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Highlights • A novel Bi 2 S 3 @Bi 2 WO 6 /WO 3 ternary composite displayed boosted photocatalytic activity. • A novel Z-scheme/traditional ternary heterojunction system was presented. • The synergistic effect of heterojunction and oxygen vacancy was proposed. Abstract Both the fabricating of heterojunction and oxygen vacancy are the effective methods for boosting the performance of semiconductor photocatalyst. However, the fast recombination of charge carriers and limited light absorption in ubiquitous binary heterojunction are still inherent problems that hinder the practical application of photocatalysts. Herein, a ternary heterojunction of Bi 2 S 3 @Bi 2 WO 6 /WO 3 was fabricated by the facile hydrothermal route combining with an in-situ growth method, and was confirmed by employing elemental mapping and high-resolution transmission electron microscopy. The oxygen vacancy was introduced into Bi 2 S 3 @Bi 2 WO 6 /WO 3 ternary heterojunction as demonstrated by X-ray photoelectron spectroscopy. Compared with Bi 2 S 3 and Bi 2 WO 6 /WO 3 samples, the obtained Bi 2 S 3 @Bi 2 WO 6 /WO 3 composites exhibited higher photocatalytic activity in photodegrading rhodamine B and Tetracycline. The high photocatalytic activity was attributed to the synergistic effect of Z-scheme/traditional heterojunction and oxygen vacancy that extended the visible-light absorption range and promoted the effective separation of photo-generated electron–hole pairs. Based on the trapping experiments and calculated positions of energy band, the photocatalytic mechanisms of the Z-scheme/traditional heterojunction with oxygen vacancy were also proposed. Graphical abstract Brief synopsis: A novel synergistic effect between Z-scheme/traditional heterojunction and oxygen vacancy to design a high-efficiency Bi 2 S 3 @Bi 2 WO 6 /WO 3 ternary photocatalyst. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Substitutive doping is a fundamental approach to introduce dopants into a crystalline structure, which resulted in generating the abundant redox centers or oxygen vacancies to promote the separation of photogenerated charge carriers. However, the recombination rate of electron–hole pairs in the single-substituted photocatalysts remained high, thus co-substituting of two sites could be further synergistically restraining the recombination of electron–hole pairs. Herein, the bismuth molybdate (Bi 2 MoO 6 ) photocatalyst, co-substituted by Gd 3+ and W 6+ ions for Bi 3+ and Mo 6+ ions, was synthesized using a hydrothermal method. X-ray photoelectron spectra indicated that the abundant oxygen vacancies were generated in the crystalline Bi 2 MoO 6 after introducing W 6+ ions, and these vacancies adsorbed the extensive O 2 molecules. Additionally, the results of photoluminescence spectra, photocurrent response and trapping experiments demonstrated that the new hydroxyl radicals can be generated by introducing Gd 3+ ions, while the introducing of W 6+ ions contributed to enhancing the productivity of • O 2 − radicals; these two species together promoted the separation and transfer of electron–hole pairs. The results of photocatalytic experiments displayed that Gd/W co-substituted Bi 2 MoO 6 shows much better visible-light photocatalytic activity. These findings developed a novel synergistic effect between redox centers (Gd substitution) and oxygen vacancies (W substitution) to design the high-efficiency photocatalysts. [ABSTRACT FROM AUTHOR]

The in‐built self‐redox couple in a heterojunction can indeed boost its photocatalytic activity. Herein, to obtain highly efficient visible‐light photocatalysis, a new Eu2O3/g‐C3N4 redox heterojunction is designed and fabricated by a facile in situ growth strategy. Compared with pure g‐C3N4, the as‐prepared Eu2O3/g‐C3N4 redox heterojunction shows extremely enhanced photocatalytic performance for the decontamination of organic contaminants under visible‐light irradiation. The presence of the Eu3+/Eu2+ self‐redox couple is identified by X‐ray photoelectron spectroscopy spectra analysis, before and after photoreaction. The boosted photocatalytic mechanism is explored systematically through UV/Vis diffuse reflectance spectroscopy, photoluminescence spectroscopy, and photocurrent measurements. Moreover, the radical trapping and electron paramagnetic resonance experiments reveal that ·O2– and h+ are the main active species, and a small amount of ·OH radical is also generated. The boosted photocatalytic performance is derived from the effective separation of photogenerated e–/h+ pairs by forming a Eu2O3/g‐C3N4 heterostructure with a self‐redox center. In particular, the self‐redox couple of Eu3+/Eu2+ can lead to more effective separation of the photogenerated charge carriers, as well as to sustainable production of ·O2–. It is anticipated that our study could provide new insight into the development of g‐C3N4‐based redox heterojunctions with high visible‐light photocatalytic performance. [ABSTRACT FROM AUTHOR]

