The halogen elements modification strategy of TiO2 encounters a bottleneck in visible-light H2 production. Herein, we have for the first time reported a hierarchical honeycomb Br-, N-codoped anatase ...TiO2 catalyst (HM-Br,N/TiO2) with enhanced visible-light photocatalytic H2 production. During the synthesizing process, large amounts of meso–macroporous channels and TiO2 nanosheets were fabricated in massive TiO2 automatically, constructing the hierarchical honeycomb structure with large specific surface area (464 m2 g–1). cetyl trimethylammonium bromide and melamine played a key role in constructing the meso–macroporous channels. Additionally, HM-Br,N/TiO2 showed a high visible-light H2 production rate of 2247 μmol h–1 g–1, which is far more higher than single Br- or N-doped TiO2 (0 or 63 μmol h–1 g–1, respectively), thereby demonstrating the excellent synergistic effects of Br and N elements in H2 evolution. In HM-Br,N/TiO2 catalytic system, the codoped Br–N atoms could reduce the band gap of TiO2 to 2.88 eV and the holes on acceptor levels (N acceptor) can passivate the electrons on donor levels (Br donor), thereby preventing charge carriers recombination significantly. Furthermore, the proposed HM-Br,N/TiO2 fabrication strategy had a wide range of choices for N source (e.g., melamine, urea, and dicyandiamide) and it can be applied to other TiO2 materials (e.g., P25) as well, thereby implying its great potential application in visible-light H2 production. Finally, on the basis of experimental results, a possible photocatalytic H2 production mechanism for HM-Br,N/TiO2 was proposed.
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IJS, KILJ, NUK, PNG, UL, UM
•We review various polymer supports reported for use in TiO2 photocatalysis.•Preparation methods, photocatalytic activity and the reuse of polymer-supported TiO2 photocatalysts have been ...discussed.•Polymer-supported buoyant photocatalysts effective in visible and/or solar light is a promising area of recent research.•Biodegradable polymer-supported TiO2 photocatalysts needs further investigation.•Challenges to be overcome in the commercialization of polymer-supported TiO2 photocatalysts.
Since the past two decades, immobilization of titanium dioxide (TiO2), a popular photocatalyst, on different substrates has been drawing a lot of attention because it eliminates the need of costly post-treatment separation processes. Considering the various substrates that have been tried for supporting TiO2 photocatalysts, polymer substrate seems to be very promising due to its several advantages such as flexible nature, low-cost, chemical resistance, mechanical stability, low density, high durability and ease of availability. This review covers over a hundred published papers in the field of polymer-based photocatalysts and presents a comprehensive study on the preparation, photocatalytic activity and reuse of TiO2/polymer photocatalysts. Polymer-supported buoyant TiO2 photocatalysts and biodegradable polymer-supported TiO2 photocatalysts are also discussed. Finally, the scope for future work and challenges for commercialization of polymer-supported TiO2 photocatalysts in visible and/or solar light have been highlighted.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Interfacial charge separation is an essential issue to restrict catalytic activity of photocatalysts. In this work, we report a promising and easy-to-handle strategy to modulate the activity of a ...C60-based photocatalyst (C60@Pt) for visible-light-driven hydrogen evolution reaction (HER) with the coupling of magnetic substance that had weak ferromagnetism (Fe3O4 microbeads as an instance). It is found that Fe3O4 microbeads played a pivotal role in boosting photocatalytic activity and apparent quantum efficiency of C60@Pt for visible-light-driven HER, as the weak local magnetic field it induced around C60@Pt contributed to facilitating the separation of photo electrons from electron-donor in reaction system.
