Photocatalytic properties of layer-by-layer thin films of hexaniobate nanoscrolls

Nunes, Barbara N.; Haisch, Christoph; Emeline, Alexei V.; Bahnemann, Detlef W.; Patrocínio, Antonio Otávio T.

doi:10.1016/j.cattod.2018.06.029

Cited by 14 publications

(17 citation statements)

References 69 publications

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“…Catalysts 2020, 10, x FOR PEER REVIEW 7 of 30 dependent on those conditions, where a 'soft' photoreduction of platinum precursors was identified as the best method for the preparation of those photocatalysts. Suspended hexaniobate layers (K4−xHxNb6O17) in tetrabutylammonium hydroxide (TBAOH) showed a good performance in designing the photocatalytic film through the layer-by-layer (LbL) deposition technique [36]. Thin films were assembled by alternative immersions of FTO substrate into exfoliated hexaniobate with pre-adsorbed [Pt(NH3)4] 2+ suspension (pH = 8) and poly(allylamine hydrochloride) solution (pH = 4) up to 25 bilayers.…”

Section: Niobium Layered Compoundsmentioning

confidence: 99%

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Recent Advances in Niobium-Based Materials for Photocatalytic Solar Fuel Production

et al. 2020

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The search for renewable and clean energy sources is a key aspect for sustainable development as energy consumption has continuously increased over the years concomitantly with environmental concerns caused by the use of fossil fuels. Semiconductor materials have great potential for acting as photocatalysts for solar fuel production, a potential energy source able to solve both energy and environmental concerns. Among the studied semiconductor materials, those based on niobium pentacation are still shallowly explored, although the number of publications and patents on Nb(V)-based photocatalysts has increased in the last years. A large variety of Nb(V)-based materials exhibit suitable electronic/morphological properties for light-driving reactions. Not only the extensive group of Nb2O5 polymorphs is explored, but also many types of layered niobates, mixed oxides, and Nb(V)-doped semiconductors. Therefore, the aim of this manuscript is to provide a review of the latest developments of niobium based photocatalysts for energy conversion into fuels, more specifically, CO2 reduction to hydrocarbons or H2 evolution from water. Additionally, the main strategies for improving the photocatalytic performance of niobium-based materials are discussed.

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Section: Niobium Layered Compoundsmentioning

confidence: 99%

“…FE-SEM image of the surface of Pt-modified hexaniobate layer-by-layer (LbL) films with 25 bilayers (the bright small spots are Pt nanoclusters). Reproduced with permission from the authors of[36]. Copyright (2019), Elsevier, Amsterdam, Netherlands.…”

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Recent Advances in Niobium-Based Materials for Photocatalytic Solar Fuel Production

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“…The high affinity of Nb 5+ for O 2– gives rise to extended 2D layered arrangements, providing a large surface area and allowing easy modification either by intercalation or superficial modification. Despite a band gap energy close to 3.5 eV that limits the photoactivity to the ultraviolet region (<390 nm), these materials feature appropriate potentials for water splitting with conduction and valence bands lower than −0.5 V and higher than +2.5 V versus an SHE, respectively. , …”

Section: Introductionmentioning

confidence: 99%

“…Improved rates for H 2 evolution from alcoholic solutions could be further achieved by exfoliated niobate samples . Exfoliation of stacked niobates has been successfully employed to yield 2D nanostructures with enhanced surface area in relation to the as-synthesized oxides. − The exfoliating agent role, generally a bulky ammonium cation, as well as that of an individual niobate layer shape (nanosheets or nanoscrolls) on H 2 evolution has been investigated by Osterloh’s group. , In all cases, no O 2 could be detected upon water photolysis even when platinum was used as the co-catalyst, a behavior also observed by us for niobate thin films assembled by the layer-by-layer technique . The same group later reported that UV-driven water photolysis in the presence of exfoliated niobates actually yields H 2 and H 2 O 2 in a 1:1 molar ratio .…”

Section: Introductionmentioning

confidence: 99%

Photoinduced H₂ Evolution by Hexaniobate Sheets Grafted with Metal Ions: The Fate of Photogenerated Carriers

Nunes

Bahnemann

Patrocínio

2021

ACS Appl. Energy Mater.

