Field Of Photocatalysis Research Articles

Novel high entropy alloy/NiAl2O4 photocatalysts for the degradation of tetracycline hydrochloride: Heterojunction construction, performance evaluation and mechanistic insights

Novel NiAl2O4 (NAO)/high entropy alloy (HEA) (Ti), NAO/HEA (Mn) and NAO/HEA (Mo) heterojunction photocatalysts with high photocatalytic activity for the degradation of tetracycline hydrochloride (TC) under simulated sunlight irradiation were synthesized by the polyacrylamide gel method combined with a low temperature sintering technique. The effects of environmental parameters, including drug concentration, catalyst content and pH value, on the photocatalytic activity of NAO/HEA photocatalysts were investigated in detail on the basis of the response surface methodology (RSM) and experimental results. The optimal initial TC concentration, catalyst content, and pH were 100 mg/L, 1 g/L, and 5, respectively. The photocatalytic activity of NAO/HEA photocatalyst (84.6 %) was significantly improved compared to the degradation percentage of HEA (Ti) photocatalyst (36.5 %). The roles of active free radicals including h+, •O2−, •OH and oxygen vacancy in photocatalysis were verified using multiple characterization methods. In-depth analysis was conducted on the degradation pathway of TC, the safety of degradation intermediates, and the photocatalytic mechanism of NAO/HEA (Ti) photocatalyst. The Z - scheme heterojunction can significantly improve the transport efficiency of photogenerated carriers and inhibit the recombination rate of electron hole pairs in the system, which provides a new idea for exploring the application of new HEA - based heterojunction photocatalysts in the field of photocatalysis.

Organophotocatalytic or Electrophotocatalytic Reduction and Functionalization Reactions with a Thioxanthone-TfOH Complex Catalyst

AbstractThioxanthone has long been a prominent catalyst in the field of photocatalysis, owing to its high triplet energy and long triplet lifetime that render it suitable for energy transfer reactions. However, its low oxidation potential and short singlet lifetime have posed challenges when employing it for electron-transfer reactions. This account summarizes our efforts in developing a potent and long-lived thioxanthone-TfOH complex (9-HTXTF) catalyst, and its application in energy-demanding redox transformations such as organophotocatalytic or electrophotocatalytic reduction and functionalization reactions.1 Introduction2 Discovery and Properties of the Catalyst 9-HTXTF3 Organophotocatalysis4 Electrophotocatalysis5 Conclusion

Boosting the Photocatalytic Performance of g-C3N4 through MoS2 Nanotubes with the Cavity Enhancement Effect.

The development of catalysts with high photon utilization efficiency is crucial for enhancing the catalytic performance of photocatalysts. Graphitic carbon nitride (g-C3N4) is a prominent material in the field of photocatalysis. However, it still exhibits drawbacks such as low utilization of visible light and severe recombination of photogenerated carriers. To address these issues, this study employs MoS2 nanotubes (NTs) as cocatalysts and constructs MoS2 NTs/g-C3N4. The MoS2 NTs/g-C3N4 exhibits a significant cavity enhancement effect through multiple light reflections. This results in a broad spectral absorption range and high photon utilization efficiency, while also reducing the recombination of photogenerated carriers. The photocatalyst demonstrates outstanding performance in both photocatalytic hydrogen production and photodegradation of organic pollutants. Specifically, the hydrogen production rate is 1921 μmol·g-1·h-1, which is approximately 2.4 times that of g-C3N4. Furthermore, the photodegradation rate of Rhodamine B reaches 98.6% within 30 min, which is approximately three times higher than that of g-C3N4. Free radical capture experiments confirm that holes (h+) are the primary active species in photodegradation. A plausible photocatalytic mechanism for the catalyst is proposed. This study provides valuable insights into the development of heterojunction photocatalysts with high photon utilization efficiency.

Cu2O based NiCo2O4/GDY double S-scheme heterojunction for enhanced photocatalytic hydrogen production

Graphdiyne (GDY) is flourishing in the field of photocatalysis due to its high conductivity and enhancement of electron transfer. Electron transport can be expedited when GDY is used as a catalytic support. Herein, a GDY/NiCo2O4 composite photocatalyst was constructed in situ using organic compounds and bimetallic oxides. Furthermore, Cu2O was introduced into the GDY/NiCo2O4 interface through interfacial engineering, which effectively enhanced the activity of the catalyst. Electrochemistry and fluorescence spectroscopy demonstrated that the load of Cu2O can reduce the electron transfer resistance and decrease the photogenerated carrier recombination carrier rate. The formation of S-scheme heterojunction formed by Cu2O, GDY and NiCo2O4 can accelerate the electron transfer through band bending and internal electric field and improve the reducing activity of the catalyst. The outcomes of this work demonstrate the potential applications of Cu2O and GDY in photocatalysis and provide insights into the construction of high-performance photocatalysts.

