Andrés Seral-Ascaso

Enabling Flexible Heterostructures for Li-Ion Battery Anodes Based on Nanotube and Liquid-Phase Exfoliated 2D Gallium Chalcogenide Nanosheet Colloidal Solutions

2D metal chalcogenide (MC) nanosheets (NS) have displayed high capacities as lithium-ion battery (LiB) anodes. Nevertheless, their complicated synthesis routes coupled with low electronic conductivity greatly limit them as promising LiB electrode material. Here, this work reports a facile single-walled carbon nanotube (SWCNT) percolating strategy for efficiently maximizing the electrochemical performances of gallium chalcogenide (GaX, X = S or Se). Multiscaled flexible GaX NS/SWCNT heterostructures with abundant voids for Li+ diffusion are fabricated by embedding the liquid-exfoliated GaX NS matrix within a SWCNT-percolated network; the latter improves the electron transport and ion diffusion kinetics as well as maintains the mechanical flexibility. Consequently, high capacities (i.e., 838 mAh g-1 per gallium (II) sulfide (GaS) NS/SWCNT mass and 1107 mAh g-1 per GaS mass; the latter is close to the theoretical value) and good rate capabilities are achieved, which can be majorly attributed to the alloying processes of disordered Ga formed after the first irreversible GaX conversion reaction, as monitored by in situ X-ray diffraction. The presented approach, colloidal solution processing of SWCNT and liquid-exfoliated MC NS to produce flexible paper-based electrode, could be generalized for wearable energy storage devices with promising performances.

Low-temperature synthesis and investigation into the formation mechanism of high quality Ni-Fe layered double hydroxides hexagonal platelets

This paper describes the wet-chemistry synthesis of highly crystalline hexagonal flakes of Ni-Fe layered double hydroxide (LDH) produced at temperature as low as 100 °C. The flakes with diameter in the range of 0.5–1.5 μm and the thickness between 15 and 20 nm were obtained by homogeneous precipitation method with the use of triethanolamine (TEA) and urea. By analyzing the intermediate products, it is suggested that, differently from previous reports, a thermodynamically metastable iron oxyhydroxide and Ni-TEA complex are firstly formed at room temperature. Subsequently, when the mixture is heated to 100 °C and the pH increases due to the thermal decomposition of urea, Ni2+ and Fe3+ are slowly released and then recombine, thus leading to formation of pure, highly-crystalline Ni-Fe LDH flakes. This material showed promising results as an electrocatalyst in oxygen evolution reaction (OER) providing an overpotential value of 0.36 V.

Synthesis of layered platelets by self-assembly of rhenium-based clusters directed by long-chain amines

Self-assembly of nanomaterials by wet chemistry methods is a suitable approach for the preparation of engineered structures with novel functionalities. In this work, we study the ability of long-chain amines to direct the growth of a layered nanomaterial, using [RexSeyClz] clusters as building blocks. The amines link to the clusters as ligands during the synthesis, directing the self-assembly due to their amphiphilic properties, which produces a platelet-shaped 2D material with sizes up to several μm in diameter and thicknesses in the range of 60–80 nm. This is, to the best of our knowledge, the first report on a one-step mild chemistry method for the preparation of 2D structures composed of alternate layers of self-assembled amines and sub-nm clusters of a rhenium chalcogenide. Furthermore, these materials can be used as a suitable source of clusters which then, conveniently released by a simple acid/base reaction, have been successfully incorporated to the surface of graphene. The simple clusters deposition method developed here offers a promising route towards the preparation of hybrid clusters/2D materials with outstanding properties arising from quantum confinement effects combined with high surface areas and the enormous compositional variety of 2D materials and clusters. These hybrids are expected to play a key role in the development of active materials for applications ranging from highly efficient energy storage systems, more active catalysts and upper-sensitivity gas sensors.Materials science: Small molecules hold atomic clusters togetherScaffolds made of chain-shaped molecules can be erected and dismantled to control the assembly of small atomic clusters. Andrés Seral-Ascaso, Valeria Nicolosi and colleagues from Trinity College Dublin, Ireland, developed a method to let grains of few Rhenium and Selenium atoms assemble into flat, circular platelets in a liquid solution. Key to the process are the organic molecules composing the solution, having a head that attaches to the clusters and a chain-like tail that makes the molecules align like poles of a scaffold. The clusters are held together in stable platelets, until the addition of another liquid breaks the alignment and disperses the clusters again. Breaking the organic scaffold in a solution that contains graphene sheets makes the re-dispersed clusters deposit on such sheets, forming composite materials that may find use in batteries or sensors.