2021
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Research axis: Manufacturing of nanostructured materials Authors: Bruno Pinho, Laura Torrente-Murciano Journal: Advanced Energy Materials AbstractNanomaterials are at the core of many scientific discoveries in catalysis, energy and healthcare to name a few. However, their deployment is limited by the lack of reproducible and precise manufacturing technologies on-demand. In this work, a precision automated technology is demonstrated for nanoparticles synthesis with wide-range tunable sizes (≈4–100 nm). Dial-a-particle capabilities are achieved by a combination of a fast integrated multipoint particle sizing combined with a “plug-n-play” modular platform with reactors in series, distributed feed and in situ multipoint analysis. Real-time early growth information accurately predicts the resulting particle properties. Such real-time simple feedback control can overcome repeatability and stability issues associated with controllable (e.g., conditions) and uncontrollable (e.g., fouling, ageing, and impurities) variations leading to self-regulated, highly stable multistage systems with no human intervention even with long residence times (from a few minutes to hours). This is a paradigm shift from machine learning (ML) methodologies, which are restricted to trained networks with rich data sets, impractical in non-reproducible processes and limited to short residence times (e.g., within few minutes). The approach is demonstrated for plasmonic silver and gold nanoparticles showing agile control within minutes, opening the door for automation of more complex multistage procedures such as composites, multielement materials, and particle functionalization. https://doi.org/10.1002/aenm.202100918 |
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Research axis: Sustainable energy Authors: Collin Smith, Laura Torrente-Murciano Journal: Advanced Energy Materials Abstract:The synthesis of ammonia through the Haber‐Bosch process has been at the foundation of the chemical industry for over 100 years, but when the energy and feedstock sources switch from fossil fuels to renewable electricity, the process needs to be reimagined. Herein, the successful integration of ammonia synthesis and separation is demonstrated in a recycle‐less process setting the foundations of green ammonia technology. The ruthenium‐based catalyst uses a nanostructured CeO2 support and Cs electronic promotion to remove hydrogen and ammonia inhibition, respectively, creating a catalyst with low‐temperature (<300 °C) activity that quickly approaches equilibrium. The absorbent uses MnCl2 to avoid the acid releasing decomposition of conventional absorbents like MgCl2, and a support of SiO2 to simultaneously enhance MnCl2dispersion and improve stabilization. https://doi.org/10.1002/aenm.202100918 |
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Research axis: Sustainable energy Authors: Collin Smith, Laura Torrente-Murciano Journal: One Earth Abstract:Sierra Leone is one of the least developed countries in the world, with an economy strangled by the necessity of importing rice to feed the population. In part, this deficit results from domestic farmers rarely using inorganic fertilizer, which is synthesized from fossil fuels internationally. Here, we evaluate the economic benefits of producing green ammonia from renewable local hydropower for low-carbon cost-effective fertilizer production. Its use as fertilizer estimates a 30-year net present value (NPV) of ∼$230M (∼165% return of investment) compared with simply importing fertilizers, which would already save at least $50M a year compared with the current situation of importing rice, but hinges on additional external factors related to implementing modern agriculture. In addition, green ammonia can buffer seasonal fluctuations of hydroelectricity from 900 MW to 50 MW and produce a consistently available 370 MW of power. Although this study presents an initial analysis of Sierra Leone as a case study, it exemplifies the possible economic and social benefits of green ammonia in developing countries. https://doi.org/10.1016/j.oneear.2020.12.015 |
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Research axis: Manufacturing of nanostructured materials Authors: Journal: ACS Sustainable Chem. Eng. Abstract:Hydrothermal methods have conventionally enabled the synthesis of a wide range of nanomaterials. However, these simple, single-step syntheses lack scalability due to the need of high temperatures and autogenous pressures to enable the dissolution of reagents and crystallization of the product. In this work, we demonstrate for the first time fast continuous synthesis of ceria nanoparticles at moderate conditions through the combination of the deep eutectic solvent reline (an eutectic mixture of choline chloride and urea) as reaction medium and the high heat and mass transfer rate offered by microreactors. Almost 100% yields are obtained within 100 s of residence time at 160 °C, with some conversion achieved even at temperatures as low as 120 °C. Such rapid synthesis takes place thanks to the molecular structure of the solvent which facilitates the fast nucleation of cerium oxycarbonate as an intermediate product. https://doi.org/10.1021/acssuschemeng.0c06949 |
2020
