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Van Hoecke L, Laffineur L, Campe R, Perreault P, Verbruggen SW, Lenaerts S (2021) Challenges in the use of hydrogen for maritime applications
Abstract: Maritime shipping is a key factor that enables the global economy, however the pressure it exerts on the environment is increasing rapidly. In order to reduce the emissions of harmful greenhouse gasses, the search is on for alternative fuels for the maritime shipping industry. In this work the usefulness of hydrogen and hydrogen carriers is being investigated as a fuel for sea going ships. Due to the low volumetric energy density of hydrogen under standard conditions, the need for efficient storage of this fuel is high. Key processes in the use of hydrogen are discussed, starting with the production of hydrogen from fossil and renewable sources. The focus of this review is different storage methods, and in this work we discuss the storage of hydrogen at high pressure, in liquefied form at cryogenic temperatures and bound to liquid or solid-state carriers. In this work a theoretical introduction to different hydrogen storage methods precedes an analysis of the energy-efficiency and practical storage density of the carriers. In the final section the major challenges and hurdles for the development of hydrogen storage for the maritime industry are discussed. The most likely challenges will be the development of a new bunkering infrastructure and suitable monitoring of the safety to ensure safe operation of these hydrogen carriers on board the ship.
Keywords: A1 Journal Article;Review article, Hydrogen Production, Hydrogen Storage, Maritime Applications; Sustainable energy, air and water technology (DuEL)
Impact Factor: 29.518
DOI: 10.1039/D0EE01545H
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“Selectivity in ligand functionalization of photocatalytic metal oxide nanoparticles for phase transfer and self‐assembly applications”. Borah R, Ninakanti R, Nuyts G, Peeters H, Pedrazo-Tardajos A, Nuti S, Vande Velde C, De Wael K, Lenaerts S, Bals S, Verbruggen S, Chemistry-A European Journal , chem.202100029 (2021). http://doi.org/10.1002/CHEM.202100029
Abstract: Functionalization of photocatalytic metal oxide nanoparticles of TiO 2 , ZnO, WO 3 and CuO with amine‐terminated (oleylamine) and thiol‐terminated (1‐dodecanethiol) alkyl chained ligands was studied under ambient conditions. A high selectivity was observed in the binding specificity of a ligand towards nanoparticles of these different oxides. It was observed that oleylamine binds stably to only TiO 2 and WO 3 , while 1‐dodecanethiol binds stably only to ZnO and CuO. Similarly, polar to non‐polar solvent phase transfer of TiO 2 and WO 3 nanoparticles could be achieved by using oleylamine, but not by 1‐dodecanethiol, while the contrary holds for ZnO and CuO. The surface chemistry of ligand functionalized nanoparticles was probed by ATR‐FTIR spectroscopy, that enabled to elucidate the occupation of the ligands at the active sites. The photo‐stability of the ligands on the nanoparticle surface was determined by the photocatalytic self‐cleaning properties of the material. While TiO 2 and WO 3 degrade the ligands within 24 hours under both UV and visible light, ligands on ZnO and CuO remain unaffected. The gathered insights are also highly relevant from an application point of view. As an example, since the ligand functionalized nanoparticles are hydrophobic in nature, they can thus be self‐assembled at the air‐water interface, for obtaining nanoparticle films with demonstrated photocatalytic as well as anti‐fogging properties.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT); AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation); Sustainable Energy, Air and Water Technology (DuEL); Intelligence in PRocesses, Advanced Catalysts and Solvents (iPRACS)
Impact Factor: 5.317
Times cited: 15
DOI: 10.1002/CHEM.202100029
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“Layer-by-Layer-Stabilized Plasmonic Gold-Silver Nanoparticles on TiO2: Towards Stable Solar Active Photocatalysts”. Dingenen F, Blommaerts N, Van Hal M, Borah R, Arenas-Esteban D, Lenaerts S, Bals S, Verbruggen SW, Nanomaterials 11, 2624 (2021). http://doi.org/10.3390/nano11102624
Abstract: To broaden the activity window of TiO2, a broadband plasmonic photocatalyst has been designed and optimized. This plasmonic ‘rainbow’ photocatalyst consists of TiO2 modified with gold–silver composite nanoparticles of various sizes and compositions, thus inducing a broadband interaction with polychromatic solar light. However, these nanoparticles are inherently unstable, especially due to the use of silver. Hence, in this study the application of the layer-by-layer technique is introduced to create a protective polymer shell around the metal cores with a very high degree of control. Various TiO2 species (pure anatase, PC500, and P25) were loaded with different plasmonic metal loadings (0–2 wt %) in order to identify the most solar active composite materials. The prepared plasmonic photocatalysts were tested towards stearic acid degradation under simulated sunlight. From all materials tested, P25 + 2 wt % of plasmonic ‘rainbow’ nanoparticles proved to be the most promising (56% more efficient compared to pristine P25) and was also identified as the most cost-effective. Further, 2 wt % of layer-by-layer-stabilized ‘rainbow’ nanoparticles were loaded on P25. These layer-by-layer-stabilized metals showed superior stability under a heated oxidative atmosphere, as well as in a salt solution. Finally, the activity of the composite was almost completely retained after 1 month of aging, while the nonstabilized equivalent lost 34% of its initial activity. This work shows for the first time the synergetic application of a plasmonic ‘rainbow’ concept and the layer-by-layer stabilization technique, resulting in a promising solar active, and long-term stable photocatalyst.
