Lucía Vizcaíno‐Anaya

A combination of an IL-POM and an IL was identified as an additive for PAO6. This significantly improved the tribological performance of PAO6 and increased its electrical conductivity by around 1800%.

Polyoxometalates (POM) are promising materials for electrochemical applications, such as supercapacitors. However, their stability in aqueous electrolytes is compromised due to POM cluster leaching. To mitigate this issue, POM can be combined with organic counter cations, which reduce their solubility in water and influence interactions with carbon support materials. Nevertheless, further research is needed to determine the optimal characteristics and electrode design for maximizing performance. In this work, a synergistic methodology to investigate POM compounds bearing cations with three core functionalities (ammonium, imidazolium, and pyridinium) and varying alkyl side chain lengths, is developed in order to elucidate and optimize the effects of hydrophobicity on the structure of organic–inorganic hybrid materials, electrode films, and their electrochemical performance. The results show that, although cations with long alkyl chains exhibit lower capacitance, they can be activated through molecular rearrangement in the solid state, facilitated by the flexibility of these chains within the structure. By combining thermal and electrochemical techniques, the electrode materials are optimized. These findings demonstrate that the careful selection of counter‐cations with the appropriate molecular structures, followed by a thermal activation protocol, is key to developing more efficient and durable energy storage systems.

Precious metal nanoparticles in electrocatalytic applications tend to be single‐use, becoming unusable afterward. Here, this is demonstrated that the electrocatalytic response of these nanoparticles, when confined at the step‐edges of corrugated carbon nanofibers interiors, can be switched on again at will by simply introducing sulfur as an inorganic mediator. To achieve this, an electrochemical methodology is developed that triggers the rapid surface reconfiguration of confined, deactivated nanoparticles (PdS _x ) involving the release of sulfur to yield highly active crystalline Pd(0) nanoparticles, confined polysulfides, and sulfur‐terminated carbon step‐edges. More importantly, the electrochemical performance can be systematically switched from a highly active mode, in which polysulfides enhance the hydrogen adsorption on palladium, to a much less active mode, called the resting mode, in which sulfur (formed by the oxidation of polysulfides) passivates the active Pd(0) nanoparticle surface. This discovery introduces a new protocol to control nanoparticle performance for catalytic reactions, and more crucially, to extend their lifespan.

The lack of selectivity toward the oxygen reduction reaction (ORR) in metal nanoparticles can be linked to the generation of intermediates. This constitutes a crucial constraint on the performance of specific electrochemical devices, such as fuel cells and metal–air batteries. To boost selectivity of metal nanoparticles, a novel methodology that harnesses the unique electrocatalytic properties of polyoxometalates (POM) to scavenge undesired intermediates of the ORR (such as HO ₂ ⁻ ) promoting selectivity is proposed. It involves the covalent functionalization of metal nanoparticle's surface with an electrochemically active capping layer containing a new sulfur‐functionalized vanadium‐based POM (AuNP@POM). To demonstrate this approach, preformed thiolate Au(111) nanoparticles with a relatively poor ORR selectivity are chosen. The dispersion of AuNP@POM on the surface of carbon nanofibers (CNF) enhances oxygen diffusion, and therefore the ORR activity. The resulting electrocatalyst (AuNP@POM/CNF) exhibits superior stability against impurities like methanol and a higher pH tolerance range compared to the standard commercial Pt/C. The work demonstrates for the first time, the use of a POM‐based electrochemically active capping layer to switch on the selectivity of poorly selective gold nanoparticles, offering a promising avenue for the preparation of electrocatalyst materials with improved selectivity, performance, and stability for ORR‐based devices.

Magnetic hyperthermia (MH) shows great potential in clinical applications because of its very localized action and minimal side effects. Because of their high saturation magnetization values, reduced forms of iron are promising candidates for MH. However, they must be protected in order to overcome their toxicity and instability (i. e., oxidation) under biological conditions. In this work, a novel methodology for the protection of iron nanoparticles through confinement within graphitic carbon layers after thermal treatment of preformed nanoparticles supported on carbon is reported. We demonstrate that the size and composition of the nascent confined iron nanoparticles, as well as the thickness of their protective carbon layer can be controlled by selecting the nature of the carbon support. Our findings reveal that a higher nanoparticle–carbon interaction, mediated by the presence of oxygen‐containing groups, induces the formation of small and well‐protected α‐Fe‐based nanoparticles that exhibit promising results towards MH based on their enhanced specific absorption rate values.