Recombination Of Electron-hole Pairs Research Articles

BiVO4-based heterojunction nanophotocatalysts for water splitting and organic pollutant degradation: a comprehensive review of photocatalytic innovation

Abstract The novel semiconductor photocatalytic material bismuth vanadate (BiVO4) is gaining significant attention in research due to its unique characteristics, which include a low band gap, good responsiveness to visible light, and non-toxic nature. However, intrinsic constraints such as poor photogenerated charge transfer, slow water oxidation kinetics, and fast electron–hole pair recombination limit the photocatalytic activity of BiVO4. Building heterojunctions has shown to be an effective strategy for enhancing charge separation and impeding electron–hole pair recombination over the last few decades. This review covers the state-of-the-art developments in heterojunction nanomaterials based on BiVO4 for photocatalysis. It explores heterojunction design, clarifies reaction mechanisms, and highlights the current developments in applications including photocatalytic water splitting and organic matter degradation. Finally, it offers a preview of the development paths and opportunities for BiVO4-based heterojunction nanomaterials in the future. This comprehensive assessment of BiVO4-based heterojunctions provides insightful knowledge to researchers in materials science, chemistry, and environmental engineering that will drive advances and breakthroughs in these important fields.

Ternary heterostructure-driven photoinduced electron-hole separation enhanced oxidative stress for triple-negative breast cancer therapy

Zinc oxide nanoparticles (ZnO NPs) stand as among the most significant metal oxide nanoparticles in trigger the formation of reactive oxygen species (ROS) and induce apoptosis. Nevertheless, the utilization of ZnO NPs has been limited by the shallowness of short-wavelength light and the constrained production of ROS. To overcome these limitations, a strategy involves achieving a red shift towards the near-infrared (NIR) light spectrum, promoting the separation and restraining the recombination of electron-hole (e−-h+) pairs. Herein, the hybrid plasmonic system Au@ZnO (AZ) with graphene quantum dots (GQDs) doping (AZG) nano heterostructures is rationally designed for optimal NIR-driven cancer treatment. Significantly, a multifold increase in ROS generation can be achieved through the following creative initiatives: (i) plasmonic Au nanorods expands the photocatalytic capabilities of AZG into the NIR domain, offering a foundation for NIR-induced ROS generation for clinical utilization; (ii) elaborate design of mesoporous core-shell AZ structures facilitates the redistribution of electron-hole pairs; (iii) the incorporation GQDs in mesoporous structure could efficiently restrain the recombination of the e−-h+ pairs; (iv) Modification of hyaluronic acid (HA) can enhance CD44 receptor mediated targeted triple-negative breast cancer (TNBC). In addition, the introduced Au NRs present as catalysts for enhancing photothermal therapy (PTT), effectively inducing apoptosis in tumor cells. The resulting HA-modified AZG (AZGH) exhibits efficient hot electron injection and e−-h+ separation, affording unparalleled convenience for ROS production and enabling NIR-induced PDT for the cancer treanment. As a result, our well-designed mesoporous core-shell AZGH hybrid as photosensitizers can exhibit excellent PDT efficacy.

Designed construction of boosted visible-light Z-scheme TiO2/PANI/Cu2O heterojunction with elaborated photocatalytic degradation of organic dyes

A novel TiO2/polyaniline/Cu2O (T/PANI/Cu) ternary nanocomposite was synthesized via a facile in-situ polymerization of aniline and a one-step solvothermal method. The ternary nanocomposite Ti/PANI/Cu with Z-scheme heterojunction exhibited excellent photocatalytic performance as well as improved stability. The photocatalytic performance of the prepared photocatalysts (T, T/PANI, and T/PANI/Cu) was investigated by the photocatalytic decomposition of Methyl Orange dye (MO) as an organic contaminant using visible light illumination. The T/PANI/Cu ternary nanocomposite revealed the highest degradation efficiency up to 99.5% after 25 min, which is much higher than that of T (47%) and T/PANI (73%). The development of Z-scheme heterojunction is credited with the increased activity and generation of an electric field that led to an improved structure, a wider visible light response range, and a lower rate of electron-hole pair recombination. Based on trapping tests, ·O2−·OH, and h+ species were the main active species involved in the photocatalytic degradation of MO dye. Even after the fifth cycle, the T/PANI/Cu composite remained effective in the successive photocatalytic decomposition of MO, maintaining over 90% of the original degradation efficiency.