Keywords: A1 Journal article; Engineering sciences. Technology; Sustainable Energy, Air and Water Technology (DuEL)
Impact Factor: 3.553
Times cited: 7
DOI: 10.3390/nano11102624
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“Effect of size distribution, skewness and roughness on the optical properties of colloidal plasmonic nanoparticles”. Borah R, Verbruggen SW, Colloids and surfaces: A: physicochemical and engineering aspects 640, 128521 (2022). http://doi.org/10.1016/j.colsurfa.2022.128521
Abstract: It is a generally accepted idea that the particle size distribution strongly affects the optical spectra of colloidal plasmonic nanoparticles. It is often quoted as one of the main reasons while explaining the mismatch between the theoretical and experimental optical spectra of such nanoparticles. In this work, these aspects are critically analyzed by means of a bottom up statistical approach that considers variables such as mean, standard deviation and skewness of the nanoparticle size distribution independently from one another. By assuming normal and log-normal distributions of the particle size, the effect of the statistical parameters on the Mie analytical optical spectra of colloidal nanoparticles was studied. The effect of morphology was also studied numerically in order to understand to what extent it can play a role. It is our finding that the particle polydispersity, skewness and surface morphology in fact only weakly impact the optical spectra. While, the selection of suitable optical constants with regard to the crystallinity of the nanoparticles is a far more influential factor for correctly predicting both the plasmon band position and the plasmon bandwidth in theoretical simulations of the optical spectra. It is shown that the mean particle size can be correctly estimated directly from the plasmon band position, as it is the mean that determines the resonance wavelength. The standard deviation can on the other hand be estimated from the intensity distribution data obtained from dynamic light scattering experiments. The results reported herein clear the ambiguity around particle size distribution and optical response of colloidal plasmonic nanoparticles.
Keywords: A1 Journal article; Engineering sciences. Technology; Sustainable Energy, Air and Water Technology (DuEL)
Impact Factor: 5.2
DOI: 10.1016/j.colsurfa.2022.128521
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“Self-assembled ligand-capped plasmonic Au nanoparticle films in the Kretschmann configuration for sensing of volatile organic compounds”. Borah R, Smets J, Ninakanti R, Tietze ML, Ameloot R, Chigrin DN, Bals S, Lenaerts S, Verbruggen SW, ACS applied nano materials 5, acsanm.2c02524 (2022). http://doi.org/10.1021/ACSANM.2C02524
Abstract: Films of close-packed Au nanoparticles are coupled electrodynamically through their collective plasmon resonances. This collective optical response results in enhanced light–matter interactions, which can be exploited in various applications. Here, we demonstrate their application in sensing volatile organic compounds, using methanol as a test case. Ordered films over several cm2 were obtained by interfacial self-assembly of colloidal Au nanoparticles (∼10 nm diameter) through controlled evaporation of the solvent. Even though isolated nanoparticles of this size are inherently nonscattering, when arranged in a close-packed film the plasmonic coupling results in a strong reflectance and absorbance. The in situ tracking of vapor phase methanol concentration through UV–vis transmission measurements of the nanoparticle film is first demonstrated. Next, in situ ellipsometry of the self-assembled films in the Kretschmann (also known as ATR) configuration is shown to yield enhanced sensitivity, especially with phase difference measurements, Δ. Our study shows the excellent agreement between theoretical models of the spectral response of self-assembled films with experimental in situ sensing experiments. At the same time, the theoretical framework provides the basis for the interpretation of the various observed experimental trends. Combining periodic nanoparticle films with ellipsometry in the Kretschmann configuration is a promising strategy toward highly sensitive and selective plasmonic thin-film devices based on colloidal fabrication methods for volatile organic compound (VOC) sensing applications.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT); Sustainable Energy, Air and Water Technology (DuEL)
Impact Factor: 5.9
Times cited: 11
DOI: 10.1021/ACSANM.2C02524
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“Assessing the potential of application of titanium dioxide for photocatalytic degradation of deposited soot on asphalt pavement surfaces”. Omranian SR, Geluykens M, Van Hal M, Hasheminejad N, Rocha Segundo I, Pipintakos G, Denys S, Tytgat T, Fraga Freitas E, Carneiro J, Verbruggen S, Vuye C, Construction and building materials 350, 128859 (2022). http://doi.org/10.1016/J.CONBUILDMAT.2022.128859
Abstract: It is known that pollutants and their irreparable influence can considerably jeopardize the environment and human health. Such disastrous, growing, hazardous particles urged researchers to find effective ways and diminish their destructive impacts and preserve our planet. This study evaluates the potential of incorporating Titanium Dioxide (TiO2) semiconductor nanoparticles on asphalt pavements to degrade pollutants without compromising bitumen performance. Accordingly, the Response Surface Method (RSM) was employed to develop an experimental matrix based on the central composite design. Image Analysis (IA) was used to determine the rate of soot degradation (as pollutant representative) using MATLAB and ImageJ software. Confocal Laser Scanning Microscopy (CLSM), Fourier Transform Infrared spectroscopy (FTIR), and Dynamic Shear Rheometer (DSR) were finally carried out to estimate the effects of adding different percentages of TiO2 on the micro -structural features and dispersion of the TiO2, chemical fingerprinting, and rheological performance of the bituminous binder. The results showed a promising potential of TiO2 to degrade soot (over 50%) during the conducted experiments. In addition, the RSM outcomes showed that applying a higher amount of TiO2 is more efficient for pollutant degradation. Finally, no negative impact was observed, neither on the rheological behavior nor on the aging susceptibility of the bitumen, even though the homogenous dispersion of the TiO2 was clearly captured via CLSM.
