In recent years, indoor environmental pollution has attracted much attention, especially the elimination of formaldehyde-based volatile organic compounds (VOCs) is highly challenging. The removal of indoor formaldehyde and other VOCs through photocatalytic oxidation has good practical significance and research prospects. Among various catalysts for the oxidation and elimination of VOC, titanium dioxide (TiO₂) is considered to be one of the most suitable photocatalysts due to its high cost-effectiveness, stability and high VOC degradation activity. This article summarizes the basic principles and factors affecting the photocatalytic reaction of using titanium dioxide (TiO₂) as a catalyst to remove formaldehyde. In recent years, the research progress of photocatalytic degradation of formaldehyde by modified titanium dioxide doped with metal and non-metal components, titanium dioxide composite materials and some new composite materials are reviewed, and the research direction and potential applications of photocatalyst degradation of formaldehyde are discussed.

A series of BiOCl/ZnO composite photocatalysts are obtained by hydrothermal method with Zn(NO₃)₂·6H₂O, NaOH, KCl and Bi(NO₃)₃·5H₂O as raw materials. The structures of BiOCl/ZnO are characterized by X-ray diffraction (XRD), X-ray photoelectron spectrum (XPS), scanning electron microscopy (SEM), energy disperse X-ray spectroscopy (EDS) and UV-Vis diffuse reflectance spectrometry (UV-Vis DRS). The results show that BiOCl/ZnO has higher absorption intensity and range than pure BiOCl, and the synergistic catalysis between BiOCl and ZnO promotes the separation and migration of photogenerated electrons/holes. The photocatalytic performance of BiOCl/ZnO photocatalysts are investigated with catechol as the research object .The results show that the 1∶1 BiOCl/ZnO composite catalyst shows the best catalytic activity, and the degradation rate of 10 mg/L pyroechol reaches 95.7% after 120 min reaction under 400 W metal halide light. The rate constants of BiOCl/ZnO are 6.09 and 4.19 times that of pure ZnO and pure BiOCl, and the stability is good. The degradation rate is still above 90.0% after repeated use for 4 times.

Graphite carbon nitride (g-C₃N₄) has attracted much attention due to its advantages such as low preparation cost, non-toxic and harmless, and stable physicochemical properties. However, the yield and photocatalytic activity of g-C₃N₄ obtained from different precursor systems are also different. In this study, urea, dicyanamide, and melamine were used as precursors to prepare carbon nitride 2D nanosheets by thermal stripping method, respectively. The effects of different precursors and thermal exfoliation temperature on the structure and photocatalytic performance of carbon nitride were systematically investigated. The results show that g-C₃N₄ 2D nanosheets with excellent photocatalytic performance can be directly prepared with urea as the precursor without thermal exfoliation, and the degradation rate of methylene blue is the highest, which is 60%. But its yield is extremely low, about 2%-3%. Carbon nitride prepared with dicyandiamide and melamine as precursors can be subjected to thermal exfoliation treatment to obtain 2D g-C₃N₄ nanosheets with a loose structure and excellent photocatalytic performance. The yields can be as high as 32.5% and 36.8%, respectively. Among them, the 2D nanosheets g-C₃N₄ prepared with dicyandiamide as a precursor treated at 580 ℃ for 4 hours exhibited the best photocatalytic activity, and its degradation efficiency of methylene blue can reach 91.1%, which is 40% higher than that of the unexfoliated sample. After 4 cycles of use, the degradation rate can still be maintained at 90%, showing good stability and repeatability.

Photocatalytic nanomaterials are nanomaterials that can directly convert solar energy into chemical energy for catalysis. Due to the property of directly utilizing the solar energy, photocatalytic nanomaterials have become the most promising type of material to alleviate energy shortages and environmental pollution. There are various preparation methods for photocatalytic nanomaterials. Among them, the microbial preparation method is to synthesize photocatalytic nanomaterials through microbial growth and metabolism. Owing to these advantages including the short microbial growth cycle, simple reaction conditions, no secondary pollution, energy saving, environmental protection, etc, microbial synthesis has become a green preparation method with great development potential. Researchers have conducted a lot of research and exploration on it. Researchers have conducted a lot of research and exploration on this. Based on the research literature on the preparation of photocatalytic nanomaterials by microorganisms in the past ten years, in this article, various nanophotocatalytic materials synthesized by microbial method are introduced, including elemental metals, chalcogen compounds, metal oxides, composites materials and others. The microbial preparation process and mechanism of the above various photocatalytic nanomaterials are mainly discribed. The photocatalytic utility and photocatalytic mechanism of photocatalytic nanomaterials are introduced. Finally, the development prospects of photocatalytic technology and microbial preparation methods are forecasted.