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Research axis: Manufacturing of nanostructured materials Authors: Yunhu Gao, Bruno Pinho, Laura Torrente-Murciano Journal: Current Opinion in Chemical Engineering Abstract:Continuous synthesis of nanoparticles in microreactors is enabled by their characteristic high mass and heat transfer rates with exquisite control of the synthetic parameters. However, their laminar regime present challenges such as tendency to clogging, broad residence time distributions and concentration profiles. Multi-phase systems (liquid–liquid, gas–liquid) overcome these issues by the creation of recirculation patterns between immiscible phases however, indirectly promotes particle–particle interaction, making necessary the addition of steric organic ligands to avoid agglomeration. Over the past few years, the design of the geometry of the reactors has been presented as an alternative approach to control the hydrodynamics in single-phase system. Secondary flows such as Dean vorteces within the laminar regime are promoted on coiled and helical reactors enhancing mass transfer and narrowing residence time distributions. This approach enables the synthesis of nanoparticles in the absence of organic surface ligands with narrow size distribution opening the door to size tuneability. https://doi.org/10.1016/j.coche.2020.03.008 |
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Research axis: Manufacturing of nanostructured materials Authors: Sukanya Datta, Changshin Jo, Michael De Volder, Laura Torrente-Murciano Abstract:Herein, we show a facile surfactant-free synthetic platform for the synthesis of nanostructured vanadium pentoxide (V2O5) using reline as a green and eco-friendly deep eutectic solvent. This new approach overcomes the dependence of the current synthetic methods on shape directing agents such as surfactants with potential detrimental effects on the final applications. Excellent morphological control is achieved by simply varying the water ratio in the reaction leading to the selective formation of V2O5 3D microbeads, 2D nanosheets, and 1D randomly arranged nanofleece. Using electrospray ionization mass spectroscopy (ESI-MS), we demonstrate that alkyl amine based ionic species are formed during the reline/water solvothermal treatment and that these play a key role in the resulting material morphology with templating and exfoliating properties. This work enables fundamental understanding of the activity–morphology relationship of vanadium oxide materials in catalysis, sensing applications, energy conversion, and energy storage as we prove the effect of surfactant-free V2O5 structuring on battery performance as cathode materials. Nanostructured V2O5 cathodes showed a faster charge–discharge response than the counterpart bulk-V2O5 electrode with V2O5 2D nanosheet presenting the highest improvement of the rate performance in galvanostatic charge–discharge tests. https://doi.org/10.1021/acsami.9b17916 |
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Research axis: Manufacturing of nanostructured materials Authors: Yunhu Gao and Laura Torrente-Murciano Journal: Nanoscale AbstractThis paper presents fundamental understanding of the mechanism of the Turkevich protocol, the method recommended by the National Institute of Standards and Technology for the synthesis of gold nanoparticles using sodium citrate as reducing agent. Herein, we reveal that the Turkevich mechanism consists of two consecutive reduction steps (Au3+ → Au+ → Au0) rather than a reduction followed by the disproportionation reaction as conventionally believed. This new understanding has profound implications: i. the second reduction step (Au+ → Au0), rather than the previously postulated first reduction step, is the rate-limiting reduction step and ii. the formation of acetone dicarboxylate (DC2−) as an intermediate product through the oxidation of citrate has a key role as stabilizer and as a reducing agent (stronger than sodium citrate). This knowledge enables the synthesis of monodispersed gold nanoparticles with sizes ranging from 5.2 ± 1.7 nm to 21.4 ± 3.4 nm, with the lower end considerably smaller than previously reported through the Turkevich route. This work provides fundamental guidance for the controllable synthesis of nanoparticles using DC2− as a reducing agent directly applicable to other precious metals. https://doi.org/10.1039/C9NR08877F |
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Research axis: Sustainable energy Authors: Yuanzhu Zhao, Joshua Dobson, Catajina Harabajiu, Elena Madrid, Tinakorn Kanyanee, Catherine Lyall, Shaun Reeksting, Mariolino Carta, Neil B. McKeown, Laura Torrente-Murciano, Kate Black, Frank Marken Journal: Bioelectrochemistry AbstractAn “indirect” photo-electrochemical sensor is presented for the measurement of a mixture of analytes including reducing sugars (e.g. glucose, fructose) and non-reducing sugars (e.g. sucrose, trehalose). Its innovation relies on the use of a palladium film creating a two-compartment cell to separate the electrochemical and the photocatalytic processes. In this original way, the electrochemical detection is separated from the potential complex matrix of the analyte (i.e. colloids, salts, additives, etc.). Hydrogen is generated in the photocatalytic compartment by a Pt@g-C3N4 photocatalyst embedded into a hydrogen capture material composed of a polymer of intrinsic microporosity (PIM-1). The immobilised photocatalyst is deposited onto a thin palladium membrane, which allows rapid pure hydrogen diffusion, which is then monitored by chronopotentiometry (zero current) response in the electrochemical compartment. The concept is demonstrated herein for the analysis of sugar content in commercial soft drinks. There is no requirement for the analyte to be conducting with electrolyte or buffered. In this way, samples (biological or not) can be simply monitored by their exposition to blue LED light, opening the door to additional energy conversion and waste-to-energy applications. https://doi.org/10.1016/j.bioelechem.2020.107499 |