Keywords: A1 Journal article; Engineering sciences. Technology; Sustainable Energy, Air and Water Technology (DuEL)
Impact Factor: 7.4
DOI: 10.1016/J.CONBUILDMAT.2022.128859
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“Correlation between the fluorination degree of perfluorinated zinc phthalocyanines, their singlet oxygen generation ability, and their photoelectrochemical response for phenol sensing”. Neven L, Barich H, Ching HYV, Khan SU, Colomier C, Patel HH, Gorun SM, Verbruggen S, Van Doorslaer S, De Wael K, Analytical chemistry 94, 5221 (2022). http://doi.org/10.1021/ACS.ANALCHEM.1C04357
Abstract: Electron-withdrawing perfluoroalkyl peripheral groups grafted on phthalocyanine (Pc) macrocycles improve their single-site isolation, solubility, and resistance to self-oxidation, all beneficial features for catalytic applications. A high degree of fluorination also enhances the reducibility of Pcs and could alter their singlet oxygen (1O2) photoproduction. The ethanol/toluene 20:80 vol % solvent mixture was found to dissolve perfluorinated FnPcZn complexes, n = 16, 52, and 64, and minimize the aggregation of the sterically unencumbered F16PcZn. The 1O2 production ability of FnPcZn complexes was examined using 9,10-dimethylanthracene (DMA) and 2,2,6,6-tetramethylpiperidine (TEMP) in combination with UV–vis and electron paramagnetic resonance (EPR) spectroscopy, respectively. While the photoreduction of F52PcZn and F64PcZn in the presence of redox-active TEMP lowered 1O2 production, DMA was a suitable 1O2 trap for ranking the complexes. The solution reactivity was complemented by solid-state studies via the construction of photoelectrochemical sensors based on TiO2-supported FnPcZn, FnPcZn|TiO2. Phenol photo-oxidation by 1O2, followed by its electrochemical reduction, defines a redox cycle, the 1O2 production having been found to depend on the value of n and structural features of the supported complexes. Consistent with solution studies, F52PcZn was found to be the most efficient 1O2 generator. The insights on reactivity testing and structural–activity relationships obtained may be useful for designing efficient and robust sensors and for other 1O2-related applications of FnPcZn.
Keywords: A1 Journal article; Organic synthesis (ORSY); Sustainable Energy, Air and Water Technology (DuEL); Antwerp Electrochemical and Analytical Sciences Lab (A-Sense Lab)
Impact Factor: 7.4
DOI: 10.1021/ACS.ANALCHEM.1C04357
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“Experimental investigation of methane hydrate formation in the presence of metallic packing”. Kummamuru NB, Verbruggen SW, Lenaerts S, Perreault P, Fuel 323, 124269 (2022). http://doi.org/10.1016/J.FUEL.2022.124269
Abstract: Clathrate hydrates gained significant attention as a viable option for large-scale storage of natural gas, primarily methane (CH4). Unlike employing the nanoconfinement for enhancing the nucleation sites and hydrate growth as in the porous materials, whose synthesis is often associated with high costs and poor batch reproducibility, a new approach for promoting CH4 hydrates using pure water (H2O) in an unstirred reactor packed with stainless steel beads (SSB) was proposed in this fundamental work, where the interstitial space between the beads was exploited for enhanced hydrate growth. SSB of two diameters, 5 mm and 2 mm, were used as. a packed bed to investigate their effects on CH4 hydrate formation at 273.65 K, 275.65 K, and 277.65 K with an initial pressure of 6 MPa. The thermal conductivity of SSB packing potentially aided hydrate growth by expelling the hydration heat, while, the results also revealed that driving force has a substantial impact on the rate of CH4 hydrate formation and gas uptake. The experiments conducted in both 5 mm and 2 mm SSB packed bed reactors showed a maximum gas uptake of 0.147 mol CH4/mol H2O at 273.65 K with water to hydrate conversion of 84.42% with no significant variation. The results established the promotion effect on the kinetics of CH4 hydrate formation in the unstirred reactor packed with 2 mm SSB due to the availability of more interstitial space offering multiple nucleation sites for CH4 hydrate by providing a larger specific surface area for H2O-CH4 reaction. Experiments with varying H2O content were also performed and the results showed that the water to hydrate conversion and rate of hydrate formation could be enhanced at a lower H2O content in a packed bed reactor. This study demonstrates that the use of costly or intricate porous materials can be made redundant, by exploiting the interstitial voids in packing of cheap and widely available SSB as a promising alternative material for enhancing the kinetics of artificial CH4 hydrate synthesis.
