Recombination Rate Of Charge Carriers Research Articles

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.

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.

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.

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.

Nitrogen-Rich Triazine-Based Covalent Organic Frameworks as Efficient Visible Light Photocatalysts for Hydrogen Peroxide Production.

Covalent organic frameworks (COFs) have been widely used in photocatalytic hydrogen peroxide (H2O2) production due to their favorable band structure and excellent light absorption. Due to the rapid recombination rate of charge carriers, however, their applications are mainly restricted. This study presents the design and development of two highly conjugated triazine-based COFs (TBP-COF and TTP-COF) and evaluates their photocatalytic H2O2 production performance. The nitrogen-rich structures and high degrees of conjugation of TBP-COF and TTP-COF facilitate improved light absorption, promote O2 adsorption, enhance their redox power, and enable the efficient separation and transfer of photogenerated charge carriers. There is thus an increase in the photocatalytic activity for the production of H2O2. When exposed to 10 W LED visible light irradiation at a wavelength of 420 nm, the pyridine-based TTP-COF produced 4244 μmol h-1 g-1 of H2O2 from pure water in the absence of a sacrificial agent. Compared to TBP-COF (1882 μmol h-1 g-1), which has a similar structure but lacks pyridine sites, TTP-COF demonstrated nearly 2.5 times greater efficiency. Furthermore, it exhibited superior performance compared to most previously published nonmetal COF-based photocatalysts.

Fabrication of novel ternary dual S-scheme ZnFe2O4/Ag3PO4/ZnIn2S4 photocatalyst with enhanced visible light-driven RhB degradation

This work synthesized a ternary dual S-scheme photocatalyst ZnIn2S4/Ag3PO4/ZnFe2O4 by co-modifying Ag3PO4 with ZnFe2O4 and ZnIn2S4 by facile co-precipitation method. XRD outcome established the formation of bare Ag3PO4, ZnIn2S4, and ZnFe2O4, and ZnIn2S4/Ag3PO4/ZnFe2O4 was shown to be pure since peaks matching these semiconductors appeared. These findings were further supported by the FTIR and XPS analyses, which revealed the shift in structural characteristics. UV–Vis spectroscopy showed a broader absorption spectrum of the nanocomposite and pointed out that it might be used as a photocatalyst in direct sunshine. Shorter charge transfer resistance and poor recombination rate of charge carriers are shown by a smaller radius in the EIS Nyquist plot and a less intense PL spectrum of ternary composite, respectively. Under simulated solar radiations, the photocatalytic performance of the ZnIn2S4/Ag3PO4/ZnFe2O4 (ZIS/SP/ZIS) nanocomposite (99.8 %) was the highest against RhB decolorization when compared to pure ZnIn2S4 (ZIS) (33.3 %), Ag3PO4 (SP) (19.6 %), ZnFe2O4 (ZF) (20.1 %) and binary Ag3PO4/ZnFe2O4 (SP/ZF) (55.4 %) nanocomposite. However, COD proved that complete mineralization took longer and took 240 min. Experiments on scavenging have shown that the radicals •O2−, h+, and •OH are created and influence RhB degradation in order: O2− >OH > h+. ESR experiment supported the scavenging study results. Out of two main schematic models used to depict the photocatalytic reaction mechanism, the S-scheme can effectively explain boosted light absorption, charge carrier separation, the synergistic effect of the components, and improved photocatalytic performance. Facile magnetic separation and photostability were observed as photocatalysts retained 90.8 % degradation efficiency after four reuse cycles.

NiFe2O4/CuO heterostructures optical, magnetic and photocatalytic properties: Methylene blue dye degradation under solar light irradiation

A series of NiFe2O4/CuO heterostructures were prepared and their photocatalytic potential was compared with bare NiFe2O4 (NFO) and CuO (CO). The prepared materials were subjected to characterization using a combination of X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), photoluminescence (PL) spectroscopy, and UV–visible (UV–Vis) spectroscopy techniques. Photocatalytic efficiency was studied for removing methylene blue (MB) dye under solar light irradiation. The NiFe2O4/CuO heterostructures demonstrated superior removal of MB dye versus other materials. The decline in PL intensity for heterostructure revealed a low recombination rate of charge carriers. Maximum dye removal over NiFe2O4/CuO heterostructure was achieved for 20 mg/L dye catalyst dose and 20 mg/L dye solution at pH 10. Scavenging studies showed that hydroxyl radicals and electrons played a major role in the degradation of dye. The removal efficiency was 80.01 %, which was reduced to 78.83 % for NiFe2O4/CuO heterostructures after four consecutive cycles, which indicates its high stability under solar light irradiation. The NiFe2O4/CuO heterostructures may find potential applications in water treatment for removing organic dyes under visible light owing to their robust catalytic performance under solar light irradiation.

