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The production of singlet oxygen during advanced oxidation processes is restricted by the precise cooperation of photogenerated carriers, energy band potentials, and surface adsorbed oxygen. Herein, we report that an in situ BiVO4/Bi4Ti3O12 S-scheme heterojunction could form oxygen vacancies by constructing crystal defects and effectively produce singlet oxygen by adsorbing oxygen on the surface. Moreover, the novel S-scheme heterojunction not only facilitates the separation of charge carriers, but also accumulates photogenerated electrons on the conduction band of the BiVO4 nanosheet, and the interaction rate between photogenerated electrons and oxygen adsorption on the surface is improved, which tremendously prolongs the life span of the singlet oxygen. Consequently, the selective oxidation of singlet oxygen was examined by the catalysis of the obstinate aromatic hydrocarbon pollutant, and BiVO4/Bi4Ti3O12, which additionally produced the singlet oxygen, showed superior catalytic performance in comparison with the pristine BiVO4. This study overcomes the current limitation of singlet oxygen production and provides a promising strategy for the development of novel catalysts. [ABSTRACT FROM AUTHOR]

• The Tb 2 O 3 /g-C 3 N 4 heterojunction composites were constructed. • The composites reveal excellent photo-degradation efficiency. • The Tb4+/Tb3+ redox center promote the charge carriers separation. • The yield of hydroxyl radical was increasing sharply. • The possible mechanism of material was systematically discussed. Recently, the issue of environmental pollution by wastewater containing dye molecules attracted researcher's attention. It is urgent that seeking high efficiency visible-light driven photocatalyst leads to mitigating environmental contamination. In this work, the novel Tb 2 O 3 /g-C 3 N 4 composite photocatalysts have been successfully synthesized, and the enhanced photocatalytic performance has been thoroughly discussed based on the fully characterization. The X-ray diffraction and scanning electron microscopy exhibited crystalline phases and morphologies of obtained samples. The chemical states and composition of composite photocatalysts were characterized by the X-ray photoelectron spectrometer. The photoluminescence and photocurrent results proved that Tb 2 O 3 /g-C 3 N 4 composite samples possessed higher separation efficiency than that of pure C 3 N 4. The decomposition of organic contaminant and cycle experiment demonstrated that 0.8%Tb 2 O 3 /g-C 3 N 4 composite photocatalyst possessed the best photo-degradation performance and had a good chemical stability. The trapping experiment illustrated that the significantly elevated photocatalytic performance could attribute to the loading of Tb 2 O 3. The in-built redox centers of Tb4+/Tb3+ efficiently promoted the utilization of photo-generated electrons and proliferated the hydroxyl radical. Simultaneously, the mechanism of enhanced photocatalytic performance of obtained composite samples was proposed. This work provides a promising strategy to design novel visible-light-driven photocatalysts and further improve the photocatalysis mechanism survey. The as-prepared Tb 2 O 3 /g-C 3 N 4 composite heterojunction semiconductor exhibited higher photocatalytic activity by degrading organic pollutant under visible light illumination and 0.8%Tb 2 O 3 /g-C 3 N 4 presented the best photo-degradation properties compare with other samples. The degradation efficiency of 0.8%Tb 2 O 3 /g-C 3 N 4 was 1.5 times higher than that of pure C 3 N 4. According to a series of experimental characteristic analysis, it proved that the heterojunction was successfully formed and the existence of Tb 2 O 3 dramatically improved photo-activity of C 3 N 4. The enhanced photocatalytic performance for Tb 2 O 3 /g-C 3 N 4 could be attributed to two aspects: (i) inhibit charge carriers recombination, (ii) the formation of redox center (Tb4+/Tb3+), raise yield of .OH. This work not only provides a thought of high efficiency visible-light-driven photocatalyst, but also further expounds mechanism of action. [Display omitted] [ABSTRACT FROM AUTHOR]

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]

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]

