Membrane-based TBADT recovery as a strategy to increase the sustainability of continuous-flow photocatalytic HAT transformations

Photocatalytic hydrogen atom transfer (HAT) processes have been the object of numerous studies showcasing the potential of the homogeneous photocatalyst tetrabutylammonium decatungstate (TBADT) for the functionalization of C(sp(3))–H bonds. However, to translate these studies into large-scale industrial processes, careful considerations of catalyst loading, cost, and removal are required. This work presents organic solvent nanofiltration (OSN) as an answer to reduce TBADT consumption, increase its turnover number and lower its concentration in the product solution, thus enabling large-scale photocatalytic HAT-based transformations. The operating parameters for a suitable membrane for TBADT recovery in acetonitrile were optimized. Continuous photocatalytic C(sp(3))-H alkylation and amination reactions were carried out with in-line TBADT recovery via two OSN steps. Promisingly, the observed product yields for the reactions with in-line catalyst recycling are comparable to those of reactions performed with pristine TBADT, therefore highlighting that not only catalyst recovery (>99%, TON > 8400) is a possibility, but also that it does not happen at the expense of reaction performance

Electrochemical impedance spectroscopy of a reverse electrodialysis stack:a new approach to monitoring fouling and cleaning

When harvesting salinity gradient energy via reverse electrodialysis (RED), stack performance is monitored using DC characterizations, which does not provide information about the nature and mechanisms underlying fouling inside the stack. In order to assess the potential of natural salinity gradients as renewable energy source, progress in the fields of fouling monitoring and controlling is vital. To improve fouling and cleaning monitoring, experiments with sodium dodecylbenzenesulfonate (SDBS) were carried out while at the same time the electrochemical impedance spectroscopy (EIS) was measured at the RED stack level. EIS showed how SDBS affected the ohmic resistance of the stack, the non-ohmic resistance of the AEM and the non-ohmic resistance of the CEM on different time scales. Such detailed investigation into the effect of SDBS on different stack elements offered by EIS is not possible with traditional DC characterization. The results presented in this work illustrate the potential of EIS at the stack level for fouling monitoring. The knowledge presented shows the possibility to include EIS in up-scaled natural salinity gradient RED applications for fouling monitoring purposes.</p

Optimizing multistage reverse electrodialysis for enhanced energy recovery from river water and seawater: Experimental and modeling investigation

Reverse electrodialysis has been established as a promising method to harvest salinity gradient energy. To achieve market viability, an optimum process configuration is needed, in addition to material and stack development, to increase energy efficiency without compromising power density. Multistage reverse electrodialysis is a practical strategy providing several degrees of freedom, such as independent electrical control of the stages, asymmetric staging, and different configurations. This study tests a two-stage configuration experimentally, using seawater and river water (NaCl only), at several residence times and changing the electrical control. Furthermore, the results are compared with a numerical model that is subsequently used to predict the behavior of alternative multistage configurations. The results show that multistage reverse electrodialysis yields higher gross power density and energy efficiency than a single-stage configuration fed with the same salinity gradient. A new strategy named “saving the gradient” (i.e., lowering the discharge current in the first stage) increased the gross overall performance of the two stages up to 17% relative to single-stage and up to 6% relative to a sequentially optimized two-stage system. Modeling different configurations revealed that only two stages are needed when feeding seawater and river water. When retrieving 40% net energy efficiency, the net power density for a single stage is 0.86 W∙m−2 and 0.94 W∙m−2 for a two-stage system, representing an improvement of 9%. Multistage reverse electrodialysis is therefore a viable concept to enhance power and energy efficiency, and benefits from optimization through electrical control

Fluoropolymeric luminescent downshifting layers for improved performance of flexible polymer solar cells

In this work, a fluorinated resin is presented as host material for luminescent downshifting (LDS) applications carried out on polymer solar cells. The results obtained by depositing coatings with increasing concentrations of an appropriate organic fluorescent molecule on polymer solar cells show a trend with a maximum short circuit current density increase (+3.74%) at intermediate concentrations (1% wt.). Such behavior has been successfully correlated with the photo-physical properties of the coatings. These results highlight the suitability of LDS as a straightforward strategy for improving the performance of polymer solar cells without modifying the chemistry of the photoactive layer

Crosslinking UV-curable polymers with organic dyes for highly stable, multifunctional, light-harvesting luminescent solar concentrators

A multifunctional luminescent system characterized by outstanding durability is presented in this work as polymeric matrix for luminescent solar concentrators (LSCs). Such coating was fabricated by embedding a modified perylene-based organic dye in a fluorinated matrix consisting in a blend of photo-curable fluorinated polymers. The coating can easily crosslink when exposed to UV-light. The presence of lateral double bonds in the organic dye molecule enables its co-crosslinking with the acrylate fluorinated matrix. Multifunctionality is granted to the coating by remarkably high water contact angle values, slightly exceeding 120°, which impart easy cleaning properties to the LSC device. Accelerated weathering tests (800 h) showed the outstanding stability of LSCs prepared using the fluorinated matrix co-crosslinked with the modified perylene presented here. These devices retained their initial optical efficiency during the intense weathering test. On the contrary, devices fabricated with the same fluorinated polymers, but incorporating a similar dye with the same chemical structure except for the lateral double bonds enabling co-crosslinking with the polymeric matrix, exhibited a 10% efficiency loss over the testing time. The increased stability can be explained by taking into account the effect of the linkage between the organic dye and the host matrix. The fast and easy preparation process presented in this work represents a scalable approach to remarkably stable and truly multifunctional LSCs

