One of the greatest intriguing approaches to address the energy and environmental crisis is the production ofH2 from photocatalytic water splitting. This comprehensive review paper explores the potential of photoactive ZnO and ZnS semiconductor for H2 evolution particularly under UV-visible radiation. However, the broad band gap energy of 3.37 eV and 3.6 eV for both ZnO and ZnS, respectively, restricts their wide scale application, confining the production of H2 to UV spectrum only. In order to enhance the overall quantum and photo efficiency, this review underscores the promising solution of integrating various binary and ternary ZnO/ZnS nanostructured materials. The main focus is on the fabrication techniques including solvothermal, hydrothermal, coprecipitation, and ion exchange that shape the structural and electrical properties of ZnO/ZnS based heterojunctions. The discussion delves into the intricate relationship between the synthesis methods and the resultant photocatalyst properties, emphasizing the influence of varying parameters on the photocatalytic activity. Special attention is given to the modification strategies for manipulating band alignments and structures in the binary and ternary ZnO/ZnS heterostructures, providing insights into optimizing photocatalytic efficacy. The review paper aims to elucidate the current state-of-the-art, challenges and future perspectives in the development of advanced ZnO/ZnS photocatalytic semiconductor for effective and scalable H2 production.

Composite engineering has the potential to convert CO2 into high-value products, addressing energy scarcity and environmental challenges. In particular, the Cs3Bi2Br9 perovskite has garnered significant attention for activating inert CO2 molecules, benefiting from its stability, lower defect density, tunable electronic structure, and high photoluminescence quantum efficiency (PLQE) value. Additionally, compounding Cs3Bi2Br9 with other components can further enhance its potential, modifying photo redox and CO2 adsorption/activation, leading to regulated C1 product selectivity. Herein, the review summarises different strategies for constructing Cs3Bi2Br9-based heterostructures and discusses advanced experimental techniques to support the shreds of evidence for the functioning of charge migration. Afterwards, the selectivity of Cs3Bi2Br9-based heterojunction for CO2 photoreduction reactions has been thoroughly comprehended. Lastly, the review also summarized conclusive remarks and future perspectives of Cs3Bi2Br9-based heterojunction on the photocatalytic conversion of CO2.

It is clear that a wide range of organic substances, including synthetic textile dyes, have the potential to negatively impact the environment. It is crucial to rationally develop highly effective photocatalysts for the degradation of such type of pollutants. In this regard, a heterostructured photocatalyst comes with enhanced charge separation and extended light absorption ability that improves photocatalytic performance. Therefore, In this study, a Bi2O3/g-C3N4/ZnO (BCNZ) ternary heterojunction photocatalyst was synthesized for the degradation of methylene blue (MB) textile dye.. Thermal polycondensation method was opted to synthesize g-C3N4, while ZnO and Bi2O3 photocatalysts were fabricated using co-precipitation method. Similarly, ternary heterojunction of BCNZ was constructed through co-precipitation method. The ternary heterojunction photocatalyst demonstrated better photodegradation ability due to dual Z-scheme charge transfer route. The dual Z-scheme heterojunction enabled the ternary heterojunction to exhibit enhanced light absorption capabilities with reduced recombination rates as well as enhanced charge separation and migration efficiency (confirmed via transient photocurrent response) that resulted in improved photocatalytic performance. The BCNZ dual Z-scheme photocatalyst displayed 92 % of degradation efficiency which was much higher than that of other (binary and pristine) photocatalysts. Scavenging tests and electron spin resonance spectroscopy revealed the significant role of the center dot O2-, and center dot OH radicals in the photodegradation of MB. Furthermore, the reusability test presented good stability and recyclability of the ternary photocatalyst with 80 % degradation efficiency after five catalytic cycles.