Using graphene oxide (GO) and AgNO₃ as precursors and N₂H₄·H₂O as reducing agent, the graphene-supported silver powder material (Ag/rGO) is successfully synthesized by chemical reduction. Through X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), Raman spectrometer (Raman), transmission electron microscope (TEM) and other technical equipment, the structure of Ag/rGO powder material and performance characterization are studied, and photocatalysis of the composite powder is explored as well. The results show that GO and Ag⁺ are simultaneously reduced by N₂H₄·H₂O during the reaction, and silver nanoparticles (AgNPs) are uniformly distributed between graphene sheets. The particle size distribution of AgNPs supported on graphene (rGO) sheets is concentrated around 30-50 nm, showing a good load effect. Through the photocatalytic reaction, it is found that Ag/rGO can efficiently catalyze the photodegradation of methylene blue solution (MB). The degradation rate of 30 min of catalytic degradation is twice that of unused catalyst, and the degradation rate of MB of catalytic degradation of 90 min is up to 99.5%.

In this article, CuBi₂O₄ nanorods are prepared by hydrothermal method, and then Ce(OH)₃ layer is deposited on the surface by wet chemical method and calcined to prepare CeO₂/CuBi₂O₄ heterojunction photocatalyst. The CeO₂/CuBi₂O₄ composite photocatalyst is characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), UV-Vis absorption spectroscopy (UV-Vis) and Mott-Schottky plot (M-S). Rhoda mine B (RhB) is used as the target pollutant to study the effect of CeO₂ doping on the photocatalytic performance of CeO₂/CuBi₂O₄ heterojunction under simulated sunlight. The results show that when 10% CeO₂ is added into the composite, the degradation efficiency of RhB reaches the maximum (93.1%, 60 min), which is 30.6% higher than that of pure CuBi₂O₄ (71.3%, 60 min). Through free radical capture experiments, it is deter mined that the active substances that play a major role in the photocatalysis experiment are ·O^-₂ and h⁺. Combined with the analysis of electron band structure, it is considered that the effective separation of photogenerated electron hole- pairs under the built-in electric field of p-n heterojunction is the main reason for the improvement of photodegradation efficiency. This study provides an application of CuBi₂O₄-based heterojunction in photocatalysis, which is of great significance to meet the growing environmental needs in the future.

The extensive application and difficult degradation of antibiotics have caused great harm to the ecological environment. Effectively and economically removing antibiotic has become a hot topic and challenge. Here, NaYF₄:Yb,Tm@TiO₂, a multi-band active composite photocatalyst is prepared by hydrothermal method for high efficiency removal of tetracycline hydrochloride (TC), a representative antibiotics in water. The upconversion material in the composite catalyst can convert near-infrared (NIR) light to ultraviolet (UV) light, which is synergistically used for the efficient photocatalytic degradation of TC. The effects of photocatalyst dosage, initial concentration of TC and pH value on photocatalytic degradation efficiency are also studied. The results show that the degradation process of TC conforms to the pseudo-first-order kinetic equation. The optimal conditions of photocatalyst dosage, initial concentration of TC and pH value for TC photocatalytic degradation are 0.67 g/L, 10^-5 mol/L and 6, respectively. The maximum reaction rate constant is 0.105. This study reveals that the composite photocatalyst modified by up-conversion material can effectively degrade environmental pollutants such as antibiotics by using multiband sunlight, which is beneficial to the water environment protection.

The composites of g-C₃N₄(GCN), MoS₂ and loaded g-C₃N₄/MoS₂ (GCN/MoS₂) layered materials and Fe doped GCN/MoS₂(Fe/GCNM) hybrid materials are prepared by high temperature calcination and hydrothermal method with melamine, ammonium molybdate and thioureas as raw materials. The morphology, size and structure of nanomaterials are characterized by SEM, TEM, FT-IR and DRS. In addition, the photocatalytic activities are evaluated by the concentration ratio C/C₀ of MO solution before and after the degradation and optimized the effect of different catalysts and the dosage of composite catalysts. The results show that compared with pure GCN, GCN/MoS₂ and Fe/GCNM significantly improve the photodegradation efficiency toward the MO with the C/C₀ of 0.38, 0.23 and 0.17, respectively. In addition, the reaction rate constant (K) of Fe/GCNM is much higher than that of GCN, GCNM and Fe/GCN, which is attributed to the separation of photogenic electron-hole pairs promoted by the synthesis of Fe and MoS₂ composited with GCN and improves the catalytic performance.

Photocatalysis is considered to be one of the effective methods to solve the global energy crisis and environmental pollution problems. However, the low energy conversion efficiency of photocatalyst inhibits the application of photocatalysis. Vacancy is the most common crystal defect, because it can regulate the electronic structure and surface properties of photocatalyst without introducing external elements, and promote the light absorption, charge separation and migration of photocatalyst and surface reaction. Therefore, this review summarizes the latest progress of vacancy defects in photocatalysis. Firstly, some primary methods for introducing vacancy defects in photocatalyst are discussed, including common methods such as chemical reduction and high temperature treatment, and uncommon but effective methods such as hydrolysis and ultrasound. Secondly, the current characterization techniques for identifying and quantifying vacancies are mainly introduced from the aspects of microscopic characterization and spectral characterization. These techniques are helpful to understand the relationship between vacancy structure and photocatalytic properties. Subsequently, the key role of vacancy in photocatalytic process is introduced from three aspects, including absorption of light, separation and migration of charge and surface reaction. Finally, the prospects and challenges of vacancy defects in photocatalytic materials are proposed. The controllability of vacancy concentration, the synergism of composite modification and the stability of vacancy are urgent problems to be solved. This review summarizes the effective strategies of vacancy modification for photocatalysis, which can provide some theoretical reference for the relevant research.

