Environmental Photocatalysis Research Articles

Fabrication of Ti3CN quasi-MXene based poly glycidyl methacrylate and poly (3,4-ethylene dioxythiophene): Poly (styrene sulfonate) conducting polymer coated materials for photocatalytic eradicator of organic pollutants

MXene, a two-dimensional (2D) transition metal carbide or nitride, has gained significant attention due to its exceptional properties and wide-ranging applications. MXenes exhibit distinctive physical and chemical characteristics, making them suitable for electrocatalysis, supercapacitors, semiconductors, batteries, sensors, biomedicine, water splitting, and photocatalysis. In environmental photocatalysis, efforts have been made to improve conductivity, structural stability, and morphology. This study synthesized a photocatalyst by coating or doping a conducting polymer onto a quasi-MXene (Ti3CN) substrate. Initially, Ti3AlCN was exfoliated using HF to form 2D Ti3CN quasi-MXene, which was then doped with GMA and PEDOT: PSS conducting polymers for photocatalytic dye degradation. The broad heterogeneous interfaces in this network significantly enhance photocatalytic performance and pollutant removal capacity. The Ti3CN@GMA/PEDOT: PSS photocatalyst was characterized through SEM, FTIR, XPS, XRD, BET, and EDX techniques and tested for the degradation of various pollutants in wastewater under visible light. The degradation rates achieved were 94.1 % for Rose Bengal, 91.6 % for Rhodamine B, and 90.6 % for Methylene Blue, with corresponding rate constants of 0.0366 min−1, 0.0400 min−1, and 0.0388 min−1 over 60 min. The photocatalyst demonstrated excellent performance, highlighting several advantages, including low energy consumption, cost-effectiveness, non-toxic properties, and environmental compatibility, making it a promising solution for wastewater treatment applications.

Carbon vacancy modified g-C3N4 hollow tubes-iron oxide composite for photocatalytic application

Graphitic carbon nitride (g-C3N4) has emerged as a non-metal, visible-light-active semiconductor with considerable potential in environmental photocatalysis. This research presents a straightforward method for creating carbon vacancy-modified g-C3N4 hollow tubes, resulting in enhanced performance. Utilizing single-step static air polymerization, we produced tubes with superior physicochemical and electronic properties, as confirmed by various characterization analyses. Remarkably, calcining the precursor at 550 ℃ greatly improved the photocatalytic efficiency in degrading methylene blue compared to other tubes synthesized under different conditions and bulk g-C3N4. Electrochemical tests revealed increased conductivity, higher charge carrier density, and an optimized conduction band edge, all contributing to the material's improved efficiency. Incorporating Fe2O3 further boosted the efficiency and stability, forming by Z-scheme heterojunction. Kinetic and thermodynamic parameters confirmed the feasibility of activity on the Fe2O3 modified surface. These features position the material as highly promising for dye photodegradation and broader environmental applications.

Interfacial contact-driven enhanced environmental photocatalysis of CdS-loaded OH-functionalized carbon nanotubes with low biotoxicity

CdS is a promising visible-light-driven photocatalyst, but it is highly toxic. Therefore, exploring alternatives that minimize toxicity while maintaining its photocatalytic properties is crucial. Carbon allotropes have been suggested as eco-friendly scaffolds for making high-performance photocatalysts with a small amount of toxic but visible light-responsive CdS additive to reduce environmental risk. However, it is unclear how small amounts of CdS in the nanocomposite can avoid a threat to environmental safety, and the role of surface functional groups on the physical interfaces for photocatalysis has not been sufficiently elucidated. Here, we used OH-functionalized carbon nanotubes (CNT-OH) as a support for CdS nanoparticles (NPs) and investigated the effect of CdS loading on photocatalytic activity and toxicity. Comprehensive microscopy coupled with machine learning-assisted spectroscopy revealed that electronic structure alterations occur uniquely at heterojunctions where CdS NPs contact CNT-OH, uncovering them as being catalytically active. Notably, the CNT-OH loaded by only 3 wt% CdS NPs resulted in a highly enhanced photocatalytic activity comparable to pure CdS NPs for selective oxidation of 2,5-hydroxymethylfurfural and degradation of 4-chlorophenol. These findings provide insight into heterocontact engineering using visible light-responsive catalysts and functionalized platforms to develop environmentally benign photocatalysts with high performance.