Keywords: A1 Journal article; Engineering sciences. Technology; Sustainable Energy, Air and Water Technology (DuEL)
Impact Factor: 7.4
DOI: 10.1016/J.FUEL.2022.124269
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“Photocatalytic soot degradation under UV and visible light”. Van Hal M, Lenaerts S, Verbruggen SW, Environmental Science and Pollution Research , 1 (2022). http://doi.org/10.1007/S11356-022-23804-0
Abstract: Particulate matter is one of the most persistent global air pollutants that is causing health problems, climate disturbance and building deterioration. A sustainable technique that is able to degrade soot using (sun)light is photocatalysis. Currently, research on photocatalytic soot oxidation focusses on large band gap TiO2-based photocatalysts and thus requires the use of UV light. It would prove useful if visible light, and thus a larger fraction of the (freely available) solar spectrum, could additionally be utilised to drive this process. In this work, a visible light-active photocatalyst, WO3, is benchmarked to TiO2 under both UV and visible light. At the same time, the versatility and drastic improvement of a recently introduced digital image-based soot degradation detection method are demonstrated. An additional step correcting for non-soot related catalyst colour changes is applied, resulting in accurate detection and quantification of soot degradation for all studied photocatalysts, even for materials such as WO3 that are inherently coloured. With this study, we aim to broaden the scope of photocatalytic soot oxidation technology to visible light-active photocatalyst. Along with this study, we provide a versatile soot degradation detection methodology based on digital image analysis that is made widely applicable.
Keywords: A1 Journal article; Engineering sciences. Technology
Impact Factor: 5.8
DOI: 10.1007/S11356-022-23804-0
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“Photoelectrochemical behavior of phthalocyanine-sensitized TiO₂, in the presence of electron-shuttling mediators”. Khan SU, Trashin S, Beltran V, Korostei YS, Pelmus M, Gorun SM, Dubinina T V, Verbruggen SW, De Wael K, Analytical chemistry 94, 12723 (2022). http://doi.org/10.1021/ACS.ANALCHEM.2C02210
Abstract: Dye-sensitized TiO(2 )has found many applications for dye sensitized solar cells (DSSC), solar-to-chemical energy conversion, water/air purification systems, and (electro)chemical sensors. We report an electrochemical system for testing dye-sensitized materials that can be utilized in photoelectrochemical (PEC) sensors and energy conversion. Unlike related systems, the reported system does not require a direct electron transfer from semiconductors to electrodes. Rather, it relies on electron shuttling by redox mediators. A range of model photocatalytic materials were prepared using three different TiO2 materials (P25, P90, and PC500) and three sterically hindered phthalocyanines (Pcs) with electron-rich tert-butyl substituents (t-Bu4PcZn, t-Bu4PcAlCl, and t-Bu4PcH2). The materials were compared with previously developed TiO(2 )modified by electron-deficient, also sterically hindered fluorinated phthalocyanine F64PcZn, a singlet oxygen (O-1(2)) producer, as well as its metal-free derivative, F64PcH2. The PEC activity depended on the redox mediator, as well as the type of TiO2 and Pc. By comparing the responses of one-electron shuttles, such as K4Fe(CN)(4), and O-1(2)-reactive electron shuttles, such as phenol, it is possible to reveal the action mechanism of the supported photosensitizers, while the overall activity can be assessed using hydroquinone. t-Bu4PcAlCl showed significantly lower blank responses and higher specific responses toward chlorophenols compared to t-Bu4PcZn due to the electron-withdrawing effect of the Al3+ metal center. The combination of reactivity insights and the need for only microgram amounts of sensing materials renders the reported system advantageous for practical applications.