The charge transfer mechanism of S-scheme heterojunction and hot electron injection process of Bi metal synergistically drove the photocatalytic hydrogen generation by non-noble metal Bi/Bi 2 MoO 6 /ZnIn 2 S 4 photocatalyst. [Display omitted] • The ternary Bi/Bi 2 MoO 6 /ZnIn 2 S 4 S-scheme heterojunction photocatalyst was successfully synthesized via hydrothermal method. • The optimum photocatalytic hydrogen production of Bi/Bi 2 MoO 6 /ZnIn 2 S 4 was 2306.90 µmol g−1 in 5 h under visible light illumination, which was about 4.3, 29.6 and 2.2 times more than those of original ZnIn 2 S 4 , Bi 2 MoO 6 /ZnIn 2 S 4 and Pt/ZnIn 2 S 4 , respectively. • The outstanding hydrogen production performance of the ternary photocatalyst may be attribute to its broad light absorption, more reactive sites and superior carriers separation. • The charge transfer mechanism of S-scheme heterojunction and hot electron injection process of Bi metal synergistically drove the photocatalytic hydrogen generation. Novel Bi/Bi 2 MoO 6 /ZnIn 2 S 4 is not only cost-effective compared to noble metals, but also shows superior hydrogen production. Comprehensive characterization illustrated that the S-scheme heterojunction and excellent photon utilization capability of the photocatalyst were the main factors that enhanced its hydrogen production performance. The X-ray photoelectron spectroscopy illustrated the elemental composition of the catalyst and the presence of Bi metal in ternary heterojunction. The photoluminescence and electrochemical characterization proved that S-scheme heterojunction Bi/Bi 2 MoO 6 /ZnIn 2 S 4 promoted the separation of photogenerated carriers. The amount of hydrogen produced by Bi/Bi 2 MoO 6 /ZnIn 2 S 4 was 2306.90 µmol g−1 under visible light illumination for 5 h. It was 4.3, 29.6 and 2.2 times more than those of ZnIn 2 S 4 , Bi 2 MoO 6 /ZnIn 2 S 4 and Pt/ZnIn 2 S 4 , respectively. The excellent hydrogen production activity of the ternary complexes may be attributed to the following: (1) Bi/Bi 2 MoO 6 could replace precious metals to enhance reactive sites of ZnIn 2 S 4. (2) Metal Bi could produce surface plasmon resonance effect facilitating light absorption, and Bi acted as an electron bridge promoting charge transfer. (3) The charge transfer mechanism of S-scheme heterojunction and hot electrons injection process of Bi metal synergistically drove the photocatalytic hydrogen production. This work provides an innovative method for the construction of visible-light-driven photocatalysts without using precious metals. [ABSTRACT FROM AUTHOR]

• All the Ln 2 O 3 -Bi 2 MoO 6 samples efficiently enhanced the photocatalytic performance. • Specific multivalence Ln 2 O 3 loaded samples additionally produced OH. • The productivity of ·OH was dominated by 4f electronic structure of Ln(n+1)+/Lnn+. • The discipline and possible mechanism of radical production have been put forward. • Provided a foundation for fabricating Ln 2 O 3 -heterojunction photocatalysts. In order to reveal the radicals production mechanism and discipline of heterojunction photocatalysts, a series of novel Ln 2 O 3 -Bi 2 MoO 6 (Ln = Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Er, Yb and Lu) were designed and successfully synthesized. The photocatalytic experiments and radical trapping experiments illustrated that all the Ln 2 O 3 -Bi 2 MoO 6 samples efficiently enhanced the photocatalytic performance, and the samples loaded by single valence Ln 2 O 3 (Nd 2 O 3 , Gd 2 O 3 , Dy 2 O 3 , Er 2 O 3 and Lu 2 O 3) could only produce superoxide radicals (·O 2 -), and holes (h+) in the photocatalytic process, and the samples loaded by multivalence Ln 2 O 3 (Ce 2 O 3 , Yb 2 O 3 , Pr 2 O 3 , Sm 2 O 3 , Eu 2 O 3 and Tb 2 O 3) additionally produced the powerful hydroxyl radical (·OH), and further enhanced the photocatalytic performance. Significantly, the Ln 2 O 3 -Bi 2 MoO 6 could produce abundant ·OH and show superior photocatalytic performance when both valence states of multivalence lanthanide ions are unstable 4f electronic structure (4f2, 4f1 in Pr3+, Pr4+ and 4f5, 4f6 in Sm3+, Sm2+), and the possible mechanism of radicals production in different Ln 2 O 3 -Bi 2 MoO 6 heterojunctions system was creatively put forward. This study deeply investigated the production discipline and mechanism of hydroxyl radical in Ln 2 O 3 -Bi 2 MoO 6 heterojunction photocatalysts, and provided a theory foundation for fabricating novel lanthanide oxide loaded photocatalysts. [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]

