Formation Of Heterojunction Research Articles

Efficient antibacterial and microbial corrosion resistant photocatalytic coating: Enhancing performance with S-type heterojunction and Cu synergy

Microbial corrosion stands as a leading cause of deterioration in metallic materials, leading to substantial economic ramifications. Cu2O coatings, envisioned as potent photocatalytic antimicrobial solutions, offer a pathway to mitigate microbial corrosion. Nevertheless, inherent limitations such as photocorrosion and suboptimal charge separation efficiency hinder their broad adoption. This study introduces a novel, highly efficient antimicrobial 2D g-C3N4/Cu2O/Cu coating synthesized successfully. The ultrathin and porous structure of the 2D g-C3N4 substrate provides ample active sites for Cu2O and Cu deposition, enhancing current efficiency while bolstering light absorption and electron transfer capabilities. Additionally, the formation of an S-type heterojunction between 2D g-C3N4 and Cu2O/Cu effectively combats Cu2O photocorrosion. Notably, the coating demonstrates rapid elimination of Escherichia coli and Staphylococcus aureus within 1 h under both illuminated and dark conditions, owing to the synergistic bactericidal effects of copper ions and the generation of reactive oxygen species facilitated by the coating. Furthermore, significant inhibition of microbial corrosion on 316L stainless steel induced by Pseudomonas aeruginosa underscores the robust antimicrobial properties of the coating. Thus, this synergistic antimicrobial coating, fusing photocatalysis with copper, holds substantial promise in protecting metallic materials against microbial corrosion, meriting widespread application consideration.

Z-scheme WO3/AgI heterojunction grown on flexible carbon fibers for efficient organic degradation and bacterial inactivation

Z-scheme WO3/AgI heterojunctions on carbon fiber (CF) cloth were fabricated through in-situ hydrothermal method and chemical bath deposition route. The CF@WO3/AgI cloth achieved highly efficient photocatalytic abilities under visible light, which could eliminate 95.7 % of Rhodamine B (RhB) in 70 min and 70.0 % of tetracycline hydrochloride (TC-HCl) in 110 min, superior to those of CF, CF@WO3 and CF@AgI cloths. Moreover, the catalyst was able to achieve 7.0 ± 0.16 log10 CFU/mL reduction of E. coli cells within 40 min. Recycling test confirmed the repeatability and stability of CF@WO3/AgI cloth. The enhanced photocatalytic performance was attributed to the increased visible light utilization, accelerated charge carriers separation and high photo-redox capabilities which came from the formation of Z-scheme heterojunction. This work provided inspiration for the construction of high-efficiency flexible photocatalysts for environmental decontamination.

Synthesis of double Z-type heterojunction AgI/Ag6Si2O7/BiOI photocatalyst for antibiotics degradation and weakening toxicity

A novel ternary photocatalyst of AgI/Ag6Si2O7/BiOI was successfully synthesized using the ultrasonic co-precipitation method. The ratio of Ag6Si2O7, AgI and BiOI in the composite were screened and the reaction conditions were optimized. Under the optimal reaction conditions, the AgI/Ag6Si2O7/BiOI-65 % (1/3AI/AS/BI-65 %) catalyst exhibited excellent performance in degrading 20 mg/L norfloxacin (NOR) with a removal rate of up to 92.96 % and the apparent rate constant (0.01241 min−1) was approximately 12.048, 27.578, 3.866 and 1.693 times as high as that of Ag6Si2O7, AgI, BiOI and AgI/Ag6Si2O7, respectively. Meanwhile, the 1/3AI/AS/BI-65 % catalyst showed good universality, salt resistance and recycling stability for antibiotics. Additionally, the toxicity of degraded NOR to wheat was significantly reduced. High-performance liquid chromatography-mass spectrometry (HPLC-MS), free radical trapping experiments and electron paramagnetic resonance (EPR) analysis were employed to deduce possible photocatalytic mechanisms and degradation pathways for NOR. The results indicate that the improved photocatalytic activity can be attributed to the formation of a double Z-type heterojunction in the 1/3AI/AS/BI-65 % which effectively promotes charge carrier separation and enhances the visible light absorption capacity. This study provides new insights into treating antibiotics in sewage using BiOI based heterojunction catalyst.