This work shows a promising strategy to enhance photocatalytic activity of C60-based photocatalyst (C60@Pt as an instance) for visible-light-driven hydrogen evolution by coupling it with magnetic substance Fe3O4 microbeads that had weak ferromagnetism. It is found that the Fe3O4 microbeads played a pivotal role in enhancing photocatalytic activity of C60@Pt as the weak local magnetic field it induced around C60@Pt contributed to promoting the separation of photo-excited electrons from electron-donor. This strategy effectively boosted hydrogen evolution rate and AQE of C60@Pt. Display omitted
•Modulate activity of C60-based photocatalyst via connecting weak magnetic substance.•Promote separation of photo-excited electrons by inducing weak local magnetic field.•AQE was boosted up to 2.5 times with the coupling of weak magnetic substance.•Hydrogen evolution improved up to 3.7 times when connecting weak magnetic substance.•Remarkably improve HER photocatalytic robustness of C60-based photocatalyst.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•The deep effects of oxygen vacancies on activating CO2 photoreduction activity was investigated.•The introduced oxygen vacancies could drive up the Fermi level, optimize the band structure.•The ...oxygen vacancies reduce the formation energy of *COOH intermediate and stabilized *CO2- and *CO intermediates.
Rationally designing highly active, low-cost and stable photocatalysts is a crucial endeavor for the development of photocatalysis as one of the most promising advanced carbon-negative technologies. Here, we explored the deep effects of oxygen vacancies on activating CO2 photoreduction via coupling theoretical calculations and experimental results. In broad themes, oxygen vacancies improved the transport and separation efficiency of the photogenerated electron-hole pairs and enhanced the photocatalytic CO2 reduction activity. The deep effects, however, were that for n-Type semiconductor, the introduced oxygen vacancies could drive up the Fermi level, optimize the band structure, boost the reduction capability of the photogenerated electrons, and enhance the adsorption properties of reactants of the photocatalyst for the photocatalytic CO2 reduction reaction. We highlighted the rational design of the photocatalysts, and how the essential theory deserves to be integrated into the exploitation of the photocatalysts to accelerate the development of photocatalysis.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Highly n-doped silicon nanowires (SiNWs) exhibit excellent hydrogen generation. Our results indicate three hydrogen generation possibilities, i.e. SiNWs oxidation, photocatalysis and the cleavage of ...dangling H bonds, are jointly responsible for the efficient hydrogen generation. Oxidation accounts for about 80% of total hydrogen, photocatalysis contributes less than 20% of total hydrogen, and about 0.1% of total hydrogen is from cleavage of dangling H bonds. SiNWs were oxidized in water and form SiOx (0 < X < 2) thin layer. Furthermore, the ratio of photo-generated hydrogen to photo-generated oxygen is about 2.4:1. It suggests that photocatalysis appears to be a process of water splitting. This study is significant to reveal the mechanism of hydrogen production on SiNWs prepared by Metal-Assisted Wet Chemical Etching (MAWC).
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•SiNWs were reported to produce H2 in water as photocatalyst. However, the mechanism of hydrogen generation on SiNWs has not been clarified. Is it real water splitting? As far as We know, there is no clear conclusion on this issue at present. A accurate numerical computation of hydrogen and oxygen generation was given in the manuscript. Our results indicate SiNWs oxidation, photocatalysis and the cleavage of dangling H bonds, are jointly responsible for the efficient hydrogen generation. The ratio of photo-generated hydrogen to photo-generated oxygen is about 2.4:1, it is close to the theoretical ration of water splitting.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In the last decades, the use of magnetic nanocomposites as a catalyst was considered for removal of organic pollutants due to its easy separation. Therefore, initially, TiO2@ZnFe2O4/Pd nanocomposite ...was prepared and then used in the photodegradation of diclofenac under direct solar irradiation in the batch and continuous systems. The structure, morphology and other specifications of produced nanocatalyst were determined via XRD, VSM, FESEM/EDX, FTIR, GTA, UV–Vis, Zeta potential, XPS and ICP-OES. The effective factors on diclofenac removal via nanophotocatalyst viz. pH, catalyst concentration, initial concentration of diclofenac, and flow rate and column length on diclofenac photodegradation were studied. Based on the results, the optimal rate for pH, catalyst concentration, and initial concentration of diclofenac was 4, 0.03 g/l and 10 mg/l respectively. Pd-coated TiO2@ZnFe2O4 magnetic photocatalyst had higher photocatalytic activity in diclofenac photodegradation in relation to ZnFe2O4 and TiO2@ZnFe2O4 under solar light irradiation. The findings showed that after five recycles, the photocatalytic efficiency did not show much reduction i.e. the removal efficiency from 86.1% in the first cycle reduced only to 71.38% in the last cycle. Likewise, in this study, with flow rate reduction and column length increase diclofenac degradation rate increased.