Optimizing photocatalytic and supercapacitive performance by β-Bi2O3@BiFeO3 modification with PVDF polymer based nanocomposites

The PVDF (Poly-Vinyl-difloride) membrane modified with Bismuth oxide (β-Bi2O3)/Bismuth Ferrite (BiFeO3) p-n heterojunction synthesized via hydrothermal process to explore its energy storage and conversion applications. The PVDF-Bi2O3/BiFeO3 nanocomposites (NCs) prepared in this study were subjected to analysis using PXRD, FTIR, UV-Vis DRS, FE-SEM with EDX, TEM, and transient photocurrent response techniques, individually. The as-prepared materials were evaluated for their photocatalytic performance in the visible light-induced degradation of Methylene Blue (MB) and Rhodamine-B (RhB) dyes. The photocatalytic performance demonstrates degradation efficiencies of 95% for MB dye and 83% for RhB dye when utilizing the PVDF-β-Bi2O3@BiFeO3 nanocatalyst. The enhancement in the photocatalytic performance of the PVDF-Bi2O3/BiFeO3 heterojunction was a result of improved visible light absorption, suppression of photogenerated electron-hole pair recombination, accelerated separation and migration of photogenerated charges. The capacitance behavior of PVDF-β-Bi2O3@BiFeO3 is significantly higher than β-Bi2O3@BiFeO3 in 3 M KOH solution which has specific capacitance of 300 F g−1at 1 A g−1 of current density and fabricated a symmetric device has10.08 Wh kg−1 and 999.39 W kg−1 specific energy and specific power at 0.5 A g−1 of current density with the 88.7% of capacitance retention and 94.12% of coulombic efficiency up to 10000 cycles.

High anti-corrosive and Scalable CDs/BCN heterostructure photocatalysts for efficient H2 production in natural seawater

Photocatalytic natural seawater-derived splitting to produce hydrogen is one of the most potential strategies to alleviate the shortage of freshwater resources and energy crisis. Nevertheless, the complicated composition of natural seawater poses substantial challenges to the activity and stability of photocatalysts. Here, we report on the fabrication of carbon dots (CDs) and B elements co-modified carbon nitride (i.e. CDs/BCN) via precursor-mediated supramolecular self-assembly and subsequent NaBH4-assisted thermal reduction as well as its implementation as seawater-derived H2 production. The fabricated CDs/BCN exhibits the flaky porous structure capable of providing more transport channels for the generated gases (e.g. H2) and precipitates (e.g. Mg(OH)2, Ca(OH)2) during the seawater splitting process. Benefitting from cooperation of CDs and B elements i.e. the inhibited recombination of electron-hole pairs as well as the extended optical absorption range of CN, the optimal CDs/BCN-2 under visible-light irradiation exhibits the high H2 production rate up to 10369 μmol g-1 h-1 in natural seawater. The proven satisfactory reusability and the corresponding structural stability demonstrate the excellent corrosion resistance of CDs/BCN-2 in natural seawater. Additionally, CDs/BCN-20 photocatalyst synthesized via 20-fold precursor amplification procedure still displays efficient photocatalytic performance of 9022 μmol g-1 h-1, indicating its potential for industrial applications.

A Functional "Key" Amplified Piezoelectric Effect Modulates ROS Storm with an Open Source for Multimodal Synergistic Cancer Therapy.

