.40 mmol g−1 h−1 under visible light irradiation, surpassing the most visible-light H2O2-producing systems. Combining various advanced characterization techniques elucidates the inner photocatalytic mechanism, and the application potential of this photocatalytic system is validated with various simulation scenarios. This work presents a significative strategy for preparing and applying highly efficient g-C3N4-based catalysts in photochemical H2O2 production.

Outstanding photocatalytic activity of a mechano-thermally synthesized Z-scheme BiFeO3- Fe2O3 heterostructure

In this study, α-Bi2O3 and α-Fe2O3 powder mixtures experienced a novel mechano-thermal procedure, which includes high-energy ball milling followed by heat treatment, resulting in the successful synthesis of a BiFeO3-Fe2O3 nanocomposite. Simultaneous thermal analysis (STA) and X-ray diffraction (XRD) showed that the formation and characteristics of BiFeO3-Fe2O3 nanocomposite are greatly influenced by the milling process, heat-treatment temperature, and the α-Bi2O3:α-Fe2O3 molar ratio. X-ray photoelectron spectroscopy (XPS) spectra confirmed the presence of Bi, Fe, and O, indicating the formation of the BiFeO3 phase. Field emission scanning electron microscopy (FESEM) analysis showed the development of plate-like microstructures in the BiFeO3 phase with an average thickness of 88 nm. Diffuse reflectance spectroscopy (DRS) indicated that the 20 h-milled nanocomposite with a molar ratio of α-Bi2O3:α-Fe2O3 (1:3) exhibited the lowest band gap of 2.38 eV after heat treatment at 750 °C. The reduction in photoluminescence (PL) peaks and increase in photocurrent in the above sample suggested a decrease in charge carrier recombination rate, leading to high photocatalytic activity of 85 and 42% for methylene blue (MB) and methyl orange (MO) degradation, respectively. The effect of various pH levels on the photocatalytic activity of both dyes was examined, with MO degrading by 94% in an acidic environment after 300 min of visible light exposure, while MB experienced similar degradation in an alkaline setting. The kinetics and mechanism of photocatalytic degradation were extensively studied using the Langmuir-Hinshelwood (L-H) model, revealing the significant role of hydroxyl radicals in photodegradation. A Z-scheme mechanism for charge transfer in the nanocomposite was postulated, drawing upon radical scavenging and Mott-Schottky experiments. The prepared photocatalyst showed excellent stability and reusability following a cyclic experiment.

Schottky junction-mediated carrier separation in BiOBr/Ti3C2Tx van der Waals heterojunction photocatalyst for increased removal of Cr(VI) under visible-light

The photocatalytic removal of pollutants can integrate efficient solar energy utilization with wastewater treatment. Herein, we report a simple strategy to construct BiOBr/Ti3C2Tx composite photocatalysts consisting of self-assembled van der Waals (vdw) heterojunction structures containing Schottky junctions. The vdW interaction between BiOBr and Ti3C2Tx and the structural stability of the catalysts were validated by density functional theory (DFT) calculations and an ab initio molecular dynamic simulation (AIMD). Compared to BiOBr, the BiOBr/Ti3C2Tx composites exhibited an enhanced light absorption capability and photocurrent response, along with a lower carrier recombination rate and charge-transfer resistance. The BiOBr/Ti3C2Tx activity for the photoreduction of hexavalent chromium (Cr(VI)) under visible-light irradiation considerably surpassed that of the original BiOBr (53.9 %). Using the BTC-0.8 catalyst (with a Ti3C2Tx: BiOBr mass ratio of 0.8 %) optimal reduction efficiency (94.0 %) for Cr(VI) with a reaction rate approximately 3.5 times that of pure BiOBr. The BTC-0.8 catalyst was viable over a wide pH range and maintained an 83.9 % photoreduction rate after four cycling experiments. The exceptional photocatalytic ability of BiOBr/Ti3C2Tx was achieved because Ti3C2Tx served as an electron injection layer that separated photogenerated carriers. The Schottky junction constructed within the BiOBr/Ti3C2Tx vdW heterojunctions suppressed electron backflow, promoting carrier separation. The excellent photocatalytic performance and strong cyclic stability of BiOBr/Ti3C2Tx demonstrated the considerable application potential of this photocatalyst.