Lead‐Free Perovskite‐Based Photocatalysts for Solar‐Driven Chemistry Technologies

AbstractThe high consumption of fossil fuels and concomitant contamination of the environment have promoted the search for new, low‐cost, and cleaner energy sources to satisfy the current energy demand around the world, decreasing the levels of greenhouse gas emissions to the atmosphere. One of the promising strategies to facilitate the generation of renewable energy involves solar‐driven chemical reactions, by using photocatalysts with improved sunlight absorption and carrier transfer abilities. Lead‐free halide perovskites (LFHPs) are good candidates, showing mesmerizing optical features, modulable band structure, oxidizing/reducing capability, and less toxicity compared to their Pb‐analogous. However, the literature reporting the photo(electro)chemical (PEC) properties of the LFHPs‐based materials for solar energy production is scarce. This review describes the current state‐of‐the‐art exhibiting the influence of the dimensionality, chemical composition and the formation of heterojunctions based on LFHPs on their photo(electro)activity for conducting solar‐driven hydrogen evolution, carbon dioxide (CO2) reduction, and the degradation of recalcitrant pollutants to obtain added‐value chemicals. In this way, it is also included the main challenges to be faced. Furthermore, we address some potential LFHPs to be explored in PEC systems, opening up the gamut of possibilities to consolidate the solar‐to‐chemical transformation as an innovative alternative to favor environmentally friendly energy production.

Electrooxidation of ethylene glycol using Ag-Pt nanotubes supported on silica: Correlating the unexpected O-vacancies creation with catalytic performance

Electrooxidation of small organic compounds is crucial in achieving clean and efficient energy production. In this context, ethylene glycol (EG) has attracted considerable interest due to its notable energy density, which is suitable for applications in direct alcohol fuel cells. In light of this, we prepared Ag-Pt nanotubes (Ag-PtNTs) supported on silica (SiO2) for the electrooxidation of this alcohol. However, our goal was not only to create an electrocatalyst that enhances electrooxidation efficiency but also to explore the interaction between the SiO2 and the nanotubes. Such an exploration aims to contest the prevailing perception of SiO2 as an inert and non-conductive material. Thus, comprehensive physicochemical characterization of the electrocatalyst was conducted, supported by density functional tight-binding (DFTB) calculations, to elucidate the correlation between composition, electronic effects, and catalytic performance, showing that Ag interacts more with the oxygen of SiO2 that Pt. The interaction between SiO2 and Ag-Pt NTs was explored through Mott-Schottky (M-S) analysis and electron paramagnetic resonance (EPR) spectroscopy, revealing the creation of oxygen vacancies (o-vacancies) and heterojunction formation, which enhance charge transfer and catalytic activity, both supported by theoretical calculations. In addition, mechanistic insights into the electrooxidation process were obtained through potential energy surface (PES) assessments, revealing a concerted pathway for glycolaldehyde formation with low barrier energy and favorable thermodynamics. Finally, the synthesized Ag-PtNTs/Si electrocatalyst exhibited an onset potential/current density of 0.45 V/0.09 mV mA cm−2 at 25 °C, demonstrating efficient electrooxidation capabilities. Therefore, this study provides valuable insights into designing efficient and stable electrocatalysts for alcohol electrooxidation, contributing to improving cleaner energy technologies.

Improved decolorization of MB using CeCoO3/PbS heterojunction as a superior‐excellent photocatalyst

Developing effective and inexpensive photocatalysts is considered a helpful approach to pollution degradation. Herein, CeCoO3/PbS photocatalyst was synthesized via the hydrothermal procedure and described by XRD, IR, SEM, EDS, PL, and DRS analyses. The results revealed the deposition of PbS on the CeCoO3 surface, as illustrated by the FE‐SEM images. The influence of photocatalyst dosage, temperature, electron acceptor, and pH toward the decolorization of MB under the irradiation of a UV lamp was considered. By CeCoO3/PbS photocatalyst, the conversion percentage achieved 98% within 10 min, around two times more than pure CeCoO3 and PbS. According to the experimental and calculated results, the Type‐II heterojunction formation was observed, which boosted the photoactivity of CeCoO3/PbS by its higher charge separation rate compared with perovskite and PbS and the stronger redox capability of charges. In addition, CeCoO3/PbS nanocomposites have impressive stability and efficiency after five cycles of experiments. Consequently, the coupling of CeCoO3 with PbS provides a favorable pathway to remove contamination.

