Pablo Palomino

Effects of architecture on the electrochemistry of binder-free inverse opal carbons as Li–air cathodes in an ionic liquid-based electrolyte

In this work, different electrodes consisting of a layer of nanostructured binderless carbon supported on a stainless steel (SS) mesh have been developed and tested as cathodes for Li–air batteries. Inverse opal (IO) carbons were developed using poly(styrene-co-methacrylic acid) (PS-MAA) spheres of different sizes as templates via a resorcinol–formaldehyde sol–gel process. The resulting electrodes, which were mechanically stable and easy to manipulate, were electrochemically tested at both 25 and 60 °C by galvanostatic cycling in an ionic liquid-based electrolyte (0.3 M LiTFSI in PYR14TFSI). Different ratios of co-monomers used in the preparation of the template polymeric spheres to control their size significantly influenced the resulting surface area, pore volume and pore distribution in IO carbons of different macropore size. From the electrochemical characterisation, transverse trends in reversibility and rate capability were identified depending on the macropore size of the inverse opal carbon. Smaller pores favor a better charge–discharge reversibility. Large pores contribute to an improved rate capability and large capacity, which are likely due, respectively, to deeper oxygen diffusion into the electrode, and to larger pore bottlenecks.

Deposition of Ni nanoparticles onto porous supports using supercritical CO2: effect of the precursor and reduction methodology

The deposition of Ni nanoparticles into porous supports is very important in catalysis. In this paper, we explore the use of supercritical CO2 (scCO2) as a green solvent to deposit Ni nanoparticles on mesoporous SiO2 SBA-15 and a carbon xerogel. The good transport properties of scCO2 allowed the efficient penetration of metal precursors dissolved in scCO2 within the pores of the support without damaging its structure. Nickel hexafluoroacetylacetonate hydrate, nickel acetylacetonate, bis(cyclopentadienyl)nickel, Ni(NO3)2⋅6H2O and NiCl2⋅6H2O were tried as precursors. Different methodologies were used: impregnation in scCO2 and reduction in H2/N2 at 400°C and low pressure, reactive deposition using H2 at 200–250°C in scCO2 and reactive deposition using ethanol at 150–200°C in scCO2. The effect of precursor and methodology on the nickel particle size and the material homogeneity (on the different substrates) was analysed. This technology offers many opportunities in the preparation of metal-nanostructured materials.

Confinement of poly(ethylene oxide) in the nanometer-scale pores of resins and carbon nanoparticles

The confinement of poly(ethylene oxide) (PEO) in porous materials derived from organic resins and carbon nanoparticles leads to the disappearance of crystallization and to a significant modification of the glass transition. Textural data on pristine and PEO-filled materials obtained by means of nitrogen physisorption link this thermal behaviour to the spatial confinement of PEO in the micro- and mesopore cavities, and it is largely dictated by the morphology and composition of the underlying substrate. High-resolution inelastic neutron scattering of PEO confined in carbon nanoparticles confirms that the chain conformations are distinctly different from those characteristic of the semicrystalline bulk, and similar to those of PEO confined in the interlayer space of graphite oxide.

Mass‐transport Control on the Discharge Mechanism in Li–O2 Batteries Using Carbon Cathodes with Varied Porosity

By comparing carbon electrodes with varying porosity in Li-O2 cells, we show that the effect of electrolyte stirring at a given current density can result in a change from 2D to 3D growth of discharged deposits. The change of morphology is evident using electron microscopy and by analyzing electrode pore size distribution with respect to discharge capacity. As a consequence, carbon electrodes with different textural properties exhibit different capacity enhancements in stirred-electrolyte cells. We demonstrate that mass transport can directly control the discharge mechanism, similar to the electrolyte composition and current density, which have already been recognized as determining factors.

Imprinted Photonic Crystals for Levodropropizine Sensing

Levodropropizine (LDPZ) imprinted inverse opal films were prepared. Photonic polymers are able to transform the recognition of template to absorbance peak shift or reflection peak shift due to the feature size changes of the imprinted polymers. First, the compositions of the imprinted polymers were optimized to obtain both good selectivity and good swelling properties. Second, silica photonic crystals were prepared by colloidal self-assembly method. Silica photonic crystals with bright green color was infiltrated into the voids with LDPZ pre-polymerization solution and polymerized under heat. Molecularly imprinted inverse opal film (MIOF) and non-imprinted inverse opal film (NIOF) were obtained by etching with 1% HF acid. Finally, molecularly imprinted inverse opal film shows imprinting effect to LDPZ at pH 5.8 in 100mM PBS buffer.