Keywords: A1 Journal article; Sustainable Energy, Air and Water Technology (DuEL); Antwerp Electrochemical and Analytical Sciences Lab (A-Sense Lab)
Impact Factor: 7.4
DOI: 10.1021/ACS.ANALCHEM.2C02210
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“Plasmon resonance of gold and silver nanoparticle arrays in the Kretschmann (attenuated total reflectance) vs. direct incidence configuration”. Borah R, Ninakanti R, Bals S, Verbruggen SW, Scientific reports 12, 15738 (2022). http://doi.org/10.1038/S41598-022-20117-7
Abstract: While the behaviour of plasmonic solid thin films in the Kretschmann (also known as Attenuated Total Reflection, ATR) configuration is well-understood, the use of discrete nanoparticle arrays in this optical configuration is not thoroughly explored. It is important to do so, since close packed plasmonic nanoparticle arrays exhibit exceptionally strong light-matter interactions by plasmonic coupling. The present work elucidates the optical properties of plasmonic Au and Ag nanoparticle arrays in both the direct normal incidence and Kretschmann configuration by numerical models, that are validated experimentally. First, hexagonal close packed Au and Ag nanoparticle films/arrays are obtained by air–liquid interfacial assembly. The numerical models for the rigorous solution of the Maxwell’s equations are validated using experimental optical spectra of these films before systematically investigating various parameters. The individual far-field/near-field optical properties, as well as the plasmon relaxation mechanism of the nanoparticles, vary strongly as the packing density of the array increases. In the Kretschmann configuration, the evanescent fields arising from p – and s -polarized (or TM and TE polarized) incidence have different directional components. The local evanescent field intensity and direction depends on the polarization, angle of incidence and the wavelength of incidence. These factors in the Kretschmann configuration give rise to interesting far-field as well as near-field optical properties. Overall, it is shown that plasmonic nanoparticle arrays in the Kretschmann configuration facilitate strong broadband absorptance without transmission losses, and strong near-field enhancement. The results reported herein elucidate the optical properties of self-assembled nanoparticle films, pinpointing the ideal conditions under which the normal and the Kretschmann configuration can be exploited in multiple light-driven applications.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT); Sustainable Energy, Air and Water Technology (DuEL)
Impact Factor: 4.6
Times cited: 11
DOI: 10.1038/S41598-022-20117-7
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“Plasmonic hybrid nanostructures in photocatalysis : structures, mechanisms, and applications”. Ninakanti R, Dingenen F, Borah R, Peeters H, Verbruggen SW, Topics in Current Chemistry 380, 40 (2022). http://doi.org/10.1007/S41061-022-00390-W
Abstract: (Sun)Light is an abundantly available sustainable source of energy that has been used in catalyzing chemical reactions for several decades now. In particular, studies related to the interaction of light with plasmonic nanostructures have been receiving increased attention. These structures display the unique property of localized surface plasmon resonance, which converts light of a specific wavelength range into hot charge carriers, along with strong local electromagnetic fields, and/or heat, which may all enhance the reaction efficiency in their own way. These unique properties of plasmonic nanoparticles can be conveniently tuned by varying the metal type, size, shape, and dielectric environment, thus prompting a research focus on rationally designed plasmonic hybrid nanostructures. In this review, the term “hybrid” implies nanomaterials that consist of multiple plasmonic or non-plasmonic materials, forming complex configurations in the geometry and/or at the atomic level. We discuss the synthetic techniques and evolution of such hybrid plasmonic nanostructures giving rise to a wide variety of material and geometric configurations. Bimetallic alloys, which result in a new set of opto-physical parameters, are compared with core–shell configurations. For the latter, the use of metal, semiconductor, and polymer shells is reviewed. Also, more complex structures such as Janus and antenna reactor composites are discussed. This review further summarizes the studies exploiting plasmonic hybrids to elucidate the plasmonic-photocatalytic mechanism. Finally, we review the implementation of these plasmonic hybrids in different photocatalytic application domains such as H2 generation, CO2 reduction, water purification, air purification, and disinfection.
Keywords: A1 Journal article; Sustainable Energy, Air and Water Technology (DuEL)
DOI: 10.1007/S41061-022-00390-W
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“Probing oxygen activation on plasmonic photocatalysts”. Dingenen F, Borah R, Ninakanti R, Verbruggen SW, Frontiers in Chemistry 10, 988542 (2022). http://doi.org/10.3389/FCHEM.2022.988542
Abstract: In this work we present an assay to probe the oxygen activation rate on plasmonic nanoparticles under visible light. Using a superoxide-specific XTT molecular probe, the oxygen activation rate on bimetallic gold-silver “rainbow” nanoparticles with a broadband visible light (> 420 nm) response, is determined at different light intensities by measuring its conversion into the colored XTT-formazan derivate. A kinetic model is applied to enable a quantitative estimation of the rate constant, and is shown to match almost perfectly with the experimental data. Next, the broadband visible light driven oxygen activation capacity of this plasmonic rainbow system, supported on nano-sized SiO 2 , is demonstrated towards the oxidation of aniline to azobenzene in DMSO. To conclude, a brief theoretical discussion is devoted to the possible mechanisms behind such plasmon-driven reactions.