Chemodynamic therapy (CDT) is a non-invasive strategy for generating reactive oxygen species (ROS) and is promising for cancer treatment. However, increasing ROS in tumor therapy remains challenging. Therefore, exogenous excitation and inhibition of electron-hole pair recombination are attractive for modulating ROS storms in tumors. Herein, a Ce-doped BiFeO3 (CBFO) piezoelectric sonosensitizer to modulate ROS generation and realize a synergistic mechanism of CDT/sonodynamic therapy and piezodynamic therapy (PzDT) is proposed. The mixed Fe2+ and Ce3+ can implement a circular Fenton/Fenton-like reaction in the tumor microenvironment. Abundant ·OH can be generated by ultrasound (US) stimulation to enhance CDT efficacy. As a typical piezoelectric sonosensitizer, CBFO can produce O2 - owing to the enhanced polarization by the US, resulting in the motion of charge carriers. In addition, CBFO can produce a piezoresponse irradiated upon US, which accelerates the migration rate of electrons/holes in opposite directions and results in energy band bending, further achieving toxic ROS production and realizing PzDT. Density functional theory calculations confirmed that Ce doping shortens the diffusion of electrons and improves the conductivity and catalytic activity of CBFO. This distinct US-enhanced strategy emphasizes the effects of doping engineering and piezoelectric-optimized therapy and shows great potential for the treatment of malignant tumors.

Highly active ZnO/Fe3+-TiO2 photocatalysts for visible-light photodegradation application and its colour change behaviour by d-d transition

Highly active novel ZnO/Fe-TiO2 composite catalysts with p-n junction heterostructure have been fabricated by adding commercial ZnO and sol–gel derived Fe-TiO2 nano-powders controlled by grinding and drying. This work reported that doped Fe (III) with TiO2 form a p-type semiconductor and whereas ZnO is an n-type semiconductor. The slight variation of electronegativity between ZnO and TiO2 causes a strong rectifying action for the formation of an interface between ZnO and Fe-TiO2. The occurrence of red shift phenomenon in absorption spectrum of the samples suggest the outcome of d-d transition of Fe3+ (2T2g → 2A2g, 2T1g) and the charge transfer transition between interacting Fe3+ ions (Fe3+ + Fe3+ → Fe4+ + Fe2+). These Fe3+ 3d states in addition to oxygen vacancies and Ti3+ centers create band states, thereby favouring the electronic transition to these levels and resulting in narrowing of TiO2 band gap. A direct confirmation is the increase of Urbach energy with the lowering in the band gap of ZnO/Fe-TiO2.The crystal field splitting of d orbitals (5 degenerate orbitals) of Fe3+ and the approach of free ligand ions which split into two sets and Fe3+ ligand field transition is discussed schematically. The photocatalytic activities of these heterostructure photocatalysts were evaluated by degrading toxic cationic organic dyes such as Methylene Blue (MB) and Malachite Green Oxalate (MG) under visible light. The mechanism of photocatalysis has been recommended which is based on the relative band structure of the semiconductor and integrated heterostructure. The formation of a spike barrier in the CB at the interface gives rise to trap sites that capture the migration of charge carriers and occurs recombination of electron-hole pair at higher Fe(III) doping concentration. The dark adsorption property of the catalysts sample has been also studied.

Solar light driven enhanced photocatalytic efficiency of Graphene based composite of co-doped Bismuth Ferrite (Ba0.5 Bi0.5 Nd0.5 Fe1.5 O3/Gr0.375) for Crystal Violet and Paracetamol

Different dyes and drugs used in industries when released without any treatment in water bodies cause water pollution. There is a need of synthesizing cost-effective and efficient photocatalyst for their degradation. Herein, Ba and Nd co-doped bismuth ferrite BFO (Ba0.5 Bi0.5 Nd0.5 Fe1.5 O3) and BFO@G (Ba0.5 Bi0.5 Nd0.5 Fe1.5 O3/Gr0.375) were successfully fabricated. X-ray Diffraction and Fourier Transform Infrared Spectroscopy were performed to confirm the synthesis of samples. Electrochemical measurements were carried out to further evaluate the characteristics of fabricated catalysts and Rct values of 3.90 Ω and 2.06 Ω were observed for BFO and BFO@G. BFO@G showed 72.72 % degradation of CV and 80.26 % of PC. The composite material showed enhanced performance due to the integration of graphene which provide additional conductive pathways and reduces the rate of electron-hole pair recombination. This research contributes valuable insights into the development of efficient photocatalytic materials for environmental applications.

