Sodium‐ion batteries (SIBs) and potassium‐ion batteries (PIBs) are prospective candidates for large‐scale energy storage systems cause of their abundant resources. However, unsatisfactory rate and ...cycling performance of carbon‐based anodes present a bottleneck for the applications of SIBs/PIBs due to the large sizes of sodium/potassium ions. Herein, oxygen‐doped vertically aligned carbon aerogels (VCAs) with hierarchically tailored channels are synthesized as anodes in SIBs/PIBs via a controllable unidirectional ice‐templating technique. VCA‐3 (cooling rate of 3 K min−1) delivers the highest reversible capacity of ≈298 mAh g−1 at 0.1 C with an excellent cycling performance over 2000 cycles at 0.5 C for SIBs, while VCA‐5 manifests a superior capacity of ≈258 mAh g−1 at 0.1 C with an 82.7% retention over 1000 cycles at 0.5 C for PIBs. Moreover, their full cells demonstrate the promising potential of VCAs in applications. This novel controllable ice‐templating strategy opens unique avenues to tune the construction of hollow aligned channels for shortening ion‐transport pathways and ensuring structural integrity. New insights into structure‐performance correlations regulated by the cooling rates of an ice‐templating strategy and design guidelines for electrodes applicable in multiple energy storage technologies are reported.
A novel controllable ice‐templating strategy is utilized to tailor low‐cost cellulose nanocrystal/polyethylene oxide‐derived, vertically aligned carbon aerogels (VCAs) as anodes of sodium‐ and potassium‐ion batteries. The construction of hierarchically tailored channels is tuned for shortening ion‐transport pathways and ensuring structural integrity. These sustainable VCAs can be easily extended to multiple energy storage systems, demonstrating their universal potential.
The creation of efficient artificial systems that mimic natural photosynthesis represents a key current challenge. Here, we describe a high-performance recyclable photocatalytic core-shell nanofibre ...system that integrates a cobalt catalyst and a photosensitizer in close proximity for hydrogen production from water using visible light. The composition, microstructure and dimensions-and thereby the catalytic activity-of the nanofibres were controlled through living crystallization-driven self-assembly. In this seeded growth strategy, block copolymers with crystallizable core-forming blocks and functional coronal segments were coassembled into low-dispersity, one-dimensional architectures. Under optimized conditions, the nanofibres promote the photocatalytic production of hydrogen from water with an overall quantum yield for solar energy conversion to hydrogen gas of ~4.0% (with a turnover number of >7,000 over 5 h, a frequency of >1,400 h
and a H
production rate of >0.327 μmol h
with 1.34 μg of catalytic polymer (that is, >244,300 μmol h
g
of catalytic polymer)).
The fabrication of stable colloidosomes derived from water‐in‐water Pickering‐like emulsions are described that were produced by addition of fluorescent amine‐modified polystyrene latex beads to an ...aqueous two‐phase system consisting of dextran‐enriched droplets dispersed in a PEG‐enriched continuous phase. Addition of polyacrylic acid followed by carbodiimide‐induced crosslinking with dextran produces hydrogelled droplets capable of reversible swelling and selective molecular uptake and exclusion. Colloidosomes produced specifically in all‐water systems could offer new opportunities in microencapsulation and the bottom‐up construction of synthetic protocells.
Ready to load: Hybrid hydrogel‐colloidosomes capable of swelling and spontaneous uptake of payloads have been fabricated from water‐in‐water emulsions.
Fiber-like micelles based on biodegradable and biocompatible polymers exhibit considerable promise for applications in nanomedicine, but until recently no convenient methods were available to prepare ...samples with uniform and controllable dimensions and spatial control of functionality. “Living” crystallization-driven self-assembly (CDSA) is a seeded growth method of growing importance for the preparation of uniform 1D and 2D core–shell nanoparticles from a range of crystallizable polymeric amphiphiles. However, in the case of poly(l-lactide) (PLLA), arguably the most widely utilized biodegradable polymer as the crystallizable core-forming block, the controlled formation of uniform fiber-like structures over a substantial range of lengths by “living” CDSA has been a major challenge. Herein, we demonstrate that via simple modulation of the solvent conditions via the addition of trifluoroethanol (TFE), DMSO, DMF and acetone, uniform fiber-like nanoparticles from PLLA diblock copolymers with controlled lengths up to 1 μm can be prepared. The probable mechanism involves improved unimer solvation by a reduction of hydrogen bonding interactions among PLLA chains. We provide evidence that this minimizes undesirable unimer aggregation which otherwise favors self-nucleation that competes with epitaxial crystallization from seed termini. This approach has also allowed the formation of well-defined segmented block comicelles with PLLA cores via the sequential seeded-growth of PLLA block copolymers with different corona-forming blocks.
