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The development of high-efficiency photocatalysts is an attractive strategy for pollutants degradation under visible light. Herein, novel photocatalysts are reported through coupling Sb2MoO6 with g-C3N4 nanotube (abbreviated as GCN nanotube) by a simple reflux method. Also, the nanocomposites were defined by applying various analyses. Under visible-light excitation, the GCN nanotube/Sb2MoO6 systems had more photoactivity than g-C3N4 (abbreviated as GCN) and the rate constant for RhB removal on optimal GCN nanotube/Sb2MoO6 (30%) nanocomposite was 48.3 times premier than the GCN. Also, compared to the pristine GCN, the GCN nanotube/Sb2MoO6 (30%) sample demonstrated supreme photoactivity towards tetracycline degradation and Cr (VI) photoreduction, which was 88.5 and 21.8 times higher than the bulk GCN, respectively. These impressive enhancements were attributed to the quick segregation of charge carriers, boosted visible-light absorption, and extended specific surface area. Moreover, the photocatalyst has enough activity after four successive cycles. Finally, a conceivable charges transfer route is presented through n-n heterojunction constructed between Sb2MoO6 and GCN nanotube.

Herein, graphitic carbon nitride nanosheets (signified as CN-NS) were anchored with Ag3BiO3 and carbon dots (abbreviated as CDs) by hydrothermal procedure with appreciably promoted photoactivity towards elimination of several contaminants. The CN-NS/CDs/Ag3BiO3 (30%) system, as optimal photocatalyst, demonstrated extremely high elimination efficiency for several pollutants such as methylene blue (MB), malachite green (MG), Rhodamine B (RhB), and methyl orange (MO) under visible light, which is 55.5, 36.5, 39.2, and 32.1 folds premier than CN material, respectively. Besides, PL, EIS, and transient photocurrent response data corroborated that the CN-NS/CDs/Ag3BiO3 (30%) material has the highest charge carriers segregation efficiency compared with the pure and binary systems. Energy band structure analysis demonstrated that the improved performance of CN-NS/CDs/Ag3BiO3 photocatalyst is allocated to Z-scheme heterojunction. Scavenging tests demonstrated that h+, •OH, and •O2− are the crucial species in the RhB degradation. Enhancement of elimination ability can be allocated to more generation of the charge carries and improvement of the segregation rate of them promoted through the Z-scheme mechanism.

In the present work, ZnO/Bi4O5I2 nanocomposites were constructed through refluxing procedure. The Nyquist plot, transient photocurrent response, and photoluminescence analyses affirmed enhancement in carrier segregation efficiency in the fabricated nanocomposite. The results exhibited that the ZnO/Bi4O5I2 (20%) nanocomposite demonstrates the best efficiency for the degradation of various pollutants, as compared to the single samples under visible light. The photoactivity of the ZnO/Bi4O5I2 (20%) photocatalyst is nearly 8.09, 26.1, 8.18, 10.4, and 19.2-times premier than that of the ZnO for decontamination of fuchsine, MB, MO, RhB, and phenol respectively. Furthermore, the ameliorated ability of the ZnO/Bi4O5I2 (20%) system is 2.45, 3.25, 2.28, 2.96, and 2.84 times higher relative to the ZnO/BiOI (20%) photocatalyst in elimination of fuchsine, MB, MO, RhB, and phenol, respectively. The boosted efficiency is because of the extension of absorption towards visible area, enhanced surface area, and more charge segregation in binary system. Moreover, with various quenchers, the outcomes of scavenging tests illustrated that ⦁O2−, ⦁OH, and h+ have considerable role in the photocatalytic removal process and the inhibition extent is as BQ > 2-PrOH > AO. Also, the ZnO/Bi4O5I2 (20%) nanocomposite possessed significant recycle efficiency, whose utilization had almost no significant change up to four consecutive cycles.

Novel ZnO/AgFeO2 nanocomposites are reported and utilized to activate persulfate (PS) ions to increase contaminant degradation under visible light. For this purpose, the ZnO/AgFeO2 photocatalysts were obtained by a facile hydrothermal procedure. The resultant materials were studied by various techniques and the ZnO/AgFeO2 (20%) photocatalyst showed premier degradation performance for methylene blue (MB), Congo red (CR), methyl orange (MO), and rhodamine B (RhB) in the presence of PS. Nearly 100% of RhB was degraded in 150 min using the ZnO/AgFeO2 (20%) nanocomposite in the presence of PS, while only 15.9%, 70.0%, and 46.9% of RhB were removed on the pure ZnO, ZnO/PS, and ZnO/AgFeO2 (20%) nanocomposite, respectively, which represents that there is synergistic effect of visible-light photocatalysis and PS activation within the ZnO/AgFeO2 (20%) nanocomposite. The improved photoactivity of the resultant photocatalyst was ascribed to the activation of PS ions by photoinduced electrons to generate sulfate radicals (·SO4−), more harvesting of visible light by AgFeO2, the improved separation of charges, and larger surface area. The results of this work accent that the novel ZnO/AgFeO2 nanocomposite can be utilized as an efficacious visible-light-induced photocatalyst for water treatment.

