Francesco D'Acierno

Hitherto, research into alkaline exchange membrane fuel cells lacked a commercial benchmark anionomer and membrane, analogous to Nafion in proton-exchange membrane fuel cells. Three commercial alkaline exchange ionomers (AEIs) have been scrutinized for that role in combination with a commercial platinum-group-metal-free Fe-N-C (Pajarito Powder) catalyst for the cathode. The initial rotating disc electrode benchmarking of the Fe-N-C catalyst's oxygen reduction reaction activity using Nafion in an alkaline electrolyte seems to neglect the restricted oxygen diffusion in the AEIs and is recommended to be complemented by measurements with the same AEI as used in the alkaline exchange membrane fuel cell (AEMFC) testing. Evaluation of the catalyst layer in a gas-diffusion electrode setup offers a way to assess the performance in realistic operating conditions, without the additional complications of device-level water management. Blending of a porous Fe-N-C catalyst with different types of AEI yields catalyst layers with different pore size distributions. The catalyst layer with Piperion retains the highest proportion of the original BET surface area of the Fe-N-C catalyst. The water adsorption capacity is also influenced by the AEI, with Fumion FAA-3 and Piperion having equally high capabilities surpassing Sustainion. Finally, the choice of the membrane influences the ORR performance as well; particularly, the low hydroxide conductivity of Fumion FAA-3 in the room temperature experiments mitigates the ORR performance irrespective of the AEI in the catalyst layer. The best overall performance at high current densities is shown by the Piperion anion exchange ionomer matched with Sustainion X37-50 membrane.

High Resolution Image Download MS PowerPoint Slide In this work, we explored a solvent-based extraction of pectin from apple pomace and evaluated the extracted pectin as a precursor for porous quasi-solid-state Na-ion battery membranes, alongside testing hard carbon derived from commercial pectin as an electrode material. A screening of 10 distinct ionic liquids (ILs) and 6 different antisolvents revealed that N, N -dimethylbutylammonium acetate ([DMBA][OAc]), combined with ethanol, was highly effective in pectin extraction, while the same IL with 1-butanol as antisolvent yielded a purer form of the pectin product. Additionally, [DMBA][OAc] did not behave as an IL and resembled a molecular mixture based on 1 H NMR and conductivity measurements. A two-level fractional design was employed with four factors, considering temperature, solid loading, acid-to-base ratio (ABR), and water content of ILs, where temperature and solid loading were significant factors. The optimized conditions for the pectin extraction were at 80 °C, 1 h, with 15 wt % of solids loading, an ABR of 1.1, and 30 wt % of water content (IL), which yielded 9.6 wt % of pectin. The resulting quasi-solid-state Na-ion half-cell exhibited a capacity of ∼130 mAh g –1 at C/20, making it an excellent candidate for energy storage applications.

Hitherto, research into alkaline exchange membrane fuel cells (AEMFCs) lacks a commercial benchmark anionomer and membrane, analogue to Nafion™ in proton-exchange membrane fuel cells (PEMFCs). Three commercial alkaline exchange ionomers (AEI) are scrutinized for that role in combination with a commercial platinum-group-metal free (PGM-free) Fe-N-C (Pajarito Powder) catalyst for the cathode. Initial rotating disc electrode (RDE) benchmarking of the Fe-N-C catalyst’s oxygen reduction reaction (ORR) activity using Nafion™ in alkaline electrolyte seems to neglect the restricted oxygen diffusion in the AEIs, and is recommended to be complemented by measurements with the same AEI as used in the AEMFC testing. Evaluation of the catalyst layer in a Gas-Diffusion-Electrode (GDE) setup offers a way to assess the performance in realistic operating conditions, without the additional complications of device-level water management. Blending of a porous Fe-N-C catalyst with different types of AEI yields catalyst layers with different pore size distributions. The catalyst layer with Piperion® retains the highest proportion of the original BET surface area of the Fe-N-C catalyst. The water adsorption capacity is also influenced by the AEI, with Fumion FAA-3® and Piperion® having equal high capabilities surpassing Sustainion®. Finally, the choice of the membrane influences the ORR performance as well, particularly the low hydroxide conductivity of Fumion FAA-3® at the room temperature experiments mitigates the ORR performance irrespective of the AEI in the catalyst layer. The best overall performance at high current densities is shown by Piperion® AEI matched with Sustainion® X37-50 AEM.

