| 1. |
- Alfakes, Boulos, et al.
(författare)
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Enhanced photoelectrochemical performance of atomic layer deposited Hf-doped ZnO
- 2020
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Ingår i: Surface & Coatings Technology. - : Elsevier BV. - 0257-8972 .- 1879-3347. ; 385
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Tidskriftsartikel (refereegranskat)abstract
- Generation of hydrogen using photoelectrochemical (PEC) water splitting has attracted researchers for the last two decades. Several materials have been utilized as a photoanode in a water splitting cell, including ZnO due to its abundance, low production cost and suitable electronic structure. Most research attempts focused on doping ZnO to tailor its properties for a specific application. In this work, atomic layer deposition (ALD) was used to precisely dope ZnO with hafnium (Hf) in order to enhance its PEC performance. The resultant doped materials showed a significant improvement in PEC efficiency compared to pristine ZnO, which is linked directly to Hf introduction revealed by detailed optical, structural and electrical analyses. The photocurrent obtained in the best performing Hf-doped sample (0.75 wt% Hf) was roughly threefold higher compared to the undoped ZnO. Electrochemical impedance spectroscopy (EIS) and open-circuit potential-decay (OCPD) measurements confirmed suppression in photocarriers' surface recombination in the doped films, which led to a more efficient PEC water oxidation. The enhanced PEC performance of Hf-doped ZnO and effectiveness of the used metal dopant are credited to the synergistic optimization of chemical composition, which enhanced the electrical, structural including morphological, and optical properties of the final material, making Hf-doping an attractive candidate for novel PEC electrodes.
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| 2. |
- Bellardita, Marianna, et al.
(författare)
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Highly stable defective TiO2-x with tuned exposed facets induced by fluorine : Impact of surface and bulk properties on selective UV/visible alcohol photo-oxidation
- 2020
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Ingår i: Applied Surface Science. - : ELSEVIER. - 0169-4332 .- 1873-5584. ; 510
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Tidskriftsartikel (refereegranskat)abstract
- Titanium dioxide samples were prepared in the presence of different amounts of fluorine via hydrothermal method. It has been found that the presence of fluoride influenced the physico-chemical properties of TiO2 in various ways as polymorphic form stability, surface hydroxylation, generation of hydroxyl radicals under irradiation and formation of Ti3+ centers and oxygen vacancies. The generation rate of (OH)-O-center dot radicals was investigated by the photoluminescence technique in the presence of terephthalic acid. X-ray diffractometry indicated that fluorine stabilized the anatase TiO2. X-Ray photoelectron spectroscopy (XPS) revealed the presence of fluorine on the surface and the shift of the valence band edge towards less negative potentials, electron paramagnetic resonance (EPR) confirmed the formation of Ti3+ in the bulk of the photocatalysts, UV-vis spectra showed the extension of the TiO2 photo-response in the visible light region. 2-Propanol degradation and 4-methoxybenzyl alcohol partial oxidation were studied as probe reactions by using the home prepared powders as photocatalysts. Surprisingly, the photocatalytic activity resulted to be mainly affected by (OH)-O-center dot radicals formation ability under irradiation, rather than by the presence of {0 0 1} facets, although it cannot be excluded that the latter could influence the ability to form radicals under irradiation.
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| 3. |
- Bericat Vadell, Robert, et al.
(författare)
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Single-electron transfer reactions on surface-modified gold plasmons
- 2023
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Ingår i: Materials Today Chemistry. - : Elsevier. - 2468-5194. ; 34
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Tidskriftsartikel (refereegranskat)abstract
- Photoredox catalysis's relevance in organic synthesis research and innovation will increase in the coming decades. However, the processes rely almost exclusively on expensive noble metal complexes, most notably iridium complexes, to absorb light and transfer a single charge to a substrate or a catalyst to initiate cascade transformations. Light-triggered plasmon resonances generate a non-Fermi-Dirac energy distribution with many hot carriers that decay in similar to 1 ps. Their ultrafast relaxation makes performing single electron transfer (SET) transformations challenging. Herein, a novel photosystem is proposed based on surface-modified gold nanoparticles (aka plasmon "molecularization"), which improved charge separation and, more importantly, enabled SET reactions, expanding the portfolio of photocatalysts available for photoredox catalysis. The photosystem was made into an electrode, permitting its use in photoelectrochemical arrangements that leverage electro- and photo-chemical approaches' benefits and chemical engineering solutions, helping the synthetic chemistry efforts towards greener synthesis and synthesis of more complex structures on a scale.