Novel TiO2/Bi3O4Br nanocomposites were prepared by hydrothermal approach to develop effective photocatalysts upon visible light for removal of contaminants from water. Different instruments have been used for characterization of physiochemical attributes of the photocatalysts. The results of photocatalytic reactions showed that the binary TiO2/Bi3O4Br (30%) heterostructure, in comparison with TiO2 and TiO2/BiOBr (30%), has excellent photocatalytic ability in the elimination of Rhodamine B (RhB). Additionally, the binary TiO2/Bi3O4Br (30%) photocatalyst exhibited superior activity towards degradations of tetracycline (TC), methylene blue (MB), and malachite green (MG). The capability of the TiO2/Bi3O4Br (30%) nanocomposite in degradation of MG, RhB, MB, and TC is 25.8, 70.1, 65.8, and 11.8-folds greater than TiO2 and 6.9, 22.6, 11.4, and 6.5 times premier than Bi3O4Br, and 2.0, 14.3, 1.50, and 1.80 times as much as TiO2/BiOBr (30%), respectively. The superoxide anion radicals, and also holes play main role during the photodegradation reactions. Such a high performance was ascribed to the facile segregation and migration of photogenerated charge carriers and extended light absorption range to visible light. This study can provide a novel method for the facile preparation of visible-light-promoted photocatalysts using TiO2 to remedy wastewater.

Herein, novel ZnO/CuBiS2 photocatalysts with p-n heterojunction were fabricated by a facile hydrothermal method and they were utilized for activation of potassium persulfate (KPS) to improve photodegradation of different pollutants under visible light. After adding KPS, ZnO/CuBiS2 (5.0%)/KPS system represented an efficient performance for degradation of Congo red (CR), Fuchsine, rhodamine B (RhB), and methyl orange (MO). The outcomes exhibited that RhB could be almost completely eliminated in 180 min, while only 17.2%, 71.4%, and 60.1% of RhB were degraded on the pristine ZnO, ZnO/KPS, and ZnO/CuBiS2 (5.0%) sample, respectively. Hence, the synergistic impact of KPS and heterogeneous photocatalysis were corroborated by the ZnO/CuBiS2 (5.0%) nanocomposite in the degradation reactions. The radical quenching tests indicated that •O2−, •SO4−, h+, and •OH all contribute to eliminate pollutants. Additionally, the ZnO/CuBiS2 (5.0%)/KPS system exhibited prominent reusability in the photocatalytic reaction system.

In the present work, ZnO/CuCo2O4 nanocomposite was successfully synthesized through a hydrothermal process and utilized for persulfate (PS)-promoted photocatalytic mitigation of tetracycline hydrochloride (TC) and three dye pollutants under visible light. The characterization of materials was performed by various techniques. Among the binary photocatalysts, the ZnO/CuCo2O4 (20%) nanocomposite represented considerable photocatalytic ability to eliminate the selected contaminants. The degradation constant of TC on the ZnO/CuCo2O4 (20%)/PS system was nearly 29.9, 45.7, 23.5, and 18.4-folds as large as the PS, ZnO, ZnO/PS, and ZnO/CuCo2O4 (20%) systems, respectively. The enhanced photocatalytic ability of the ZnO/CuCo2O4 (20%)/PS system can be related to more visible-light absorption, efficacious electrons transfer resulting from the construction of p-n heterojunction among ZnO and CuCo2O4, and activation of PS to generate sulfate radicals. It is anticipated that this study could provide new visions for the preparation and utilization of efficacious heterogeneous photocatalysts for impressive activation of PS to be utilized for remediation of polluted water with antibiotics and dye contaminants.

The construction of efficient photocatalysts based on TiO2, with sever activity under visible light, has gained significant attention for the treatment of water contaminations. Therefore in this work, Bi2SiO5 nanoparticles were combined with TiO2 to fabricate binary TiO2/Bi2SiO5 nanocomposites with n-n heterojunction using a facile hydrothermal method. The performance of TiO2/Bi2SiO5 photocatalysts was assessed by the degradation of Malachite green, Fuchsine, methyl orange, Congo red, and Rhodamine B contaminants under visible light. The results of photocatalytic experiments revealed that TiO2/Bi2SiO5 photocatalysts have an outstanding potency in the removal of these organic contaminants. The best photocatalytic ability was observed for the TiO2/Bi2SiO5 (5%) nanocomposite with the activity of 4.5, 4.6, 7.1, 5.2, and 6.6 times as much as Bi2SiO5 and 9.2, 11.2, 17.5, 10.9, and 16.7 folds greater than TiO2 in the degradation of Fuchsine, Malachite green, methyl orange, Congo red, and Rhodamine B contaminants, respectively. The suppression of charges through the formation of n-n heterojunction, enhanced visible-light absorption, and boosted surface area have caused improvement in the photocatalytic activity TiO2/Bi2SiO5 nanocomposites. Moreover, the TiO2/Bi2SiO5 (5%) nanocomposite exhibited good photostability. This study suggests efficient design of visible-light-responsive photocatalysts based on TiO2, which could have appropriate potential in sewage treatment.