Keywords: A1 Journal article; Sustainable Energy, Air and Water Technology (DuEL)
Impact Factor: 5.5
DOI: 10.3389/FCHEM.2022.988542
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“Benchmarking the photocatalytic self-cleaning activity of industrial and experimental materials with ISO 27448:2009”. Peeters H, Lenaerts S, Verbruggen SW, Materials 16, 1119 (2023). http://doi.org/10.3390/MA16031119
Abstract: Various industrial surface materials are tested for their photocatalytic self-cleaning activity by performing the ISO 27448:2009 method. The samples are pre-activated by UV irradiation, fouled with oleic acid and irradiated by UV light. The degradation of oleic acid over time is monitored by taking water contact angle measurements using a contact angle goniometer. The foulant, oleic acid, is an organic acid that makes the surface more hydrophobic. The water contact angle will thus decrease over time as the photocatalytic material degrades the oleic acid. In this study, we argue that the use of this method is strongly limited to specific types of surface materials, i.e., only those that are hydrophilic and smooth in nature. For more hydrophobic materials, the difference in the water contact angles of a clean surface and a fouled surface is not measurable. Therefore, the photocatalytic self-cleaning activity cannot be established experimentally. Another type of material that cannot be tested by this standard are rough surfaces. For rough surfaces, the water contact angle cannot be measured accurately using a contact angle goniometer as prescribed by the standard. Because of these limitations, many potentially interesting industrial substrates cannot be evaluated. Smooth samples that were treated with an in-house developed hydrophilic titania thin film (PCT/EP2018/079983) showed a great photocatalytic self-cleaning performance according to the ISO standard. Apart from discussing the pros and cons of the current ISO standard, we also stress how to carefully interpret the results and suggest alternative testing solutions.
Keywords: A1 Journal article; Engineering sciences. Technology
Impact Factor: 3.4
DOI: 10.3390/MA16031119
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“Recent trends in plasmon‐assisted photocatalytic CO₂, reduction”. Ciocarlan R-G, Blommaerts N, Lenaerts S, Cool P, Verbruggen SW, Chemsuschem 16, e202201647 (2023). http://doi.org/10.1002/CSSC.202201647
Abstract: Direct photocatalytic reduction of CO2 has become an highly active field of research. It is thus of utmost importance to maintain an overview of the various materials used to sustain this process, find common trends, and, in this way, eventually improve the current conversions and selectivities. In particular, CO2 photoreduction using plasmonic photocatalysts under solar light has gained tremendous attention, and a wide variety of materials has been developed to reduce CO2 towards more practical gases or liquid fuels (CH4, CO, CH3OH/CH3CH2OH) in this manner. This Review therefore aims at providing insights in current developments of photocatalysts consisting of only plasmonic nanoparticles and semiconductor materials. By classifying recent studies based on product selectivity, this Review aims to unravel common trends that can provide effective information on ways to improve the photoreduction yield or possible means to shift the selectivity towards desired products, thus generating new ideas for the way forward.
Keywords: A1 Journal article; Engineering sciences. Technology; Laboratory of adsorption and catalysis (LADCA)
Impact Factor: 8.4
DOI: 10.1002/CSSC.202201647
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“A review on self‐assembly of colloidal nanoparticles into clusters, patterns, and films : emerging synthesis techniques and applications”. Borah R, Ag KR, Minja AC, Verbruggen SW, Small methods , 1 (2023). http://doi.org/10.1002/SMTD.202201536
Abstract: The colloidal synthesis of functional nanoparticles has gained tremendous scientific attention in the last decades. In parallel to these advancements, another rapidly growing area is the self-assembly or self-organization of these colloidal nanoparticles. First, the organization of nanoparticles into ordered structures is important for obtaining functional interfaces that extend or even amplify the intrinsic properties of the constituting nanoparticles at a larger scale. The synthesis of large-scale interfaces using complex or intricately designed nanostructures as building blocks, requires highly controllable self-assembly techniques down to the nanoscale. In certain cases, for example, when dealing with plasmonic nanoparticles, the assembly of the nanoparticles further enhances their properties by coupling phenomena. In other cases, the process of self-assembly itself is useful in the final application such as in sensing and drug delivery, amongst others. In view of the growing importance of this field, this review provides a comprehensive overview of the recent developments in the field of nanoparticle self-assembly and their applications. For clarity, the self-assembled nanostructures are classified into two broad categories: finite clusters/patterns, and infinite films. Different state-of-the-art techniques to obtain these nanostructures are discussed in detail, before discussing the applications where the self-assembly significantly enhances the performance of the process.
Keywords: A1 Journal article; Engineering sciences. Technology
Impact Factor: 12.4
DOI: 10.1002/SMTD.202201536
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“Sunlight-powered reverse water gas shift reaction catalysed by plasmonic Au/TiO₂, nanocatalysts : effects of Au particle size on the activity and selectivity”. Volders J, Elen K, Raes A, Ninakanti R, Kelchtermans A-S, Sastre F, Hardy A, Cool P, Verbruggen SW, Buskens P, Van Bael MK, Nanomaterials 12, 4153 (2022). http://doi.org/10.3390/NANO12234153
Abstract: This study reports the low temperature and low pressure conversion (up to 160 °C, p = 3.5 bar) of CO2 and H2 to CO using plasmonic Au/TiO2 nanocatalysts and mildly concentrated artificial sunlight as the sole energy source (up to 13.9 kW·m-2 = 13.9 suns). To distinguish between photothermal and non-thermal contributors, we investigated the impact of the Au nanoparticle size and light intensity on the activity and selectivity of the catalyst. A comparative study between P25 TiO2-supported Au nanocatalysts of a size of 6 nm and 16 nm displayed a 15 times higher activity for the smaller particles, which can only partially be attributed to the higher Au surface area. Other factors that may play a role are e.g., the electronic contact between Au and TiO2 and the ratio between plasmonic absorption and scattering. Both catalysts displayed ≥84% selectivity for CO (side product is CH4). Furthermore, we demonstrated that the catalytic activity of Au/TiO2 increases exponentially with increasing light intensity, which indicated the presence of a photothermal contributor. In dark, however, both Au/TiO2 catalysts solely produced CH4 at the same catalyst bed temperature (160 °C). We propose that the difference in selectivity is caused by the promotion of CO desorption through charge transfer of plasmon generated charges (as a non-thermal contributor).