Recently, the photocatalysis process has emerged as a favourable wastewater treatment approach. Therefore, we constructed a novel visible-light-driven magnetic ternary heterojunction of GCN/CdO/CaFe2O4 photocatalyst for Congo red (CR) dye degradation. This work employed facile and cost-effective methods to fabricate all photocatalysts. g-C3N4 was synthesized via thermal polycondensation, while CdO and CaFe2O4 were fabricated using co-precipitation. Similarly, the co-precipitation method constructed binary (GCN/CdO) and ternary heterojunction of GCN/CdO/CaFe2O4. The dual Z-scheme heterojunction charge transferal path led to a lower recombination rate and boosted charge separation efficiency with prolonged light absorption, which enhanced the photodegradation ability. The obtained CR degradation efficiency of GCN/CdO/CaFe2O4 dual Z-scheme ternary heterojunction was 88 % within 60 min of light irradiation, more remarkable than other photocatalysts. ESR and scavenging tests confirmed the vital role of O-center dot(2)-, and (OH)-O-center dot radicals during CR degradation. Additionally, the magnetic nature of ternary heterojunction caused excellent separation of photocatalysts, which resulted in good stability and recyclability with 80 % removal efficiency even after 5 catalytic cycles (confirmed by reusability/recyclability test).

Background: Light harvesting and reusability are the key factors for highly effective solar photocatalysis. Floating photocatalysts can maximize light utilization and be recycled easily, making them a strong candidate for real-world environmental applications. Methods: In this article, a novel dual s-scheme-based g-C3N4/ZnO/TiO2/Cork photocatalyst was constructed via a co-precipitation process followed by physical blending of the floating materials. In g-C3N4/ZnO/TiO2/Cork photocatalyst, cork acted as a floating substrate to enhance light exposure, oxygen availability, and reusability. The dual S-scheme charge transfers between g-C3N4, ZnO, and TiO2 improves carriers' charge separation and concentration. Advanced Spectral techniques were utilized to compare and analyze the morphological, structural, and optical characteristics. The photocatalytic activity was further analyzed by using methyl orange (MO) and doxycycline hydrochloride (DCl) as target pollutants. Significant findings: The g-C3N4/ZnO/TiO2/Cork heterojunction exhibited excellent photodegradation activity against MO dye (98.25 %) and DCl antibiotic (79.27 %) within 60 min under visible light. The scavenger experiment revealed that the O-center dot(2)- and (OH)-O-center dot radicals were the major reactive species in this photocatalytic experiment. Additionally, a better recyclability was also demonstrated by the g-C3N4/ZnO/TiO2/Cork heterojunction photocatalyst.

Photocatalysis is an environmentally friendly approach for harnessing solar light to degrade pollutants. This study investigates the degradation of Congo red (COR) dye by a visible light-active photocatalyst, with a primary focus on the efficiency and reusability of the photocatalytic material. We synthesized phosphorus- and potassium-doped graphitic carbon nitride photocatalysts attached to graphene oxide and MgFe2O4 (KPCN/GO/MgFe2O4). Doping graphitic carbon nitride enhanced light absorption, while graphene oxide improved the adsorption properties. The addition of magnetic MgFe2O4 enhanced charge separation and reusability. The KPCN/GO/MgFe2O4 composite was analyzed using a range of techniques. The activity of the synthesized materials for Congo red (COR) dye degradation was analyzed under visible light. The photocatalytic activities of bare, binary, and ternary photocatalysts were compared, and KPCN/GO/MgFe2O4 exhibited the highest photoactivity among all. The KPCN/GO/MgFe2O4 photocatalyst (60 mg) showed a 76% removal efficiency for 5 x 10-6 M Congo red within 60 min, which was 2.5 times higher than that of pure graphitic carbon nitride. The OH and O2- were the major reactive species during COR photodegradation. The photocatalyst also displayed good reusability after five cycles, enhancing its overall effectiveness.