Highly dispersed Au nanoparticles are in-situ loaded on the surface of p-type TiO₂ with metal defects (APT) and combined with g-C₃N₄ to obtain p-TiO₂/Au/g-C₃N₄ indirect Z scheme (PTC-x). The composition and structure of the as-prepared PTC-x are characterized by inductively coupled plasma Mass spectrometry (ICP-MS), high-resolution transmission electron microscope (HRTEM), X-ray diffraction (XRD), thermogravimetric analysis (TG), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS), electrochemical impedance spectroscopy (EIS) and free radical quenching experiments. Meanwhile, the photo/electrocatalysis performance and charge transfer mechanism of the composites are studied. The results indicate that due to the anchoring effect of surface defects on Au nanoparticles, the loaded Au in PTC-x is highly dispersed and the content is extremely. Moreover, the existence of Au over the interface changes the charge transfer mechanism from type-II to Z-scheme, which realizing the spatial separation of charge carriers as well as keeping higher redox capability, and thus showing higher photocatalysis performance. Under illumination, the as-fabricated p-TiO₂/Au/g-C₃N₄ Z-schemes exhibit an order of photocatalysis performance of PTC-1 > PTC-1.25 > PTC-0.75 > APT > g-C₃N₄. In particularly, the degradation rate for phenol of PTC-1 is 7.9-fold, 2.3-fold than that of g-C₃N₄ and APT, respectively.

Photocatalytic technology is regarded as one of the most promising pathways to solve the global energy shortage and environmental crisis, and the development of efficient photocatalysts with visible light response has always been a research hotspot in the photocatalytic field. As the continuation and development of traditional photocatalyst bismuth oxyhalides (BiOX, X=Cl, Br, I), the bismuth-rich bismuth oxyhalides (Bi_xO_yX_z) shows tunable band structure which benefits to improve the photocatalytic activity. The methods of controlled synthesis of Bi_xO_yX_z were summarized, including solid phase thermal conversion method, alkaline precipitation/hydrothermal/solvothermal method, etc. The photocatalytic applications of Bi_xO_yX_z were also introduced in degrading organic pollutants, splitting water to hydrogen, reducing carbon dioxide and nitrogen fixation. Finally, the current problems and future development directions of Bi_xO_yX_z were proposed. The review will deepen the understanding of Bi_xO_yX_z and open new directions for the design and optimization bismuth-based photocatalytic materials for energy and environmental applications.

With copper acetate as raw material, NaOH as additive, and glutamic acid and sorbitol 1∶1 as reducing agent, Cu₂O skeleton crystal with empty crystal surface is obtained under hydrothermal conditions. XRD, SEM and UV-VIS are used to characterize the crystal structure of Cu₂O and its effect on photocatalysis is researched. According to the analysis, the mixture of glutamic acid and sorbitol results in the reduction of a large amount of Cu²⁺ in the solution to Cu⁺. The solution is extremely saturated, and the crystal edge grows rapidly while the crystal surface does not develop, thus forming the skeleton crystal morphology of Cu₂O. The photocatalytic performance of the skeleton crystal of Cu₂O is better than that of smooth octahedral crystal.

As a new strategy for the synthesis of nanomaterials, the microwave method not only has the characteristics of uniform heating and fast reaction speed, but also high sensitivity and selectivity. As a result, this review briefly introduces the microwave theory and heating mechanism, and then summarizes the single photocatalytic material, doped materials with different elements. Furthermore, the microwave fabrication strategy for constructing nanocomposites as well as the effect of microwave method on the microstructure and crystallization of the catalyst is well elucidated. We provide insights on the synthesis of high-performance semiconductor photocatalysts with high efficiency and low energy consumption. Finally, this review also puts forward the challenges facing by microwave synthesis of photocatalytic materials in practical applications and prospects for future development.

In this work, Li₂SnO₃/WO₃ composite photocatalysts with different mass fractions are prepared by heat treatment. The photocatalysts are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and ultraviolet-visible spectrophotometer. The photocatalytic activity is tested by degradation of Rhodamine B (RhB). Compared with single phase catalyst, Li₂SnO₃/WO₃ heterojunction photocatalyst has higher degradation efficiency because of the excellent band structure matching between Li₂SnO₃ and WO₃ (Type-II), which enhances the efficient separation of photo-generated carriers. The experimental results show that the optimal performance of Li₂SnO₃/WO₃ composite can be obtained when the mass ratio of WO₃ to Li₂SnO₃ is 3%, which photocatalytic activity is 2.5 times and 8.2 times higher than that of pure Li₂SnO₃ and WO₃, respectively.

Zinc hydroxyl stannate (ZnSn(OH)₆) is a representative hydroxyl compound with perovskite structure, and also a transition metal stannate with multiple valence states (Sn²⁺/Sn⁴⁺). Besides, the wide band gap of ZHS, and the positions of the valence and conduction bands make it have a high redox potential, thus showing good photocatalytic activity and strong stability. In this paper, the crystal structure, preparation method and the main influencing factors of photocatalytic performance over ZnSn(OH)₆ materials were introduced. Meantime, the modification strategies and application of ZnSn(OH)₆-based photocatalysts in energy and environmental field were well exemplified.