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•TiO2@ZnFe2O4/Pd nanocomposite was prepared using the photodeposition method.•Distributed Pd nanoparticles on TiO2 significantly increased its photocatalytic activity.•DCF degradation rate was increased by flow rate reduction and column length increase.•TiO2@ZnFe2O4/Pd is highly efficient up to 5 cycles of magnetic separation and recovery.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Photocatalytic H2 evolution technique has been proved to be one of the promising approaches to overcome the present energy and environmental issues caused by the combustion of fossil fuel. ...Constructing heterojunction can realize the efficient separation and migration of charges and thus achieve enhanced H2 evolution performance. Herein, we designed and prepared a ZnIn2S4/BiFeO3 heterojunction photocatalyst with a 3D/2D structure via an ultrasonic self‐assembly process. The typical 3D/2D structure with intimate interface was obtained, which not only provided more active sites but also boosted the migration of photogenerated charges. The optimal mass ratio of BiFeO3 in ZnIn2S4/BiFeO3 was determined to be 10%, and a 10.5‐fold increase in H2 evolution rate in comparison with of pure ZnIn2S4 was achieved. Furthermore, the ZnIn2S4/BiFeO3 composite exhibited excellent recyclability and structural stability based on cycling experiment. A S‐scheme heterojunction mechanism was revealed according to the experimental results of photocatalytic H2 evolution and electrochemical tests.
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BFBNIB, DOBA, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UILJ, UKNU, UL, UM, UPUK
Nanosheets of silicon have attracted a great deal of attention due to its tunable optical and electronic properties. However, the development of facile and easily scalable synthesis process has ...remained a great contest. Endeavor has been made in this research to find a waste inferred effective photocatalyst to deliver hydrogen (H2) through visible light responsive water splitting.
One-pot solid phase reaction was applied to synthesis catalyst and adopted ultrathin structure. The photocatalytic efficiency of catalyst was examined by XRD, XPS, and UV–VIS absorption spectra, PL, FESEM, HRTEM and EDX. The HRTEM and FESEM images revealed the interconnected nanosheets with Si having the average thickness of 5 nm and their band gaps were 2.3–2.5 eV corresponding to the absorption of visible light range. The H2 production rate on photocatalyst was originated to 3200 μmol h−1 without utilizing any conciliatory electron givers, voltage or pH alteration, which beats the Pt, Ru, Rh, Pd and Au stacked photocatalyst ever detailed up until this point. The significant increase in photocatalytic activity could be the fast charge migration and separation from the silicon-hydrogen and silicon-hydroxyl bonds on Si surface and facilitation of charge separation could results from the multiple reflections of visible light on ultrathin nanosheets. It has been confirmed that the electron/hole recombination rate in ultrathin nanosheets of Si declined due to the oxidation of Si surface. It would be presumed that the approach of surface chemistry of silicon could not be limited towards the photocatalytic water splitting and could be applicable to remedy water pollution.
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•Ultrathin nanostructured noble metal free Si/MgO photocatalyst was reported.•Visible light responsive Si/MgO was prepared via one step solid phase reaction method.•XPX showed that the formation of Si-H and Si-OH bonds of Si facilitated the H2 production.•The highest H2 production was found to 3200 μmol h−1g−1 without being affected by any reagent.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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