Advanced oxidation processes, mainly photocatalysis, are utilized as an effective and alternative prospect for industrial wastewater treatment, especially in the non-biodegradable compounds. Among various photocatalysts, Co3O4 is a visible light active photocatalyst that exhibits superb photocatalytic activity in various photocatalytic applications. However, photocatalytic activity of bare Co3O4 nanoparticles remains inacceptable because of inherent shortcomings such as rapid recombination. Significant efforts were done in the last several years to advance performance and figure out the mechanisms involved. This review begins with structural & optical properties (and DFT studies), synthesis methods and goes detail about recent advances and strategies for refining the performance of Co3O4-based photocatalysts, for instance structural design and creation of Co3O4-based composites. Construction of Co3O4-based heterojunction results in a distinct photogenerated photocarriers mechanism, which reduces the recombination and increases photoactivity. The sole emphasis of this review is on the latest developments in environmental applications for Co3O4 as well as photocatalysts based on them. In conclusion, the varied environmental applications of Co3O4-based materials, such as pollutant degradation (i.e., dyes, antibiotics, phenols, pesticides, and Cr (VI) reduction) and energy conversion (e.g., H2 production, CO2 reduction/CO evolution, and O2 evolution), are summarized in detail. To summarize the bottlenecks, exciting challenges, current progress, and future perspectives for innovative opportunities are also presented.

In the present work, we have explored the construction of ternary alpha-Fe2O3/CdS/SiO2 S-scheme nanocomposite for the removal of tetracycline (TC) antibiotic. The ternary alpha-Fe2O3/CdS/SiO2 nanocomposite was fabricated using the co-precipitation method and was characterized via various analytical and spectroscopic techniques to explore their structural properties. The alpha-Fe2O3/CdS binary magnetic nanocomposite was attached to the surface of SiO2 nanoparticles, which served as an effective support material with improved chemical stability and good visible-light absorption capabilities. Among the synthesized bare (alpha-Fe2O3, CdS, SiO2) and ternary photocatalysts, the alpha-Fe2O3/CdS/SiO2 nanocomposite exhibited the highest TC photodegradation efficiency (99 %) at pH 3 within 120 min of light illumination using 60 mg/L catalyst dose and 7 x 10(-4) M of H2O2 concentration (30 % V/V). In comparison to bare photocatalysts, the photo-Fenton assisted photocatalytic reactions of ternary heterojunction boosted charge carrier separation and mobility (confirmed from PL and EIS analysis). Additionally, it could prolong the reactive oxygen species generation which significantly improved the degradation rate of TC by ternary nanocomposite. Furthermore, the generation of superoxide (O-center dot(2)-) and hydroxyl ((OH)-O-center dot) radicals, i.e. reactive oxygen species, played an imperative role in the TC degradation process which were validated through scavenging experiments and ESR analysis. This study displayed the effectiveness of the S-scheme alpha-Fe2O3/CdS/SiO2 ternary heterostructure-based Photo-Fenton system exhibiting enhanced charge separation and migration for boosted photocatalytic efficiency. After four rounds, the photocatalytic activity demonstrated only a minor decline in catalytic efficiency.

Solar irradiance is a renewable energy source that can be utilized to generate electricity and accelerate chemical reactions. However, the actual process conversion productivity is limited which is governed by the migration and separation of photoinduced carriers. To heighten the conversion efficacy, it would be necessary to suppress the EHP recombination and expand the low redox potentials. However, nowadays, countless semiconductor-based photocatalysts have been studied with good photocatalytic activity and superior charge carrier separation. Here, we review Bi-based semiconductor photocatalyst mainly sillenite Bi12TiO20 (band gap ranging from 2.3 to 3.2 eV) with improved photocatalytic activity. However, like other single photocatalysts, Bi12TiO20 (BTO) also exhibits a few shortcomings such as rapid recombination, inadequate visible light absorption, and restriction of the broader-range applicability of BTO. So, to overcome these constraints we have focused on appropriate strategies like doping, and heterojunctions including conventional, Z-scheme, and S-scheme along their mechanism. Furthermore, synthesis methods such as chemical solution decomposition, hydrothermal, and microwave methods are discussed to study the morphology and structural properties of the BTO photocatalyst. The DFT studies are also deliberated to examine the optoelectronic, and structural properties of BTO photocatalyst. Lastly, we concluded with photocatalytic applications such as dyes and antibiotics degradation, NO removal, phenol degradation, and other pollutants degradation over BTO heterojunctions. The concluding remarks with future challenges/perspectives are also discussed.