Photocatalytic technology is an effective way to solve the two major problems of environmental problems and energy crisis. The development of efficient photocatalysts has become a research hotspot in this field. As new type of carbon nanomaterial, Carbon quantum dots (CQDs) have garnered much attention in the field of photocatalysis because of their unique up-conversion luminescence and excellent photogenerated electron transfer properties. In this paper, the mechanism of photocatalytic degradation of pollutants and the properties of carbon quantum dots was introduced, the research progress of photocatalytic degradation of organic pollutants in water by carbon quantum dots was reviewed with emphasis, followed by an outlook on their future and potential development.

Photocatalytic reaction has important applications in the fields of degradation of harmful pollutants, conversion of greenhouse gases, production of hydrogen, elimination of harmful bacteria and so on. In recent years, ferroelectric materials with spontaneous polarization have been considered as a new candidate. Their spontaneous polarization can produce a built-in electric field and provide a driving force for the transmission of photogenerated carriers. This characteristic is expected to solve the thorny problem encountered in the field of photocatalysis, the recombination of electron hole pairs. Because of this characteristic, the research on the photocatalytic properties of ferroelectric materials mainly focuses on reducing the recombination of holes and electrons. But in fact, to improve the photocatalytic efficiency, we need to consider the whole catalytic process, including three key stages, photon absorption, separation and migration of photogenerated electron holes and terminal reaction. Focusing on the above three stages of photocatalytic process, this paper sorts out the typical achievements in recent years, and combs the effective means to improve the catalytic performance of ferroelectric materials in different stages of photocatalysis. It is hoped that our summary can provide a useful reference for the follow-up research work.

In this paper, four perovskite type composite metal oxide lanthanum cobaltate catalysts with different ratios are prepared by hydrothermal synthesis. The ratios of La(NO₃)₂, Co(NO₃)₂ and citric acid are 1∶1∶3, 1∶1∶4, 1∶1∶5 and 1∶1∶6, respectively. The structure and properties of the catalyst are characterized by XRD, SEM and TEM. Acid red B is used as the research object. Xenon lamp is used to simulate the degradation of acid red B dye wastewater under sunlight. The results show that the degradation rates of acid red B by the four catalysts are more than 80%, while the LaCoO₃ catalyst with the ratio of 1∶1∶6 has the best degradation effect on acid red B, and the degradation rate reaches 88.52% after visible light irradiation at 20 ℃ for 1 h. It is found that lanthanum cobaltate catalyst with large specific surface area has the best photocatalytic degradation effect on acid red B, on the contrary, the degradation effect of lanthanum cobaltate catalyst with small specific surface area is poor. The degradation of acid red B by four ratios of lanthanum cobaltate catalysts accords with the first-order reaction kinetic equation.

The pristine metal-organic framework materials (MOFs) and graphite-phase carbon nitride (g-C₃N₄) have shown excellent photocatalytic performance in H₂ production, CO₂ reduction, Cr reduction and organic pollutant degradation. The combination of MOFs and g-C₃N₄ to construct binary or ternary heterojunctions could overcome the shortcomings of the two materials, such as rapid recombination of photogenerated electron-hole pairs, further improving their photocatalytic performance under visible light or sunlight irradiation. In this minireview, the preparation methods, photocatalytic properties of several typical g-C₃N₄/MOFs composites were expatiated. Also, the prospect and challenges of this research field were declared.

A series of TiO₂ nanosheets/carbon (TNS/C) composites are prepared in situ by calcination at high temperature. In the method, the biomass corn stalks which are used as template and carbon source are impregnated in tetrabutyl titanate, then the corn stalks including tetrabutyl titanate are calcined. In the calcination process, biomass forms carbon skeleton and supports TiO₂ nanoparticles, resulting in TiO₂ nano-sheets structure and TNS/C heterogeneous junction. The effect of calculation temperature and template amount on the photocatalytic property of TNS/C composites is investigated. The results show that TNS/C composites prepared at calcination temperature of 700 ℃ and the dosage of template of 0.75 g exhibits optimal photocatalytic performance. The excellent photocatalytic performance of TNS/C composites possibly result from the introdution of carbon. A proper amount of carbon in composite are beneficial to improve the electron-hole separation efficiency, bringing about the significantly improvement of the removal efficiency for phenol under the visible light and mineralization ability.

Nano-photocatalysts have high efficiency, low energy consumption, no/low pollution, and are widely used in buildings dominated by cement-based materials, showing a good application prospect. The introduction of photocatalysts into cement-based materials can effectively improve their structural compactness, optimize their mechanical properties, endow them with the functions of pollutant degradation and surface self-cleaning, thus reducing the corrosion rate of cement-based materials and alleviating environmental pollution. This paper summarizes the different preparation methods of photocatalytic cement-based materials, introduces the influence of photocatalyst types on the photocatalytic properties of cement-based materials in detail, discusses the shortcomings of the current photocatalytic cement-based materials modified by nano-photocatalysts, and looks forward to them future development direction.