Steering electron–hole migration pathways from plasmon-induced resonance energy transfer in hematite to enhance their photoelectrochemical water splitting

The strategy of Plasmon-Induced Resonance Energy Transfer (PIRET) holds promise in mitigating the recombination of photo-generated electron-hole pairs, thereby amplifying the efficiency of an electrode in photoelectrochemical (PEC) reactions geared towards solar-driven PEC. Nevertheless, the PIRET mechanism, particularly from the view of charge separation and extraction dynamics, remains unclear. Herein, we examined PEC water splitting activities of Au nanoparticles decorated α-Fe2O3 nanoarrays (α-Fe2O3/Au NRs) and systematically investigated the PIRET mechanism by the combination of ultraviolet-visible spectra, field distribution simulation, and transient absorption spectroscopy. The PIRET effect of Au nanoparticles (NPs) generates a localized electromagnetic field near the surface of the α-Fe2O3 NRs and the significant near-field coupling between α-Fe2O3 NRs and Au NPs promotes cross-sectional absorption that markedly enhances plasmonic energy transfer from Au NPs to α-Fe2O3 NRs. TA measurement uncovers the proximate electric field around α-Fe2O3 NRs, which emanates from the Au NPs' PIRET, orchestrates the instantaneous segregation of electrons and holes upon their formation and births enduring photogenerated holes in α-Fe2O3/Au NRs. Additionally, the FeOOH overlayers, as cocatalyst, are effective in boosting hole transfer kinetics. Consequently, the photocurrent density exhibited by the α-Fe2O3/Au/FeOOH arrays is amplified by 3.5 times in comparison to the pristine α-Fe2O3 NR arrays.

Recent progress of modified CeO2-based materials for photocatalytic environmental remediation and antibacterial activity

The rapid development of industrialization and urbanization has led to serious environmental pollution. As an environmentally friendly and sustainable energy source, solar-driven semiconductor photocatalysis has been widely applied in environmental remediation and antibacterial activity owing to its gentle reaction conditions. The use of CeO2-based nanomaterials in green energy production, CO2 conversion, pollutant degradation, and antibacterial is increasing. The photocatalytic performance of CeO2 can be enhanced by appropriate modification strategies that suppress the rapid recombination of electron-hole pairs. This paper provides a systematic introduction to various modification strategies for CeO2, and reviews the research progress of modified CeO2 materials in photocatalytic CO2 reduction, photocatalytic hydrogen evolution, heavy metal removal, photodegradation of organic pollutants, and antibacterial fields, finally offering perspectives on its future development direction.

Rapid degradation of high-concentration antibiotic via heterogeneous photocatalysis coupling Fenton-like oxidation with MIL-53(Fe) under visible light irradiation

The photocatalytic technology based on Metal-Organic Frameworks (MOFs) has shown promising applications in the field of antibiotic pollution control. However, it still faces challenges in efficiently removing high-concentration antibiotic wastewater. A typical Fe-containing MOF, MIL-53(Fe), was successfully synthesized and demonstrated efficient photocatalytic activity under visible light irradiation for high-concentrations of tetracycline hydrochloride (TCH). However, the bare MIL-53(Fe) exhibited unsatisfactory photocatalytic performance. To overcome the low degradation efficiency resulting from the rapid recombination of light-induced electron-hole pairs, H2O2 was introduced as an external electron acceptor to establish a synergistic Fenton-like system to couple with the photocatalysis process. The results showed that in the MIL-53(Fe)/H2O2/Vis system, 99% of 1 g/L TCH was degraded within 80 min, while the degradation efficiency of the MIL-53(Fe)/Vis process was only 4.89% under identical conditions. The degradation mechanism of the coupling system was performed by radical scavenging experiments and Electron Spin Resonance characterization. The results indicated that ·OH was the dominant radical in the coupled reaction, and ·O2- and h+ also played a role in this system. The significant improvement in TCH degradation efficiency during the coupling process was attributed to the following three factors: (1) In the coupling reaction process, photo-generated electrons can stimulate H2O2 to form ·OH radicals, inhibiting the recombination of photo-generated electrons and holes, improving the efficiency of the photocatalytic reaction. (2) FeIII in MIL-53(Fe) can be excited by photo-generated electrons and converted to FeII, which then stimulates H2O2 to form ·OH radicals. (3) FeIII in MIL-53(Fe) can convert with FeII, stimulate H2O2 to form ·OH radicals, and participate in the degradation reaction. In addition, the reusability and stability of the MIL-53(Fe) photocatalyst in the coupled system, as well as the impact of operational parameters, were systematically studied. This work demonstrates a feasible strategy for environmental remediation by enhancing the efficiency of MIL-53(Fe) in photocatalytic Fenton-like systems, thereby providing a viable approach for the treatment of high-concentration antibiotic wastewater.