Exploration of morphological, structural, and photocatalytic behaviours of MoS2/WO3 nanocomposites

A lot of people are interested in hybrid nanostructures made of two-dimensional materials like transition metal dichalcogenides and transition metal oxides because they could be used as photocatalysts. This interest stems from their outstanding structural, electronic, and optical properties. The main objective of this paper is how to make a photocatalyst that works better by combining a special photocatalytic system made of MoS2/WO3 nanocomposites in an easy hydrothermal process. The crystalline structure of MoS2, WO3, and MoS2/WO3 nanocomposites was verified by powder X-ray diffraction (PXRD) investigation. Furthermore, scanning electron microscopy (SEM) analysis showed the creation of highly pure MoS2 and MoS2/WO3 composites, which showed a clustering of several spherical nanorods. We performed photocatalytic experiments using methylene blue dye under visible light in the presence of MoS2, WO3, and MoS2/WO3 nanocomposites. We observed that the formation of heterojunction and the increase of active sites were the optimal parameters affecting the photodegradation of methylene blue. The degradation percentages were observed to be 59 %, 55 %, and 90 %, respectively, within 120 min of light irradiation. The results of consecutive experiments explicitly demonstrate the enrichment of the photocatalytic properties of the MoS2/WO3 nanorods. Furthermore, we thoroughly investigated and discussed the mechanism of photodegradation in the MoS2/WO3 nanocomposites.

P-N Heterojunction formation: Metal Sulfide@Metal Oxide Chemiresistor for ppb H2S Detection from Exhaled Breath and Food Spoilage at Flexible Room Temperature.

The development of a portable, low-cost sensor capable of accurately detecting H2S gas in exhaled human breath at room temperature is highly anticipated in the fields of human health assessment and food spoilage evaluation. However, achieving outstanding gas sensing performance and applicability for flexible room-temperature operation with parts per billion H2S gas sensors still poses technical challenges. To address this issue, this study involves the in situ growth of MoS2 nanosheets on the surface of In2O3 fibers to construct a p-n heterojunction. The In2O3@MoS2-2 sensor exhibits a high response of 460.61 to 50 ppm of H2S gas at room temperature, which is 19.5 times higher than that of the pure In2O3 sensor and 322.1 times higher than that of pure MoS2. The In2O3@MoS2-2 also demonstrates a minimum detection limit of 3 ppb and maintains a stable response to H2S gas even after being bent 50 times at a 60° angle. These exceptional gas sensing properties are attributed to the increase in oxygen vacancies and chemisorbed oxygen on In2O3@MoS2-2 nanofibers as well as the formation of the p-n heterojunction, which modulates the heterojunction barrier. Furthermore, in this study, we successfully applied the In2O3@MoS2-2 sensor for oral disease and detection of food spoilage conditions, thereby providing new design insights for the development of portable exhaled gas sensors and gas sensors for evaluating food spoilage conditions at room temperature.

Sludge reduction and hydrogen production in a microbial photoelectrochemical cell with a g-C3N4/CQDs/BiOBr composite photocathode

ABSTRACT Hydrogen (H2) remains a pivotal clean energy source, and the emergence of Solar-powered Microbial Photoelectrochemical Cells (MPECs) presents promising avenues for H2 production while concurrently aiding organic matter degradation. This study introduces an MPEC system employing a g-C3N4/CQDs/BiOBr photocathode and a bioanode, successfully achieving simultaneous H2 production and sludge reduction. The research highlights the effective formation of a Z-type heterojunction in the g-C3N4/CQDs/BiOBr photocathode, substantially enhancing the photocurrent response under light conditions. Operating at – 0.4 V versus RHE, it demonstrated a current density of – 3.25 mA·cm−2, surpassing that of g-C3N4/BiOBr (−2.25 mA·cm−2) by 1.4 times and g-C3N4 (−2.04 mA·cm−2) by 1.6 times. When subjected to visible light irradiation and a 0.8 V applied bias voltage, the MPEC system achieved a current density of 1.0 mA·cm−2. The cumulative H2 production of the MPEC system reached 8.9 mL, averaging a production rate of 0.13 mL·h−1. In the anode chamber, the degradation rates of total chemical oxygen demand (TCOD), soluble chemical oxygen demand (SCOD), total suspended solids (TSS), volatile suspended solids (VSS), proteins, polysaccharides, and volatile fatty acids (VFA) in the sludge were recorded at 57.18%, 82.64%, 64.98%, 86.39%, 42.81%, 67.34%, and 29.01%, respectively.

