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Using density-functional theory (DFT) calculations within the generalized gradient corrected approximation, the models that nonmetallic impurities X (X = C, N, S, F) substituted for O or Ti sites in anatase TiO 2 were investigated. By calculating the formation energy of X-monodoped TiO 2 with X substituted for O, we suggested that X dopants existed as C 4− , N 3− , S 2− and F − ions, respectively. Meanwhile, the X dopants existed as C 4+ , N 3+ , and S 6+ for X-monodoped (X = C, N, S) TiO 2 with X substituted for Ti. The conclusion of the valence states of nonmetallic impurities X substituted for O or Ti sites in TiO 2 is also supported by the results of optimized cell parameters and the local structures. Furthermore, an effective nonmetallic passivated codoping approach to modify the band edges of TiO 2 is proposed. Based on the first-principle calculations, we suggested that nonmetallic passivated groups such as (S 2− + C 4+ ) and (C 4− + S 6+ ) could reduce the band gap largely and make less perturbation in conduction band minima (CBM), thus lead to an ideal visible-light absorption region without affecting the reducing power. This work provides some new results and is anticipated to give some inspiration and guidance for design visible-light-driven TiO 2 photocatalyst with high efficiency. [ABSTRACT FROM AUTHOR]

It has been rarely reported the morphological control of derivatives of metal‐organic frameworks (MOFs) in hydrothermal conditions for photocatalytic applications. We report here a family of highly efficient composite photocatalysts composed of terephthalic acid/terephthalate (TPA) ligand and TiO2 with various morphologies (e. g. nanoparticles, nanosheets, and nanorods). The composites are synthesized by a simple one‐step hydrothermal method in various solvents (i. e. H2O, HF, H2SO4, HCl, and HNO3) using Ti‐based MOF (MIL‐125(Ti)) as precursor. The formation mechanism of composite materials with different morphological features is discussed. Impressively, the composite of TiO2 nanoparticles/TPA synthesized using H2O as solvent under hydrothermal condition exhibits the highest photocatalytic H2 activity among the studied materials, with a photocatalytic H2 production rate of 6.38 mmol g−1 h−1, which is approximately 7.5‐fold higher than pure TiO2 (Degussa, P25) and prominent apparent quantum efficiency (AQE) of 65 % at 365 nm. Furthermore, the mechanism of boosted photocatalytic H2 production is discussed. [ABSTRACT FROM AUTHOR]

As a visible-light photocatalyst, bismuth iodide oxide (BiOI) is widely applied in water photocatalytic pollution degradation. However, due to the inherent high recombination rate of electron−hole pairs, an efficient photocatalytic performance could realize rarely by bare BiOI, resulting in its limited practical application. In this study, a novel type-II BiOI−C 3 N 5 heterostructure was prepared by a feasible solvothermal method to inhibit the recombination of photoexcited electrons and holes. The photocatalytic activity of the heterostructure was evaluated by degradation of tetracycline (TC) and penicillin G sodium. The results showed that compared with bare C 3 N 5 and BiOI, the photodegradation efficiency of tetracycline and penicillin G sodium was remarkable improved after heterostructure formation and the BiOI−C 3 N 5 (10% wt) samples demonstrated a higher degradation efficiency. The improvement of photocatalytic degradation activities can be attributed to the formation of type-II heterostructures with a close contact. Under the synergistic effect and interface structure in BiOI−C 3 N 5 , the spatial separation and transfer of charge carriers were increased significantly, which is in favor of enhancing the photocatalytic oxidation capacity of BiOI. [Display omitted] • A new BiOI-C 3 N 5 heterostructure was successfully constructed to heighten the photocatalytic oxidation capacity of BiOI. • Synergistic effect and interfacial fusions in BiOI −C 3 N 5 were formed for accelerating the charge carriers transfer. • The BiOI−C 3 N 5 heterostructures exhibit remarkable tetracycline (TC) and sodium penicillin G degradation performances. [ABSTRACT FROM AUTHOR]

