Highly concentrated aqueous binary solutions of acetate salts are promising systems for different electrochemical applications, for example, energy storage devices. The very high solubility of CH3COOK allows us to obtain water-in-salt electrolyte concentrations, thus reducing ion activity and extending the cathodic stability of an aqueous electrolyte. At the same time, the presence of Li+ or Na+ makes these solutions compatible with intercalation materials for the development of rechargeable alkaline-ion batteries. Although there is a growing interest in these systems, a fundamental understanding of their physicochemical properties is still lacking. Here, we report and discuss the physicochemical and electrochemical properties of a series of solutions based on 20 mol kg-1 CH3COOK with different concentrations of CH3COONa. The most concentrated solution, 20 mol kg-1 CH3COOK + 7 mol kg-1 CH3COONa, gives the best compromise between transport properties and electrochemical stability, displaying a conductivity of 21.2 mS cm-1 at 25 °C and a stability window of up to 3 V in "ideal" conditions, i.e., using a small surface area and highly electrocatalytic electrode in a flooded cell. Careful Raman spectroscopy analyses help to address the interaction network, the phase evolution with temperature, and the crystallization kinetics.
A novel route for the valorization of waste into valuable products was developed. Surgical masks commonly used for COVID 19 protection by stopping aerosol and droplets have been widely used, and their disposal is critical and often not properly pursued. This work intended to transform surgical masks into platinum group metal-free electrocatalysts for oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) as well as into crude oil. Surgical masks were subjected to controlled-temperature and -atmosphere pyrolysis, and the produced char was then converted into electrocatalysts by functionalizing it with metal phthalocyanine of interest. The electrocatalytic performance characterization towards ORR and HER was carried out highlighting promising activity. At different temperatures, condensable oil fractions were acquired and thoroughly analyzed. Transformation of waste surgical masks into electrocatalysts and crude oil can open new routes for the conversion of waste into valuable products within the core of the circular economy.
COVID-19 , Petroleum , Humans , Masks , Pyrolysis , SARS-CoV-2
Water-in-salt solutions, i.e. solutions in which the amount of salt by volume or weight is larger than that of the solvent, are attracting increasing attention in electrochemistry due to their distinct features that often include decomposition potentials much higher than those of lower concentration solutions. Despite the high solubility of potassium acetate (KAC) in water at room temperature (up to 25 moles of salt per kg of solvent), the low cost, and the large availability, the use of highly concentrated KAC solutions is still limited to a few examples in energy storage applications and a systematic study of their physical-chemical properties is lacking. To fill this gap, we have investigated the thermal, rheological, electrical, electrochemical, and spectroscopic features of KAC/water solutions in the compositional range between 1 and 25 mol kg-1. We show the presence of a transition between the "salt-in-solvent" and "solvent-in-salt" regimes in the range of 10-15 mol kg-1. Among the explored compositions, the highest concentrations (20 and 25 mol kg-1) exhibit good room temperature conductivity values (55.6 and 31 mS cm-1, respectively) and a large electrochemical potential window (above 2.5 V).
Is It Possible to Obtain Solvent-Free, Li+ -Conducting Solid Electrolytes Based on Pure PVdF? Comment on "Self-Suppression of Lithium Dendrite in All-Solid-State Lithium Metal Batteries with Poly(vinylidene difluoride)-Based Solid Electrolytes".
Hybrid polymer-ceramic electrolytes with high ceramic loading are currently investigated as a promising solution to achieve high safety and optimal mechanical properties in all-solid-state rechargeable batteries. In this study composite poly(ethylene oxide)/Li1.3Al0.3Ti1.7(PO4)3 (PEO/LATP) electrolytes, with and without lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) as the Li+ salt, were investigated through a combination of physicochemical and electrochemical techniques, including X-ray diffraction, scanning electron microscopy, thermal analysis, solid-state MAS-NMR and impedance spectroscopy. We were able to shed light on the interactions between the ceramic and the polymer phases, and on the mechanisms for Li+ transport. Membranes containing 70 wt% of LATP and 30 wt% of P(EO)15LiTFSI exhibit conductivity values of 4 × 10-5 Ω-1 cm-1 at 25 °C and in excess of 10-4 Ω-1 cm-1 at 45 °C. These promising results, obtained on a quasi-ceramic electrolyte through room temperature processing, suggest that further improvements in the transport properties of "polymer-in-ceramic" systems may be sought by increasing the amorphous polymer content, and by carefully investigating the role of the ceramic particles' composition, dimensions and dispersion on the transport properties of the hybrid system.