The design and synthesis of photocatalytic materials and their application in environmental pollution control and resource recycling have been reported in many literatures. However, most photocatalytic materials contain transition metal ions, and the environmental risks of leaching limit the application of catalytic materials. Silicon carbide (SiC), as the representative of the third generation of semiconductor materials, has a good potential application prospect in environmental pollution prevention because of its characteristics such as no transition metal ions, high temperature and acid-alkali resistance, strong stability and so on. In recent years, some literatures have reported the synthesis, modification and application of SiC as photocatalyst in environment and resource recycling fields. However, few literatures have reviewed the application progress of SiC photocatalyst. In view of the above situation, the progress in the field of SiC photocatalysis application in recent years was reviewed in this paper, including synthesis method, doping modification and application, and the prospects of the photocatalyst system were also prospected.

Environmental pollution is an important problem that needs to be solved in the process of industrial production. We synthesized g-C₃N₄/TiO₂ heterojunction photocatalyst by biological template method, which showed better photocatalytic performance than pure TiO₂ water solution in the process of degrading MO wastewater. The Yeast as soft biological template provided the materials with a porous structure and a large specific surface area, which increased the reactive sites in the aqueous solution and respectively, the g-C₃N₄/TiO₂ heterojunction structure acted as an electron transfer channel. light conditions, by the influence of internal electric field and Coulomb force, relatively useless electron-hole pairs got recombination and supreme redox ability electron-hole pairs are retained, respectively the retained electron-hole pairs provied the materials with the strongest redox capacity. XPS analysis verified that the direction of electron transfer was from g-C₃N₄ to TiO₂ The radical trapping experiment revealed that ·OH and O^-₂ molecules appeared around the composites, which were the main active ingredient in the photocatalytic degradation process. Therefore, the g-C₃N₄/TiO₂ composites prepared by the biotemplate and calcination method are promising photocatalysts for degrading organic dye wastewater.

Graphite carbon nitride (g-C₃N₄) has been a research hotspot in the field of hydrogen production due to its unique properties and low-cost raw materials. Nevertheless, the photocatalytic efficiency of graphite carbon nitride is usually limited by its low specific surface area, insufficient visible light utilization, the fast recombination of photo-induced electron-hole pairs and other demerits. Herein, in the review, methods of molecular modification on g-C₃N₄ were reviewed from the aspects of copolymerization, covalent bonding and surface modification with functional groups. Moreover, the review also summarized the mechanism of structure modified carbon nitride in improving photocatalytic hydrogen production activity in terms of visible light absorption, separation efficiency of electrons and holes and reactivity of active sites. The review ended with perspectives on the challenges and future prospects of molecular modification of graphite carbon nitride.

Zr doped TiO₂ nanoparticles with different contents are prepared by sol-gel method.The properties of Zr doped TiO₂ nanoparticles are characterized by XRD,SEM,UV-Vis,PL and photocatalytic performance analysis.The results show that the structure of all Zr doped TiO₂ nanoparticles is anatase, and the diffraction peak is sharp. There are no other impurity peaks and their purity and crystallinity are high. By analyzing the cell parameters,it is found that Zr is successfully doped into the lattice of TiO₂.The distribution of TiO₂ nanoparticles without Zr doping is uneven,and the size deviation is large.After adding a small amount of Zr,the particle dispersion is slightly improved, and the particles show a regular spherical shape. The surface roughness increases slightly, and when Zr content is 3 wt%,the improvement effect is the best. When the Zr content is 5 wt%, excess Zr would adhere to the TiO₂ surface, resulting in poor smoothness and dispersion and surface activity reducement. The absorption sideband of TiO₂ nanoparticles doped with different content of Zr has a slight red shift, which enhances the light absorption ability of TiO₂ nanoparticles and improves the photocatalytic performance under visible light.The incorporation of Zr significantly weakens the recombination of photogenerated electrons and holes in TiO₂ nanoparticles,which is helpful to improve the photocatalytic performance of TiO₂ nanoparticles.The degradation efficiency of undoped Zr TiO₂ nanoparticles is 12.3% at 120 min. When the content of Zr is 3 wt%,the degradation efficiency of TiO₂ nanoparticles is the highest of 87.3%.However,when the content of Zr is large,the photocatalytic performance decreases slightly. It could be seen that the optimum content of Zr is 3 wt%.

Photocatalytic technology is driven by solar energy and has a very broad application prospect in the fields of environmental governance and hydrogen energy preparation. g-C₃N₄ is a promising green photocatalyst, but its limited visible light response range and wide energy gap limit the further improvement of its photocatalytic performance. Non-metallic element doping is an effective method to improve the photocatalytic activity of g-C₃N₄. In this paper, the influence mechanism of B element doping on the photocatalytic activity of g-C₃N₄ was studied by first-principles calculation, and the electronic structure and optical properties before and after doping were investigated. The results show that the H site on the g-C₃N₄ (001) surface is the most stable site for B atom doping, and the doping energy is - 7.81 eV. The addition of B element reduced the energy gap of g-C₃N₄ (001) surface from 1.468 eV to 0.732 eV, and the work function decreased from 4.055 eV to 3.108 eV and improved the reactivity of surface C atoms, so that the photocatalytic activity of g-C₃N₄ (001) surface was effectively improved. The study of optical properties shows that the addition of B element makes the g-C₃N₄ (001) surface have an obvious “red shift” phenomenon, which improves the light response ability of the surface and obtains higher photocatalytic ability.