Elucidating Structural Disorder in Ultra-Thin Bi-Rich Bismuth Oxyhalide Photocatalysts.

Advancing the field of photocatalysis requires the elucidation of structural properties that underpin the photocatalytic properties of promising materials. The focus of the present study is layered, Bi-rich bismuth oxyhalides, which are widely studied for photocatalytic applications yet poorly structurally understood, due to high levels of disorder, nano-sized domains, and the large number of structurally similar compounds. By connecting insights from multiple scattering techniques, utilizing electron-, X-ray- and neutron probes, the crystal phase of the synthesized materials is allocated as layered Bi24O31X10 (X = Cl, Br), albeit with significant deviation from the reported 3Dcrystalline model. The materials comprise anisotropic platelet-shaped crystalline domains, exhibiting significant in-plane ordering in two dimensionsbut disorder and an ultra-thin morphology in the layer stacking direction. Increased synthesis pH tailored larger, more ordered crystalline domains, leading to longer excited state lifetimes determined via femtosecond transient absorption spectroscopy (fs-TAS). Although this likely contributes to improved photocatalytic properties, assessed via the photooxidation of benzylamine, increasing the overall surface area facilitated the most significant improvement in photocatalytic performance. This study, therefore, enabled both phase allocation and a nuanced discussion of the structure-property relationship for complicated, ultra-thin photocatalysts.

Rational design and synthesis of BiOF micro/nanostructures with enhanced photocatalytic properties

BiOF with tunable morphologies (polygonal disk-shaped columns, polygonal flakes and square flakes) have been prepared via a facile hydrothermal route, in which nitrilotriacetic acid (NTA) was used as a structure directing reagent. It was found that the morphologies and crystalline structures of the as-obtained BiOF were dependent on the NTA dosage and the pH value. Based on the observation of the photocatalytic selectivity of typical polygonal disk-shaped columns of BiOF towards different types of organic dyes, we further investigated the photocatalytic activities of the BiOF with different morphologies by the degradation of malachite green (MG) solution under UV light irradiation. The results showed that disk-shaped columns of BiOF had the best photocatalytic activity, and the degradation rate of MG reached 95.34 % after 20 min of irradiation. The photocatalytic efficiency was much higher than those of other morphological BiOF micro/nanostructures. The results of this study strongly indicate that BiOF has a broad application prospect in the field of photocatalysis.

The research progress on photocatalytic performance of graphene-based nanocomposites

As soon as nanomaterials were discovered, they attracted a lot of attention because of their unique and excellent properties and became major hot research. They are regarded as the most promising materials in the 21st century. With the growth of industrial production, photocatalytic technology has been pursued as an efficient, green, and economical way of industrial production and treatment of pollution. However, the low light energy utilization of traditional semiconductor materials is a drawback that cannot be ignored. Graphene, as one of the most common and widely used 2D nanomaterials, has a special structure and characteristics that can effectively solve this problem. The paper briefly introduces the structure, properties, preparation method, and basic principle of photocatalysis of graphene. At the same time, a review is provided on the application of graphene-based composite materials in the field of photocatalysis, including dye degradation, photocatalytic treatment of other emerging pollutants, photocatalytic treatment of air pollutants, and water decomposition. By summarizing and integrating the photocatalytic properties of several graphene-based composites, this article lays the foundation and helps to discover new graphene composites.

Heterogeneous Organocatalysts for Light-Driven Reactions in Continuous Flow.

Within the realm of organic synthesis, photocatalysis has blossomed since the beginning of the last decade. A plethora of classical reactivities, such as selective oxidation of alcohol and amines, redox radical formation of reactive species in situ, and indirect activation of an organic substrate for cycloaddition by EnT, have been revised in a milder and more sustainable fashion via photocatalysis. However, even though the spark of creativity leads scientists to explore new reactions and reactivities, the urgency of replacing the toxic and critical metals that are involved as catalysts has encouraged chemists to find alternatives in the branch of science called organocatalysis. Unfortunately, replacing metal catalysts with organic analogues can be too expensive sometimes; however, this drawback can be solved by the reutilization of the catalyst if it is heterogeneous. The aim of this review is to present the recent works in the field of heterogeneous photocatalysis, applied to organic synthesis, enabled by continuous flow. In detail, among the heterogeneous catalysts, g-CN, polymeric photoactive materials, and supported molecular catalysts have been discussed within their specific sections, rather than focusing on the types of reactions.