Field emission from two-dimensional (2D) CdSSe flake flowers structure grown on gold coated silicon substrate: An efficient cold cathode.

Field emission finds a vital space in numerous scientific and technological applications, including high-resolution imaging at micro- and nano-scales, conducting high-energy physics experiments, molecule ionization in spectroscopy, and electronic uses. A continuous effort exists to develop new materials for enhanced field emission applications. In the present work, two-dimensional (2D) well-aligned CdSSe flake flowers (CdSSe-FFs) were successfully grown on gold-coated silicon substrate utilizing a simple and affordable chemical bath deposition approach at ambient temperature. The time-dependent growth mechanism from nanoparticles to FFs was observed at optimized parameters such as concentration of precursors, pH (~11), deposition time, and solution temperature. The crystalline nature of CdSSe-FFs is confirmed by high-resolution transmission electron microscopy (HRTEM) results, and selected area electron diffraction (SAED) observations reveal a hexagonal crystal structure. Additionally, the CdSSe-FFs thickness was confirmed by TEM analysis and found to be ~20-30 nm. The optical, photoelectric, and field emission (FE) characteristics are thoroughly explored which shows significant enhancement due to the formation of heterojunction between the gold-coated silicon substrate and CdSSe-FFs. The UV-visible absorption spectra of CdSSe-FFs show enhanced absorption at 700 nm, corresponding to the energy band gap (Eg) of 1.77 eV. The CdSSe-FFs exhibited field emission and photosensitive field emission (PSFE) characteristics. In FE study CdSSe-FFs shows an increase in current density of 387.2 μ A cm-2 in an applied field of 4.1 V m-1 which is 4.08 fold as compared to without light illumination (95.1 μ A cm-2). Furthermore, it shows excellent emission current stability at the preset value of 1.5 μA over 3 h with a deviation of the current density of less than 5% respectively. RESEARCH HIGHLIGHTS: Novel CdSSe flake flowers were grown on Au-coated Si substrate by a cost-effective chemical bath deposition route. The growth mechanism of CdSSe flake flowers is studied in detail. Field emission and Photoluminescence study of CdSSe flake flowers is characterized. CdSSe flake flowers with nanoflakes sharp edges exhibited enhanced field emission properties.

Construction of novel BiOI/CuInS2/ZnO dual S-scheme charge transfer pathway for efficient antibiotic degradation

The present work explored the photocatalytic activity of BiOI–CuInS2–ZnO ternary heterojunction for the photodegradation of the tetracycline (TCl). The bare photocatalysts were prepared via hydrothermal method while the ternary heterojunction was synthesized using simple physical mixing route. The ternary heterojunction of BiOI, CuInS2 and ZnO followed the S-scheme charge transfer pathway exhibiting superior photodegradation ability compared to other synthesized photocatalysts. The attained degradation efficiency of BiOI–CuInS2–ZnO S-scheme ternary heterojunction was 96.75 % within 90 min of light illumination which was much higher than other photocatalysts. Electron spin resonance (ESR) investigations and scavenging experiment indicated that •O2−, and •OH radicals plays an important role in photodegradation of TCl. Furthermore, the structural analysis of synthesized bare photocatalysts was also done via density functional theory (DFT) calculations. The results showed that after the formation of S-scheme heterojunction, the ternary heterojunction showed lower recombination rate (validated via PL analysis) with boosted charge carriers separation rate (confirmed through EIS and TPR analysis) and light absorption ability. This had led to upgradation in photodegradation efficiency of ternary BiOI–CuInS2–ZnO photocatalyst. The reusability test of the photocatalysts confirmed excellent stability of ternary photocatalysts with 90.25 % degradation rate up to five catalytic cycles.