Using C₄H₆O₄Zn·2H₂O as raw material, Ag doped ZnO nanomaterials were prepared by hydrothermal method. The effects of Ag doped molar mass on the structure and photocatalytic performance of ZnO nanomaterials were studied using XRD, SEM, FT-IR, PL spectroscopy and photocatalytic performance tests. The results showed that the Ag doped ZnO nanomaterials prepared by hydrothermal method had a hexagonal wurtzite structure and high crystallinity. Ag doping didn't change the lattice structure of ZnO nanomaterials and the appearance was irregular spherical. After appropriate amount of Ag doping, the particle morphology of ZnO nanomaterials tended to change to regular spherical, with particle sizes ranging from 260 to 480 nm. With the increase of Ag doping ratio, the photoluminescence intensity of ZnO nanomaterials decreased first and then increased. ZnO nanomaterials with Ag doping molar ratio of 3% had the lowest photoluminescence intensity. Taking Rhodamine B (RhB) as the degradation target, at 180 min, the degradation rate of RhB by Ag doped ZnO nanomaterials with a molar ratio of 3% reached a maximum of 93.05%, which was 64.22% higher than that of pure ZnO. After repeated use for 5 times, the degradation rate of RhB by ZnO nanomaterials in 180 min was 81.22%, and the retention rate was as high as 87.29%, indicating a high reusability.

Organic pollutants are an important source of water pollution, and their harmless treatment is necessary before discharge. Photocatalytic degradation has attracted extensive attention in recent years due to its mild reaction conditions, high efficiency and wide application range. ZnO is a cheap, stable and non-toxic semiconductor material, which is an ideal photocatalyst. However, its application is limited by the large band gap and easy recombination of photogenerated carriers. Reasonable modification can effectively improve ZnO's light absorption range, promote the separation of photogenerated carriers, and further facilitate the formation of more key intermediate oxidant species and improve its photocatalytic efficiency. In this paper, the design of ZnO-based photocatalyst and its application in photocatalytic degradation of organic pollutants in recent years are reviewed from the perspective of modification methods, including element doping, heterojunction formation and morphology design.

ZnO nanocomposites with different molar ratios of Ce doping were prepared by hydrothermal method using ZnO as a photocatalyst and rare earth element Ce as an additive phase. The effect of Ce doping molar ratio on the lattice structure, microstructure and photocatalytic performance of ZnO nanocomposites was studied using methyl orange (MO) dye as the degradation object. The results showed that the Ce-ZnO nanocomposites prepared were all hexagonal wurtzite structured with an irregular granular appearance. Ce doping increased the surface roughness of ZnO. After Ce doping, no new products were produced in ZnO,      which did not affect the structure of ZnO. As the Ce doping molar ratio increased, the specific surface area of Ce ZnO gradually increased, the absorption edge first increased and then decreased, the bandgap width first decreased and then increased, and the photoluminescence intensity first decreased and then increased. The specific surface area of 0.6%Ce-ZnO reached 33.91 m²/g, with a maximum absorption edge of 394 nm and a minimum bandgap width of 2.97 eV, corresponding to the lowest photoluminescence intensity. The photocatalytic degradation test showed that with the increase of Ce doping molar ratio, the photocatalytic degradation of MO by Ce-ZnO first increased and then decreased. The degradation rate of MO by 0.6%Ce-ZnO reached its maximum value of 95.36% at 180 min. Under strong acidic or alkaline conditions, it wasn't conducive to the progress of photocatalytic reactions. Under weak acidic conditions with a pH value of 5, the degradation rate of MO by 0.6%Ce-ZnO reached a maximum of 99.16%. When the 0.6%Ce-ZnO photocatalyst was reused for 5 times, the degradation rate of MO still exceeded 70%, indicating good usage stability and economic benefits.

Using ammonium molybdate as molybdenum source and thiourea as sulfur source, binary planar CdS / MoS₂ heterojunction was prepared by hydrothermal method. The heterojunctions were characterized by XRD, SEM, TEM, PL and UV-vis techniques. The results showed that the heterojunction (the mass fractions of MoS₂ were 1%, 5% and 10%, respectively) can effectively improve the visible light absorption intensity of CdS. The photogenerated carriers and holes were effectively separated, thus the composite catalyst exhibited excellent photocatalytic performance. The performance of CdS/MoS₂-10% was the best . The photocatalytic degradation of 10 mg samples to 20 mg/L Roda min B can reach 99%. The catalytic activity of the binary CdS/MoS₂ heterojunction did not decay significantly in the five-cycle experiment.