Integrating machine learning with experimental investigation for optimizing photocatalytic degradation of Rhodamine B using neodymium-doped titanium dioxide: a comprehensive approach with toxicity assessment.

In this study, neodymium-doped titanium dioxide (Nd-TiO2) nanoparticles were synthesized via a hydrothermal method for the photocatalytic degradation of Rhodamine B (RhB) under UV and sunlight conditions. The properties of these NPs were comprehensively characterized. And optimization of RhB degradation was conducted using control-variable experiment and artificial neural networks (ANN) under various operational conditions and in the presence of competing compounds. The acute toxicity of both NPs, RhB, and the environmental impact of the photocatalytic treatment effluent on Danio rerio were evaluated. The Nd modification increased the catalyst's specific surface area and thermal stability. X-ray diffraction confirmed the tetragonal anatase phase in undoped TiO2, while Nd-doped TiO2 exhibited shifts in peaks and the presence of brookite and rutile phases. Nd (1mol%) doped TiO2 demonstrated superior RhB photocatalytic degradation efficiency, achieving 95% degradation and 82% total organic carbon (TOC) removal within 60min under UV irradiation. Optimization under sunlight conditions yielded 95.14% RhB removal with 0.28g/L photocatalyst and 1% doping. Under UV light, 98.12% RhB removal was optimized with 0.97% doping, along with the presence of humic acid and CaCl2. ANN modeling achieved high precision (R2 of 0.99) in modeling environmental photocatalysis. Toxicity assessments indicated that the 96-h LC50 values were 681.59mg L-1 for both NPs, and 23.02mg L-1 for RhB. The treated dye solution exhibited a significant decline in toxicity, emphasizing the potential of 1% Nd-TiO2 in wastewater treatment.

Fifty Years of Research in Environmental Photocatalysis: Scientific Advances, Discoveries, and New Perspectives

Fifty Years of Research in Environmental Photocatalysis: Scientific Advances, Discoveries, and New Perspectives

Ti-doped synergistic hollow thin-walled Bi2O3 nano-microspheres for efficient tetracycline hydrochloride photodegradation

Bismuth oxide (Bi2O3) has been extensively investigated in the fields of environmental photocatalysis, owing to its exceptional charge transport performance and remarkable resistance to photocorrosion. However, the limited absorption spectrum of light and rapid recombination of photogenerated charge results in a low quantum efficiency. Herein, an efficient photocatalytic system for tetracycline hydrochloride (TCH) photodegradation based on titanium (Ti)-doped hollow, thin-walled Bi2O3 with nano-microspheres is fabricated via a facile self-assembly strategy. It is shown that doping Ti in Bi2O3 can generate oxygen vacancies, in addition, the addition of Ti in the solvothermal process inhibits the conversion of Bi3+ to bismuth at high temperature, making the content of each component in the heterostructure controllable. The hybrid catalyst exhibits superior performance in visible-light-driven photocatalytic degradation of TCH (about 95.1 % degradation efficiency after 120 min) and excellent stability (up to 4 cycles) under visible light irradiation. The optimized catalyst exhibits excellent performance in visible light catalytic degradation, owing to the synergistic effect of high specific surface area, Bi plasma resonance effect and charge mobility. Moreover, the photocatalytic mechanism of Ti-Bi2O3 have been deeply analyzed through experimental investigation and DFT theoretical calculations. The findings contribute to the synthesis of efficient visible-light-driven Bi-based photocatalysts and to the understanding of photocatalytic degradation reactions.