Synthesis of type-II TiO2 nanoparticle/ZnO nanorods heterostructure for enhanced photocatalytic activity

A type-II TiO2/ZnO heterostructure is fabricated by coating TiO2 nanoparticles (2, 4 and 6 layers) over ZnO nanorods using sol–gel method to obtain the optimized system with enhanced photocatalytic activity. TiO2/ZnO:6 layer exhibited a higher optical absorption and lowest bandgap value among the synthesized samples. A lower photoluminescence (PL) intensity is noticed for TiO2/ZnO:6 layer sample, ensuring efficient reduction of carrier recombination rate. Moreover, TiO2/ZnO:6 layer exhibited maximum methylene blue (MB) and phenolphthalein dyes degradation efficiency of 86.3% and 76.5% respectively under UV light illumination for 180 min. Our study proposes that formation of type-II heterostructure enhances the photocatalytic activity.

Enhanced performance of HTM-free perovskite solar cells with free-standing carbon electrode via surface treatment and conductive support

This study explores the optimization of hole transport material (HTM)-free perovskite solar cells featuring laminated free-standing carbon film as a back electrode. Surface treatment of perovskite film using different types of solvent (chlorobenzene, toluene, and ethyl acetate) was carried out to improve the electrical contact at the carbon/methylammonium lead iodide interface. Overall, the surface treatment improved mechanical adhesion between the perovskite and carbon film. The conductivity of the free-standing carbon electrode was further improved by attaching the carbon film to various types of conductive support. Our results show that the selection of both solvents used during surface treatment and the type of conductive substrate has a considerable impact on the resulting performance, wherein all modifications gave rise to substantial improvement over the benchmark unmodified carbon electrode. A power conversion efficiency (PCE) of 7.74% was achieved by the perovskite solar cell with laminated carbon electrode on Al foil combined with the application of chlorobenzene as surface treatment, demonstrating a tremendous increase in performance compared to that of untreated free-standing carbon electrode that produced PCE less than 1%. The main contributor to the improved performance is presumably due to the low carrier recombination rate and improved charge carrier extraction as implied by the electro-impedance spectroscopy and photoluminescence analysis. This work demonstrates a facile approach for resolving the challenges in developing low-cost HTM-free perovskite solar cells with a free-standing carbon film electrode.

Oxygen-deficient WO3 for stable visible-light photocatalytic degradation of acetaldehyde within a wide humidity range

Indoor VOCs pollution has attracted broad attention for its harm to mankind’s health recent years. Photocatalytic degradation of indoor VOCs holds great prospects in addressing these health concerns in daily life. However, traditional photocatalysts have a large recombination rate of charge carriers and a decrease of the photocatalytic degradation efficiency under high relative humidity. Herein, uniform tungsten oxide nanoparticles with enriched oxygen vacancies (WO3-U) were synthesized by a direct annealing method with urea addition, which exhibited superior performance in the visible-light photocatalysis. The reaction rate constant value of photocatalytic acetaldehyde degradation over WO3-U catalyst was above 3 times higher than that of pristine WO3 sample. More importantly, the WO3-U catalyst maintained stable and excellent photocatalytic performance at relative humidity range of 25–100 %. Except for the enhanced photogenerated charges separation, abundant oxygen vacancies could effectively accelerate O2 activation to generate •O2−, which accounted mainly for the initial conversion of acetaldehyde. Then the subsequent transformation of •O2− into •OH to promoted the final mineralization of acetaldehyde. In addition, the presence of oxygen vacancies also facilitated H2O dissociation to form surface hydroxyl groups, which increased the adsorption of acetaldehyde, resulting in the consistent photocatalytic performance of WO3-U catalyst within a wide humidity range. This work provides guidelines to design visible-light responsive photocatalysts with efficient activity at high humidity conditions for indoor VOCs degradation.