Determining Excited-State Absorption Properties of a Quinoid Flavin by Polarization-Resolved Transient Spectroscopy.

As important naturally occurring chromophores, photophysical/chemical properties of quinoid flavins have been extensively studied both experimentally and theoretically. However, little is known about the transition dipole moment (TDM) orientation of excited-state absorption transitions of these important compounds. This aspect is of high interest in the fields of photocatalysis and quantum control studies. In this work, we employ polarization-associated spectra (PAS) to study the excited-state absorption transitions and the underlying TDM directions of a standard quinoid flavin compound. As compared to transient absorption anisotropy (TAA), an analysis based on PAS not only avoids diverging signals but also retrieves the relative angle for ESA transitions with respect to known TDM directions. Quantum chemical calculations of excited-state properties lead to good agreement with TA signals measured in magic angle configuration. Only when comparing experiment and theory for TAA spectra and PAS, do we find deviations when and only when the S0 → S1 of flavin is used as a reference. We attribute this to the vibronic coupling of this transition to a dark state. This effect is only observed in the employed polarization-controlled spectroscopy and would have gone unnoticed in conventional TA.

Constructing electron transfer bridge of Pr doping MIL-125(Ti) for high-efficient photoreduction CO2

MIL-125(Ti) is well known for having stable structure, tunable electron structure, and multiple active sites, which is commonly studied in the field of photocatalysis. In this work, a series of rare earth (RE) doped MIL-125(Ti) (RE=Ce, Pr, Tm, Dy, Eu, and Sm) are prepared via the one-step hydrothermal method. Notably, Pr-MIL-125 displays a significantly enhanced catalytic performance than other RE-doped MIL-125, resulting in a maximal CO and CH4 yield of 13.30 and 0.87 µmol·g−1·h−1, respectively, which are 2.53-fold and 4.14-fold of the pristine MIL-125. The layered morphology endows Pr-MIL-125 with more active sites and facilitates the reaction of photoreduction CO2. Furthermore, the promoted photoactivities attributed to Pr ion dopant can act as electron transfer bridge and suppress charge recombination. This work would provide insight and guidance for designing RE-MOF based photocatalysts and enhancing the performance of photoreduction CO2.

Synthesis Of Nano-Porous Strontium Titanate Materials for Photocatalysis

Strontium titanate semiconductor materials have been widely used in the field of photocatalysis due to their high dielectric constant and band gap. Uniform, micron-sized SrTiO3 particles didn’t tend to aggregate, and the low surface area of larger particles could be improved by incorporating porous structures, thus offering superior performance for a range of applications. In this study, six mainly methods to prepare nano-porous SrTiO3 particles were showed and discussed. The methods include hydrothermal method，sol gel method, chemical co-precipitation method, high temperature solid phase method, hard template method and soft template method. These processes and their advantages and disadvantages were analysised.

Altering defect population during the solvothermal growth of ZnO nanorods for photocatalytic applications

High abundance and low toxicity make zinc oxide very attractive for broad application in the field of photocatalysis for remediation of toxic compounds from water. Its performance could be elegantly improved by inducing native defects into ZnO semiconductor nanocrystals. However, this typically requires post-processing at high temperatures, during which many of the benefits of the original batch of monodisperse small grains are lost due to agglomeration and/or crystal growth. Within this research we show how variations in defect population are inherent to recrystallization process and that they can be tuned to some extent by choosing optimal pathways. The defects were studied by Raman, photoluminescence and EPR spectroscopy, while the surface chemistry of the ZnO nanorods, solvothermally recrystallized from ZnO nanodots, was evaluated by X-ray photoelectron spectroscopy. The produced nanorods with different dimensions were also utilized to show how effective the samples are for degradation of a model pollutant, namely caffeine. Unexpectedly, we found that the surface chemistry of our samples is not the main factor in photocatalytic efficiency. Instead, we show that the differences in photocatalytic activity are mainly determined by the defect population within the bulk formed during the recrystallization process under altered solvothermal conditions.