Bandgap engineering of novel Cu-vanadate/g-C3N4 hierarchical nanoflowers for enhanced photodegradation and excellent biosensing capability

Copper vanadate and graphitic carbon nitride (g-C3N4) are pivotal materials in the realm of advanced materials science, owing to their distinctive optical and electronic conductive properties. In the context of environmental photocatalysis and biosensing applications, their synergistic combination holds significant promise. Copper vanadate, renowned for its optical and electronic properties, complements the unique architecture and optical conduction characteristics of g-C3N4. Together, these materials exhibit immense potential for driving advancements in environmental sustainability and diagnostic techniques. In this study, we report the synthesis of copper vanadate (Cu0.261V2O5) and its composite with graphitic carbon nitride. XRD confirms the synthesis of the novel phase, FESEM and TEM analysis reveals hierarchical nanoflowers and UV-Visible spectroscopy divulges the visible light activation of the synthesized material and aids in the calculation of the optical bandgap. Interfacial charge transfer was studied with the help of EIS and Mott-Schottky analysis was employed to reveal the semiconductor type (n or p type) and determine the band edges. The as-prepared material was tested for the photocatalytic removal of methylene blue (MB), followed by the study of reaction kinetics, cyclic stability and active radicals participating in the photocatalysis process. The synthesized heterojunction showed 100 % removal of MB within a tenure of 90 minutes. The results of the experiment revealed that Cu0.261V2O5 decorated with g-C3N4 displays 1.5 and 1.4 times better photocatalytic degradation capability than pure Cu0.261V2O5 and g-C3N4, respectively. Furthermore, the synthesized material was evaluated for electrochemical biosensing of ascorbic acid in PBS (pH 7) analyte using a 3-electrode system. Compared to the pure material, the heterojunctions drew 1.9 times more current and provided near unity correlation (R2). It is evident that Cu0.261V2O5 decorated with g-C3N4 can be implemented for commercial eco-remediation and electrochemical ascorbic acid sensing.

S-Scheme heterojunction of Cs2SnBr6/C3N4 with interfacial electron exchange toward efficient photocatalytic NO abatement

Photocatalytic technology is of great significance in environmental purification due to its eco-friendly and cost-effective operations. However, low charge-transfer efficiency restricts the photocatalytic activity of the catalyst. Herein, we report Cs2SnBr6/C3N4 composite catalysts that exhibit a robust interfacial electron exchange thereby enhancing photocatalytic nitric oxide (NO) oxidation. A comprehensive study has demonstrated the S-scheme electron transfer mechanism. Benefiting from the interfacial internal electric field, the C-Br bond serves as a direct electron transfer channel, resulting in enhanced charge separation. Furthermore, the S-scheme heterojunction effectively traps high redox potential electrons and holes, leading to the production of abundant reactive oxygen radicals that enhance photocatalytic NO abatement. The NO removal rate of the Cs2SnBr6/C3N4 heterogeneous system can reach 86.8 %, which is approximately 3-fold and 18-fold that of pristine C3N4 and Cs2SnBr6, respectively. The comprehensive understanding of the electron transfer between heterojunction atomic interfaces will provide a novel perspective on efficient environmental photocatalysis.

“Light battery” role of long afterglow phosphor for round-the-clock environmental photocatalysis

Owing to its convenient, sustainable and green process, photocatalysis has become a feasible technique for solving environmental pollution issues. So far, significant achievements have been realized in photocatalytic pollutant elimination. Nevertheless, photocatalytic processes require a continuous external light illumination to drive photoredox reactions, seriously prohibiting their applications in darkness. In this context, exploring a photocatalyst with reliable photocatalytic activity in dark condition is therefore highly meaningful and an ultimate target of photocatalysis technique. Recently, long afterglow phosphor has aroused great attention due to its “light battery” role for driving catalytic reactions in dark conditions. To be specific, long-afterglow phosphor or long-afterglow phosphor/semiconductor composite can be used as a photocatalyst to simultaneously promote the photoredox processes and store extra photoexcited charges in the trapping states upon light irradiation. When the light illumination terminates, a gradual release of the charges from trapping states occurs in long-afterglow phosphor, which can continuously spur photoredox reactions under the dark environment and even maintains the photocatalysis around the clock. In this work, we comprehensively reviewed the recent advances of long afterglow phosphor based round-the-clock photocatalysts in environmental pollutant elimination. Meanwhile, the inherent mechanism of long afterglow photocatalysis was discussed in depth. More importantly, the relationship between the improved long afterglow photocatalytic capability and the engineering of long afterglow system is correlated systematically. Finally, the ongoing challenges and future prospects for the mass production and commercial utilization of round-the-clock photocatalysts are analyzed and outlooked.