One-pot microwave synthesize bandgap tunable g-C3N4 for highly efficient photocatalytic H2O2 production

Graphitic carbon nitride (g-C3N4) faces limitations in photocatalytic application due to its limited light response and high recombination rate of photo-generated charge carriers. Herein, we synthesized a K, P co-doped g-C3N4 (KPCN) with cyano defects via microwave-assisted heating of the mixture of KH2PO4 and melamine in just 7 min. The KPCN exhibits a reduced bandgap of 2.37 eV and introduces a mid-gap of 1.77 eV, which broadens light absorption to the visible-near-infrared (vis-NIR) spectrum with light absorption to 867 nm. Impressively, the co-doped K and P adjust the interlayer and in-plane electron distribution of g-C3N4, enhancing charge separation and transfer. The KPCN exhibits a remarkable improvement in H2O2 yield of 7.74 mM g−1 h−1, demonstrating superior catalytic activity compared to microwave pure g-C3N4 (MCN, 5.1 times) and bulk g-C3N4 (BCN, 19.2 times). The results indicate that the K, P co-doped g-C3N4 synthesized rapidly and efficiently by microwave method has relatively stable and considerable photocatalytic activity, which has great potential application in the industrial production of H2O2.

Interfacial engineering of TiO2@Bi-BiOBr by constructing hierarchical core–shell heterojunction to boost charge transfer for photothermal CO2 reduction

CO2 reduction by a sustainable pathway such as photothermal catalysis is highly demanded currently, high carrier recombination rate still severely limits the performance of photothermal catalysis. Constructing heterojunction interfaces with high exposed area is an effective strategy to solve the problem of carrier recombination. However, fine control of the interface structure is still highly challenging. Herein, Density functional theory (DFT) calculations were constructed to reveal that metallic Bi leads to more densities of states (DOS) generation at the conduction band edge in Bi-BiOBr, which argues that photogenerated electrons are more likely to be delivered to metallic Bi. A TiO2@Bi-BiOBr hollow hierarchical core–shell heterojunction was designed, providing a highly exposed interface and Bi between interfaces. Such structure endows the catalyst with excellent photothermal catalytic performance, achieving a CO yield of 30.4 μmol·h−1·g−1. The highly improved performance is attributed to interfacial thermoelectrons transfer boosted by the construction of TiO2@BiOBr heterojunction as well as metal Bi. And a possible CO2 reduction pathway is proposed, which is consistent with the Carbine pathway. This study provides an exciting idea for the modulation of photoelectron transfer at catalyst interfaces.

Performance analysis of un-doped and doped titania (TiO ) as an electron transport layer (ETL) for perovskite solar cells.

Density functional theory (DFT) calculations are carried out on pure and doped rutile TiO . The bandgap (E ) for pristine, S-doped, Fe-doped, and Fe/S co-doped materials is direct, with values of 2.98 eV, 2.18 eV, 1.58 eV, and 1.40 eV. The effective mass of charge carriers (m*) and ratio of effective masses of holes to effective masses of electrons (R) are also investigated, and it is discovered that Fe/S co-doped materials have the lowest charge carrier recombination rate. The Fe/S co-doped material has the highest . of doped materials shifted into the visible range. Due to the high dopant concentration in Fe and Fe/S-doped cases, the E is lowered to a relatively small value; hence, only pristine and S-doped materials are verified as electron transport layer (ETL). A solar cell device analysis employing pure and S-doped rutile TiO as ETL is completed using DFT-derived parameters in SCAPS-1D modeling software for the first time. For the optimized solar cells, current-voltage (IV) characteristics, quantum efficiency (QE), capacitance-voltage (CV) characteristics, and capacitance-frequency (Cf) characteristics are provided. The aim of the present study is to improve efficiency of perovskite solar cell by doping as well as to improve accuracy of simulation by applying DFT extracted parameters as input. From the analysis, improvement is found in efficiency of doped TiO compared to un-doped TiO . The efficiency of the PSC with S-doped ETL is 1.418% higher than the PSC with un-doped ETL. Quantumwise Automistic Tool Kit (ATK) is used to extract DFT parameters. Using these DFT parameters as input in SCAPS-1D (Solar Cell Capacitance Simulator), solar cells for doped and un-doped material are simulated. The density functional theory (DFT)-based orthogonalized linear combination of atomic orbital (OLCAO) technique is used. Structural optimization is done using the LBFGS (Limited-memory Broyden-Fletcher-Goldfarb-Shanno). PBESol-GGA (Perdew-Burke-Ernzerhof solid-generalized gradient approximation) is applied as exchange correlation for calculating structural parameters, while MGGA-TB09 (meta-generalized gradient approximation-Tran and Blaha) is applied as exchange correlation for calculating optical and electronic properties.