Thermal stability is a crucial property of materials, especially when they have a wide range of thermally sensitive applications. Cellulose nanomaterials (CNMs) extracted from cellulosic biomass have garnered significant attention due to their abundance, biodegradability, sustainability, production scalability, and industrial versatility. To explore the correlation between the structure, chemistry, and morphology of CNMs and their thermal stability, we present a comprehensive literature review. We identify five major factors affecting CNMs' thermal stability, namely type, source, reaction conditions, post-treatment, and drying method, and analyze their impact on CNMs' thermal stability using several case studies from the literature. Using multiple linear least-squares regression (MLR), we establish a quantitative relationship between thermal stability and seven variables: crystallinity index of the source, dissociation constant of the reactant used, reactant concentration, reaction temperature, reaction time, evaporation rate, and post-treatment presence. By understanding these interdependencies, our statistical analysis enables the design of CNMs with predictable thermal properties and identification of optimal conditions for achieving high thermal stability. The results of our study provide crucial insights that can guide the development of CNMs with enhanced thermal stability for use in a variety of industrial applications.

Cellulose nanocrystal (CNC)-based chiral nematic films are important optical materials due to their ability to selectively reflect circularly polarized light but are often limited in application by their instability in water. Improving the mechanical performance and stability of photonic CNC-based materials in water is therefore of great importance for advancing the utility of CNCs. Here, water-resistant covalently crosslinked chiral photonic composite films of CNCs were formed by the incorporation of an epoxy resin (ER). The resulting materials can adapt their stiffness and toughness through the mediation of inter-CNC and CNC–water interactions upon exposure to water. Dry films of CNC–ER exhibit improved mechanical strength and toughness, likely related to the uniform and continuous chiral nematic structures in which stress transfer is facilitated by interrod interactions. In water, the interrod interactions are switched off by establishing rod–water interactions, resulting in up to ∼4-fold increase in toughness relative to the dry composites. Moreover, the composite films display tunable chiral photonic properties across the visible spectrum and moderate red shifting of reflection in response to slight swelling in water. The switchable rod–rod/water interaction enabled by a hydrogen-bonded/covalent dual network opens a path to develop CNC-based materials with mechanical adaptability and responsive chiral optical properties.

Multicomponent low molecular weight gelators (LMWGs) may self-assemble by co-assembly (CA), social self-sorting (SSS), or narcissistic self-sorting (NSS). Understanding the nuances of the self-assembly processes is important to predict the behavior of multicomponent organogels. Here, we investigate the effect of molecular structure on self-assembly in a series of amino-acid based bicomponent LMWGs that differ in headgroup and alkyl chain length. Packing preference of the organogels was determined using differential scanning calorimetry, nuclear magnetic resonance spectroscopy and small angle X-ray scattering. From 66 bicomponent samples we found 50 CA, 14 SSS and 2 NSS. Furthermore, we performed statistical analysis to investigate the role of hydrophobicity and chain length on the overall pathway of self-assembly for these systems. We found the hydrophobicity of the headgroup strongly affected the assembly preference of the organogel, but alkyl chain length only played a small role.

