“How gas flow design can influence the performance of a DBD plasma reactor for dry reforming of methane”. Uytdenhouwen Y, Hereijgers J, Breugelmans T, Cool P, Bogaerts A, Chemical Engineering Journal 405, 126618 (2021). http://doi.org/10.1016/j.cej.2020.126618
Abstract: DBD plasma reactors are commonly used in a static ‘one inlet – one outlet’ design that goes against reactor design principles for multi-component reactions, such as dry reforming of methane (DRM). Therefore, in this paper we have developed a novel reactor design, and investigated how the shape and size of the reaction zone, as well as gradual gas addition, and the method of mixing CO2 and CH4 can influence the conversion and product com position of DRM. Even in the standard ‘one inlet – one outlet’ design, the direction of the gas flow (i.e. short or long path through the reactor, which defines the gas velocity at fixed residence time), as well as the dimensions of the reaction zone and the power delivery to the reactor, largely affect the performance. Using gradual gas addition and separate plasma activation zones for the individual gases give increased conversions within the same operational parameters, by optimising mixing ratios and kinetics. The choice of the main (pre-activated) gas and the direction of gas flow largely affect the conversion and energy cost, while the gas inlet position during separate addition only influences the product distribution.
Keywords: A1 Journal article; Engineering sciences. Technology; Laboratory of adsorption and catalysis (LADCA); Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT); Applied Electrochemistry & Catalysis (ELCAT)
Impact Factor: 6.216
DOI: 10.1016/j.cej.2020.126618
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“On the kinetics and equilibria of plasma-based dry reforming of methane”. Uytdenhouwen Y, Bal Km, Neyts Ec, Meynen V, Cool P, Bogaerts A, Chemical Engineering Journal 405, 126630 (2021). http://doi.org/10.1016/j.cej.2020.126630
Abstract: Plasma reactors are interesting for gas-based chemical conversion but the fundamental relation between the plasma chemistry and selected conditions remains poorly understood. Apparent kinetic parameters for the loss and formation processes of individual components of gas conversion processes, can however be extracted by performing experiments in an extended residence time range (2–75 s) and fitting the gas composition to a firstorder kinetic model of the evolution towards partial chemical equilibrium (PCE). We specifically investigated the differences in kinetic characteristics and PCE state of the CO2 dissociation and CH4 reforming reactions in a dielectric barrier discharge reactor (DBD), how these are mutually affected when combining both gases in the dry reforming of methane (DRM) reaction, and how they change when a packing material (non-porous SiO2) is added to the reactor. We find that CO2 dissociation is characterized by a comparatively high reaction rate of 0.120 s−1 compared to CH4 reforming at 0.041 s−1; whereas CH4 reforming reaches higher equilibrium conversions, 82% compared to 53.6% for CO2 dissociation. Combining both feed gases makes the DRM reaction to proceed at a relatively high rate (0.088 s−1), and high conversion (75.4%) compared to CO2 dissociation, through accessing new chemical pathways between the products of CO2 and CH4. The addition of the packing material can also distinctly influence the conversion rate and position of the equilibrium, but its precise effect depends strongly on the gas composition. Comparing different CO2:CH4 ratios reveals the delicate balance of the combined chemistry. CO2 drives the loss reactions in DRM, whereas CH4 in the mixture suppresses back reactions. As a result, our methodology provides some of the insight necessary to systematically tune the conversion process.
Keywords: A1 Journal article; Laboratory of adsorption and catalysis (LADCA); Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 6.216
DOI: 10.1016/j.cej.2020.126630
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“Tuning the turnover frequency and selectivity of photocatalytic CO2 reduction to CO and methane using platinum and palladium nanoparticles on Ti-Beta zeolites”. Blommaerts N, Hoeven N, Arenas Esteban D, Campos R, Mertens M, Borah R, Glisenti A, De Wael K, Bals S, Lenaerts S, Verbruggen SW, Cool P, Chemical Engineering Journal 410, 128234 (2021). http://doi.org/10.1016/j.cej.2020.128234
Abstract: A Ti-Beta zeolite was used in gas phase photocatalytic CO2 reduction to reduce the charge recombination rate and increase the surface area compared to P25 as commercial benchmark, reaching 607 m2 g-1. By adding Pt nanoparticles, the selectivity can be tuned toward CO, reaching a value of 92% and a turnover frequency (TOF) of 96 µmol.gcat-1.h-1, nearly an order of magnitude higher in comparison with P25. By adding Pd nanoparticles the selectivity can be shifted from CO (70% for a bare Ti-Beta zeolite), toward CH4 as the prevalent species (60%). In this way, the selectivity toward CO or CH4 can be tuned by either using Pt or Pd. The TOF values obtained in this work outperform reported state-of-the-art values in similar research. The improved activity by adding the nanoparticles was attributed to an improved charge separation efficiency, together with a plasmonic contribution of the metal nanoparticles under the applied experimental conditions.