Broadband and strong visible-light driven photocatalytic enhancement utilizing two-dimensional plasmonics of Au/Cu-modified SrTiO3 perovskite nanostructures

Addressing limited access to clean drinking water demands innovative solutions to energy and environmental crises. Photocatalysis offers promise without eliciting secondary pollution, yet traditional metal oxide semiconductor photocatalysts encounter impediments in solar energy utilization and charge carrier recombination rates. To overcome these limitations, we present for the first time, a novel design, fabrication, and characterization of two-dimensional plasmonic noble metal/perovskite nanostructure hybrids for photocatalysis, combining Au as the plasmonic material with Cu-modified SrTiO3 as the semiconductor, fabricated on elastomeric polydimethylsiloxane substrates. Integrating localized surface plasmon resonance and Schottky junction-related band-bending significantly extends optical absorption into the ultraviolet-visible-infrared bands and enhances the effective carrier lifetimes, ensuring state-of-the-art photocatalytic efficiency. Exceptional photocatalytic performance in a 5-ppm aqueous methylene blue solution can be attained with 72.69-wt% Cu incorporation in the perovskite oxide, reaching a visible light-mediated photodegradation efficiency of 26% - an astounding 62.5-% efficiency increase compared to previous experiments without Cu modification. This advancement underscores the synergistic potential of noble metals and photocatalytic semiconductors in managing water purification challenges.

Double Z-scheme Ag2CrO4/Bi2O3–KBi6O9Br nanophotocatalysts designed via microwave-assisted combustion-precipitation method for degrading toxic organic dyes

This study introduces novel double Z-scheme Ag2CrO4/Bi2O3–KBi6O9Br nanophotocatalysts for effectively degrading organic dyes, namely Crystal Violet, Acid Orange 7, Rhodamine B, and Eosin Y, from contaminated wastewater. The photocatalysts were thoroughly characterized using advanced techniques, including X-ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), Transmission Electron Microscopy (TEM), Energy Dispersive X-ray Spectroscopy (EDX-Dot Mapping), Brunauer-Emmett-Teller (BET), Barrett-Joyner-Halenda (BJH), Diffuse Reflectance Spectroscopy (DRS), and Photoluminescence (PL). XRD confirmed the formation of desired crystalline phases without impurities. FESEM and TEM observations revealed the unique morphology of Bi2O3–KBi6O9Br, with distributed Ag2CrO4 nanoparticles on the surface, as confirmed by EDX-dot mapping. BET-BJH analyses indicated a specific surface area of 7.33 m2/g, including meso and macro pores with an average diameter of 10 nm and a total pore volume of 0.018 cm3/g for Ag2CrO4(25%)/Bi2O3–KBi6O9Br sample. DRS revealed notable shifts in absorption edges, suggesting the formation of a heterojunction, and PL analysis indicated a reduced charge carrier recombination rate, further enhancing the photocatalyst's efficacy. In a series of photocatalytic experiments lasting 240 min, using 1 g/L of Ag2CrO4(25%)/Bi2O3–KBi6O9Br, remarkable degradation efficiencies of 95.1%, 94.2%, 98.0%, and 89.6% were achieved for Crystal Violet, Acid Orange 7, Rhodamine B, and Eosin Y, respectively, at an initial concentration of 10 mg/L. The nanophotocatalyst also showed favourable stability after five consecutive reuses. Overall, the double Z-scheme heterostructure in the composite significantly improved the sample's properties and photocatalytic performance, making it highly effective in removing various organic dyes from wastewater.