Self-doped zinc-mediated ZnIn2S4 microflowers towards optimized visible-light photocatalytic hydrogen production

Doping is a favorable strategy for modifying the performance of ZnIn2S4 (ZIS). However, the doped heteroatoms are prone to be the sites of carrier complexation. According to the coordination structure and the bond order relationship in hexagonal ZIS, we synthesized Zn self-doped ZIS as an efficient hydrogen evolution reaction (HER) photocatalyst by one-step hydrothermal method. By adjusting the content of Zn in the reaction precursor, the excess Zn competes with In and S to form a tetrahedral coordination structure. The doping of Zn in the In-S tetrahedron makes the conduction band shift negatively, which is conducive to the redox reaction. Moreover, the transfer rate of electrons and holes is accelerated, which is beneficial to inhibit the recombination of electron-hole pairs. The optimized Zn-doped ZIS exhibits enhanced HER efficiency of 10.8 mmol/g/h under visible light, which is 2.9 times higher than that of the pristine ZIS.

G-C3N4/TiO2 nanotube array for enhanced photoelectrochemical water splitting

Graphitic carbon nitride (g-C3N4) and TiO2 nanotubes (TNT) have made significant breakthroughs in the field of photocatalysis because of their unique features, such as environmental friendliness, low cost and good stability. Herein, we present the improved photo-electrochemical performance under AM 1.5G irradiation of three different photoanodes based on TNT coated with g-C3N4 via the effortless thermal treatment of anodized TNT sheets over melamine (TNT-M), urea (TNT-U) and dicyanamide (TNT -D). A maximum photocurrent of up to 0.14 mA cm−2 at 1.23 V (vs. RHE) is obtained under illumination using AM 1.5 G light source for TNT-D, which is ten times greater than pristine TNT (0.014 mA cm−2). A good photoelectrochemical stability with efficient charge transfer is observed, and electrochemical impedance spectra reveal that better photoelectrochemical performance is due to the reduced electron-hole pair recombination via the development of heterojunction between TNT and g-C3N4 compared to the bare-TNT electrode.

Enhanced piezocatalytic degradation of mixed organic dyes using BaTiO3–MoS2 heterostructure nanocomposites: A mechanistic investigation

Piezocatalysis garners significant interest as a potential solution to environmental issues, specifically regarding dye pollutants. Nonetheless, the main obstacle in the piezoelectric efficiency of materials for eliminating organic pollutants from water has been the recombination of charge carriers. Here we report on the fabrication of a piezoelectric nanocomposite of BaTiO3 (BT) Nanoparticles and MoS2 (MS) Nanosheets for the enhanced piezocatalytic degradation of dye pollutants. The sample with 1.0 wt % MoS2 content (BT/MS1) demonstrates greater efficacy compared to both 2.0 wt % MoS2 (BT/MS2) and BaTiO3 (BT) alone in degrading Rhodamine B (Rh B) and Methyl Orange (MO). Specifically, BT/MS1 exhibits 1.84- and 2.8-times enhanced performance for Rh B and MO degradation respectively, in comparison to BT alone. It is demonstrated that the charge transfer system at the interface of BT and MS effectively lowers the recombination of electron-hole (e‒- h+) pairs, generated during piezocatalysis thereby enhancing the degradation. The composite sample was further used for the successful degradation of a mixture of dyes. This study introduces a novel approach to enhance catalysis by hybrid composite in piezoelectric materials.

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

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

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

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

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

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

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

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

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

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

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

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