As a new and efficient heating preparation technology, microwave has been widely used in the field of material preparation due to its advantages of cleanness, high efficiency, low energy consumption, high yield and good selectivity. TiO₂ has attracted great attention in the degradation of pollutants in the environment due to its high catalytic activity, non-toxicity and stable chemical and physical properties. The application of microwave heating technology in the preparation of TiO₂ photocatalyst can reduce the heat treatment time, the cost, and effectively the agglomeration of TiO₂ materials, resulting in more uniform products. In this paper, five preparation methods of TiO₂ photocatalyst assisted by microwave in recent years, microwave hydrothermal method, microwave sol-gel method, microwave liquid phase deposition method, microwave drying method, and microwave microemulsion method were reviewed, and as well as its application in photocatalytic degradation of organic pollutants. The purpose is to provide reference for promoting the application and development of microwave heating technology in the field of TiO₂ photocatalyst.

In this experiment, graphite phase carbon nitride (g-C₃N₄) has been use as a photocatalyst to study the problems of small specific surface area and low visible light efficiency. Firstly, the graphene oxide (GO) and reduced graphene oxide (rGO) were respectively synthesized with g-C₃N₄ in a certain proportion by ultrasonic assisted synthesis method. And the composites were characterized and analyzed by XRD, SEM, FT-IR, XPS, UV-Vis and other characterization methods. Secondly, the photocatalytic degradation and kinetics of rhodamine B (RhB) under simulated sunlight were studied. Finally, the experimental results show that the GO/CN and rGO/CN composite photocatalysts have the same phase structure and more porous morphology as g-C₃N₄, and the graphene composite material can improve the visible light absorption capacity of g-C₃N₄, and reduce its band gap width. Also, according to the analysis of visible light photocatalytic performance, rGO/CN2 has stronger adsorption capacity, and the adsorption rate f RhB at 30 min is up to 64.79%, 5.2 times that of g-C₃N₄ under the same conditions. GO/CN1.5 shows excellent photocatalytic activity, and its catalytic reaction rate constant is 9.108×10^-2/min. When RhB is degraded for 10 min, the degradation rate reaches 86.34%, which is 1.5 times that of g-C₃N₄ under the same conditions.

ZnO/HNTs nanocomposites are prepared by in-situ growth of ZnO nanoparticles on the surface of halloysite nanotubes (HNTs) using zinc nitrate as zinc source. The ZnO/HNTs are characterized by X-ray diffraction, scanning electron microscope, X-ray energy spectrometer, specific surface area and porosity analyzer, UV visible near infrared diffuse reflectance, and ZetaSizer Nano 90 dynamic light scattering (DLS) particle size analyzer tester. The adsorption and photocatalytic degradation performance of HNTs, nano-ZnO and ZnO/HNTs composite materials for methylene blue (MB) under UV illumination are investigated. The results show that the nano-ZnO is evenly distributed on the surface of HNTs. Compared with nano-ZnO, the specific surface area of ZnO/HNTs is as high as 44.305 m²/g, which is 1.2 times higher. For ZnO/HNTs, the degradation rate of 15 mg/L methylene blue with degradation time of 1.5 h is close to 100%, which is much higher than that of nano-ZnO (80.2%), and its repetitive catalytic efficiency maintains remains 80.4% after 10 cycles. It is shown that the introduction of HNTs greatly improved the catalytic activity of ZnO/HNTs.

In this paper, the high-titanium slag-based slag wool blown from titanium-containing blast furnace slag is selected and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray fluorescence spectroscopy (XRF), fluorescence analysis and Raman spectroscopy. In addition, formaldehyde solution is used as reactant for photocatalytic degradation experiments to explore the photocatalytic degradation ability of high titanium slag based slag cotton to formaldehyde. The results show that the phase of high titanium slag cotton fiber contains perovskite. The average fiber diameter is 0.93 μm. The main oxide composition of high titanium slag based cotton fiber is basic metal oxide, in which the percentage of TiO₂ is 32.99%. Under the irradiation of 254 nm ultraviolet light, the electron-hole pair can be generated, which indicates that the fiber has photocatalytic performance. Perovskite plays a catalytic role in high titanium slag based slag cotton. Under the conditions of room temperature, 1.0 g dosage, 10 min reaction time and 2.5 mW/cm² UV light intensity, the best photocatalytic degradation ability of 400 mL formaldehyde solution with a concentration of 8.0 μg/L is obtained. The total removal rate of formaldehyde is 23.61%, and the photocatalytic degradation rate is 8.96%, accounting for 37.84% of the total removal rate.

Metal-organic framework (MOFs) materials show great potential in the field of photocatalysis due to their unique pore structure and easily regulatable chemical properties. As a photocatalytic material, zeolite imidazole skeleton material (ZIF-8) faces the serious problem of light absorption. In view of the difficulties existing in the application of ZIF-8 at the present stage, the functional modification method is used to improve the band gap of ZIF-8, so as to improve the photocatalytic activity of ZIF-8. ZIF-8 modified with 2,2′-bipyridine (2-BP) exhibits the strongest photocatalytic activity, and its photocatalytic hydrogen evolution efficiency is about 910.14 μmol/g/h, which is 7.3 times than that of unmodified ZIF-8.