Enhanced solar Photocatalysis: Zinc oxide modified Yb2Zn-TiO6 doped g-C3N4 heterostructures for bromothymol blue mineralization and bacterial inhibition

A new composite material, ZnO/Yb2Zn-TiO6@g-C3N4 has been synthesized by simple hydrothermal process. This composite has been characterized using various material characterization techniques and was found to have a heterojunction amongst Yb2Zn-TiO6 and g-C3N4, leading to higher light absorption and poorer charge carrier recombination rates. Furthermore, the evaluation of the charge carrier density revealed that the incorporation of small sized ZnO (40 nm) into Yb2Zn-TiO6@g-C3N4 led to heightened disintegration of the photoinduced charge carriers. This observation implies that the presence of said metal oxide enhances the photocatalytic performance by greatly promoting the effective separation of charge carriers for various applications. When tested with bromothymol blue, the 20 wt% ZnO/Yb2Zn-TiO6@g-C3N4 composite showed a photodegradation rate several times greater (98 %) than individual ZnO, C3N4 and Yb2Zn-TiO6, respectively. The degradation efficiency of the ZnO/Yb2Zn-TiO6@g-C3N4 nanostructure in the absence of light was 24 %. The increased photoactivity of the composite material is due to the efficient separation of charge carriers and also due to the high redox capabilities resulting from the heterojunction. The composite also demonstrated stable photocatalytic performance over five cyclic runs and was effective in treating real printed ink wastewater. Furthermore, ZnO/Yb2Zn-TiO6@g-C3N4 was found to have excellent antibacterial properties in opposition to Escherichia coli, (Inhibition = 16(±0.2) mm) as well as Bacillus subtilis (Inhibition = 22(±0.3) mm). The MIC of the said nanomaterials against Escherichia coli as well as Bacillus subtilis were 50 µg/mL and 30 µg/mL respectively. The detailed explanation of the photodegradation mechanism was also provided. The use of this composite material can help to reduce the harmful effects of contaminants and microbes in aquatic environments and promote environmental sustainability.

Symbiotic coupling of ZnO nanoparticles and coumarin photosensitizer in soft polyurethane matrices for boosting visible-light photocatalytic performance

Photocatalysis provides a practical and efficient solution to eliminate harmful substances from the environment by using light energy to activate the catalysts, and the development of sustainable photocatalysts easily recoverable and highly efficient in visible light remains a significant challenge. To address this issue, herein we present a facile approach to immobilize silane-functionalized ZnO NPs in polyurethanes with coumarin chromophore, resulting in highly active recyclable and reusable hybrid materials as photocatalytic systems for the degradation of organic dyes. Characterization of ZnO NPs revealed that the attachment of silane units to nanoparticles' surface decreased band gap values (up to 2.83 eV) and reduced the rate of charge carrier recombination. The performed investigations showed that incorporation of ZnO NPs into macromolecular chains via quaternization near to coumarin units promoted efficient photoinduced charge transfer between semiconductor nanoparticles and photosensitizer molecules. The band gap energy for hybrid films ranged between 2.73 eV and 2.32 eV, and the best photodegradation results for malachite green (MG) under visible-light irradiation were attained after 17 min (k = 17.7 × 10−2 min−1). The photocatalytic mechanism was clarified using scavenger tests and the photocatalytic efficiency of the best performing sample was tested for the degradation of other dyes (brilliant blue R, sunset yellow, congo red, rhodamine B, s.o.) and for the removal of MG from binary dye mixtures. The stability and integrity evaluation after 7 catalysis cycles reveals that the photocatalytic potential is retained without substantial structural changes.

Hot-Antisolvent Assisted Morphological Regulation of Perovskites for Semitransparent Photovoltaics Employing Hot-Pressing Approach

The processing of halide perovskites in the air significantly influences their morphology and surface coverage, often leading to the presence of numerous trap densities that adversely affect device performance. In this study, we explored the development of perovskite films using a solvent extraction method, where the temperature of the anisole antisolvent was varied. Our findings demonstrate that the hot-antisolvent strategy effectively controls nucleation, resulting in the formation of highly dense, pinhole-free, and crack-free perovskite films with reduced surface roughness. Films fabricated using this hot-antisolvent approach exhibited enhanced photoluminescence, indicating lower trap density and increased recombination resistance. They also showed slower charge carrier recombination rates and efficient charge extraction, suggesting the suppression of nonradiative recombination. Furthermore, the superior quality of perovskite films obtained through the hot-antisolvent strategy significantly enhanced the power conversion efficiency (PCE) of hot-pressed semitransparent perovskite solar cells. The PCE remarkably increased from 0.13% to an impressive 12.65% while maintaining an average visible transmittance of 26.55% and exceptional air stability for 2000 hours with no significant degradation in initial PCE. This study achieves a record-breaking light utilization efficiency of 3.36% in the realm of research on hot-press processes.