Researchers have sought to improve the thermal performance of cellulose nanocrystals (CNCs) via new production routes, often by incorporating carboxylate groups on CNC surfaces. The CNC properties responsible for increased thermal stability, however, are not well understood. This study investigated carboxylated CNCs with varying physicochemical properties and benchmarked their thermal performance with two counterions (H+ and Na+) against typical sulfated CNCs. Carboxylated CNCs were more thermally stable in acid form than sodium form (the opposite of sulfated CNCs), highlighting that CNCs with different surface chemistries cannot be compared with the same counterion when making claims about thermal behavior. Thermogravimetric analysis and solid-state NMR spectroscopy were used to evaluate five types of CNCs. Overall, sulfate group content affected CNC thermal stability more than carboxylate content─sulfated CNCs showed both the highest and lowest onsets of thermal degradation in sodium and acid form, respectively. Carboxylated CNCs displayed a variety of “intermediate” thermal behaviors: CNCs with higher carboxylate contents and larger specific surface areas had lower degradation temperatures and tended toward one main pyrolysis step (instead of two) as surface area increased. The catalytic effect of sodium in highly charged 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized carboxylated CNCs, and the formation of sodium carbonate in moderately charged, esterified CNCs, led to more structural degradation of cellulose in sodium form than acid form. Due to the generated sodium carbonate, decarboxylation reactions upon heating decreased for esterified CNCs in sodium form but increased in acid form. This new understanding will allow optimized performance of CNC-based materials at high temperatures and may enable the development of bionanomaterials with targeted thermal properties.

The properties of iridescent and colorless cellulose nanocrystal (CNC) films can be modified through external stimuli. Here, the optical and thermal properties of CNC films were tuned by treating the aqueous suspension prior to casting. Three rapid and scalable methods (ultrasound treatment, dilution, and ion exchange) were selected, and the energy input, concentration, and alkali/alkaline-earth hydroxide were varied over a wide extent. The simultaneous change of the parameters enabled the synthesis of 360 CNC films with different properties, unlocking unprecedented photonic and thermal control spanning a broad range. The library of films showed systematic variations of nearly 50% of the range in film transparency, structural color peak wavelengths spanning two-thirds of the visible spectrum, and optimization of the thermal stability by more than 160 °C. A multiple linear regression of the effects of the three stimuli allows the prediction and choice of desired optical and thermal characteristics.

Dynamic covalent bonds bear great potential for the development of adaptive and self-healing materials. Herein, we introduce a versatile concept not only for the design of low-molecular-weight liquid crystals but also for their in situ postsynthetic modification by using the dynamic covalent nature of imine bonds. The methodology allows systematic investigations of structure–property relationships as well as the manipulation of the materials’ behavior (liquid crystallinity) and the introduction of additional properties (here, fluorescence) by a solvent-free method. For the first time, the transamination reaction is followed by variable-temperature 19F solid-state NMR in the mesophase, providing insights into the reaction dynamics in a liquid crystalline material. Finally, the application potential for the design of liquid crystalline materials with adaptive properties is demonstrated by a sequential combination of these reactions.

Diffraction gratings are important for modern optical components, such as optical multiplexers and signal processors. Although liquid crystal (LC) gratings based on thermotropic LCs have been extensively explored, they often require expensive molecules and complicated manufacturing processes. Lyotropic LCs, which can be broadly obtained from both synthetic and natural sources, have not yet been applied in optical gratings. Herein, a facile grating fabrication method using a biosourced lyotropic LC formed by cellulose nanocrystals (CNCs), a material extracted from plants, is reported. Hydrogel sheets with vertically aligned uniform periodic structures are obtained by fixing the highly oriented chiral nematic LC of CNCs in polymer networks under the cooperative effects of gravity on phase separation and a magnetic field on LC orientation. The hydrogel generates up to sixth-order diffraction spots and shows linear polarization selectivity, with tunable grating periodicity controlled through LC concentration regulation. This synthesis strategy can be broadly applied to various grating materials and opens up a new area of optical materials from lyotropic LCs.

Bioderived cellulose nanocrystals (CNCs) are used to create light, flexible, biocompatible, and biodegradable electronic devices. Herein, surface modification of cellulose nanocrystals was employed to fabricate cationic and anionic CNCs. Subsequently, we demonstrated rectification behavior from a fixed junction between two agarose hydrogels doped with cationic and anionic cellulose nanocrystals. The current rectification ratio reaches 70 reproducibly, which is significantly higher than that for analogous diodes generated with microfibrillated cellulose (∼15) and the first polyelectrolyte gel diode (∼40). The current-voltage characteristics of the CNC-hydrogel diode are influenced by concentration, gel thickness, scanning frequency, and applied voltage. The high surface area of CNC resulted in high charge density after surface modification, which in turn resulted in good rectification behavior from only small amounts of dopant material.