• A novel noble-metal-free Mo 2 C-In 2 S 3 photocatalyst was synthesized by hydrothermal method. • Mo 2 C facilitates the separation of charge carriers and extends the visible light absorption of In 2 S 3. • The H 2 generation rate of the optimal Mo 2 C-In 2 S 3 composite was 25.8 times higher than In 2 S 3 -1% Pt. • The possible photocatalytic hydrogen production mechanism was discussed. Currently, designing novel noble-metal-free photocatalysts with efficient carriers migration and catalytically active sites have been a researching hotspot in photocatalytic hydrogen evolution. In this paper, a novel noble-metal-free Mo 2 C-In 2 S 3 heterojunction was synthesized by a simple hydrothermal method. Morphology characterization revealed In 2 S 3 was attached to Mo 2 C. Electrochemical results showed Mo 2 C improved the interface conductivity, and promoted the transportation of photogenerated carriers. Under visible light, the optimal Mo 2 C-In 2 S 3 composite achieved a H 2 generation rate of 535.58 μmol h−1 g−1, which was 175.6 and 25.8 times higher than pristine In 2 S 3 (3.05 μmol h−1 g−1) and In 2 S 3 -1% Pt (20.73 μmol h−1 g−1). In addition, a reasonable mechanism of the elevated photocatalytic activity was also discussed. This study demonstrates commercial Mo 2 C has an important effect of separating carriers and replacing Pt as co-catalyst in heterojunctions. This research also provides a method to design and synthesize new noble-metal-free photocatalysts for excellent hydrogen production activity. [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]

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]

In this study, a novel SnS 2 /BiOBr heterojunction photocatalyst was synthesized via a facile in-situ growth strategy. The heterojunction interface was formed by loading BiOBr nanosheets on the surface of ultrathin hexagonal SnS 2 nanoplates. UV/Vis diffuse reflectance spectroscopy (DRS) indicated that SnS 2 /BiOBr composites possessed stronger visible-light absorption. The as-fabricated SnS 2 /BiOBr heterojunction nanoplates exhibited considerable improvement in terms of photocatalytic activity for the degradation of rhodamine B (RhB) under visible light irradiation as compared with BiOBr and SnS 2 . The enhanced photocatalytic activity was attributed to the closely contacted interface between BiOBr and SnS 2 , thereby resulting in faster transfer of the photoinduced electron–hole pairs through their interface, as shown by the results of photoluminescence spectroscopy (PL) and photocurrent measurements. Radical trapping experiments demonstrated that holes (h + ) and superoxide anion radicals ( O 2 − ) were the main active species in the photocatalytic oxidation process. The mechanism of the excellent photocatalytic activity of SnS 2 /BiOBr heterojunction composite was also discussed. [ABSTRACT FROM AUTHOR]

In this study, a novel Bi 2 O 2 CO 3 /BiOBr p-n heterojunction was synthesized via a two-step solvothermal method. The p-n interface was formed by loading Bi 2 O 2 CO 3 nanoparticles on the surface of BiOBr nanosheets. The crystal structure, morphology, and optical property of the as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and UV–vis diffuse reflectance spectroscopy, respectively. The obtained Bi 2 O 2 CO 3 /BiOBr p-n heterojunction composites exhibited the superior photocatalytic activity for the degrading rhodamine B (RhB) under visible light irradiation as compared with Bi 2 O 2 CO 3 and BiOBr. Four times cycling experiments demonstrated that the composites had good photostability and recyclability. The enhanced photocatalytic activity of Bi 2 O 2 CO 3 /BiOBr composites was mainly attributed to the formation of p-n heterojunction between Bi 2 O 2 CO 3 and BiOBr, thereby resulting in faster transfer of the photoinduced electron–hole pairs through their interface. Radical trapping experiments confirmed that h + and O 2 − were two main active species in the photocatalytic process. The possible mechanism of the enhanced photocatalytic activity was proposed, which revealed the transfer of the charge carriers and the formation of the active species in photocatalytic process. [ABSTRACT FROM AUTHOR]

Direct Z-scheme photocatalyst systems with efficient charge separation as well as outstanding oxidation and reduction ability have been under immense investigation. In our work, direct Z-scheme MoS 2 /Bi 2 WO 6 heterojunctions were prepared by a facile method. The heterostructure was formed by loading MoS 2 nanoparticles on the surface of Bi 2 WO 6 nanosheets. It was found that the as-prepared MoS 2 /Bi 2 WO 6 composites showed superior photocatalytic activity than that of individual MoS 2 and Bi 2 WO 6 . The optimal composite with 4 at% MoS 2 content exhibited the highest photocatalytic activity. Based on the active species trapping experiments, photoluminescence spectroscopy analysis, and photocurrent responses, the possible enhanced photocatalytic mechanism could be ascribed to a direct Z-scheme heterojunction system which can not only increase the separation efficiency of photogenerated electron-hole pairs but also possess a splendid oxidation and reduction ability for high photocatalytic performances. This work provides an effective approach to develop other Bi 2 WO 6 -based direct Z-scheme photocatalytic systems for environmental purification and energy conversion. [ABSTRACT FROM AUTHOR]