Novel Ag-Bridged Z-Scheme CdS/Ag/Bi2WO6 Heterojunction: Excellent Photocatalytic Performance and Insight into the Underlying Mechanism

The construction of semiconductor heterojunction photocatalysts that improve the separation and transfer of photoinduced charge carriers is an effective and widely employed strategy to boost photocatalytic performance. Herein, we have successfully constructed a CdS/Ag/Bi2WO6 Z-scheme heterojunction with an Ag-bridge as an effective charge transfer channel by a facile process. The heterostructure consists of both CdS and Ag nanoparticles anchored on the surface of Bi2WO6 nanosheets. The photocatalytic efficiency of the CdS/Ag/Bi2WO6 system was studied by the decontamination of tetracycline (TC) and Rhodamine B (RhB) under visible light irradiation (λ ≥ 420). The results exhibited that CdS/Ag/Bi2WO6 shows markedly higher photocatalytic performance than that of CdS, Bi2WO6, Ag/Bi2WO6, and CdS/Bi2WO6. The trapping experiment results verified that the •O2− and h+ radicals are the key active species. The results of photoluminescence spectral analysis and photocurrent responses indicated that the CdS/Ag/Bi2WO6 heterojunctions exhibit exceptional efficiency in separating and transferring photoinduced electron−hole pairs. Based on a series of characterization results, the boosted photocatalytic activity of the CdS/Ag/Bi2WO6 system is mostly due to the successful formation of the Ag-bridged Z-scheme heterojunction; these can not only inhibit the recombination rate of photoinduced charge carriers but also possess a splendid redox capacity. The work provides a way for designing a Z-scheme photocatalytic system based on Ag-bridged for boosting photocatalytic performance.

Selective vanadium etching and in-situ formation of δ-Bi2O3 on m-BiVO4 with g-C3N4 nanosheets for photocatalytic degradation of antibiotic tetracycline

Antibiotics play a vital role in treating microbial illnesses, but their presence in water bodies is a global concern. Despite the potential of polymeric graphitic carbon nitrate (g-C3N4) as a photocatalyst for wastewater treatment, its effectiveness is hindered by a fast charge carrier recombination rate. To overcome this challenge, we have developed a novel approach involving the surface etching-oxidation technique to introduce δ-Bi2O3 onto m-BiVO4. Subsequently, the modified δ-Bi2O3/m-BiVO4 (BBV) was synergistically coupled with g-C3N4 (CN) to create a hybrid photocatalyst (BBVCN). The photocatalytic activity of BBVCN was evaluated using tetracycline hydrochloride (TC) as a model wastewater antibiotic pollutant, demonstrating a 92 % degradation of TC within a 1 h reaction time. Total organic carbon analysis demonstrated a TC removal efficiency of 76 %, indicating significant mineralization by BBVCN.

Investigation of novel, green synthesized and photocatalytic Sn-doped MoO3 nanomaterial for the degradation of methyl orange

Nowadays, water resources are being contaminated owe to the waste organic pollutants. A novel Sn-doped MoO3 nanomaterial was developed in the presence of extract from the skin of Capsicum annuum fruit to decontaminate the waste water by degrading this organic pollutant. For the preparation of these nanomaterials, a facile green synthesis approach was adopted by using Capsicum annuum extract. The as designed nanomaterials were thoroughly characterized by X-ray diffraction spectroscopy (XRD, scanning electron microscopy (SEM), ultraviolet visible spectroscopy (UV–vis) and photoluminescence spectroscopy (PL) techniques. The photocatalytic activity of as designed nanomaterials was observed against the methyl orange (MO) a model dye under the irradiation of visible light. The results obtained from the characterization of these nanomaterials have shown reduced sized particles with cone, sphere and rod like morphologies. In comparison to pure MoO3 prepared without extract (Sample-1) and MoO3 prepared with extract (Sample-2), the Sn-doped MoO3 prepared in the presence of extract (Sample-3) has shown a reduced optical energy bang gap value i.e 2.84 eV and an enhanced photocatalytic activity against MO i.e about 95%. This optimized sample has also shown a low charges recombination rates. This excellent photocatalytic performance is credited to the increased active sites owe to the development of large surface area and a significant decrease in the recombination rate of charge carriers along with a reasonable decrease in optical band gap. These results have exhibited a boosted photocatalytic performance of this material in visible light region.