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| 4. |
- Dey, Ananta, et al.
(författare)
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Exploiting hot electrons from a plasmon nanohybrid system for the photoelectroreduction of CO2
- 2024
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Ingår i: Communications Chemistry. - : Springer Nature. - 2399-3669. ; 7:1
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Tidskriftsartikel (refereegranskat)abstract
- Plasmonic materials convert light into hot carriers and heat to mediate catalytic transformation. The participation of hot carriers (photocatalysis) remains a subject of vigorous debate, often argued on the basis that carriers have ultrashort lifetime incompatible with drive photochemical processes. This study utilises plasmon hot electrons directly in the photoelectrocatalytic reduction of CO2 to CO via a Ppasmonic nanohybrid. Through the deliberate construction of a plasmonic nanohybrid system comprising NiO/Au/ReI(phen-NH2)(CO)3Cl (phen-NH2 = 1,10-Phenanthrolin-5-amine) that is unstable above 580 K; it was possible to demonstrate hot electrons are the main culprit in CO2 reduction. The engagement of hot electrons in the catalytic process is derived from many approaches that cover the processes in real-time, from ultrafast charge generation and separation to catalysis occurring on the minute scale. Unbiased in situ FTIR spectroscopy confirmed the stepwise reduction of the catalytic system. This, coupled with the low thermal stability of the ReI(phen-NH2)(CO)3Cl complex, explicitly establishes plasmonic hot carriers as the primary contributors to the process. Therefore, mediating catalytic reactions by plasmon hot carriers is feasible and holds promise for further exploration. Plasmonic nanohybrid systems can leverage plasmon’s unique photophysics and capabilities because they expedite the carrier’s lifetime.
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| 5. |
- Fernandes, Arthur B., et al.
(författare)
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Recoverable and Reusable Polymer Microbead-Supported Metal Nanocatalysts for Redox Chemical Transformations
- 2020
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Ingår i: ACS APPLIED NANO MATERIALS. - : AMER CHEMICAL SOC. - 2574-0970. ; 3:2, s. 1722-1730
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Tidskriftsartikel (refereegranskat)abstract
- Metal nanoparticles have been widely exploited in catalysis, but their full impact on the environment and human health is still under debate. Here we describe the one-step fabrication of recoverable and reusable polymer microbead-supported metal and metal oxide nanocatalysts for application in batch reactions and flow systems. Au, Ag, and Fe3O4 nanoparticles were prepared directly at the surface of commercial benzylamine-coated spherical polymer beads in water by using low-energy microwave radiation for 5 min. The functionalization of microbead surface with betalamic acid, an antioxidant from plant origin, before irradiation changes the morphology and catalytic properties of the grafted nanoparticles. No leaching of the active phase was observed during the application of these effective and ready-to-use nanocatalysts on the reduction of 4-nitrophenol and oxidation of dihydrorhodamine 123. The supported nanocatalysts were recovered by filtration and/or magnetic separation and reused up to three times without significant drop in catalytic performance. These results can stimulate the controlled and facile synthesis of recoverable microbead-supported magnetic and nonmagnetic nanocatalysts that can be applied under myriad reaction conditions and reused multiple times.
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| 6. |
- Oladipo, Habeebllah, et al.
(författare)
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Unveiling the role of bisulfide in the photocatalytic splitting of H2S in aqueous solutions
- 2020
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Ingår i: Applied Catalysis B. - : ELSEVIER. - 0926-3373 .- 1873-3883. ; 270
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Tidskriftsartikel (refereegranskat)abstract
- Anaerobic photocatalytic conversion of aqueous H2S to H-2 was tested on Pt-decorated N-doped TiO2 grown on graphene. The hydrogen production increased linearly (rate: 32.3 mu mol/h/g, quantum yield: 1.4 x 10(-4)) with HS- concentration, until the critical value of 0.029 mol/dm(3), after which it declined to negligible values. The latter was attributed to photon-blockage caused by sulfur-containing species formed on catalyst surface, which could be removed by simple washing of the catalyst leading to its regeneration, as highlighted by the characterization of fresh and used catalyst. Similar tests performed at constant HS- concentration and variable pH did not yield a correlation, thus suggesting HS- as the major source of H-2, and not H+. A new kinetic model assessing the competitive adsorption mechanism reiterated the important role of sulfide ionic species in hydrogen production. A strong correlation between the latter and HS- concentration was established based on the reactivity results and proposed mechanism.