It is an effective strategy to improve photocatalytic degradation performance by constructing step scheme (S-scheme) heterojunction photocatalysts with superior photo-redox capacity and high charge transfer efficiency. In this study, a series of two-dimensional/two-dimensional (2D/2D) La 2 Ce 2 O 7 /g-C 3 N 4 (LCO/CN) S-scheme heterojunction photocatalysts were synthesized via in-situ solid-phase sintering by regulating the mass ratio of raw materials. The large junction area between La 2 Ce 2 O 7 nanosheets and ultra-thin graphitic carbon nitride (g-C 3 N 4) endows the composite with significantly enhanced separation and transfer efficiency of photogenerated carriers within a satisfactory light response region. The LCO/CN-2 composite not only shows the highest photocatalytic activity with a reaction rate constant of 0.02701 min−1 to degrade Rhodamine B (RhB) under visible light irradiation for 90 min but also demonstrates stable reusability after four runs. Moreover, based on the Mott-Schottky calculations, radical trapping experiments, and ESR analysis,·O2- and·OH are identified as the main active species, and an S-scheme charge transfer mechanism is suggested to explain the enhanced photocatalytic activity. This work inspires the application of fluorite-type photocatalysts to wastewater purification and environmental restoration. [Display omitted] • La 2 Ce 2 O 7 /g-C 3 N 4 2D heterojunction photocatalyst was successfully synthesized. • The dual active species synergistically degraded RhB pollutants. • LCO/CN-2 shows a reaction rate constant of 0.02701 min−1 under visible light. • La 2 Ce 2 O 7 /g-C 3 N 4 inspires the design of fluorite-type photocatalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] • [Mo 3 S 13 ]2− nanoclusters are highly dispersed into the micropores of TpPa-1-COF. • The size and micro-environment of micropores play a central role in anchoring MS-c. • The photocatalytic H 2 evolution rate of MS-c@TpPa-1 is increased by 4.7 times. • The coordinated Mo − N groups between MS-c and TpPa-1-COF result in enhanced stability. • The favorable electron–proton transfer to form H* occurs on the S instead of N sites. Non-noble-metal-based [Mo 3 S 13 ]2− nanoclusters (MS-c) as a co-catalyst face the problems of instability and inevitable aggregation, which limit its photocatalytic applications. Herein, β-ketoenamine-linked covalent organic framework (COF), namely TpPa-1-COF, was utilized to embed MS-c. The micropores of TpPa-1-COF could not only limit the growth of MS-c to achieve its high dispersion but also play a central role in anchoring MS-c. Moreover, the structural stability of MS-c is highly enhanced due to the confinement effect of TpPa-1-COF, and the visible-light-driven photocatalytic H 2 evolution rate of 528 μmol g−1h−1 for MS-c@TpPa-1 (0.3: 1), which is increased by 4.7 times as compared with that of TpPa-1-COF. The density functional theory (DFT) calculations indicate that the electrons transfer from TpPa-1 to MS-c occurs at the interface of MS-c@TpPa-1 in the ground state based on the charge density difference analysis. With the irradiation of visible light, the photoexcited electrons derived from the π-conjugated TpPa-1-COF backbone could be delivered to the embedding MS-c through the coordinated Mo − N groups, and the favorable electron–proton transfer to form H* and efficient desorption of H 2 occurs on the S sites instead of N sites in MS-c@TpPa-1, resulting in the enhanced photocatalytic H 2 evolution rate. Overall, this work provides a novel approach for embedding the unstable MS-c with low cost into the micropores of COF via coordination bonds to improve the structural stability and photocatalytic activity. [ABSTRACT FROM AUTHOR]

