• Energy Research

The valorisation of lignin obtained as a by-product of the pulping and biofuel industries is one of the most promising topics in the bioresource field. Despite its potential value as the only massively available aromatic biopolymer feedstock, technical lignin is nowadays mostly burnt as low cost energy source because of its chemical recalcitrance. The high heterogeneity of this material, largely dependent on the different vegetal sources and the specific biomass recovery methods, restricts its direct use and hinders also the optimization of depolymerisation approaches. The development of effective technical lignin fractionation strategies is therefore today one of the most challenging topic in the green chemistry field. In this study, the fractionation of an industrial commercial lignin (Protobind 1000) was developed by a three step procedure set-up either in aqueous or in an environmentally friendly organic solvent in order to obtain sustainable and scalable processes. The first step consisted in a microfiltration or a Soxhlet extraction, depending on the type of solvent used. Then a cascade membrane-mediated ultrafiltration allowed to obtain at the end three refined lignin fractions. The parent lignin and the different lignin fractions were fully characterized. The two-step process reported here allows accessing lignin fractions with well-defined physico-chemical properties (including mass distribution, glass transition temperature, aliphatic and phenolic hydroxyl groups concentration, syringyl/guaiacyl unit ratio) and represents a valuable approach towards the development of bio-based polymers and the preparation of key platform chemicals, thereby paving the way for an effective exploitation and valorization of this remarkable resource.

The combination of a de novo design approach and micellar catalysis enables the preparation of innovative luminophores connecting efficiency and sustainability for the preparation of thin film luminescent solar concentrators.

AbstractIn this study, the design, fabrication, and characterization of semi‐transparent large‐area luminescent solar concentrators (LSCs) in thin‐film configuration is reported, incorporating a novel organic luminophore (PFPBNT) emitter based on a π‐conjugated core flanked by two naphthothiophene units obtained through a chemically sustainable synthetic approach. As found experimentally and validated through computational modeling, PFPBNT exhibits aggregation‐induced emission (AIE) behavior, broad absorption in the UV–vis spectrum and significant Stokes shift (≈4632 cm–1), thereby making it an excellent candidate as luminophore in thin‐film LSCs based on a poly(methyl methacrylate) (PMMA) matrix, where it is found to show good compatibility, homogeneous distribution, and excellent photostability. After extensive device optimization, PFPBNT/PMMA LSCs with suitable luminophore concentration (12.5 wt%) showed an internal photon efficiency of 17.3% at a geometrical gain of 6.25 under solar‐simulated illumination. The size scalability of these systems was also evaluated by means of ray‐tracing simulations on devices of up to 1 m2 surface area. This work demonstrates semi‐transparent large‐area thin‐film LSCs incorporating chemically sustainable AIEgen luminophores, thus opening the way to the development of synthetically affordable, efficient, and stable emitters for the photovoltaic field.

In the present work, rice husks (RHs), which, worldwide, represent one of the most abundant agricultural wastes in terms of their quantity, have been treated and fractionated in order to allow for their complete valorization. RHs coming from the raw and parboiled rice production have been submitted at first to a hydrothermal pretreatment followed by a deep eutectic solvent fractionation, allowing for the separation of the different components by means of an environmentally friendly process. The lignins obtained from raw and parboiled RHs have been thoroughly characterized and showed similar physico-chemical characteristics, indicating that the parboiling process does not introduce obvious lignin alterations. In addition, a preliminary evaluation of the potentiality of such lignin fractions as precursors of cement water reducers has provided encouraging results. A fermentation-based optional preprocess has also been investigated. However, both raw and parboiled RHs demonstrated a poor performance as a microbiological growth substrate, even in submerged fermentation using cellulose-degrading fungi. The described methodology appears to be a promising strategy for the valorization of these important waste biomasses coming from the rice industry towards a circular economy perspective.

Abstract In the field of photovoltaics, achieving high efficiency in both light absorption and light trapping simultaneously remains challenging. Photon management, which refers to the engineering of materials and device architectures to control the spatial or spectral distribution of optical energy, offers a number of promising approaches for the optimization of this tradeoff. Among these are antireflective structures with pronounced surface patterned profiles that reduce surface reflectivity, light trapping approaches but also spectral conversion concepts. With the continuous development of photovoltaic device architectures and designs, the engineering of novel photon management strategies and the availability of suitably tailored polymeric materials for such applications will contribute to enhanced device efficiencies as well as sustained long-term performance. In this review, we summarize the recent progress in the development and implementation of photon management strategies for different photovoltaic technologies specifically based on the use of polymeric materials, and we discuss their contribution to the field.

The use of micellar catalysis enables the sustainable synthesis of persistent, luminescent radicals that are suitable for the preparation of colourless luminescent solar collectors with minimal reabsorption losses and distortion of the transmitted light.

Abstract Polymer-based thin-film luminescent solar concentrators (LSCs) currently rely on poly(methyl-methacrylate) (PMMA) as host matrix material. However, PMMA-based LSCs still suffer from degradation due to the limited photostability of the polymer. In this work, a new crosslinked fluoropolymer-based system is presented as a potential alternative host matrix material for the fabrication of durable polymer-based LSC devices. The new host matrix system is obtained by crosslinking a functional chloro-trifluoro-ethylene-vinyl-ether copolymer with an aliphatic isocyanurate crosslinker. It is shown that efficiency values comparable to those obtained with optimized PMMA-based thin film LSC devices can be reached with the new crosslinked fluoropolymer-based LSC system. In addition, superior long-term operational stability compared to PMMA-based devices can be obtained with the new fluoropolymer-based host matrix, as evidenced by long-term continuous light exposure tests (over 500 h) on operating LSC devices. The results of this work demonstrate that crosslinked fluorinated polymers represent a class of promising host matrix materials to achieve environmentally stable LSC devices.