Hydrothermally synthesized ZnFe2O4/ZnO heterojunction nanocomposites for enhanced RB dye degradation via Z-scheme photocatalysis

ZnFe2O4/ZnO nanocomposites with 1:1, 1:2, 1:3 and 1:4 wt ratios synthesized by hydrothermal method are used as a photocatalyst to degrade Rose Bengal (RB) dye. For structural investigation X-ray diffraction (XRD) and Fourier transform Infrared (FTIR) was performed. The presence of both phases corresponding to ZnFe2O4 and ZnO in XRD suggests the successful formation of a nanocomposite. Value of crystallite size varies from 25.01 nm to 18.61 nm for 1:1 to 1:4 nanocomposite. Almost spherical morphology of nanocomposite obtained through High-resolution transmission electron microscopy (HRTEM). FTIR demonstrated Zn–O and Fe–O bonds in as synthesized samples. Also, X-ray photoelectron spectroscopy (XPS) is used to detect the presence of Fe2+, Zn2+ and O2− ions in synthesized nanocomposites. In UV-DRS, values of band gap vary from 1.73 to 1.88 eV in nanocomposite as the weight ratio of ZnO increases. The formation of heterojunction is responsible for enhancing electron hole mobility. Due to this enhancement, degradation efficiency of 88% is achieved in 90 min irradiation of UV light by ZnFe2O4/ZnO (1:4) nanocomposites for RB dye followed Z-scheme mechanism. Also, the magnetization value of different nanocomposites changes from 0.9 to 0.1 emu/g. Magnetization nature is responsible for separating the catalyst from the reaction mixture after use. So, the nanocomposite can be reused which maintains the green protocol in the environment. ZnFe2O4/ZnO nanocomposite with 1:4 wt ratio can be reused up to 5 cycles. The formation of such nanocomposites can offer unique properties and advantages by combining the characteristics of both materials can lead to enhanced functionalities suitable for various applications such as catalysis, sensors, and magnetic devices.

In situ construction of Ag/Bi2O3/Bi5O7I heterojunction with Bi-MOF for enhance the photocatalytic efficiency of bisphenol A by facet-coupling and s-scheme structure

In this study, Ag/Bi2O3/Bi5O7I with s-scheme heterostructures were successfully synthesized in situ by nano-silver modification of CUA-17 and halogenated hydrolysis.The growth rate of Bi2O3 crystals was effectively controlled by adjusting the doping amount of Ag, resulting in the formation of a facet-coupling heterojunctions. Through the investigation of the microstructure and compositional of catalysts, it has been confirmed that an intimate facet coupling between the Bi2O3 (120) facet and the Bi5O7I (312) facet, which provides robust support for charge transfer. Under visible light irradiation, the AgBOI.3 heterojunction photocatalyst exhibited an outstanding degradation rate of 98.2% for Bisphenol A (BPA) with excellent stability. Further characterization using optical, electrochemical, impedance spectroscopy, and electron spin resonance techniques revealed significantly enhanced efficiency in photogenerated charge separation and transfer, and confirming the s-scheme structure of the photocatalyst. Density functional theory calculations was employed to elucidate the mechanism of BPA degradation and the degradation pathway of BPA was investigated by LC-MS. Finally, the toxicity of the degradation intermediates was evaluated using T.E.S.T software.

Ruddlesden-Popper 2D Perovskite-MoS2 Hybrid Heterojunction Photocathodes for Efficient and Scalable Photo-Rechargeable Li-Ion Batteries.

Photo-rechargeable batteries (PRBs) can provide a compact solution to power autonomous smart devices located at remote sites that cannot be connected with the grid. The study reports the Ruddlesden-Popper (RP) metal halide perovskite (MHP) and molybdenum disulfide (MoS2) hybrid heterojunction-based photocathodes for Li-ion photo-rechargeable battery (Li-PRB) applications. Hybrid Lithium-ion batteries (LIBs) have demonstrated an average discharge specific capacity of 144.46 and 129.17 mAhg-1 for 50 cycles when operating at 176 and 294 mAg-1, respectively compared to the pristine LIBs which have shown specific capacity of 37.48 and 25.60 mAhg-1 under similar conditions. Hybrid Li-PRB has achieved an average dark discharge specific capacities of 128.66 mAhg-1 (capacity retention: 96.56%) which enhanced to 180.67 mAhg-1 under illumination (capacity retention: 97.39%; photo-enhancement: 40.42%) at 64 mAg-1. Excellent performance of hybrid Li-PRB is attributed to the formation of type-II heterojunction that leads to improved crystallinity and film morphology. The PRB has demonstrated a high photo conversion and storage efficiency (PC-SE) of 0.52% under standard 1 Sun illumination, which outperforms other previously reported MHP based LIBs and PRBs. This work provides a novel approach of harnessing the potential of MHPs for PRBs and offers new avenues for MHP photocathodes for various applications beyond PRBs.