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Layered niobates are well-known photocatalysts for H2 evolution with a rich surface chemistry. Their photoactivity, however, is limited by their wide band gap energy (∼3.5 eV) and partial deactivation due to surface poisoning by photogenerated H2O2. In this way, a surface modification method able to induce novel electronic processes without changing the bulk properties can improve their performance. In this work, the surface of exfoliated hexaniobate (K4–x H x Nb6O17) layers was modified by grafting with metal ions such as Co(II) and Fe(III) and their photocatalytic properties were fully investigated. Morphological characterization showed that grafting ions are attached to the niobate surface forming amorphous clusters. These species induce an additional absorption feature in the UV-A region, which is attributed to an interfacial charge transfer from the niobate valence band to the metal ion centers. Enhanced UV-driven photoactivity was observed for 0.1% grafted samples, especially for those modified with Co(II) ions, while smaller H2 evolution rates are observed as the concentration of the grafting ions increases. When Pt was added to the photocatalyst, the H2 evolution rate for the 0.1% Co-grafted sample in plain water was 70% higher than that observed for the nongrafted Pt-hexaniobate. Full characterization by electron paramagnetic resonance, transient absorption spectroscopy, and photoelectrochemical measurements reveals that grafted ions can work as both electron and hole acceptors. In the presence of Pt as a preferential electron acceptor, Co(II) ions act as hole acceptors forming Co(III) centers, favoring the formation of OH• radicals from water and avoiding surface poisoning. At higher Co(II) concentrations and in the absence of Pt clusters, electrons are trapped at the Co centers, decreasing the H2 evolution rate. Thus, grafted Co(II) ions act as active redox shuttles in the hexaniobate sheets, contributing to more efficient charge separation.

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“…K 4 Nb 6 O 17 is a layered compound that is biocompatible, chemically stable and displays characteristics of a wide-band semiconductor [20]. Hexaniobate nanosheets have also shown evidence of photocatalytic activity under UV light [21,22]. The encapsulation or in situ growth of nanoparticles within the hollow spaces of the scrolls is important when considering the potential development of new nanodevices.…”

Section: Introductionmentioning

confidence: 99%

Directed assembly of barium titanate nanopeapods via solvothermal processing with a mixed surfactant system

Blanco

Webb

DiMarco

2021

Journal of Experimental Nanoscience

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Barium titanate (BaTiO 3 ) peapod nanocomposites were prepared by the controlled capture of nanoparticles (NPs) in scrolling hexaniobate (HNB) nanosheets. BaTiO 3 NPs and proton-exchanged potassium hexaniobate were treated solvothermally at 220 C for 6 h in toluene to produce linear NP chains confined within multiwalled HNB nanoscrolls. This method consistently produced nanopeapods with average filling fractions greater than 70%. The controlled introduction of nanocomponents along with a combination of oleylamine and oleic acid surfactants was critical to the success of these reactions. The ability to form BaTiO 3 @HNB significantly expands the number of important peapod composites accessible by the controlled NP capture.

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Photocatalytic properties of layer-by-layer thin films of hexaniobate nanoscrolls

Cited by 14 publications

References 69 publications

Recent Advances in Niobium-Based Materials for Photocatalytic Solar Fuel Production

Recent Advances in Niobium-Based Materials for Photocatalytic Solar Fuel Production

Photoinduced H₂ Evolution by Hexaniobate Sheets Grafted with Metal Ions: The Fate of Photogenerated Carriers

Directed assembly of barium titanate nanopeapods via solvothermal processing with a mixed surfactant system

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Photocatalytic properties of layer-by-layer thin films of hexaniobate nanoscrolls

Cited by 14 publications

References 69 publications

Recent Advances in Niobium-Based Materials for Photocatalytic Solar Fuel Production

Recent Advances in Niobium-Based Materials for Photocatalytic Solar Fuel Production

Photoinduced H2 Evolution by Hexaniobate Sheets Grafted with Metal Ions: The Fate of Photogenerated Carriers

Directed assembly of barium titanate nanopeapods via solvothermal processing with a mixed surfactant system

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Photoinduced H₂ Evolution by Hexaniobate Sheets Grafted with Metal Ions: The Fate of Photogenerated Carriers