The effectiveness of photocatalysis is constrained by the insufficient efficiency of charge separation, migration, and utilization that are generated by light [1], [2]. Enhanced photocatalytic efficiency is significantly achieved through the important technique of integrating Metal-Organic Frameworks (MOFs) with other materials to form heterojunction structures. In this study, NH2-MIL-125/MnO2 (NMM) composite photocatalyst has been designed, featuring a Z-scheme heterojunction structure with enhanced interfacial charge transfer and an improved lifetime of charges. The physicochemical properties of the NMM composite were analysed by multiple techniques. The photocatalytic efficiency of the NMM composite is notably superior to pristine NH2-MIL-125 and MnO2. This enhanced performance can be credited to the improvement in the recombination rate, charge transfer resistance, and adsorption site, as revealed by the characterization data. The photocatalytic performance of the NMM composite was analysed for ornidazole antibiotics degradation, which showed 91.31% degradation efficiency at optimum conditions. In the photocatalytic degradation mechanism, •O2- free radicals were the major oxidative species responsible for the ornidazole degradation.

Developing an affordable and abundant electrocatalyst for generating green hydrogen is crucial for achieving sustainable energy with zero carbon emissions. In this context, nanostructured transition metal chalcogenides were seen as ideal cathode materials for water splitting due to their tuneable structure, large surface area, strong conductivity, and widespread availability. Herein, we have developed Cu-Mo Bimetal Sulfo-Selenide Nanocomposite (CuMoSSe) by incorporating Cu into the MoSSe system through a single-step hydrothermal method and explored it as a catalyst for electrochemical hydrogen evolution. The Cu0.25Mo0.75SSe, consisting of a Cu2Se/ MoSSe composite structure, exhibited excellent electrochemical HER activity with an overpotential of 290 mV vs. RHE at 10 mA/cm2 compared to its various compositions and pristine counterparts, with remarkable stability for more than 1500 cycles and 12 h in an acidic medium. The enhanced electrochemical activity with smaller charge-transfer resistance (47.8 Omega) and larger double-layer capacitance (14.74 mF/cm2) values with a low Tafel slope of 79.1 mV/dec can be attributed to the effective kinetics and enhanced electrical conductivity of the composite due to the hybrid structure which is backed by the decrease in Gibbs free energy value calculated through theoretical studies. These discoveries open the door to creating new electrocatalysts using combinations of MoSSe and Cu or other metals. This approach aims to design electrode materials that are not only low cost but also mechanically strong and electrically conductive for the process of electrocatalytic water splitting.

Photocatalysis has great potential for transforming sustainable solar energy into chemical energy, offering significant benefits for environmental applications. However, the rapid charge carrier recombination in pristine semiconductors is a big challenge. S-scheme heterojunction strategy is one of the effective strategies to overcome this challenge. The present work explored the photodegradation ability of the BiOCl-CuInS2-WO3 heterojunction against Victoria blue (VIB) dye. The pristine photocatalysts (i.e. BiOCl, CuInS2, WO3) were fabricated hydrothermally, however the BiOCl-CuInS2-WO3 ternary photocatalyst was constructed via a facile physical mixing. The BiOCl-CuInS2-WO3 ternary photocatalyst followed dual S-scheme charge migration route as per the band alignments which lead to upgraded photodegradation ability in comparison to other pristine photocatalysts. The S-Scheme heterojunction formation offered enhanced charge separation and the separated charge carriers carry out degradation process in presence of light. The photodegradation rate of BiOCl-CuInS2-WO3 dual S-scheme heterojunction was 99.24 % after 90 min, that was superior than other photocatalysts. Similarly, via ESR studies and scavenging experiments, the significant role of O-center dot(2)-, and (OH)-O-center dot radicals was determined in the degradation of VIB. Also, the S-scheme heterojunction resulted in extended light absorption ability with reduced recombination rate (verified by PL analysis) and higher separation rate of photocarriers (confirmed by EIS and TPR analysis) in ternary heterojunction. This resulted in improved photodegradation effectiveness of the ternary BiOCl-CuInS2-WO3 photocatalyst. The stability of the formed heterojunction was verified via reusability tests which displayed 90.25 % degradation efficiency after 5 successive catalytic cycles.