Sonochemical surface modification of a novel Sm2O3@g-C3N4@Bi2O3 ternary hybrid photocatalyst exhibiting efficient solar light harvesting: Degradation of Azure b and photoelectrochemical water splitting

Engineered Z-scheme photocatalysts have a strong redox activity while also reducing the annihilation of light-induced charge bearers. In this investigation, a solid state twin Z-scheme Sm2O3@g-C3N4@Bi2O3 nanocomposite has been successfully prepared employing bismuth (III) nitrate, samarium chloride and urea as precursor chemicals in a single co-calcination procedure followed by sonochemical surface modification. The formation of flower like multiphasic material is confirmed from SEM and HRTEM images. BET findings suggested the enhancement in specific surface area of Sm2O3@g-C3N4@Bi2O3 and reduced band gap from UV–visible data. Photoluminescence results confirmed the reduction in rate of charge carrier recombination of Sm2O3@g-C3N4@Bi2O3. Presence of samarium is confirmed from XPS analysis. Under direct solar radiation, the surface modified Sm2O3@g-C3N4@Bi2O3 hybrid demonstrated amplified photo-assisted catalytic activity for the degradation of Azure B (AzB) than pristine g-C3N4 and their binary composite Sm2O3@g-C3N4. It is possible to attribute the better solar light absorption, higher separation efficacy of photo-promoted electron-holes to the amplified photo-assisted degradation performance of the Sm2O3@g-C3N4@Bi2O3 composite. The photodegradaton of AzB follows pseudo-first order kinetics and the observed rate constants are 0.0014, 0.0026, and 0.0316 min−1 for g-C3N4, Sm2O3@g-C3N4, and Sm2O3@g-C3N4@Bi2O3 ternary composite. The nanocomposite also demonstrates good stability and recyclability. A unique solid-state twin Z-scheme photocatalytic pathway was also hypothesized in light of the findings. The fabricated ternary hybrid shown efficient photoelectrochemical water splitting reaction for H2 and O2 generation.

Superior visible-light absorbing Ag@ZnO nanorods hybrid photocatalyst for efficient decomposition of commercial pharmaceuticals tetracycline and amoxicillin

This work assesses the role of the noble metal silver in the visible-light sensitization of UV-active ZnO by introducing a localized plasmonic resonance effect and enhancing the spatial charge carrier separation. We herein synthesize ZnO nanorods via a solvothermal approach, yielding nanorods of length and diameter 1.356 ± 0.619 μm and 120.56 ± 25.09 nm, respectively. Silver nanoparticles are reduced on the surface of ZnO nanorods via the photodeposition route. XRD spectra reveal a high crystallinity and wurtzite-type structure for ZnO with new peaks for cubic phase Ag upon Ag-loading. The diffraction peaks shift upon Ag modification, indicating partial incorporation of Ag into the ZnO lattice. Further, upon Ag-decoration, a slight increase in dislocation density and micro strain is obtained, which could suppress the recombination rate of charge carriers. The DRS spectra reveal a band gap contraction of materials from 3.19 to 2.98 eV with increasing Ag density. The PL spectra confirmed that the optimum Ag concentration of 3 wt% is proficient in harvesting visible light towards high photocatalytic degradation efficiencies of tetracycline (92.1 %) and amoxicillin (76.4 %) in 90 min as compared to 49.4 % and 38 % over pristine ZnO nanorods. TOC studies reveal only partial mineralization of ∼42.7 % (tetracycline) and ∼31.3 % (amoxicillin) due to the formation of reaction intermediates identified by HR-MS chromatograms. In addition, degradation pathways are proposed through the fragments at different m/z ratios.

Box–Behnken Design and experimental studies on novel fibrous g-C3N4 towards water splitting and degradation of indigo carmine dye

Graphitic carbon nitride (g-C3N4) is robust and stable metal free polymeric materials that have recently gained interest towards photocatalytic applications. It shows visible-light driven photocatalytic activity with a major drawback of higher recombination rate of charge carriers and moderate oxidation ability. These issues are overcome by structural modifications using facile polymerization of acidized melamine thus controlling the structure of graphitic carbon nitride. The major factors affecting the photocatalytic activity were experimentally optimized and effect of these parameters was evaluated using the Box–Behnken Design of response surface methodology. The fabricated fibrous graphitic carbon nitride (NFgCN) shows a superior activity of 81.0 μmol g−1 h−1 hydrogen generation and 99.9 % degradation of indigo carmine (IC) dye in 90 min. The NFgCN shows 5 times higher activity for hydrogen generation compared to the pristine g-C3N4.