Keywords: A1 Journal article; Engineering sciences. Technology; Laboratory of adsorption and catalysis (LADCA); Sustainable Energy, Air and Water Technology (DuEL)
Impact Factor: 5.3
DOI: 10.3390/NANO12234153
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“Efficient iron phosphide catalyst as a counter electrode in dye-sensitized solar cells”. Yildiz A, Chouki T, Atli A, Harb M, Verbruggen SW, Ninakanti R, Emin S, ACS applied energy materials 4, 10618 (2021). http://doi.org/10.1021/ACSAEM.1C01628
Abstract: Developing an efficient material as a counter electrode (CE) with excellent catalytic activity, intrinsic stability, and low cost is essential for the commercial application of dye-sensitized solar cells (DSSCs). Transition metal phosphides have been demonstrated as outstanding multifunctional catalysts in a broad range of energy conversion technologies. Here, we exploited different phases of iron phosphide as CEs in DSSCs with an I–/I3–-based electrolyte. Solvothermal synthesis using a triphenylphosphine precursor as a phosphorus source allows to grow a Fe2P phase at 300 °C and a FeP phase at 350 °C. The obtained iron phosphide catalysts were coated on fluorine-doped tin oxide substrates and heat-treated at 450 °C under an inert gas atmosphere. The solar-to-current conversion efficiency of the solar cells assembled with the Fe2P material reached 3.96 ± 0.06%, which is comparable to the device assembled with a platinum (Pt) CE. DFT calculations support the experimental observations and explain the fundamental origin behind the improved performance of Fe2P compared to FeP. These results indicate that the Fe2P catalyst exhibits excellent performance along with desired stability to be deployed as an efficient Pt-free alternative in DSSCs.
Keywords: A1 Journal article; Engineering sciences. Technology; Sustainable Energy, Air and Water Technology (DuEL)
DOI: 10.1021/ACSAEM.1C01628
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“Gas phase photofuel cell consisting of WO₃- and TiO₂-photoanodes and an air-exposed cathode for simultaneous air purification and electricity generation”. Van Hal M, Campos R, Lenaerts S, De Wael K, Verbruggen SW, Applied Catalysis B-Environmental 292, 120204 (2021). http://doi.org/10.1016/J.APCATB.2021.120204
Abstract: Research has shown the potential of photofuel cells (PFCs) for waste water treatment, enabling the (partial) recovery of the energy released from the degraded compounds as electricity. Literature on PFCs targeting air pollution on the other hand is extremely scarce. In this work an autonomously operating air purification device targeting sustainable electricity generation is presented. Knowledge on gas phase operation of PFCs was gathered by combining photocatalytic and photoelectrochemical measurements, both for TiO2 and WO3-based photocatalysts. While TiO2-based photocatalysts performed better in direct photocatalytic experiments, they were outperformed by WO3-based photoanodes in all-gas-phase PFC operation. Not only do WO3-based photocatalysts generate the highest steady state photocurrent, they also achieved the highest fuel-to-electricity conversion (>65 %). The discrepancies between gas phase photocatalytic and photoelectrochemical processes highlight the difference in driving material properties. This study serves as a proof-of-concept towards development of an autonomous, low-cost and widely applicable waste gas-to-electricity PFC device.