A Cu-based metal-organic frameworks-modified BiOCl heterojunction for enhanced photodegradation of rhodamine B

Environmental pollution caused by organic dyes has attracted increasing attention and prompts people to develop an effective treating method. Photocatalysis isregarded as one of the most promising treatment methodsowing to low cost, flexibility, and high efficiency. Herein, we reported a copper-based metal–organic frameworks (Cu-MOF) modified BiOCl heterojunction Cu-MOF/BiOCl (CMB) to treat organic dye rhodamine B (RhB) under white light illumination. The optimal photodegradation efficiency is shown to be 97 % within 40 min, exhibiting a higher photocatalytic ability than individual BiOCl and Cu-MOF. The enhanced photocatalytic activity is attributed to the formation of CMB heterojunction improving the visible light utilization efficiency and promoting significantly the separation/transfer of carriers. This study highlights the importance of combining narrow band gap nanomaterial with wide counterpart in environmental remediation.

2D/2D SnOx/TiO2 Z-scheme heterojunction with oxygen vacancies for boosted photocatalytic performance and mechanistic insight

A Z-Scheme heterojunction two-dimensional/two-dimensional (2D/2D) SnOx/TiO2 photocatalyst modified with oxygen vacancies (OVs) was successfully prepared using a hydrothermal method. Compared with SnOx and TiO2, the optimized SnOx/TiO2 heterojunction exhibited significantly higher photocatalytic activity for degrading methyl orange (MO). The apparent reaction rate of the SnOx/TiO2 heterostructure under visible light illumination reached 1.8355 min−1, approximately 15.74 times higher than that of SnOx alone. The results confirmed the presence of abundant oxygen vacancies on SnOx/TiO2, which acted as electron traps accelerating electron transfer. Furthermore, analyses including UPS, ESR, and reactive active species trapping experiments indicating a Z-scheme heterojunction were presented between SnOx and TiO2. According to density functional theory (DFT) calculations, the energy bands’ alignment enabled the Z-scheme heterojunction formation, while the inherent electric field drove the reaction. The experimental and computational findings demonstrated that the combined influence of the Z-Scheme heterojunction and OVs enhanced the photocatalytic reaction mechanism, facilitating efficient electron transport and preserving charge carriers with excellent redox capability. And a possible mechanism degradation pathway of MO dye is proposed. This study serves as a source of inspiration for future endeavors in the design and development of Z-Scheme heterojunction photocatalysts incorporating oxygen vacancies, with the aim of achieving enhanced efficiency in environmental remediation processes.

Enhanced photocatalytic CO2 reduction over Z-scheme β-Ga2O3/TiO2 heterojunction composite catalyst: Synthesis, performance, and mechanism

TiO2, a highly promising photocatalyst, suffers from rapid recombination of photogenerated electron-hole pairs, which impedes its practical application in industrial aspect. Herein, we report the in-situ solvothermal growth of TiO2 on Ga2O3 to form a composite photocatalyst. Compared to pristine TiO2, the TiO2/Ga2O3 composite exhibited a 2.5-fold enhancement in the photocatalytic reduction of CO2 to CO and a remarkable 9.6-fold increase in CH4 production. Through experimental characterizations and density functional theory (DFT) calculations, the underlying mechanisms for the improved catalytic performance were investigated. The synergistic effects between TiO2 and Ga2O3, including efficient charge separation and transfer, as well as the creation of active sites, are believed to contribute to the enhanced photocatalytic activity of the TiO2/Ga2O3 composite for CO2 reduction. The introduction of the wide bandgap Ga2O3 allowed the formation of a Z-scheme heterojunction with TiO2 at the interface, which greatly improved the efficiency of electron-hole pairs separation and migration, as well as the redox capability, thereby unleashing the performance of the TiO2 catalyst. This approach provides insights into the development of efficient, simple, and low-cost composite catalysts for the photocatalytic reduction of CO2 to valuable fuels.