Keywords: A1 Journal article; Engineering sciences. Technology; Sustainable Energy, Air and Water Technology (DuEL); Electron microscopy for materials research (EMAT); Laboratory of adsorption and catalysis (LADCA); AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 6.216
Times cited: 15
DOI: 10.1016/j.cej.2020.128234
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“ZnAl layered double hydroxide based catalysts (with Cu, Mn, Ti) used as noble metal-free three-way catalysts”. Van Everbroeck T, Wu J, Arenas-Esteban D, Ciocarlan R-G, Mertens M, Bals S, Dujardin C, Granger P, Seftel EM, Cool P, Applied clay science 217, 106390 (2022). http://doi.org/10.1016/j.clay.2021.106390
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Laboratory of adsorption and catalysis (LADCA)
Impact Factor: 5.6
Times cited: 6
DOI: 10.1016/j.clay.2021.106390
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“Use of nanoscale carbon layers on Ag-based gas diffusion electrodes to promote CO production”. Pacquets L, Van den Hoek J, Arenas Esteban D, Ciocarlan R-G, Cool P, Baert K, Hauffman T, Daems N, Bals S, Breugelmans T, ACS applied nano materials 5, 7723 (2022). http://doi.org/10.1021/ACSANM.2C00473
Abstract: A promising strategy for the inhibition of the hydrogen evolution reaction along with the stabilization of the electrocatalyst in electrochemical CO2 reduction cells involves the application of a nanoscale amorphous carbon layer on top of the active catalyst layer in a gas diffusion electrode. Without modifying the chemical nature of the electrocatalyst itself, these amorphous carbon layers lead to the stabilization of the electrocatalyst, and a significant improvement with respect to the inhibition of the hydrogen evolution reaction was also obtained. The faradaic efficiencies of hydrogen could be reduced from 31.4 to 2.1% after 1 h of electrolysis with a 5 nm thick carbon layer. Furthermore, the impact of the carbon layer thickness (5–30 nm) on this inhibiting effect was investigated. We determined an optimal thickness of 15 nm where the hydrogen evolution reaction was inhibited and a decent stability was obtained. Next, a thickness of 15 nm was selected for durability measurements. Interestingly, these durability measurements revealed the beneficial impact of the carbon layer already after 6 h by suppressing the hydrogen evolution such that an increase of only 37.9% exists compared to 56.9% without the use of an additional carbon layer, which is an improvement of 150%. Since carbon is only applied afterward, it reveals its great potential in terms of electrocatalysis in general.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT); Laboratory of adsorption and catalysis (LADCA); Applied Electrochemistry & Catalysis (ELCAT)
Impact Factor: 5.9
Times cited: 3
DOI: 10.1021/ACSANM.2C00473
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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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“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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“Hydrogen clathrates : next generation hydrogen storage materials”. Gupta A, Baron GV, Perreault P, Lenaerts S, Ciocarlan R-G, Cool P, Mileo PGM, Rogge S, Van Speybroeck V, Watson G, Van Der Voort P, Houlleberghs M, Breynaert E, Martens J, Denayer JFM, Energy Storage Materials 41, 69 (2021). http://doi.org/10.1016/J.ENSM.2021.05.044
Abstract: Extensive research has been carried on the molecular adsorption in high surface area materials such as carbonaceous materials and MOFs as well as atomic bonded hydrogen in metals and alloys. Clathrates stand among the ones to be recently suggested for hydrogen storage. Although, the simulations predict lower capacity than the expected by the DOE norms, the additional benefits of clathrates such as low production and operational cost, fully reversible reaction, environmentally benign nature, low risk of flammability make them one of the most promising materials to be explored in the next decade. The inherent ability to tailor the properties of clathrates using techniques such as addition of promoter molecules, use of porous supports and formation of novel reverse micelles morphology provide immense scope customisation and growth. As rapidly evolving materials, clathrates promise to get as close as possible in the search of “holy grail” of hydrogen storage. This review aims to provide the audience with the background of the current developments in the solid-state hydrogen storage materials, with a special focus on the hydrogen clathrates. The in-depth analysis of the hydrogen clathrates will be provided beginning from their discovery, various additives utilised to enhance their thermodynamic and kinetic properties, challenges in the characterisation of hydrogen in clathrates, theoretical developments to justify the experimental findings and the upscaling opportunities presented by this system. The review will present state of the art in the field and also provide a global picture for the path forward.
Keywords: A1 Journal article; Engineering sciences. Technology; Laboratory of adsorption and catalysis (LADCA); Sustainable Energy, Air and Water Technology (DuEL)
DOI: 10.1016/J.ENSM.2021.05.044
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“Plasma-catalytic ammonia synthesis : packed catalysts act as plasma modifiers”. Ndayirinde C, Gorbanev Y, Ciocarlan R-G, De Meyer R, Smets A, Vlasov E, Bals S, Cool P, Bogaerts A, Catalysis today 419, 114156 (2023). http://doi.org/10.1016/J.CATTOD.2023.114156
Abstract: We studied the plasma-catalytic production of NH3 from H2 and N2 in a dielectric barrier discharge plasma reactor using five different Co-based catalysts supported on Al2O3, namely Co/Al2O3, CoCe/Al2O3, CoLa/Al2O3, CoCeLa/Al2O3 and CoCeMg/Al2O3. The catalysts were characterized via several techniques, including SEM-EDX, and their performance was compared. The best performing catalyst was found to be CoLa/Al2O3, but the dif-ferences in NH3 concentration, energy consumption and production rate between the different catalysts were limited under the same conditions (i.e. feed gas, flow rate and ratio, and applied power). At the same time, the plasma properties, such as the plasma power and current profile, varied significantly depending on the catalyst. Taken together, these findings suggest that in the production of NH3 by plasma catalysis, our catalysts act as plasma modifiers, i.e., they change the discharge properties and hence the gas phase plasma chemistry. Importantly, this effect dominates over the direct catalytic effect (as e.g. in thermal catalysis) defined by the chemistry on the catalyst surface.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Laboratory of adsorption and catalysis (LADCA); Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 5.3
Times cited: 3
DOI: 10.1016/J.CATTOD.2023.114156
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