Methylene blue is a recognized carcinogen with detrimental effects on both people and marine life. Henceforth, in this study, the photocatalytic activity of Ag3PO4/g-C3N4/Bi2MoO6 (AP/GCN/BMO) photocatalyst was investigated for the degradation of MB dye from an aqueous system. g-C3N4, BMO and AP photocatalysts bare photocatalysts were synthesized via thermal polycondensation, hydrothermal and co-precipitation methods, respectively. Similarly, binary (GCN/BMO) and ternary heterojunctions (AP/GCN/BMO) was constructed through in-situ hydrothermal and co-precipitation methods, respectively. Morphological and structural analysis validated close interaction amongst Ag3PO4, g-C3N4, and Bi2MoO6 photocatalysts. Furthermore, density functional theory simulations were employed to explore the structural and electronic properties of the bare (Ag3PO4, g-C3N4, and Bi2MoO6) photocatalysts. The photocatalytic degradation experiments revealed that AP/GCN/BMO exhibited highest adsorption and photocatalytic degradation efficacy of methylene blue (MB) dye pollutant as compared to other photocatalysts. The achieved MB dye degradation efficiency of dual Z-scheme AP/GCN/BMO ternary photocatalyst was approx. 94

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

To date, the prevalence of commonly used plastics like Polyethylene terephthalate (PET), polylactic acid (PLA), and polybutylene terephthalate (PBT) extends across diverse industries, from textiles to beverage bottles and daily packaging applications. Originally designed for up to 50 years of durable shelf life, these plastics face accelerated disposal challenges due to the pervasive "throw-away" culture. The rapid expansion of single-use plastic manufacturing, notably PET, has led to an astonishing global output of one million tons of plastic each year, highlighting the urgent requirement for efficient solutions in managing plastic waste. Carbon-based nanomaterials derived from PET are synthesized using chemical reactions in solution or high-temperature environments. This review discusses molten salt, hydrothermal, and one-step solvent-based synthesis techniques. We investigate advances in converting PET plastic into nanostructured materials, revealing their potential for energy storage, adsorption, supercapacitors, and sensors. As we navigate the challenges of plastic waste, this review scrutinizes the environmental impact by bridging the gap between plastic pollution and the utilization of upcycled nanomaterials of these pioneering methods, offering insights into their sustainability.

The design and development of green and chemical nanomaterials is crucial because these systems can possess desired and manipulative photocatalysis and electrocatalysis. To achieve these features at the same time, Klockmannite Copper selenide (CuSe) emerging as a potential p-type semiconductor exhibits shape and size-dependent functional, optical, and electrical properties. Additionally, alterable bandgap, metallic character, localized surface plasmon resonance, and significant light absorption variability of CuSe make this class of material an efficient technological material. To cover the gaps in the field of CuSe and explore the potential to manage a sustainable environment, this review provides an overview of the design and development of green and chemical (but acceptable) CuSe for various advanced applications due to its indirect bandgap of 0.15-2.7eV and scaled up synthesis using both top-down and bottom-up approaches. Despite numerous advantages, the limitations related to CuSe such as a small bandgap, charge carrier recombination, and a restricted ability to absorb visible light are also discussed in this article. Further, various modification possibilities, including doping or creating heterojunctions utilizing traditional (Type-I, -II, -III) and conventional techniques (Z-, Dual-Z-, S-scheme, etc.) to overcome these restrictions are also discussed carefully and critically. Functions of CuSe in energy conversion, supercapacitors, sensors, and environmental issue solutions have been covered in this study. Future outlooks, viewpoints, and conclusions on the subject have all been presented. We believe that this article will serve as a key document to project and promote CuSe for next-generation photocatalysis.