BiVO4/CuIn5S8 heterojunction with rich sulphur vacancies for boosting visible light-driven photocatalytic water oxidation

The efficient conversion of water into clean energy using solar energy presents a sustainable solution to environmental challenges, albeit constrained by the slow kinetics of the oxygen evolution reaction. This study introduces a series of novel BiVO4/CuIn5S8 heterojunctions, developed and employed as photocatalysts for water oxidation. The photocatalytic activity of these heterojunctions was systematically enhanced by optimizing the BiVO4/CuIn5S8 ratio and hydrothermal reaction temperature. Notably, the heterojunction comprising BiVO4 coupled with 5 % CuIn5S8, synthesized at 180 °C (BiVO4/CuIn5S8/180–5), exhibited superior photocatalytic performance compared to its individual components. This enhancement was further augmented by the introduction of sulfur vacancies (VS) in VS-BiVO4/CuIn5S8/180–5, achieving approximately 3 and 1.4 times the photocatalytic activity of BiVO4 and BiVO4/CuIn5S8/180–5, respectively. Our findings demonstrate that CuIn5S8 effectively grows on decahedral BiVO4, forming n-n heterojunctions that not only improve visible light absorption but also facilitate the separation of photogenerated carriers. The incorporation of VS significantly lowers the charge carrier recombination rate and promotes the formation of additional active sites for H2O adsorption, thereby further elevating the efficiency of photocatalytic water oxidation.

Organic-inorganic hybrids of BiI3-polymers with embedded conductive carbon fillers displaying high SNR for direct X-ray imaging detectors

Organic polymers are light weight, low toxic and environmentally stable candidates of interest in X-ray detection application. But low attenuation and high recombination rate of charge carriers cause low sensitivity is major limitation of these detectors. In this work, organic polymers (PS/PMMA) composites were prepared with high-Z inorganic BiI3 by simple dry mixing technique. The organic-inorganic hybrid further embedded with conductive carbon filler (MWCNT, CB, GP) to improve the charge collection of the samples. Resistivity and mobility of the samples were studied with help of Hall measurements and mobility-lifetime was calculated by Hecth equation and found (2.1 ± 0.2) × 10−3 cm2V−1. The elemental analysis of the samples had been done by XPS analysis. The X-ray investigations done by using dental X-ray source and the sensitivity of the samples increases from 3.4 to 200 μGy−1 cm−3 by incorporating CB filler with a low leakage current of order of 33.3 pA/cm2.

Pore walls as high-way for efficient bulk charge transfer in porous SrTiO3 single crystals boosting photocatalytic overall water splitting

Suppressing carrier recombination in bulk and facilitating carrier transfer to surface via rational structure design is of great significance to improve solar-to-H2 conversion efficiency. We demonstrate a facile hydrothermal method to synthesize porous SrTiO3 single crystals (SrTiO3-P) with exposed (001) facets by introducing carbon spheres as templates. The obviously increased surface photovoltage and photocurrent response indicate that the interconnected pore walls act as enormous charge transfer “highways”, accelerating carrier transport from bulk to surface. Furthermore, the absence of grain boundaries and high crystallinity could also lower the carrier recombination rate. Thus, the SrTiO3-P photocatalyst loaded with Rh/Cr2O3 as cocatalyst exhibits 1.5 times higher overall water splitting activity than that of solid SrTiO3, with gas evolution rate of 19.99 μmol h−1 50 mg−1 for H2 and 11.37 μmol h−1 50 mg−1 for O2. Additionally, SrTiO3-P also shows superior stability without any decay during cycling testing. This work provides a new insight into designing efficient multicomponent photocatalysts with a single-crystal porous structure.