Introducing hierarchical pore structure to microporous materials such as metal-organic frameworks (MOFs) can be beneficial for reactions where the rate of reaction is limited by low rates of ...diffusion or high pressure drop. This advantageous pore structure can be obtained by defect formation, mostly via post-synthetic acid etching, which has been studied extensively on water-stable MOFs. Here we show that a water-unstable HKUST-1 MOF can also be modified in a corresponding manner by using phosphoric acid as a size-selective etching agent and a mixture of dimethyl sulfoxide and methanol as a dilute solvent. Interestingly, we demonstrate that the etching process which is time- and acidity- dependent, can result in formation of defective HKUST-1 with extra interconnected hexagonal macropores without compromising on the bulk crystallinity. These findings suggest an intelligent scalable synthetic method for formation of hierarchical porosity in MOFs that are prone to hydrolysis, for improved molecular accessibility and diffusion for catalysis.
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Many high-performance sails are flexible, carbon-fibre-reinforced polymer composites. For example, 30% by weight of ‘3Di’ sails produced by the world’s largest sail maker, North ...Sails, are made up by carbon fibres (CF). The yachting industry currently has no end-of-life (EOL) waste-management plan for these sails, meaning valuable materials, including CF, mostly end up as waste which is detrimental to our environment. In this paper, a recycling pathway for EOL 3Di sails is described. CFs, reclaimed via the DEECOM® superheated steam/pressure-swing process, retained 95% virgin stiffness, 94% retained virgin strength, and 97% virgin strain to failure. The reclaimed CFs were subsequently aligned into discontinuous short fibre reinforced prepreg-like tape using the University of Bristol’s water-based, High-Performance Discontinuous Fibre (HiPerDiF) manufacturing technology. The tensile and flexural properties of this material were characterised, and two yachting-based demonstrators manufactured to show the possibility of a circular recycling pathway from EOL sail to structure.
Although micelles derived from the solution self-assembly of amphiphilic molecules and polymers have been prepared with a wide variety of shapes, examples with well-defined branched structures have ...remained elusive. We describe a divergent, directed self-assembly approach to low dispersity dendritic micelles with a high degree of structural perfection and tailorable branch numbers and generations. We use block copolymer amphiphiles as precursors and a crystallization-driven seeded growth approach whereby the termini of fiber-like micelles function as branching sites. Different dendrimeric generations are accessible by adjusting the ratio of added unimers to pre-existing seed micelles where the branch positions are determined by the reduced coronal chain grafting density on the surface of the micelle crystalline core. We demonstrate the spatially defined decoration of the assemblies with emissive nanoparticles and utility of the resulting hybrids as fluorescent sensors for anions where the dendritic architecture enables ultrahigh sensitivity.
Ionic diodes are components in ionic circuits for AC‐electricity driven desalination and ion extraction processes. Independent of the ionic diode type/mechanism, achieving ionic current rectification ...at high ionic strengths is challenging but important, for example in seawater desalination and treatment of brine. Here, the butylation of a molecularly rigid (glassy) polymer of intrinsic microporosity (PIM‐EA‐TB) is shown to give anionic diodes with ultrahigh rectification effects (associated with interfacial resistivity) even in high ionic strength aqueous 2 M NaCl solution. The effect is rationalised based on polymer structure affecting ion transport.
Butylation of an intrinsically microporous polyamine lowers the anion flux when compared to the methylated polymer (PIM‐EA‐TB). However, it increases diode rectification effects in high salinity electrolyte and could therefore be used for seawater desalination.
Urea and phosphoric acid are essential for the isolation of phosphorylated cellulose nanocrystals (CNCs). Besides limiting dissolution of nanocrystals, urea facilitates the swelling of fibres thus ...increasing access for the phosphorylating agent. The aim of this study was to determine optimal conditions for isolation of highly charged phosphorylated CNCs. Using a design of experiments approach, seventeen experiments in which reaction time, urea, and acid concentrations were varied, were conducted. A two-step process was used, in which CNCs were first isolated by treatment in phosphoric acid, and then treated with metaphosphoric acid, and urea. It is shown that a design of experiments approach to the phosphorylation of CNCs allows a much lower ratio of urea to acid than has previously been reported. CNCs with high surface charge (~1800 mmol kg-1) are possible using this method. This information is instructive to phosphorylation of cellulose nanomaterials which have a variety of applications e.g., water purification and medical biomaterials.
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