Novel Bi2W2O9 and Bi2Mo2O9 with irregular polyhedron structure were successfully synthesized by a hydrothermal method. Compared to ordinary Bi2WO6 and Bi2MoO6, the modified structure of Bi2W2O9 and Bi2Mo2O9 were observed, which led to an enhancement of photocatalytic performance. To investigate the possible mechanism of enhancing photocatalytic efficiency, the crystal structure, morphology, elemental composition, and optical properties of Bi2WO6, Bi2MO6, Bi2W2O9, and Bi2Mo2O9 were examined. UV-Vis diffuse reflectance spectroscopy revealed the visible-light absorption ability of Bi2WO6, Bi2MO6, Bi2W2O9, and Bi2Mo2O9. Photoluminescence (PL) and photocurrent indicated that Bi2W2O9 and Bi2Mo2O9 pose an enhanced ability of photogenerated electron–hole pairs separation. Radical trapping experiments revealed that photogenerated holes and superoxide radicals were the main active species. It can be conjectured that the promoted photocatalytic performance related to the modified structure, and a possible mechanism was discussed in detail. [ABSTRACT FROM AUTHOR]

Novel g-C 3 N 4 @Bi/BiOBr ternary heterostructured composites were successfully fabricated by a facile solvothermal method, in which ethylene glycol functioned as both a solvent and a reductant. As observed by scanning electron microscopy (SEM), Bi/BiOBr nanoplates were embedded on the surface of layered g-C 3 N 4 to form three-dimensional hierarchical structure. Under visible-light irradiation, the ternary g-C 3 N 4 @Bi/BiOBr composites displayed notably boosted photocatalytic performance for photodegrading tetracycline and rhodamine B. As revealed via the UV–visible diffuse reflection spectra (UV–vis DRS) and photocurrent experiments, the three-dimensional hierarchical structure obviously enhanced the visible-light photoresponse and the ternary heterojunction greatly promoted the separation of photo-induced carriers, thus leading to the high photocatalytic performance. Based on the results of trapping radical experiments and the energy band potentials, an indirect Z-scheme system was proposed to illuminate the possible photodegradation mechanism. This work provides a novel strategy to design the multiple heterostructured photocatalysts with high efficiency for environmental purification and energy conversion. A novel Z-scheme heterojunction was designed to obtain a high-efficiency g-C 3 N 4 @Bi/BiOBr ternary photocatalyst. Image 1 • A novel g-C 3 N 4 @Bi/BiOBr ternary composites displayed boosted photocatalytic activity. • A novel indirect Z-scheme heterojunction system was presented. • Efficient photocatalyst was fabricated combining with multiple methods. [ABSTRACT FROM AUTHOR]

Highlights • Gd/Er/Lu co-doping enhances the photocatalytic activity of Bi 2 MoO 6. • The oxidizing ability, light absorption, and separation have all been improved by co-doping. • A new synergistic effect of redox center, upconversion & oxygen vacancy is developed. • All the oxidizability, light absorption and charge separation have been boosted. • Lanthanide ion triple doping is a new approach to boost photocatalytic activity. Abstract Lanthanide doping is an effective and controllable approach for optimizing the oxidation ability, light absorption and charge separation of photocatalysts. However, the multiple drawbacks of mono-component photocatalysts have not been adequately resolved by the doping of only one or two lanthanide ions. Herein, a novel Gd/Er/Lu-triple-doped Bi 2 MoO 6 photocatalyst was synthesized using a hydrothermal method. The results of trapping and 4-Chlorophenol degradation experiments suggested that the oxidizing efficiency of Bi 2 MoO 6 was clearly enhanced by the generation of hydroxyl radicals after doping with the Gd3+ redox centers. The obtained diffuse reflectance spectra demonstrated that introducing Er3+ ions provides energy upconversion centers to improve light absorption. The obtained X-ray photoelectron and photoluminescence spectra demonstrated that abundant oxygen vacancies were produced in the Bi 2 MoO 6 crystal after the doping of Lu3+ ions, contributing to promoting the separation of charge carriers. In summary, Gd/Er/Lu-triple-doped Bi 2 MoO 6 displays much better photocatalytic performance than single- and double-doped Bi 2 MoO 6 materials, which is attributed to the synergistic effects of the Gd3+, Er3+ and Lu3+ ions. These discoveries demonstrate a novel synergistic effect of the redox centers (Gd3+ doping), energy upconversion (Er3+ doping) and oxygen vacancies (Lu3+ doping) for the design and fabrication of high-efficiency photocatalysts. [ABSTRACT FROM AUTHOR]

