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Development of nanostructured supported photocatalysts for hydrogen production and inorganic pollutants removal
Full text linkSemiconductor photocatalysis has emerged as one of the most promising approach to exploit a renewable energy source (i.e. sunlight irradiation) for several environmental purposes such as the production of clean energy (e.g. photocatalytic H2 evolution), the removal of organic and inorganic pollutants in natural water, purification of air and antibacterial activity.
In view of these recent trends, the focus of this thesis was directed towards the study of different supported photo(electro)catalytic materials for topical environmental applications:
i) Photocatalytic hydrogen gas evolution from aqueous solutions under UV light irradiation (365 nm) over highly ordered TiO2 nanotubes decorated through a sputtering/dewetting approach with a well-defined stacked co-catalyst (a WO3 layer decorated with Pt NPs);
ii) Photocatalytic hydrogen gas evolution from aqueous solutions under UV light irradiation (365 nm) over highly ordered TiO2 nanotubes decorated through a sputtering/dewetting approach with dewetted-alloyed NiCu nanoparticles;
iii) Photocatalytic reduction/scavenging of inorganic mercury (Hg(II)) from water under solar light irradiation over templated-dewetted Au on TiO2 nanotubes;
iv) Photoelectrocatalytic oxidation/abatement of inorganic arsenic (As(III)) over hematite-based photoanodes under solar light irradiation.
After a general introduction about photocatalytic processes and materials, each chapter of this dissertation contains the outcomes of the above listed studies
Template-Dewetted Au Nanoparticles on TiO2 Nanocavities for Photocatalytic Reduction and Scavenging of Hg(II)
No full textThermal-Oxidative Growth of Sub-Stoichiometric WO3-x Nanowires at Mild Conditions
Full text linkHerein, the growth of substoichiometric tungsten oxide (WO3–x) nanowires (NWs) via thermal oxidation of W films (a few 10 to a few 100 nm thick) deposited by Ar‐plasma sputtering on fluorine‐doped tin oxide (FTO) substrates is reported. A thermal treatment at relatively low temperature (525–550 °C) in Ar at atmospheric pressure leads to the conversion of the W films into W suboxide (WO3–x) NW arrays. Such NWs have a length of ≈500 nm and their diameter ranges from 10 to 40 nm depending on the duration of the annealing process. These growth conditions for the formation of WO3–x NWs are significantly milder and more straightforward than those reported in previous literature. This avoids high temperatures (e.g., above 600 °C), vacuum conditions, or the addition of catalysts. A thermal‐oxidative approach of these sputtered films is suitable to directly form WO3–x NWs on various surfaces, including conductive substrates to fabricate photoelectrodes or large‐scale supports, e.g., for smart windows
Site-selective Pt dewetting on WO3-coated TiO2nanotube arrays: An electron transfer cascade-based H2evolution photocatalyst
No full textAmong several parameters that affect the yield of a photocatalytic process mediated by a metal oxide semiconductor, key is the efficient separation and transfer of photo-generated charge carriers. To overcome kinetic limitations and enable charge transfer, an effective strategy is to decorate the photocatalyst surface with cocatalytic nanoparticles of either a second semiconductor metal oxide or a noble metal. Nevertheless, classical deposition techniques based on powder technology approaches lead to randomly placed cocatalytic nanoparticles at the photocatalytic surface. The poor control over cocatalyst placement can drastically hamper the photocatalytic efficiencies, and can also prevent a full understanding of the charge carrier dynamics and photocatalytic mechanism. Here we investigate a highly defined charge separation platform for photocatalytic H2evolution based on a Pt-WO3-TiO2“stacked” structure constructed on anodically grown TiO2nanotube arrays. Key is the formation of a site-selective and sequential W and Pt metal sputter-decoration only at the mouth of highly-ordered TiO2nanotubes. After placing the W-Pt bilayer at the nanotubes mouth, a suitable thermal treatment forms a WO3layer atop the nanotubes while the Pt film undergoes solid state dewetting into 2–6 nm-sized Pt nanoparticles. These structures show strongly improved photocatalytic H2evolution efficiency compared to any other single-cocatalyst system (Pt-TiO2and WO3-TiO2) and pristine TiO2nanotubes. The photocatalytic activity improvement is ascribed to an enhanced charge carrier separation mechanism enabled by the well-defined TiO2-WO3-Pt architecture that provides swift electron transfer through WO3and towards Pt for H2evolution
Integration of photogrammetry from unmanned aerial vehicles, field measurements and discrete fracture network modeling to understand groundwater flow in remote settings: test and comparison with geochemical markers in an Alpine catchment
No full textGoing Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Dewetting-Alloying of Nicu Bilayers on TiO2 Surfaces for Noble Metal-Free Photocatalytic H2 Evolution
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