BiOBr have received extensive interest for photocatalytic nitrogen fixation due to their special layered structure. In this paper, a series of P-doped BiOBr photocatalysts were successfully synthesized using sodium hypophosphite and bismuth nitrate pentahydrate as precursors through solvothermal process. The XRD, SEM, XPS, UV-Vis DRS, and photocatalytic materials were used to characterize the as-prepared catalyst. The photocatalytic nitrogen fixation performance under visible light irradiation was investigated. The results showed that P-doping increased the specific surface area of BiOBr and did not change its crystal structure. At the same time, P-doping improved the separation efficiency and visible light response of photogenerated carriers. Compared with BiOBr, the photocatalytic ammonia production of P-doped BiOBr (n(Bi):n(P) =15: 1) was 31.68 mg/(L·h·g)_cat, which was 4.7 times higher than that of BiOBr. Finally, the P-doped BiOBr has good stability after four cycles of experiments.

Here, with bismuth nitrate (Bi(NO₃)₃·5H₂O) as the source of bismuth, tungsten acid sodium (Na₂WO₆·2H₂O) as tungsten sources and alkaline titanium carbide (Ti₃C₂-OH) as catalyst promoter, auxiliary by CTAB with simple hydrothermal method, we have succeeded in preparation of the composite photocatalyst Ti₃C₂-OH/Bi₂WO₆ with the photocatalytic properties. In under the irradiation of visible light (300 w xenon lamp), the degradation of rhodamine B (RhB) dye solution is used to assess the photocatalytic performance of the catalyst, and its degradation mechanism is finally analyzed. The results show that the degradation efficiency of pure Bi₂WO₆ on pollutants reaches 60.8% after 20 min of visible light irradiation, while the photocatalytic performance of the complex is significantly improved after supporting the catalyst Ti₃C₂-OH. Specifically, when the load of Ti₃C₂-OH is 20 mg, the degradation efficiency of RhB by the composite catalyst 20 mg-Ti₃C₂-OH/Bi₂WO₆ (short for 20 mg-TB) reaches 96% within 20 min, and the photodegradation performance is significantly better than that of pure Bi₂WO₆. Kinetic analysis shows that the Changshu kinetics of pure Bi₂WO₆ is k=0.0262 min^-1, while that of 20 mg-TB is k=0.1239 min^-1, 4.72 times of that of pure Bi₂WO₆. Furthermore, the crystal structure and microstructure of the catalyst are thoroughly analyzed. In order to clarify the mechanism of photodegradation, we have carried out the capture experiment of active species, and the results show that the species that play a major role in the degradation of organic matter is h⁺.

The iron-doped TiO₂ nanotube arrays (TNTs) are prepared by anodizing and atmospheric hot water self-assembly methods with titania as the substrate and Fe(NO₃)₃ as the iron source. The degradation rate of methyl orange (MO) is used as an evaluation index to investigate the influence of different factors on the degradation rate of MO under the visible light. The preparation conditions are optimized by response surface methodology, and the scanning electron microscope (SEM) and X-ray diffraction (XRD), X-ray energy spectroscopy (EDS) and other test methods are used to characterize the as-prepared catalysts. The results show that the photocatalytic performance of Fe/TNTs is the best and the degradation rate of MO can reach 95.96% when the process conditions are Fe(NO₃)₃ concentration 0.30 mol/L, reaction temperature 75 ℃, reaction time 8.42 h, The results are in accordance with the prediction of 96.04% which is 61.81% higher than that before doping. The as-prepared Fe/TNTs are anatase crystals, the doping of iron does not destroy their ordered tubular array structure, and the light response range extends to the visible light region.

As the core material of photocatalytic technology, TiO₂ has a great potential in sewage treatment, energy and medical beauty, due to its unique structure and performance. However, the large band gap, the length of excitation wave and the easy recombination of photogenerated electrons have become one of the important bottlenecks in its application. Therefore, this paper introduces the photocatalytic principle and influencing factors of TiO₂ materials, focuses on the photocatalytic mechanism and application fields of doped TiO₂. Meanwhile, the shortcomings in the modification process of TiO₂ photocatalyst were put forward, and the future research direction is prospected.

Developing integrated photocatalysts with multifunction in energy conversion and environmental improvement is an effective strategy for promoting solar-to-chemical application under the dual challenges of energy crisis and environmental pollution. Herein, this work uses hexagonal CoAl-LDH nanosheets as carriers and constructs a type Ⅱ heterojunction of CoAl-LDH/CdS by in-situ growth of CdS nanoparticles. By utilizing the broad absorption and excellent carrier properties of CoAl-LDH nanosheets in the visible light region, combined with the high optical quantum yield of CdS, and through the construction of heterostructures, a multifunctional CoAl-LDH/CdS composite photocatalytic material is obtained. Moreover, by optimizing the loading amount of CdS, the photodegradation rate of the photocatalyst with a mass ratio of CoAl-LDH/CdS-2 is the highest (degradation rate=88.48% at t=60 minutes), which is 1.18 times and 8.62 times higher than that of CdS and CoAl-LDH monomers, respectively. Meanwhile, the highest CO production of CoAl-LDH/CdS-1 is 39.02 mol/g (t=5 h), which is 4.2 and 2.5 times of bare CoAl-LDH and bare CdS, respectively. These results are mainly attributed to the construction of a tight heterojunction between CoAl-LDH nanosheets and CdS nanoparticles in composite, and the rich coupling interface greatly reduces the recombination rate of photogenerated carriers. This provides a theoretical basis for the development of multifunctional photocatalysts.