Graphical abstract A novel heterojunction between Bi 2 O 2 CO 3 and Ag 2 CrO 4 was proposed, which contributed to designing a high-efficiency Ag 2 CrO 4 /Bi 2 O 2 CO 3 photocatalyst. Highlights • Faracation of Ag 2 CrO 4 /Bi 2 O 2 CO 3 heterojunction can boost the photocatalytic activity. • The heterojunction make for enhanced charge separation and light absorption. • The possible mechanism for improved photocatalytic activity was discussed in detail. Abstract In this study, Ag 2 CrO 4 /Bi 2 O 2 CO 3 composites were synthesized through a simple chemical precipitation process. XRD, SEM, TEM and XPS characterization suggested that the close heterojunction successfully formed between Ag 2 CrO 4 and Bi 2 O 2 CO 3. Diffuse Reflectance Spectra (DRS) experiments suggested that Ag 2 CrO 4 /Bi 2 O 2 CO 3 composites had a wide light absorption band throughout the whole visible light region. The photoluminescence spectra (PL) implied that the formation of the heterojunction notably suppressed the recombination of photo-generated electron-hole. The excellent photocatalytic activity of Ag 2 CrO 4 /Bi 2 O 2 CO 3 heterojunction for the degradation of RhB, MO and MB should be ascribed to both the wide visible-light absorption and the efficient separation of photo-generated electron-hole. In addition, the possible mechanism for the enhanced photocatalytic activity was also proposed. [ABSTRACT FROM AUTHOR]

The ternary heterojunction of silver bromide@bismuth tungstate/tungsten trioxide (AgBr@Bi 2 WO 6 /WO 3 ) was designed and synthesised by hydrothermal and deposition–precipitation approaches. The composites were characterised by X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy (XPS). The photoabsorption range and bandgaps of the photocatalysts were analysed by ultraviolet-visible diffuse reflectance spectroscopy (UV–vis DRS). Compared with Bi 2 WO 6 /WO 3 or AgBr alone, the AgBr@Bi 2 WO 6 /WO 3 composites displayed higher visible-light photocatalytic performance for degrading rhodamine B (RhB). AgBr@Bi 2 WO 6 /WO 3 with 40% AgBr concentration was optimum for photocatalytic activity. Radical-trapping experiments revealed that superoxide anion radicals ( O 2 − ) and holes (h + ) were the active species during photocatalytic degradation and that O 2 − was the dominant active species. Therefore, the increased photocatalytic activity of AgBr@Bi 2 WO 6 /WO 3 was attributed to the atypical double Z-scheme system, which effectively improved the transfer and separation of electron–hole pairs in ternary heterojunction structures. [ABSTRACT FROM AUTHOR]

A new Pt nanoparticles decorated Gd-doped Bi 2 MoO 6 photocatalyst was synthesized by the hydrothermal process and in-situ reduction method. The crystal structure, morphology, chemical state and optical property of the obtained photocatalysts were investigated. The activities of photocatalysts were also evaluated by the degradation of Rhodamine B, Tetracyclines and 4-Chlorophenol under visible light irradiation, and the results indicated that the Gd/Pt co-modified Bi 2 MoO 6 sample shows better photocatalytic activity. Meanwhile, the results of trapping experiments and Electron Spin Resonance (ESR) spectra demonstrated that the OH radicals can be formed by doping of Gd 3+ ions, and the addition of Pt was conducive to the producing of more • O 2 − and OH radicals. Also the results from the degradation of 4-chlorophenol implied that the formed OH radicals in the system of Gd/Pt-BMO possess stronger oxidizability than • O 2 − radicals for degrading the special organics which are difficult to be mineralized. Additionally, the mechanism about the excellent photocatalytic activity of Gd/Pt co-modified Bi 2 MoO 6 was also discussed. [ABSTRACT FROM AUTHOR]