Electrode segmentation in reverse electrodialysis: Improved power and energy efficiency

Reverse electrodialysis harvests energy from salinity gradients establishing a renewable energy source. High energy efficiencies are fundamental to up-scale the process and to minimize feedwater pre-treatment and pumping costs. The present work investigates electrode segmentation to strategically optimize the output power density and energy efficiency. Electrode segmentation allows the current density to be tuned per electrode segment. Segmentation experiments were performed with a dedicated electrode configuration in a cross-flow stack using a wide range of residence times. Moreover, an experimentally validated model was extended and used to further compare single and segmented electrode configurations. While operating the electrode segments, the highest efficiencies were obtained when considering the overall power, i.e. not maximized by segment. Results show that at a given net power density (0.92 W·m−2), electrode segmentation increases the net energy efficiency from 17% to 25%, which is a relative increase of 43%. Plus, at 40% net energy efficiency the net power output for a segmented electrode configuration (0.67 W·m−2) is 39% higher than in a single electrode configuration. Higher power density reduces capital investment and higher energy efficiency reduces operating costs. Electrode segmentation increases these parameters compared to a single electrode and can be potentially applied for up-scaling

UV-curable fluoropolymers crosslinked with functional fluorescent dyes: The way to multifunctional thin-film luminescent solar concentrators

A novel photo-curable multifunctional luminescent system with high durability is presented in this work for application in thin-film luminescent solar concentrators (LSC), based on a fluorinated polymer matrix covalently linked to a newly synthesized functional perylene-derived luminescent organic dye. The UV-curable fluoropolymeric matrix consists of a blend of three different UV-curable fluorinated polymers. Such a matrix was co-reacted upon UV-light exposure with a suitably functionalized perylene-based luminescent organic dye bearing lateral carbon double bonds, to yield the solid crosslinked LSC thin film. A thorough characterization of the new luminescent system evidenced its excellent chemical, physical and optical properties, while its functional performance was evaluated in terms of LSC device response at varying dye concentrations. To assess the long-term stability of the new UV-curable LSC system, a long term (>800 h) light-exposure durability study was conducted on the LSC devices which fully retained their initial performance. In contrast, reference host/guest luminescent systems based on the same UV-curable fluoropolymeric matrix doped with a conventional fluorescent dye exhibited an overall â\u88¼10% efficiency loss in the same time frame. In addition, such a novel UV-curable fluoropolymeric LSC system presented a highly hydrophobic character and moderate oleophobicity, which impart easy cleanability to the LSC coating, as a result of the highly perfluorinated nature of the polymeric matrix. This study represents the first demonstration of highly stable multifunctional UV-curable thin-film LSC systems and gives a clear demonstration of a straightforward room-temperature preparation process that may offer an easily scalable approach to highly stable and multifunctional LSC devices

An all-in-one multipurpose robotic platform for the self-optimization, intensification and scale-up of photocatalysis in flow

The optimization, intensification, and scaling up of chemical processes are essential and time-consuming aspects of contemporary chemical manufacturing, necessitating expertise and precision due to their intricate and sensitive nature. However, these process development problems are often carried out independently and consecutively, which can exacerbate the already significant consumption of time and resources involved in the process. In this work, we present a versatile, all-in-one robotic platform for the autonomous optimization, intensification, and scaling up of photocatalytic reactions in flow. This platform overcomes associated challenges through the integration of readily available hardware and custom software, offering a hands-off solution. Our open source platform combines a liquid-handler, syringe pumps, a tunable high-powered photoreactor, cheap IoT devices and an in-line NMR to enable automated, data-rich optimization using a Closed-Loop Bayesian Optimization strategy. The use of a high-power continuous-flow capillary photoreactor enables highly reproducible data to be obtained, as it mitigates issues related to mass, heat, and photon transport that are often the main sources of irreproducibility in photocatalytic transformations. A user-friendly graphical interface allows chemists without programming or machine learning expertise to easily optimize, monitor, and analyze photocatalytic reactions for chemical spaces of both continuous and discrete variables. The system\u27s effectiveness was demonstrated by testing it on challenging photocatalytic transformations, which resulted in increased overall reaction yields and an impressive up to 550-fold improvement in space-time yields compared to batch processes. Additional tests on literature-reported reactions previously optimized in flow yielded substantial increases in both yield and space-time yield. Overall, our studies demonstrate that combining flow-based reactor technology with Bayesian optimization yields superior and unbiased results compared to human effort and intuition in terms of pace, precision, and outcomes for the optimization of photocatalytic reactions. Finally, due to its ability to autonomously generate datasets that include both optimal and suboptimal conditions, our RoboChem platform also contributes to advancing the field towards a digitally-driven era in synthetic chemistry