Advanced oxidation processes (AOPs): Navigating from MOS to COS and X-COS systems - Unraveling strategies, tackling challenges, and pioneering advances

This article presents a significant advancement in the field of photocatalysis through the synthesis of a MSO(Metal oxide semiconductor), COS (coupled oxide semiconductor) and X-COS(doped coupled oxide semiconductor) nanocomposite systems with diverse morphologies, including nanoflowers, nanorods, nanosheets, nanotubes and spherical shapes. In this particular study, we propose a hybrid methodology that amalgamates the coupling of CuO and ZnO oxides and the doping of various elements resulting in a comprehensive study of the relationship between morphology and photocatalysis. The degradation efficiency for various pollutants, including Methylene Blue (MB), Methyl Orange (MO), Green Malachite (GM), and Rhodamine B (RhB), was systematically investigated, employing distinct degradation mechanisms. Our study reveals that X-COS materials exhibit superior surface area, heightened porosity, and elevated specific capacitance, higher light absorption while minimizing energy and surface losses (VELF and SELF), accompanied by a well-suited morphology. These distinctive structural features of X-COS contribute to its enhanced photocatalytic efficiency when compared to MOS and COS systems. Our research not only consolidates the fundamental principles governing the photocatalytic properties of materials but also unveils critical strategies for fabricating highly efficient catalysts. In conclusion, this work significantly contributes to the evolving landscape of photocatalysis, offering a nuanced understanding of the synergistic relationship between morphology and catalytic efficiency. The findings not only broaden the scope of fundamental principles but also pave the way for the development of highly effective catalytic materials with diverse morphologies for environmental remediation applications.

Exploring the ferroelectric photocatalytic potential of R3c-structured InVO3: A computational study

Ferroelectric oxides with large band gaps or band edge positions that are difficult to cross the water oxidation-reduction potential are not conducive to photocatalytic hydrogen production. This study systematically investigates the potential application of R3c-structured InVO3 in the field of photocatalysis through density functional theory calculations. The mechanical and phonon frequency stability of InVO3 is verified through stability analysis, followed by the confirmation of its excellent ferroelectric properties through first-principles calculations. The calculated optical properties of InVO3 are explored to reveal its strong absorption of visible light and high photoelectric conversion efficiency. InVO3 exhibits excellent charge carrier transport properties through calculations of electron mobility, promising efficient energy conversion in photocatalytic water splitting. The band edge positions of InVO3 can cross the water oxidation-reduction potential, providing theoretical support for its application in the field of photocatalysis. R3c-structured InVO3 is a potential high-performance ferroelectric photocatalytic material.

Advances in Defect Engineering of Metal Oxides for Photocatalytic CO2 Reduction.

Photocatalytic CO2 reduction technology, capable of converting low-density solar energy into high-density chemical energy, stands as a promising approach to alleviate the energy crisis and achieve carbon neutrality. Semiconductor metal oxides, characterized by their abundant reserves, good stability, and easily tunable structures, have found extensive applications in the field of photocatalysis. However, the wide bandgap inherent in metal oxides contributes to their poor efficiency in photocatalytic CO2 reduction. Defect engineering presents an effective strategy to address these challenges. This paper reviews the research progress in defect engineering to enhance the photocatalytic CO2 reduction performance of metal oxides, summarizing defect classifications, preparation methods, and characterization techniques. The focus is on defect engineering, represented by vacancies and doping, for improving the performance of metal oxide photocatalysts. This includes advancements in expanding the photoresponse range, enhancing photogenerated charge separation, and promoting CO2 molecule activation. Finally, the paper provides a summary of the current issues and challenges faced by defect engineering, along with a prospective outlook on the future development of photocatalytic CO2 reduction technology.

Bismuth (Bi3+) based lead-free halide perovskitoid for light driven applications: A potential low-toxic alternative for lead (Pb2+)

Bismuth-based perovskite-like materials are recognised as feasible optoelectronic alternatives to lead-based perovskites. High toxicity and limited environmental stability of Pb-based perovskite are the principal hurdles for their practical use, whereas Bismuth (Bi3+) based materials exhibit relatively low toxicity. In this study, we fabricated (FPEA)BiI4 (FPEA = Fluorophenylethyl amine, as a hydrophobic aromatic spacer) and explored its compatibility in the field of photocatalysis and solar cells. UV–Vis, photoluminescence (PL) and time-correlated single photon counting (TCSPC) techniques were used to understand the optoelectronic properties of the material. These fabricated thin films were used towards toxic MBT remediation. Solar cells (in n-i-p configuration) were also fabricated using (FPEA)BiI4 and their photo conversion efficiency (PCE) was tested under AM1.5 illumination.

