A novel phase-mixed MgTiO3-MgTi2O5 heterogeneous nanorod for high efficiency photocatalytic hydrogen production

A review of advances in multifunctional XTiO3 perovskite-type oxides as piezo-photocatalysts for environmental remediation and energy production

Over more than three decades, the field of engineering of photocatalytic materials with unique properties and enhanced performance has received a huge attention. In this regard, different classes of materials were fabricated and used for different photocatalytic applications. Among these materials, recently multifunctional XTiO₃ perovskites have drawn outstanding interest towards environmental remediation and energy conversion thanks to their unique structural, optical, physiochemical, electrical and thermal characteristics. XTiO₃ perovskites are able to initiate different surface catalytic reactions. Under ultrasonic vibration or heating, XTiO₃ perovskites can induce piezo-catalytic reactions due to the titling of their conduction and valence bands, resulting in the formation of separated charge carriers in the medium. In addition, under light irradiation, XTiO₃ perovskites are considered as a new class of photocatalysts for environmental and energy related applications. Herein, we addressed the recent advances on variously synthesized, doped and formulated XTiO₃ perovskite-type oxides showing piezo- and/or photocatalytic exploitation in environmental remediation and energy conversion. The control of structural crystallite size and phase, conductivity, morphology, oxygen vacancy control, doping agents and ratio has a significant role on the photocatalytic and piezocatalytic activities. The different piezo or/and photocatalytic processes mechanistic pathways towards varying applications were discussed. The current challenges facing these materials and future trends were addressed at the end of the review.

Preparation of MgTi2O5 nanoparticles for sonophotocatalytic degradation of triphenylmethane dyes

MgTi2O5 (magnesium dititanate) nanoparticles were prepared by a simple hydrothermal assisted post-annealing method and characterized with various analytical techniques. The catalytic properties (sonocatalytic, photocatalytic and sonophotocatalytic activity) were evaluated using the degradation of triphenylmethane dyes (crystal violet, basic fuchsin, and acid fuchsin). The sonophotocatalytic activity of MgTi2O5 nanoparticles towards crystal violet was found to be ~2.9 times higher than the photocatalytic activity and ~20 times higher than that of the sonocatalytic processes. In addition, the sonophotocatalytic efficiency of MgTi2O5 nanoparticles was found to be remarkable for the degradation of basic fuchsin (cationic dye) and acid fuchsin (anionic dye). The mechanism of these catalytic activities has been discussed in detail.

Ti2O3/TiO2 heterophase junctions with enhanced charge separation and spatially separated active sites for photocatalytic CO2 reduction

Ti₂O₃/TiO₂ heterophase junctions with enhanced charge separation and spatially separated active sites for photocatalytic CO₂ reduction.

Solid-State, Low-Cost, and Green Synthesis and Robust Photochemical Hydrogen Evolution Performance of Ternary TiO2/MgTiO3/C Photocatalysts

Solar-driven photochemical hydrogen evolution is a promising route to sustainable hydrogen fuel production. Large-scale preparation of highly active photocatalysts using elementally abundant and less-expensive materials is urgently required for widespread practical application. Here, we report a highly efficient and low-cost TiO₂/MgTiO₃/C heterostructure photocatalyst for photochemical water splitting, which was synthesized on gram scale via a facile mechanochemical method. The heterostructure and carbon sensitization offer excellent photoconversion efficiency as well as good photostability. Under irradiation of one AM 1.5G sunlight, the optimal TiO₂/MgTiO₃/C photocatalyst can show a great solar-driven hydrogen evolution rate (33.3 mmol·h⁻¹·g⁻¹), which is much higher than the best yields ever reported for MgTiO₃-related photocatalysts or pure TiO₂ (P-25). We hope this work will attract more attention to inspire further work by others for the development of low-cost, efficient, and robust photocatalysts for producing hydrogen in artificial photosynthetic systems.

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The synthetic process does not involve any organic solvents and hazardous by-products

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The optimal sample shows a H₂ evolution rate of 33.3 mmol·h⁻¹·g⁻¹ under one sunlight

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The optimal sample keeps a H₂ evolution rate of 1.46 mmol·h⁻¹·g⁻¹ under visible light

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Uniform carbon layer was ingeniously deposited on the surface of photocatalysts

Novel stable metal–organic framework photocatalyst for light-driven hydrogen production

A novel stable Dye-based Dy-MOF exhibits efficient photocatalytic activity for hydrogen generation.

Coupling of Nanocrystalline Anatase TiO₂ to Porous Nanosized LaFeO₃ for Efficient Visible-Light Photocatalytic Degradation of Pollutants

In this work we have successfully fabricated nanocrystalline anatase TiO₂/perovskite-type porous nanosized LaFeO₃ (T/P-LFO) nanocomposites using a simple wet chemical method. It is clearly demonstrated by means of atmosphere-controlled steady-state surface photovoltage spectroscopy (SPS) responses, photoluminescence spectra, and fluorescence spectra related to the formed OH⁻ radical amount that the photogenerated charge carriers in the resultant T/P-LFO nanocomposites with a proper mole ratio percentage of TiO₂ display much higher separation in comparison to the P-LFO alone. This is highly responsible for the improved visible-light activities of T/P-LFO nanocomposites for photocatalytic degradation of gas-phase acetaldehyde and liquid-phase phenol. This work will provide a feasible route to synthesize visible-light responsive nano-photocatalysts for efficient solar energy utilization.

Enhanced photoredox chemistry in surface-modified Mg2TiO4 nano-powders with bidentate benzene derivatives

The absorption of Mg₂TiO₄ nano-powder was extended to visible spectral region upon surface modification with salicylate-and catecholate-type of ligands. Degradation of crystal violet over synthesized powders indicated their photocatalytic ability.