[Display omitted] • [Mo 3 S 13 ]2− nanoclusters are highly dispersed into the micropores of TpPa-1-COF. • The size and micro-environment of micropores play a central role in anchoring MS-c. • The photocatalytic H 2 evolution rate of MS-c@TpPa-1 is increased by 4.7 times. • The coordinated Mo − N groups between MS-c and TpPa-1-COF result in enhanced stability. • The favorable electron–proton transfer to form H* occurs on the S instead of N sites. Non-noble-metal-based [Mo 3 S 13 ]2− nanoclusters (MS-c) as a co-catalyst face the problems of instability and inevitable aggregation, which limit its photocatalytic applications. Herein, β-ketoenamine-linked covalent organic framework (COF), namely TpPa-1-COF, was utilized to embed MS-c. The micropores of TpPa-1-COF could not only limit the growth of MS-c to achieve its high dispersion but also play a central role in anchoring MS-c. Moreover, the structural stability of MS-c is highly enhanced due to the confinement effect of TpPa-1-COF, and the visible-light-driven photocatalytic H 2 evolution rate of 528 μmol g−1h−1 for MS-c@TpPa-1 (0.3: 1), which is increased by 4.7 times as compared with that of TpPa-1-COF. The density functional theory (DFT) calculations indicate that the electrons transfer from TpPa-1 to MS-c occurs at the interface of MS-c@TpPa-1 in the ground state based on the charge density difference analysis. With the irradiation of visible light, the photoexcited electrons derived from the π-conjugated TpPa-1-COF backbone could be delivered to the embedding MS-c through the coordinated Mo − N groups, and the favorable electron–proton transfer to form H* and efficient desorption of H 2 occurs on the S sites instead of N sites in MS-c@TpPa-1, resulting in the enhanced photocatalytic H 2 evolution rate. Overall, this work provides a novel approach for embedding the unstable MS-c with low cost into the micropores of COF via coordination bonds to improve the structural stability and photocatalytic activity. [ABSTRACT FROM AUTHOR]

Herein, we report a one-dimensional (1D) S-doped K3Ti5NbO14@TiO2 (STNT) core-shell heterostructured composite with an enhanced photocatalytic degradation activity under visible light, which was prepared by a simple reassembly-calcination method using thiourea as the S source. The anisotropically shaped rods are favorable for the rapid transport of photogenerated charge carriers. The substitution of Ti4+ by S6+ is primarily incorporated into the lattice of the TiO2 shell so as to create an intra-band-gap state below the conduction band (CB) position, giving rise to Ti−O−S bonds and thus the visible light response. The presence of electron-deficient S atoms is of benefit to the decreased recombination rate of photogenerated electrons and holes by capturing electrons (e−). Meanwhile, a tight close interface between K3Ti5NbO14 and TiO2 was formed to achieve a nano-heterojunction structure, leading to the fostered separation of its interfacial photogenerated electrons and holes. The visible-light-driven photocatalytic degradation of methylene blue (MB) by STNT composites is higher than that by pure K3Ti5NbO14, owing to the synergistic effects of S doping and heterojunction. A possible photocatalytic mechanism was proposed with a reasonable discussion. This work may provide an insight into constructing highly efficient core-shell photocatalysts used toward sustainable environmental remediation and resource shortages. [ABSTRACT FROM AUTHOR]

A novel N-doped K3Ti5NbO14@TiO2 (NTNT) core-shell heterojunction photocatalyst was synthesized by firstly mixing titanium isopropoxide and K3Ti5NbO14 nanobelt, and then calcinating at 500 °C in air using urea as the nitrogen source. The samples were analyzed by X-ray diffraction pattern (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-Vis absorption spectroscopy and X-ray photoelectron spectroscopic (XPS) spectra. Anatase TiO2 nanoparticles were closely deposited on the surface of K3Ti5NbO14 nanobelt to form a nanoscale heterojunction structure favorable for the separation of photogenerated charge carriers. Meanwhile, the nitrogen atoms were mainly doped in the crystal lattices of TiO2, resulting in the increased light harvesting ability to visible light region. The photocatalytic performance was evaluated by the degradation of methylene blue (MB) under visible light irradiation. The enhanced photocatalytic activity of NTNT was ascribed to the combined effects of morphology engineering, N doping and the formation of heterojunction. A possible photocatalytic mechanism was proposed based on the experimental results. [ABSTRACT FROM AUTHOR]