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| 7. |
- Ozer, Lütfiye Y., et al.
(författare)
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Long-Lasting Non-hydrogenated Dark Titanium Dioxide : Medium Vacuum Anneal for Enhanced Visible Activity of Modified Multiphase Photocatalysts
- 2018
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Ingår i: ChemCatChem. - : Wiley. - 1867-3880 .- 1867-3899. ; 10:14, s. 2949-2954
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Tidskriftsartikel (refereegranskat)abstract
- Multiphase TiO2 was stably modified by vacuum treatment for a dramatic improvement in visible-light absorption and photocatalytic reactivity. The samples were made of rutile-brookite, bare or N doped, and were grown on reduced graphene oxide. The stable introduction of Ti3+ species and oxygen vacancies resulting in mitigated electron?hole recombination was identified as the main responsible factor, along with a change in surface charges.
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| 8. |
- Pavliuk, Mariia
(författare)
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Accumulative Charge Separation in Photocatalysis : From Molecules to Nanoparticles
- 2019
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Konstnärligt arbete (övrigt vetenskapligt/konstnärligt)abstract
- Photochemical energy conversion into solar fuel involves steps of light absorption, charge separation and catalysis. Nature has taught us that the effective accumulation of redox equivalents and charge separation are the key steps in sunlight conversion. The focus of this thesis is to unveil photophysical and photochemical processes that lead to accumulative charge separation. The optimization of electron transfer process will be held by minimization of losses via recombination, and extension of the lifetime of the charge separated state by usage of the electron relay.The goal is to couple light induced electron transfer process with the multi-electron catalytic process of hydrogen evolution. In this regard, light harvesters (molecules, metal nanostructures) that generate at least two electrons per absorbed photon will be studied. Additionally, semiconductors that generate long-lived charge separated states are utilized to accumulate several redox equivalents necessary for hydrogen evolution.The hybrid systems produced by the combination of the advantageous properties of molecules, semiconductors, and metal nanoparticles are under the scope of investigation. Metal nanoparticles are advantageous because of their high absorption cross-section. The molecular linkers provide control and flexibility in tuning the connection between the light absorber and the electron relay. Semiconductor nanoparticles offer the desired charge separation properties via prolonging the lifetime sufficiently to perform photocatalysis.The detailed understanding, investigation and development of the hybrid systems is at the heart of the progress of photochemical solar fuel production.
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| 9. |
- Shylin, Sergii I., et al.
(författare)
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Efficient visible light-driven water oxidation catalysed by an iron(IV) clathrochelate complex
- 2019
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Ingår i: Chemical Communications. - 1359-7345 .- 1364-548X. ; 55:23, s. 3335-3338
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Tidskriftsartikel (refereegranskat)abstract
- A water-stable FeIV clathrochelate complex catalyzes fast and homogeneous photochemical oxidation of water to dioxygen with a turnover frequency of 2.27 s−1 and a maximum turnover number of 365. An FeV intermediate generated under catalytic conditions is trapped and characterised using EPR and Mössbauer spectroscopy.
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| 10. |
- Yurdakal, Sedat, et al.
(författare)
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Selective photocatalytic oxidation of 3-pyridinemethanol on platinized acid/base modified TiO2
- 2021
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Ingår i: Catalysis Science & Technology. - : Royal Society of Chemistry. - 2044-4753 .- 2044-4761. ; 11:13, s. 4549-4559
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Tidskriftsartikel (refereegranskat)abstract
- TiO2 catalysts, modified with acidic or alkaline solutions and then platinized, were used for the partial photocatalytic oxidation of 3-pyridinemethanol to 3-pyridinemethanal and vitamin B-3 under environmentally friendly conditions. The reaction took place in water under UVA light and air oxygen. Catalysts were characterized by TEM, photoluminescence, DRIFT-IR, Raman, DRS, XPS, and photocurrent measurements. The photocatalytic activity results show that Pt loading of untreated samples leads to a significant activity improvement (hence product yield) as much as acid and alkaline treatments do. Moreover, the alkaline treated TiO2 samples exhibit a further increase in activity after loading with Pt. Pt acts as an electron scavenger promoting electron transfer from the TiO2 conduction band, consequently boosting the photogenerated pair numbers available for the reactive process. Photocurrent measurements show that the TiO2 photocatalysts' active sites increase significantly after platinization and alkaline/acid treatment. The treated and/or Pt loaded catalysts showed good thermal stability (at least up to 400 degrees C).
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