Arsenic (As) contaminated water, especially groundwater reservoirs, is a major issue worldwide owing to its hazardous consequences on human health and the global environment issues. Also, irrigating agricultural fields with As-contaminated water not only produces an accumulation of As in the soil but also compromises food safety due to As entering into agricultural products. Hence, there is an urgent need to develop an efficient method for As removal in water. Fe-based MOFs have attained special attention due to their low toxicity, high water stability, better physical and chemical properties, and high abundance of iron. The arsenic species removal by Fe-MOF follows the adsorption and oxidation mechanism where As (III) converts into As (V). Moreover, the adsorption mechanism is facilitated by electrostatic interactions, H-bonding, acid-base interaction, hydrophobic interactions, van der Waals forces, π-π stacking interactions, and coordinative bindings responsible for Fe-O-As bond generation. This review thoroughly recapitulates and analyses recent advancements in the facile synthesis and potential application of Fe-based MOF adsorbents for the elimination of As ions. The most commonly employed hydro/solvothermal, ultrasonic, microwave-assisted, mechanochemical, and electrochemical synthesis for Fe-MOF has been discussed along with their adsorptive and oxidative mechanisms involved in arsenic removal. The effects of factors like pH and coexisting ions have also been discussed. Lastly, the article also proposed the prospects for developing the application of Fe-based MOF in treating As-contaminated water.

NH2-functionalized metal-organic frameworks (NH2-functionalized MOFs) can abate organic pollutants, predominantly favored by their chemical, mechanical, and thermal stabilities. The present review stated the chemistry of identifying NH2-functionalization and its role in enhancing the properties of bare MOFs. The integration of the amine group bestows several advantages: 1.) enabling band structure modification, 2.) establishing strong metal-NH2 bonds, 3.) preserving MOF structures from reactive oxygen species, and 4.) shielding MOF structures against pH alterations. Consequently, the NH2-functionalized MOFs are promising materials for the photodegradation of organic contaminants. The following section illustrates the two approaches (pre-synthetic and post-synthetic) for NH2-functionalized MOFs. Nevertheless, specific intrinsic limitations, entailing a high recombination rate of charge carriers and inadequate optical adsorption, restrain the applicability of NH2-functionalized MOFs. Accordingly, the succeeding segment presents strategies to elevate the photocatalytic activities of NH2-functionalized MOFs via heterojunction fabrication. The importance of the NH2-functionalized MOFs-based heterojunction has been evaluated in terms of the effect on the enhancement of charge separation, optical adsorption, and redox ability of charge carriers. Subsequently, the potential application for organic pollutant degradation via NH2-functionalized MOFs-based heterojunctions has been scrutinized, wherein the organic pollutants. Eventually, the review concluded with challenges and potential opportunities in engaging and burgeoning domains of the NH2-functionalized MOFs-based heterojunctions.

Silver tungstate (Ag2WO4) as a captivating visible light active photocatalyst, is non-toxic in nature, chemically stable and possess good thermal stability. Extensive researcheshave lately centred on Ag2WO4 photoactivity for wastewater treatment. However, bare Ag2WO4 photocatalyst always showed low adsorption and high recombinant rate which inhibited its proficiency to work as a photocatalyst. So, recently, many advancement strategies have been introduced to overcome these difficulties such as doping, surface modification, conventional heterojunction, Z-scheme, and S-scheme heterojunction. But, in recent times, modern strategies including Z-scheme and S-scheme have attained typical consideration due to improved charge migration, and excellent light capture capability as well as longer the spatial life time of photocarriers while keeping the appropriate redox capability. So, this review offers an overview of current state-of-the-art in Ag2WO4-based heterojunctions and providing the insightful comments on the fabrication of these heterostructures. This review primarily focuses on structural and electronic properties via theoretical studies (DFT studies) as well as various synthesis methods to construct heterojunction of Ag2WO4. Also, exploration of different experimental approaches was done which provide confirmation for the operation of photocarriers migration between Ag2WO4 with another component. In addition, instances demonstrating the enhanced efficiency of Ag2WO4-based Z-scheme and S-scheme heterojunctions for several crucial photocatalytic processes includes dye colourization, antibiotic deterioration, heavy metal ions reduction, and bacterial disinfection. Designing rational Ag2WO4 heterojunction with small size particles and controlled morphology for suitable interfacial contact has received especial attention. Finally, the shortcomings of current research on Ag2WO4 based heterojunction photocatalysts are reviewed and prospected.