Fuel cell anode catalyst performance can be stabilized with a molecularly rigid film of polymers of intrinsic microporosity (PIM)

There remains a major materials challenge in maintaining the performance of platinum (Pt) anode catalysts in fuel cells due to corrosion and blocking of active sites.</p

A Cationic Diode Based on Asymmetric Nafion® Film Deposits

A thin film of Nafion®, of approximately 5 microm thickness, asymmetrically deposited onto a 6 microm thick film of poly(ethylene terephthalate) (PET) fabricated with a 5, 10, 20, or 40 microm microhole, is shown to exhibit prominent ionic diode behaviour involving cation charge carrier ("cationic diode"). The phenomenon is characterized via voltammetric, chronoamperometric, and impedance methods. Phenomenologically, current rectification effects are comparable to those observed in nano-cone devices where space-charge layer effects dominate. However, for microhole diodes a resistive, a limiting, and an over-limiting potential domain can be identified and concentration polarization in solution is shown to dominate in the closed state.</p

Ordered mesoporous particles in titania films with hierarchical structure as scattering layers in dye-sensitized solar cells

This work aimed to understand the relationship between the physical properties of scattering particle layers in dye-sensitized solar cells (DSSCs) and their performance, to assist optimization of this component of the DSSC. Highly ordered anatase 2D-hexagonal mesoporous titania (meso-TiO₂) nanoparticles with a high surface area and large pore size were fabricated. Meso-TiO₂ was used as scattering particles and mixed with titania nanocrystallites at weight proportions ranging from 0 to 100%. Films made from the composites were used as scattering layers in DSSCs. The influence of meso-TiO₂ proportion on the structure, morphology, and optical properties of the films were investigated. The results show that the films became more porous, with a larger surface roughness, and had higher surface areas and greater light-scattering effects when meso-TiO₂ was incorporated. The performance of these scattering layers in relatively large, 1 cm² area, DSSCs was studied to link cell performance to the detailed physical properties of the meso-TiO₂/nanoparticle films. The optimum composition of scattering layers was obtained by mixing 50 wt % meso-TiO₂ with titania nanoparticles

Sulfur-Doped Cubic Mesostructured Titania Films for Use as a Solar Photocatalyst

Sulfur-doped titania thin films with cubic mesostructures were prepared by dip coating via the evaporation induced self-assembly route. The effect of sulfur doping on structure, morphology, porosity, optical properties, and photocatalytic activity of the mesoporous films was studied. Compared to undoped titania films, the S-doped films showed better long-range ordering, bigger pore size, higher porosity, less shrinkage of the structure during calcination, a red-shift of the band gap, and a more hydrophilic surface. These characteristics led to an improved photocatalytic activity when the S-doped and undoped titania films were tested for degradation of methylene blue in aqueous solutions under the irradiation of 1 sun from a solar simulator. The photocatalytic activity of the sulfur doped titania film was stable during three consecutive experiments under solar light irradiation, confirming the mechanical stability and reusability of the doped nanostructured thin film photocatalysts

Reagentless Electrochemiluminescence from a Nanoparticulate Polymer of Intrinsic Microporosity (PIM-1) Immobilized onto Tin-Doped Indium Oxide

In contrast to most common electrochemiluminescence (ECL) techniques that require either an additional reagent or continuous pulsing between oxidative and reductive potentials, here a fluorescent polymer of intrinsic microporosity (PIM-1) is shown to exhibit intrinsic ECL without the need for a co-reactant at positive applied potentials and as a function of pH. PIM-1 is known to possess high microporosity (based on its rigid and contorted molecular structure) and excellent fluorescence properties. By depositing a nanoparticulate form of the PIM-1 material onto tin-doped indium oxide, we achieve a hierarchically porous deposit with good sustained ECL activity in aqueous media. The mechanism for this reagentless ECL is suggested to be linked to reactive oxygen species produced at positive potentials and discussed in terms of potential analytical applications.EPSRC [EP/K004956/1, EP/K008102/2]SCI(E)[email protected]

Customizable fabrication for auxetic graphene assembled macrofilms with high conductivity and flexibility

Auxetic materials with negative Poisson's ratios unusually exhibit intuitive mechanical behaviors, such as cross-section expansion instead of contraction during tension. Such behaviors are interesting because they may enhance unusual mechanical properties. However, controllable preparation of materials with negative Poisson's ratio is still a major challenge. In this study, we report the synthesis of a flexible auxetic graphene assembled macrofilm (GAMF) from graphene oxide nanosheets by a thermal annealing and press assistant method. The obtained materials exhibit good flexibility and significantly wide tunable negative Poisson's ratios ranging from −0.11 to −0.53. We also develop a reconstruction model for characterization the uniaxial tension of GAMF based on X-ray tomographic images. The tensile simulation result predicts the function relationship between Poisson's ratio and critical thickness of pore channels, which is in good agreement with the experimental data. As a result, an effective tunable way is proposed for customizable fabrication of GAMF with tunable negative Poisson's ratios, and the GAMF materials with good flexibility, high electrical conductivity and superior auxetic behavior looks promising for future development of wearable electronics

Molecularly Rigid Microporous Polyamine Captures and Stabilizes Conducting Platinum Nanoparticle Networks

A molecularly rigid polyamine based on a polymer of intrinsic microporosity (PIM-EA-TB) is shown to capture and stabilize platinum nanoparticles during colloid synthesis in the rigid framework. Stabilization here refers to avoiding aggregation without loss of surface reactivity. In the resulting rigid framework with embedded platinum nano particles, the volume ratio of platinum to PIM-EA-TB in starting materials is varied systematically from approximately 1.0 to 0.1 with the resulting platinum nanoparticle diameter varying from approximately 4.2 to 3.1 nm, respectively. Elemental analysis suggests that only a fraction of the polymer is &quot;captured&quot; to give nanocomposites rich in platinum. A transition occurs from electrically conducting and electrochemically active (with shorter average interparticle distance) to, nonconducting and only partially electrochemically active (with longer average interparticle,distance) polymer-platinum composites. The Conducting nanoparticle network in the porous rigid macromolecular framework could be beneficial in electrocatalysis and in sensing-applications.Royal Society; Leverhulme Foundation [RPG-2014-308]SCI(E)[email protected]

Ionic diodes based on regenerated α-cellulose films deposited asymmetrically onto a microhole

Cellulose films of approximately 5 mm thickness, reconstituted from ionic liquid media onto a poly-ethylene-terephthalate (PET) film with a 5, 10, 20, or 40 mm diameter microhole, show current rectification when immersed in aqueous NaCl. For “asymmetric cellulose deposits” this rectification, or ionic diode behaviour, is then investigated as a function of ionic strength and microhole diameter. Future applications are envisaged in sustainable cellulose-based desalination, sensing, or energy harvesting processes<br/