Keywords: A1 Journal article; Engineering sciences. Technology; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation); Sustainable Energy, Air and Water Technology (DuEL)
Impact Factor: 9.446
DOI: 10.1016/J.APCATB.2021.120204
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“Surface plasmon resonance-induced visible light photocatalytic TiO₂, modified with AuNPs for the quantification of hydroquinone”. Mendonça CD, Khan SU, Rahemi V, Verbruggen SW, Machado SAS, De Wael K, Electrochimica Acta 389, 138734 (2021). http://doi.org/10.1016/J.ELECTACTA.2021.138734
Abstract: The impregnation of size-controlled gold nanoparticles (AuNPs) on an anatase TiO2 structure (AuNPs@TiO2) was studied for the photoelectrochemical detection of hydroquinone (HQ) under visible light illumination integrated into a flow injection analysis (FIA) setup. The crystalline form of TiO2 was preserved during synthesis and the homogeneous distribution of AuNPs over the TiO2 structure was confirmed. Its photoelectrocatalytic activity was improved due to the presence of AuNPs, preventing charge recombination in TiO2 and improving its light absorption ability by the surface plasmon resonance effect (SPR). The FIA system was used in order to significantly reduce the electrode fouling during electroanalysis through periodic washing steps of the electrode surface. During the amperometric detection process, reactive oxygen species (ROS), generated by visible light illumination of AuNPs@TiO2, participate in the oxidation process of HQ. The reduction of the oxidized form of HQ, i.e. benzoquinone (BQ) occurs by applying a negative potential and the measurable amperometric response will be proportional to the initial HQ concentration. The influencing parameters on the response of the amperometric photocurrent such as applied potential, flow rate and pH were investigated. The linear correlation between the amperometric response and the concentration of HQ was recorded (range 0.0125 – 1.0 µM) with a limit of detection (LOD) of 33.8 nM and sensitivity of 0.22 A M−1 cm−2. In this study, we illustrated for the first time that the impregnation of AuNPs in TiO2 allows the sensitive detection of phenolic substances under green laser illumination by using a photoelectrochemical flow system.
Keywords: A1 Journal article; Engineering sciences. Technology; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation); Sustainable Energy, Air and Water Technology (DuEL)
Impact Factor: 4.798
DOI: 10.1016/J.ELECTACTA.2021.138734
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“Tapping hydrogen fuel from the ocean : a review on photocatalytic, photoelectrochemical and electrolytic splitting of seawater”. Dingenen F, Verbruggen SW, Renewable &, Sustainable Energy Reviews 142, 110866 (2021). http://doi.org/10.1016/J.RSER.2021.110866
Abstract: Direct splitting of earth-abundant seawater provides an eco-friendly route for the production of clean H2, but is hampered by selectivity and stability issues. Direct seawater electrolysis is the most established technology, attaining high current densities in the order of 1–2 A cm−2. Alternatively, light-driven processes such as photocatalytic and photoelectrochemical seawater splitting are particularly promising as well, as they rely on renewable solar power. Solar-to-Hydrogen efficiencies have increased over the past decade from negligible values to about 2%. Especially the absence of large local pH changes (in the order of several tenths of a pH unit compared to up to 9 pH units for electrolysis) is a strong asset for pure photocatalysis. This may lead to less adverse side-reactions such as Cl2 and ClO− formation, (acid or base induced) corrosion and scaling. Besides, additional requirements for electrolytic cells, e.g. membranes and electricity input, are not needed in pure photocatalysis systems. In this review, the state-of-the-art technologies in light-driven seawater splitting are compared to electrochemical approaches with a focus on sustainability and stability. Promising advances are identified at the level of the catalyst as well as the process, and insight is provided in solutions crossing different fields.
Keywords: A1 Journal article; Engineering sciences. Technology; Sustainable Energy, Air and Water Technology (DuEL)
Impact Factor: 8.05
DOI: 10.1016/J.RSER.2021.110866
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“Black titania by sonochemistry : a critical evaluation of existing methods”. Raes A, Ninakanti R, Van den Bergh L, Borah R, Van Doorslaer S, Verbruggen SW, Ultrasonics sonochemistry 100, 106601 (2023). http://doi.org/10.1016/J.ULTSONCH.2023.106601
Abstract: In the field of photocatalysis, the fabrication of black titania is a booming topic, as it offers a system with improved solar light harvesting properties and increased overall efficiency. The darkening of white TiO2 powders can be ascribed to surface hydroxylation, oxygen vacancies, Ti3+ centres, or a combination thereof. A handful of studies suggests these defects can be conveniently introduced by acoustic cavitation, generated during sonochemical treatment of pristine TiO2 powders. In reproducing these studies, P25 TiO2 samples were ultrasonicated for various hours with a power density of 8000 W/L, resulting in powders that indeed became gradually darker with increasing sonication time. However, HAADF–STEM revealed that extensive erosion of the sonotrode tip took place and contaminated the samples, which appeared to be the primary reason for the observed colour change. This was confirmed by UV–Vis DRS and DRIFTS, that showed no significant alteration of the catalyst surface after sonication. EPR measurements showed that only an insignificant fraction of Ti3+ centres were produced, far less than in a TiO2 sample that was chemically reduced with NaBH4. No evidence of the presence oxygen vacancies could be found. The enhanced photocatalytic activities of ultrasonicated materials reported in literature can therefore not be ascribed to the synthesis of actual black (defected) TiO2, but rather to specific changes in morphology as a result of acoustic cavitation. Also, this study underlines the importance of considering probe erosion in sonochemical catalyst synthesis, which is an unavoidable side effect that can have an important impact on the catalyst appearance, properties and performance.
Keywords: A1 Journal article; Theory and Spectroscopy of Molecules and Materials (TSM²); Laboratory of adsorption and catalysis (LADCA)
Impact Factor: 8.4
DOI: 10.1016/J.ULTSONCH.2023.106601
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