Advanced metal–organic frameworks for superior carbon capture, high-performance energy storage and environmental photocatalysis – a critical review

Metal–organic frameworks (MOFs) have emerged as a transformative class of materials, offering unprecedented versatility in applications ranging from energy storage to environmental remediation and photocatalysis.

Recent Advances in Constructing Three-Dimensional Graphitic Carbon Nitride Based Materials and Their Applications in Environmental Photocatalysis, Photo-Electrochemistry, and Electrochemistry

Recently, graphitic carbon nitride (g-C3N4), a promising visible-light-driven semiconductor material, has received enormous attention for photocatalytic water splitting, organic pollutant degradation, and CO2 reduction. However, the photocatalytic activity of bulk g-C3N4 is restricted due to the insufficient light adsorption, ineffective utilization of photogenerated charge carriers, and low specific surface area. Compared with bulk g-C3N4, the three-dimensional graphitic carbon nitride based materials (3D CNBMs) have outstanding physical and chemical characteristics, such as large specific area, plentiful active sites, and excellent electrical conductivity. This article reviews the latest achievements in 3D CNBMs, and presents the state-of-the-art advances in the synthetic methods of 3D CNBMs. Meanwhile, various applications of 3D CNBMs in photocatalysis, photo-electrochemistry, and electrochemistry are systematically reviewed and discussed. In addition, possible improvements and perspectives of 3D CNBMs are proposed. This review aims to summarize a panorama of the up-to-date processes of 3D CNBMs in environmental and energy applications and provide some innovative thoughts to accelerate the ground-breaking research and development of 3D CNBMs for a sustainable future.

Designing step-scheme AgI decorated Ta2O5-x heterojunctions for boosted photodegradation of organic pollutants

Step-scheme (S-scheme) AgI decorated Ta2O5-x heterojunctions have been designed and synthesized via a combination of solvothermal and chemical deposition methods for enhanced visible-light harvesting and high-performance photocatalysis. The AgI nanoparticles showed great influences on the visible-light absorption and charge separation between AgI and Ta2O5-x microspheres. The experimental results indicated that the as-prepare AgI/Ta2O5-x composites achieved enhanced photocatalytic performance towards tetracycline degradation under visible light, and the AgI/Ta2O5-x-11 sample displayed the highest photocatalytic performance and the maximum rate constant of approximately 0.09483 min−1, which was 7.22 times that of Ta2O5-x microspheres and 2.56 times that of AgI, respectively. The highly enhanced photocatalytic performance was mainly attributed to the construction of S-scheme heterostructure and formation of oxygen vacancies in Ta2O5-x microspheres. In addition, the trapping experimental and DMPO spin-trapping ESR spectra confirmed the ⸱O2− and ⸱OH species as the main radicals during tetracycline degradation. Current work indicates an S-scheme tantalum-based composites for high-performance environmental photocatalysis.

Electrochemical Synthesis of Tungsten Oxide in Chloride Solutions for Environmental Photocatalysis

Electrochemical Synthesis of Tungsten Oxide in Chloride Solutions for Environmental Photocatalysis

Retraction Note to: Organic acid precursor synthesis and environmental photocatalysis applications of mesoporous anatase TiO2 doped with different transition metal ions

Retraction Note to: Organic acid precursor synthesis and environmental photocatalysis applications of mesoporous anatase TiO2 doped with different transition metal ions

Enhanced natural sunlight driven photocatalytic degradation under outdoor inconstant weather by Bi2WO6/WO3 heterojunctions