Carbon-coated nickel phosphide enhances efficiently electron transfer of cadmium sulfide for photocatalytic hydrogen production

The capacitance of a co-catalyst can be likened to a “double-edged sword”. Α co-catalysts with high capacitance can store photoexcited electrons, thereby facilitating charge separation within the host catalyst. However, this property simultaneously restricts electron release. Both effects are enhanced with an increasing capacitance value, implying that excessively high capacitance can significantly hinder the photocatalytic hydrogen (H2) production reaction. Herein, we have designed a metal-organic framework (MOF) -derived carbon-coated nickel phosphide (C-Ni5P4) as the co-catalyst of cadmium sulfide (CdS). When C-Ni5P4 and CdS are closely interconnected, electrons spontaneously migrate from CdS to C-Ni5P4 under irradiation due to the higher work function (WF) of C-Ni5P4 compared to CdS. Most importantly, although the WF of C-Ni5P4 is 0.1 eV lower than that of Ni5P4, its specific capacitance (1.2 mF/cm2) is also lower than that of Ni5P4 (1.3 mF/cm2). This difference dramatically promotes electron release. Thereby exerting a strong positive effect on capacitance catalysis. Therefore, 7% C-Ni5P4/CdS exhibits exceptional cyclic stability and has a remarkably high activity level of 12283 μmol/h/g and 3.8 times as many as 3.0 %Ni5P4/CdS. This study provides a theoretical basis for the advancement of photocatalysts with high efficiency in H2 production and is expected to be applied in other fields of photocatalysis.

Environmental significance of the interaction between titanium dioxides and soil solutions

Nanotechnology, especially in the field of photocatalysis, has witnessed rapid advancements, with titanium dioxide being one of the most widely used photocatalysts. As the use of products containing photoactive nanomaterials increases, concerns have arisen regarding their potential release into the environment over time. This release can impact soil, groundwater, and surrounding ecosystems, resulting in nanoparticles being dispersed in water and eventually depleted from the system. This study aimed to investigate how different soil solutions affect the structural, textural properties, and photocatalytic activity of titanium dioxide-based, commercial reference Evonik Aeroxide P25. The Regosol soil solution, characterized by acidic pH, low ionic content, and high organic matter content, induced nanoparticle aggregation and bandgap changes. In addition, the acidic pH hindered the adsorption process, potentially affecting the photocatalytic processes. In contrast, the Chernozem soil solution, with slightly alkaline pH, high ionic content, and low organic matter content, did not significantly alter the morphology or structure of the material. However, various organic compounds were absorbed on the surface, reducing the availability of active sites. The study highlights the importance of understanding the influence of soil solutions on nanomaterials, as it impacts their properties and environmental risks. Results show that the material is still activated, i.e., it can exert its photoactive effect on the environment. This sheds light on the challenges posed by nanoparticles in soil, particularly in terms of their toxicity and consequences for the surrounding ecosystems. The study underlines the need for further research in this area to assess potential risks and optimise the use of nanomaterials in environmental remediation.

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

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

Molybdate modified ZnCdS to construct fast carrier transfer channels for efficient hydrogen evolution

In the field of photocatalysis, when it comes to performance, ZnCdS can be said to be second to none, as its suitable bandgap structure and electron rich properties are highly sought after by most researchers. However, how to solve the severe photo corrosion and recombination of photo generated carriers has become a huge challenge that needs to be addressed. Constructing heterojunctions is an effective method to solve this problem. In this work, ZnCdS and NiMoO4 S-scheme heterojunctions were first constructed. This catalyst tightly combines two elements together, and the synergistic effect of Ni and Mo elements in NiMoO4 effectively suppresses the photo corrosion of ZnCdS and greatly improves its performance. The electron rich nature of ZnCdS causes its own electrons to transfer to NiMoO4, which in turn promotes the hydrogen evolution reaction of NiMoO4. In fact, the built-in electric field between catalyst interfaces provides power for electron transfer. It is worth noting that studying in situ XPS and density functional theory calculations has provided a deeper understanding of charge dynamics. This work provides ideas for improving charge transfer and designing high-performance catalysts to address energy issues.