Cellulose-derived materials, such as microcellulose and nanocellulose, are sustainable materials with a wide range of applications. Here, through a multi-analytical approach, we investigate the thermal degradation of microfibrillar cellulose filaments (CFs); acidic cellulose nanocrystals (CNC-H), containing sulfate half-ester groups on the surface; and neutralized cellulose nanocrystals (CNC-Na), where the protons are replaced by sodium ions. CFs have a simple degradation mechanism, associated with extensive dehydration, decarboxylation, and decarbonylation, and the highest thermal stability of the three (∼325 °C) despite the abundance of amorphous regions and inhomogeneous fibrous mass that make them structurally and morphologically less homogeneous than high-crystallinity CNCs. CNC-H decompose in a complex way below 200 °C, with large char fractions and evaporation of sulfur compounds at high temperatures, while sodium counterions in CNC-Na can improve the thermal stability up to 300 °C, where the pyrolysis leads to partial rehydration and formation of sodium hydroxide on the surface.

Polysuccinimide is a biodegradable and tissue-friendly polymer made from the renewable monomer L-aspartic acid. However, under physiological conditions (pH = 7.4) it hydrolyzes to form water-soluble poly(aspartic acid). In order to utilize this polymer to produce drug-eluting fiber mats or tissue scaffolds via electrospinning, it needs to be crosslinked. This paper will discuss the functionalization of this polymer with allyl groups (Figure 1), electrospinning it into fiber mats and crosslinking it via non-equilibrium low pressure air plasma treatment. The polymers and mats were characterized before and after plasma treatment using NMR, FTIR, XPS and SEM. After plasma treatment the fiber mat became insoluble in its original solvents (DMF and DMSO). After hydrolysis of the amide bonds into aspartic acid fiber morphology changed as shown in Figure 2. This electrospun crosslinked fiber mat shows great promise for biomedical applications.

The functionalization of cellulose nanocrystal (CNC) aerogels was achieved through a two-step synthetic procedure. CNC aerogels were prepared under hydrothermal conditions, followed by solvent exchange and critical point drying. The CNC aerogels were functionalized with a methacrylate group and then underwent thiol–ene click chemistry to impart a range of functionalities onto the surface of the CNC aerogel. The use of the functionalized aerogels as oil absorbents was then investigated, with the most hydrophobic CNC aerogel, 1H,1H,2H,2H-perfluorodecanethiol-functionalized CNC aerogel, exhibiting the highest absorption of xylenes at 2.9 mL g–1.

We present the biotemplating of γ-Al2O3 aerogels with chitosan nanofibrils. Aluminum–chitosan interactions cause the swelling of iridescent chitosan structures into helicoidal hydrogels and the subsequent aqueous dissolution of swollen fibrils to form Al–chitosan solutions. Viscous aqueous solutions of Al3+–chitosan hybrid nanofibers were freeze-dried to give lightweight cotton-like aerogels. Homogeneous incorporation of Al3+ ions into chitosan yields water-soluble nanofibrils that can serve as polymeric templates to support Al3+ ions in the aerogel composites. We investigated thermal removal of chitosan in the composites to obtain lightweight γ-Al2O3 nanocrystal aerogels that retain the weblike fiber networks of the chitosan template. These biotemplated alumina aerogel materials are promising candidates for catalyst supports and thermal insulation.

Considering the constant expansion of the areas of application of composite materials, is increasingly crucial to deepen the research for the correct evaluation of the potential application of these materials. In this job, the de termination of the impact strength value, as well as the maximum load and the rigidity of the ma terial, has been obtained by means of an instrumented pendulum impact test. More in details, the characterization of four different composite materials, based on a polymeric matrix an d reinforced with carbon fibres, will be presented. The materials tested will differ for the type of the reinforcement and the degree of crystallinity of their matrix. The influence of these factors on the aforementioned impact properties will be the presented and discussed, lea ding to the identification of the composite material with the best impact properties for a spec ific application.