Weak sunlight irradiation intensity and inconstant weather conditions limit the practical application of photocatalysis in natural environment. In this work, efficient Bi2WO6 was synthesized using surfactant assistance strategy, which possesses superior photocatalytic activity under natural environment with outdoor sunlight as illumination source. Rod-like and sheet-like WO3 were synthesized by controlling rich and poor Cl− contents in precursor solutions, respectively, which were utilized to construct Bi2WO6/WO3 heterojunctions. Compared with pristine samples, Bi2WO6/WO3 exhibit enhanced tetracycline photodegradation performance under natural environment, whether on sunny day (sunlight intensity from 44.29 to 69.48 mW/cm2) or cloudy day (from 5.07 to 54.67 mW/cm2), even overcast day (from 2.83 to 18.99 mW/cm2), and the tetracycline degradation efficiencies reached 74.3% and 54.2% within 150 min on sunny and overcast days, respectively. Moreover, Bi2WO6/WO3 exhibit the effective photodegradation performances toward methyl orange and rhodamine b, with elimination efficiencies of 63.7% and 99.0% within 50 min irradiation, respectively.

Construction of highly active Fe/N-CQDs/MCN1 photocatalytic self-Fenton system for degradation of ciprofloxacin

In the graphitic carbon nitride-based photocatalytic reaction, the redox ability and electron transport ability of photocatalyst have an important influence on its activity. The Photo-Fenton reaction system was constructed by modifying N-doped carbon quantum dots (N-CQDs) on the surface of supramolecular self-assembled carbon nitride and introducing Fe ions into the carbon nitride planar structure. The xFe/N-CQDs/MCN1 catalysts with different iron contents were prepared, which had significant degradation effect on organic pollutants. Among them, 0.2Fe/N-CQDs/MCN1 degraded 76% of ciprofloxacin (CIP) within 120 min. Various characterizations demonstrate that photocatalytic activity are enhanced due to the surface modification of N-CQDs enhancing electron transfer rate on the surface of photocatalysts and the doping of Fe ions providing active sites for Fenton reaction. At the same time, the formation of chemical bonds limits the leaching of iron and avoids secondary environmental pollution. These results indicate that the novel catalyst has excellent application potential in the field of environmental photocatalysis.

AgO@InGaZnO4 composites for environmental photocatalysis

AbstractWe reported AgO@InGaZnO4 as a novel photocatalyst for environmental photocatalysis. X‐ray diffraction, Raman spectrum, fluorescence spectroscopy, fourier infrared spectroscopy, scanning electron microscope, X‐ray photoelectrons spectroscopy, and electrochemical tests were utilized to identify the composition, chemical valence states, morphology, and photocatalytic potential of AgO@InGaZnO4. In the experiments of photo‐reduction Cr(VI) ion and photodegradation Rhodamine B (RhB) reactions, the kinetic constants of AgO@InGaZnO4 samples are 1.7 and 7.1 times of the parent, respectively. The analysis of photocatalytic mechanism indicates that AgO acts as an electron trap to promote photogenerated charge separation and enhance photocatalytic performance. Moreover, AgO also plays an important role in the adsorption of the catalyzed substrate in the composite.

Strong Metal-Support Interaction (SMSI) in Au/TiO2 photocatalysts for environmental remediation applications: Effectiveness enhancement and side effects

Strong Metal−Support Interaction (SMSI) is a well-known phenomenon of heterogeneous catalysis that have not been extensively investigated in photocatalytic applications. Moreover, the reactions previously studied for photocatalysts under SMSI state are mainly restricted to energy related uses. The present work seeks to explore the effect of SMSI induced by soft wet-chemistry in a Au/TiO2 photocatalyst with specific focus on photocatalytic environmental remediation. With this aim, the developed photocatalyst has been evaluated considering liquid, gas and solid pollutants in order to represent the wide range of environmental photocatalysis applications. These photooxidation scenarios were methylene blue dissolved in water, gaseous NO, and soot directly deposited on the photocatalyst. The results revealed that the SMSI induction has a generally positive effect on photoactivity promoting the MB and soot removal by 53% and 60%, respectively. However, the SMSI did not provide any additional benefit in the NOx elimination compared to the non-SMSI Au/TiO2 photocatalyst, because the enveloping of AuNPs limits the gold-pollutant interaction.