Solar-matched S-scheme ZnO/g-C3N4 for visible light-driven paracetamol degradation

In pursuit of an efficient visible light driven photocatalyst for paracetamol degradation in wastewater, we have fabricated the ZnO/g-C3N4 S-Scheme photocatalysts and explored the optimal percentage to form a composite of graphitic carbon nitride (g-C3N4) with zinc oxide (ZnO) for enhanced performance. Our study aimed to address the urgent need for a catalyst capable of environmentally friendly degradation of paracetamol, a common pharmaceutical pollutant, using visible light conditions. Here, we tailored the band gap of a photocatalyst to match solar radiation as a transformative advancement in environmental catalysis. Notably, the optimized composite, containing 10 wt.% g-C3N4 with ZnO, demonstrated outstanding paracetamol degradation efficiency of 95% within a mere 60-min exposure to visible light. This marked enhancement represented a 2.24-fold increase in the reaction rate compared to lower wt. percentage composites (3 wt.% g-C3N4) and pristine g-C3N4. The exceptional photocatalytic activity of the optimized composite can be attributed to the band gap narrowing that closely matched the maximum solar radiation spectrum. This, coupled with efficient charge transfer mechanisms through S-scheme heterojunction formation and an abundance of active sites due to increased surface area and reduced particle size, contributed to the remarkable performance. Trapping experiments identified hydroxyl radicals as the primary reactive species responsible for paracetamol photoreduction. Furthermore, the synthesized ZnO/g-C3N4 composite exhibited exceptional photostability and reusability, underscoring its practical applicability. Thus, this research marks a significant stride towards the development of an effective and sustainable visible light photocatalyst for the removal of pharmaceutical contaminants from aquatic environments.

Low-temperature NO2 sensor based on γ-In2Se3/In2O3 nanoflower heterojunction

The γ-In2Se3/In2O3 nanoflower-like heterojunctions were synthesized by solvothermal treatment followed by thermal oxidation in Air. The nanoflower-like γ-In2Se3/In2O3-based chemiresistive-type sensor showed a significantly enhanced response to NO2 at an operating temperature of 170°C. The sensor achieves a response of 2.69–0.2 ppm NO2 at 170°C. The sensor exhibits remarkable selectivity to several possible interferents such as carbon monoxide, ammonia, formaldehyde, acetone, methanol, and toluene, and good stability at 170°C. The nanoflower structure increases the specific surface area and introduces more active sites, which improves the sensitivity of the sensor to NO2. The heterojunction formed between γ-In2Se3 and In2O3 improves the charge carrier transfer between NO2 gas molecules and sensing materials, thereby increasing the response of the sensor to NO2. Density functional theory was used to elucidate this sensing mechanism, and it was found that improved sensing performance is mainly due to heterojunction formation, which increases the adsorption energy of nitrogen dioxide molecules on a sensing material surface and facilitates charge transfer between molecules.

CuS@MoS2 p[sbnd]n heterojunction photocatalyst integrating photothermal and piezoelectric enhancement effects for tetracycline degradation

Photocatalysis is an environmentally friendly and low-cost technology for the degradation of pollutants. In addition to the construction of heterojunction which may decrease the recombination of charge carriers and extend the photo-response range, the utilization of piezoelectricity and photothermal conversion also provides the promising routes to improve the photocatalytic performance. Herein, a CuS@MoS2 heterostructure was developed to simultaneously meet the needs of these enhancement mechanisms. The formation of pn heterojunction was confirmed and the associated energy band diagram was constructed with band gaps of CuS and MoS2 as 1.56 and 1.80 eV, respectively. For the degradation of tetracycline, it was demonstrated that the inherent piezoelectric property of MoS2 surface enhanced the piezocatalytic activity by inducing an electric field to aid charge separation. The heat generated by illumination raised the photocatalytic reaction rate by supplying extra energy to carriers. The CuS@MoS2 heterostructure exhibited significantly better catalytic performance than the individual CuS or MoS2 due to the formation of pn heterojunction. Furthermore, the combination of piezoelectricity and photothermal conversion also led to a significant synergistic effect, achieving a degradation efficiency of over 95% within 30 min. As compared to the conditions under ultrasonic vibration, visible light irradiation and visiblenearinfrared light irradiation alone, the combination of visiblenearinfrared irradiation and ultrasonic vibration could lead to 96, 205 and 81% enhancement. This work provides valuable insights into the design of novel heterojunction photocatalysts integrating the piezoelectric and photothermal enhancement effects.