The construction of Z-scheme heterojunction ZnIn2S4@CuO with enhanced charge transfer capability and its mechanism study for the visible light degradation of tetracycline

In this study, copper oxide (CuO) was prepared by the microwave-assisted hydrothermal technique subsequently, CuO was grown in situ onto different rare metal compounds to prepare Z-scheme heterojunctions to improve the degradation efficiency of tetracycline (TC) in water environments. Various characterization proved the successful synthesis of all composite materials, and the formation of tight heterojunction interfaces, among which, the core–shell structure ZnIn2S4@CuO exhibited excellent photocatalytic degradation capability. Research results indicated that the degradation efficiency of ZnIn2S4@CuO for TC (50 mg/L) in the water environment reached 95.8 %, and the degradation rate is 2.41 times and 12.93 times that of CuO and ZnIn2S4 alone, respectively, the reason is because of the introduction of ZnIn2S4, Z-scheme heterojunction structures and internal electric field (IEF) is constructed and formed to extend the visible light response range of photocatalysts to improve electron-hole separation efficiency, and enhance charge transfer. In addition, ZnIn2S4@CuO-2 exhibited good stability and reproducibility, with no significant loss of activity after five cycles. Finally, the precise locations of free radical attack on TC were investigated by the combined use of high-resolution mass spectrometry (HR-MC) and frontier electron densities (FEDs), and a reasonable degradation pathway was provided. The results of this research provide a new and viable approach to overcome the limitations of conventional photocatalytic materials in terms of limited visible light absorption range and fast carrier recombination rates, which offers promising prospects for a wide range of applications in the field of wastewater purification.

Carbon Dots Anchoring Single-Atom Pt on C3N4 Boosting Photocatalytic Hydrogen Evolution.

Carbon nitride (C3N4) has gained considerable attention and has been regarded as an ideal candidate for photocatalytic hydrogen evolution. However, its photocatalytic efficiency is still unsatisfactory due to the rapid recombination rate of photo-generated carriers and restricted surface area with few active sites. Herein, we successfully synthesized a single-atom Pt cocatalyst-loaded photocatalyst by utilizing the anchoring effect of carbon dots (CDs) on C3N4. The introduction of CDs onto the porous C3N4 matrix can greatly enhance the specific surface area of C3N4 to provide more surface-active sites, increase light absorption capabilities, as well as improve the charge separation efficiency. Notably, the functional groups of CDs can efficiently anchor the single-atom Pt, thus improving the atomic utilization efficiency of Pt cocatalysts. A strong interaction is formed via the connection of Pt-N bonds, which enhances the efficiency of photogenerated electron separation. This unique structure remarkably improves its H2 evolution performance under visible light irradiation with a rate of 15.09 mmol h-1 g-1. This work provides a new approach to constructing efficient photocatalysts by using CDs for sustainable hydrogen generation, offering a practical approach to utilizing solar energy for clean fuel production.

Constructing B─N─P Bonds in Ultrathin Holey g-C3N4 for Regulating the Local Chemical Environment in Photocatalytic CO2 Reduction to CO.

The lack of intrinsic active sites for photocatalytic CO2 reduction reaction (CO2RR) and fast recombination rate of charge carriers are the main obstacles to achieving high photocatalytic activity. In this work, a novel phosphorus and boron binary-doped graphitic carbon nitride, highly porous material that exhibits powerful photocatalytic CO2 reduction activity, specifically toward selective CO generation, is disclosed. The coexistence of Lewis-acidic and Lewis-basic sites plays a key role in tuning the electronic structure, promoting charge distribution, extending light-harvesting ability, and promoting dissociation of excitons into active carriers. Porosity and dual dopants create local chemical environments that activate the pyridinic nitrogen atom between the phosphorus and boron atoms on the exposed surface, enabling it to function as an active site for CO2RR. The P-N-B triad is found to lower the activation barrier for reduction of CO2 by stabilizing the COOH reaction intermediate and altering the rate-determining step. As a result, CO yield increased to 22.45µmolg-1h-1 under visible light irradiation, which is ≈12 times larger than that of pristine graphitic carbon nitride. This study provides insights into the mechanism of charge carrier dynamics and active site determination, contributing to the understanding of the photocatalytic CO2RR mechanism.