Various Ln a /Ln b co-doped bismuth molybdate (Bi 2 MoO 6 ) photocatalysts were synthesized by a hydrothermal process. The result of photocatalytic experiment demonstrated that the relevant Ln 1 3+ 4 f 7+x /Ln 2 3+ 4 f 7−x (Ln 1 /Ln 2 = Tb/Eu, Dy/Sm, Er/Nd; x = 1, 2, 4) co-doped Bi 2 MoO 6 samples shows higher photocatalytic activities. Moreover, all the photocatalytic activities of Ln 1 /Ln 2 co-doped Bi 2 MoO 6 were higher than that of the corresponding single-doped Bi 2 MoO 6 . The crystalline structures, morphology, constituent contents, chemical state and optical properties of the samples were analyzed in detail. Meanwhile, a new conjecture about the complementary distribution of 4 f orbital electrons in the Ln 1 /Ln 2 redox couple was proposed through co-doping with Ln 1 and Ln 2 ions to improve the photocatalytic activity of Bi 2 MoO 6 . For the Bi 2 MoO 6 photcatalyst, Dy/Sm co-doping displayed the strongest photocurrent response as well as the best photocatalytic activity, while Tb/Eu co-doping displayed the apparently extended visible-light absorption region. These findings provides a novel strategy to fabricate and engineer high-efficiency photocatalysts by selecting appropriate Ln 1 /Ln 2 redox couple. [ABSTRACT FROM AUTHOR]

Lanthanide titanate (La 2 Ti 2 O 7 ) with strong reduction-oxidation ability has been regarded as a new promising photocatalyst. To boost its photocatalytic activity, g-C 3 N 4 /La 2 Ti 2 O 7 composites were designed and constructed. The results reveal that La 2 Ti 2 O 7 nanosheets were well attached to the surface of g-C 3 N 4 and the composites had good visible-light absorption properties. Significantly, compared to pure La 2 Ti 2 O 7 and g-C 3 N 4 , the composites exhibited outstanding photocatalytic performance under visible-light irradiation. The enhanced photocatalytic activity could be derived from the effective transportation of photogenerated electrons from g-C 3 N 4 to La 2 Ti 2 O 7 . The electrons with high reduction ability can generate more active species to participate in the photodegradation reaction. [ABSTRACT FROM AUTHOR]

A new acting mechanism of oxygen vacancy that effected on the charge separation and light absorption in Lu-doped Bi 2 MoO 6 was proposed, and the formed oxygen vacancies resulted in improving photocatalytic activity. [Display omitted] • Doping of Lu3+ could obviously improve the photocatalytic activity of Bi 2 MoO 6. • The shape transformed from nanosheet to nanorod due to the exposed {0 1 0} facets. • The oxygen vacancies were formed in the lattice of Lu-doped Bi 2 MoO 6. • The formed oxygen vacancy make for enhanced charge separation and light absorption. Lu-doped Bi 2 MoO 6 nanosheets were successfully synthesized by a hydrothermal process. The morphology of Bi 2 MoO 6 can be controlled from nanosheets to nanorods by doping different content of Lu3+, which ascribed to the selectively exposed {0 1 0} facets as the main external surfaces. The results of the first principles calculation and the characterization revealed that the oxygen vacancies were formed in the lattice of Lu-doped Bi 2 MoO 6. What's more, the formed oxygen vacancies played a role in improving charge separation and enhancing light absorption, which confirmed with Photoluminescence spectra (PL) and Diffuse Reflectance Spectra (DRS), respectively. And these results lead to the enhanced photocatalytic activity of Bi 2 MoO 6 for the degradation of RhB and phenol. The introduction of the oxygen vacancies by doping of Lu3+ ions will provide the new strategies to improve the efficiency of photocatalysts. [ABSTRACT FROM AUTHOR]