Modification Strategies with Inorganic Acids for Efficient Photocatalysts by Promoting the Adsorption of O2

Efficient photocatalysis for degrading environmental organic pollutants on semiconductors requires photogenerated charge carrier separation to drive the photochemical processes. To ensure charge separation, it is indispensable to make charges captured effectively. Generally, the step for capturing the photogenerated electrons by the surface adsorbed O2 is relatively slow as compared to that for capturing holes by the surface adsorbed hydroxyl groups so that it is taken as the rate-determining step. However, it is frequently neglected. Thus, it is greatly desired to develop feasible strategies to promote the adsorption of O2 for efficient photocatalysts. In this paper, we have mainly discussed surface modification with inorganic acids, such as H3PO4, HF, and H3BO3, to enhance photogenerated charge carrier separation based on oxygen adsorption promotion for photocatalytic degradation of environmental pollutants. Among these acids, the function and mechanism of H3PO4 are highlighted because of its good performance and universality. Several important photocatalyst systems, mainly including TiO2, α-Fe2O3, and g-C3N4, along with the nanostructured carbons as electron acceptors in nanocomposites, are addressed to improve the ability to adsorb O2. A key consideration in this review is the development of a strategy for the promotion of adsorbed O2 for efficient photocatalysts, along with the process mechanisms by revealing the relationships among the adsorbed O2, photogenerated charge carrier separation, and photocatalytic performance. Interestingly, it is suggested that the enrichment in surface acidity be favorable for promotion of O2 adsorption, leading to the improved charge carrier separation and then to the enhanced photoactivities of various semiconductor photocatalysts. Moreover, several outlooks are put forward.

ZnO-dotted porous ZnS cluster microspheres for high efficient, Pt-free photocatalytic hydrogen evolution

The Pt-free photocatalytic hydrogen evolution (PHE) has been the focus in the photocatalysis field. Here, the ZnO-dotted porous ZnS cluster microsphere (PCMS) is designed for high efficient, Pt-free PHE. The PCMS is designed through an easy "controlling competitive reaction" strategy by selecting the thiourea as S(2-) source and Zn(Ac)₂·2H₂O as Zn source in ethylene glycol medium. Under suitable conditions, one of the PCMS, named PCMS-1, with high SBET specific area of 194 m(2)g(-1), microsphere size of 100 nm and grain size of 3 nm can be obtained. The formation of PCMS is verified by TEM, XAES, XPS, Raman and IR methods. Importantly, a series of the experiments and theoretical calculation demonstrate that the dotting of ZnO not only makes the photo-generated electrons/hole separate efficiently, but also results in the formation of the active catalytic sites for PHE. As a result, the PCMS-1 shows the promising activity up to 367 μmol h(-1) under Pt-free condition. The PHE activity has no obvious change after addition 1 wt.% Pt, implying the presence of active catalytic sites for hydrogen evolution in the PCMS-1. The easy synthesis process, low preparation cost of the PCMS makes their large potential for Pt-free PHE.

In situ carbon-coated yolk-shell V2O3 microspheres for lithium-ion batteries

Metal oxide-based materials with yolk-shell morphology have been intensively investigated as important anodes for Li-ion batteries due to their large ion storage ability, high safety, and excellent cycling stability. In this work, in situ carbon-coated yolk-shell V2O3 microspheres were synthesized via a template-free polyol solvothermal method. The growth of yolk-shell microspheres underwent coordination and polymerization, followed by an inside-out Ostwald-ripening process and further calcination in N2 atmosphere. The thin amorphous carbon layers coating on the microspheres' surface came from polyol frameworks which could protect V2O3 during the charge-discharge process and led to a better stability in Li-ion batteries. The in situ carbon-coated yolk-shell V2O3 microspheres showed a capacity of 437.5 mAh·g(-1) after 100 cycles at a current density of 0.1 A·g(-1), which was 92.6% of its initial capability (472.5 mAh·g(-1)). They were regarded as excellent electrode materials for lithium-ion batteries and exhibit good electrochemistry performance and stability.

The hierarchical structure of cubic K0.5La0.5TiO3 layers and enhanced photocatalytic hydrogen evolution after surface acidification

A puzzle-like 3D hierarchical structure constructed with K_0.5La_0.5TiO₃ nanosheets was first synthesized. After a modest acidification, the 3D hierarchical structure transforms to a unique core–shell nanostructure, which exhibits remarkably enhanced photocatalytic H₂ production.

The promotion effect of surface negative electrostatic field on the photogenerated charge separation of BiVO4 and its contribution to the enhanced PEC water oxidation

The surface-carried negative charge of BiVO₄ is favorable for the charge separation, leading to obviously enhanced visible-light-activity for PEC water oxidation.

Ultra-small nanoparticles of MgTi2O5 embedded in carbon rods with superior rate performance for sodium ion batteries

Confinement of ultra-small MgTi₂O₅ nanoparticles in carbon is demonstrated as to be an efficient method for fabricating long cycle-life anode material for sodium ion batteries.

Pure phase orthorhombic MgTi2O5 photocatalyst for H2 production

An undesirable phase transformation was overcome and pure phase MgTi₂O₅ nanocrystals with excellent photocatalytic H₂ production efficiency were facilely prepared.

Improved photoactivity of TiO2–Fe2O3 nanocomposites for visible-light water splitting after phosphate bridging and its mechanism

The phosphate bridges built are favorable for charge transfer and separation, leading to a greatly-enhanced photoactivity for water splitting.