Conversion of carbon dioxide (CO2) to value-added products is imperative to combat global warming. In this regard, herein we report a metal-free heterogeneous catalyst, boron-doped graphitic carbon nitride for effective conversion of CO2 to cyclic carbonates at atmospheric pressure under solvent-free conditions. The developed catalyst possesses acid-base dual functionality as active sites, which activate both epoxides as well as CO2 simultaneously to carry out the cycloaddition reaction. The catalyst showed a maximum yield up to 99 % with a turnover number of 173. Detailed optimization studies have been performed to find out the best doping content of boron and best conditions by varying the reaction time, temperature and catalysts amount. Furthermore, the ease of catalyst recovery and excellent recyclability demonstrate the sustainability and versatility of the catalyst for selective and efficient conversion of CO2 to cyclic carbonates at mild conditions.

The water pollution caused by releasing widespread organic dyes into wastewater is one of the most important concerns affecting the human life. Providing visible-light-responsive photocatalysts based on TiO2 can be noticed as a promising approach for the remedy of water contaminations. Herein, Bi5O7I nanoparticles were integrated with TiO2 to establish efficient TiO2/Bi5O7I heterojunction photocatalysts with the aid of hydrothermal method. Several complementary analyses of XRD, SEM, EDS, BET, photocurrent density, UV–vis DRS, TEM, HRTEM, PL, EIS, and XPS were applied to investigate the structure, texture, optical feature, and charge transfer efficiency of the as-prepared photocatalysts. The obtained results of the mentioned analyses revealed that the Bi5O7I particles have been successfully introduced to the surface of TiO2. The photocatalytic property of TiO2/Bi5O7I nanocomposites was evaluated by the elimination of fuchsine, MB, MO, and RhB pollutants under visible light. According to the photocatalytic tests, the binary photocatalysts manifested a prominent ability in the degradation of these pollutants than the single components. The outstanding photocatalytic ability belonged to the TiO2/Bi5O7I (15%) sample. The photocatalytic performance of TiO2/Bi5O7I (15%) was 3.8, 4.1, 3.6, and 15.1 times more than Bi5O7I and 16.8, 14.8, 18.4, and 50.5 times premier than TiO2 in the elimination of MB, fuchsine, MO, and RhB contaminants, respectively. The charge separation efficiency of the electron-hole pairs in TiO2/Bi5O7I photocatalysts was confirmed by photoelectrochemical tests. The increased surface area, boosted visible-light absorption, as well as extended lifetime of photogenerated charges have led to enhanced photocatalytic efficiency in the TiO2/Bi5O7I nanocomposites. Based on the radical trapping tests, the h+ and •O2− identified as the active species in the degradation reaction. A possible photocatalytic mechanism and photo-degradation pathway were proposed based on the outcomes obtained from the trapping experiments and photoelectrochemical analysis. Moreover, the TiO2/Bi5O7I samples exhibited good photostability over four cycles. This work presented that the TiO2/Bi5O7I photocatalysts can be a proper candidate for environmental purification.

In this work, novel TiO2/FeOCl photocatalysts were prepared trough calcination process and they were utilized as visible-light-induced photocatalysts for eliminating various pollutants in the presence of persulfate (PS) ions. Structural, morphological, photoelectrochemical, textural, and optical features of the obtained photocatalysts were extensively analyzed. The experimental outcomes illustrated that the weight percentage of FeOCl has significant impact on the photodegradation capability of the nanocomposites and the TiO2/FeOCl (20%) photocatalyst has the best photocatalytic efficiency in degradation of methylene blue (MB), methyl orange (MO), rhodamine B (RhB), and fuchsine. The elimination rate constant of RhB over the TiO2/FeOCl (20%) photocatalyst in the existence of 1.48 mM of PS ions was almost 36.1, 10.9, 8.5, and 24.8-times larger than the pure TiO2, PS ions, TiO2/PS, and TiO2/FeOCl (20%) sample, respectively. The improved photocatalytic ability was assigned to the more absorption of visible light and more inhibition of the charge carriers from recombination. Lastly, based on the heterojunction formation at the interface of n-TiO2, and n-FeOCl semiconductors, the photocatalytic mechanism in the presence of PS ions was discussed.