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Research axis: Manufacturing of nanostructured materials Authors: Julien Mahin and Laura Torrente-Murciano Journal: Chemical Engineering Journal AbstractThe first continuous synthesis of magnetic Fe@Fe3O4 core@shell nanoparticles with a metallic core is presented herein with precise control over size, narrow size distribution and a high production rate of 2.6 g per hour. This approach opens the door to large-scale production for their deployment in a range of applications such as drug delivery, separation, MRI contrasting agents, magnetically separable catalysts, magnetic hyperthermia for cancer treatment, etc. A systematic study of key reaction parameters in continuous microreactors reveal the main mechanistic steps involved in the thermal decomposition of the iron pentacarbonyl precursor. The presence of surfactants enables not only the post-synthesis particle stabilisation but also facilitates the initial ligand exchange in the precursor and the in situ CO production. We demonstrate that such gas production leads to a combined Dean-Taylor flow regime in the helical microreactors. Optimisation of the flow rate and reactor length leads to a high level of mixing and sufficient residence time (>12 s) resulting in narrow size distribution and high precursor conversion respectively. https://doi.org/10.1016/j.cej.2020.125299 |
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Research axis: Sustainable energy Authors: Collin Smith, Alfred K. Hill, Laura Torrente-Murciano Journal: Energy & Environmental Science AbstractThe future of a carbon-free society relies on the alignment of the intermittent production of renewable energy with our continuous and increasing energy demands. Long-term energy storage in molecules with high energy content and density such as ammonia can act as a buffer versus short-term storage (e.g. batteries). In this paper, we demonstrate that the Haber–Bosch ammonia synthesis loop can indeed enable a second ammonia revolution as energy vector by replacing the CO2 intensive methane-fed process with hydrogen produced by water splitting using renewable electricity. These modifications demand a redefinition of the conventional Haber–Bosch process with a new optimisation beyond the current one which was driven by cheap and abundant natural gas and relaxed environmental concerns during the last century. Indeed, the switch to electrical energy as fuel and feedstock to replace fossil fuels (e.g. methane) will lead to dramatic energy efficiency improvements through the use of high efficiency electrical motors and complete elimination of direct CO2 emissions. Despite the technical feasibility of the electrically-driven Haber–Bosch ammonia, the question still remains whether such revolution will take place. We reveal that its success relies on two factors: increased energy efficiency and the development of small-scale, distributed and agile processes that can align to the geographically isolated and intermittent renewable energy sources.
https://doi.org/10.1039/C9EE02873K |
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Research axis: Manufacturing of nanostructured materials Authors: Bruno Pinho and Laura Torrente-Murciano Journal: Reaction Chemistry & Engineering AbstractThe physical and chemical properties of metal nanoparticles are strongly dependent on their size and shape. In this work, we present a flexible manufacturing approach for the synthesis of spherical silver nanoparticles with tuneable sizes between 5 to 80 nm. This unique size flexibility is enabled by rapid online characterisation coupling spectroscopy and a mathematical Mie theory-based algorithm for size and shape evaluation. While it is conventionally believed that narrow size distributions require a fast nucleation step, herein, we demonstrate that fast and controllable growth is also required. To achieve this, a combination of chemical and engineering approaches is presented to limit thermodynamically driven size focus, coalescence and secondary nucleation. We show that an optimum reducing agent to silver precursor to seeds ratio and pH range need to be maintained throughout the growth stage. Such demanding conditions can be achieved by accurate control of the feed points and fluid dynamics across a series of microfluidic helical reactors leading to low mixing times. In this way, particle sizes with narrow size distributions and spherical shapes can be easily tuned by just varying the reducing agent-to-precursor concentration in the growth stage in an approach directly applicable to other metal nanoparticles. https://doi.org/10.1039/C9RE00452A |