Facile low-temperature supercritical carbonization method to prepare high-loading nickel single atom catalysts for efficient photodegradation of tetracycline

Environmental photocatalysis is a promising technology for treating antibiotics in wastewater. In this study, a supercritical carbonization method was developed to synthesize a single-atom photocatalyst with a high loading of Ni (above 5 wt.%) anchored on a carbon-nitrogen-silicate substrate for the efficient photodegradation of a ubiquitous environmental contaminant of tetracycline (TC). The photocatalyst was prepared from an easily obtained metal-biopolymer-inorganic supramolecular hydrogel, followed by supercritical drying and carbonization treatment. The low-temperature (300°C) supercritical ethanol treatment prevents the excessive structural degradation of hydrogel and greatly reduces the metal clustering and aggregation, which contributed to the high Ni loading. Atomic characterizations confirmed that Ni was present at isolated sites and stabilized by Ni-N and Ni-O bonds in a Ni-(N/O)6C/SiC configuration. A 5% Ni-C-Si catalyst, which performed the best among the studied catalysts, exhibited a wide visible light response with a narrow bandgap of 1.45 eV that could efficiently and repeatedly catalyze the oxidation of TC with a conversion rate of almost 100% within 40 min. The reactive species trapping experiments and electron spin resonance (ESR) tests demonstrated that the h+, and ·O2− were mainly responsible for TC degradation. The TC degradation mechanism and possible reaction pathways were provided also. Overall, this study proposed a novel strategy to synthesize a high metal loading single-atom photocatalyst that can efficiently remove TC with high concentrations, and this strategy might be extended for synthesis of other carbon-based single-atom catalysts with valuable properties.

Selective Control and Characteristics of Water Oxidation and Dioxygen Reduction in Environmental Photo(electro)catalytic Systems.

ConspectusEmploying semiconductor materials is a popular engineering method to harvest solar energy, which is widely investigated for photocatalysis (PC) and photoelectrocatalysis (PEC) that convert solar light to chemical energy. In particular, environmental photo(electro)catalysis has been extensively studied as a sustainable method for water treatment, air purification, and resource recovery. Environmental PC/PEC processes working in ambient conditions are initiated mainly through hole transfer to water (water oxidation) and electron transfer to dioxygen (O2 reduction) and the subsequent photoredox transformation of water and dioxygen serves as a base of various PC/PEC systems. Through the redox transformations, different products can be generated depending on the number of transferred electrons and holes. The single electron/hole transfer generates radical species and reactive oxygen species (ROS) which initiate the degradation/transformation of various pollutants in water and air, while the multicharge transfer can generate energy-rich chemicals (e.g., H2, H2O2). Therefore, understanding the characteristics of the photoredox reactions of water and dioxygen on the semiconductor surface is critically important in controlling the selectivity and efficiency of photoconversion processes.In this Account, we describe various environmental PC/PEC conversions with a particular focus on how the phototransformation of dioxygen and water is related to the overall processes occurring on diverse semiconductor materials. The activation of water or dioxygen can be controlled by modifying the properties of semiconductors, changing the kind of counterpart half-reaction and the experimental conditions. If water can be used as a ubiquitous reductant under solar irradiation, many kinds of reductive transformations can be carried out under ambient environmental conditions. For example, various toxic oxyanions (or metal ions) can be reductively transformed to harmless or less harmful species or useful chemicals/fuels can be synthesized under ambient conditions if water can provide electrons and protons via solar water oxidation. On the other hand, dioxygen can turn into reactive oxygen species (ROS) as a versatile oxidant or to a chemical like H2O2. There should be many more possibilities of utilizing the photoconversion of water and dioxygen for environmentally significant purposes, which are yet to be further developed and demonstrated. In this Account, we highlight the recent strategies and the novel functional materials for effective activation of water and dioxygen in environmental PC/PEC systems. Design of environmentally functional PC/PEC systems should be based on better understanding of water and dioxygen activation.