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Volumetric changes associated with solvent/electrolyte exchange in electronic conducting polymers (ECPs) play an important role in the mechanical stability of the polymers, as these changes are a critical factor in ECP-based energy storage devices. Thus, the present work explores the hindering of such volumetric deformations for polypyrrole films doped with dodecylbenzenesulphonate (PPy(DBS)) by employing highly concentrated aqueous electrolytes (or water-in-salt electrolytes, WiSEs), and their effects over the corresponding electrochemical capacitor cell energy retention. Electrochemical quartz crystal microbalance with dissipation monitoring measurements for thin PPy(DBS) films in the WiSEs revealed negligible dissipation changes (ΔDn ≈ 0), in contrast with those in dilute aqueous electrolyte (ΔDn ≠ 0), indicating inexpressive structural deformation of PPy(DBS) in the WiSE. This phenomenon is observed for thick freestanding PPy(DBS) films, which presented a maximum bending angle decay from ∼56° (diluted aqueous electrolyte) to 3.5° when working in the WiSE, thus proving the hindering of film bending. The observed trends are reflected in the PPy(DBS) cell energy retention, where the use of a WiSE decreased cell energy fading by 30% after 600 cycles, in comparison with cells based on diluted electrolytes.

Shape‐controlled metal nanoparticles are significantly improving the electrocatalysis of many relevant reactions. By controlling the shape of nanoparticles, it is possible to engineer their surface to exhibit a preferential structure. However, to facilitate the incorporation of shaped nanomaterials into practical electrochemical devices, it is indispensable to overcome limitations caused by their large particle size (typically >5 nm). For practical applications, nanoparticles must have a size lower than 5 nm with a clean surface to decrease costs and provide a sufficiently large specific surface area. This is a major challenge that has remained unexplored up to now. Herein, we present the synthesis and electrochemical characterization of 3–5 nm, with well‐defined cubic Pt nanoparticles supported on carbon. The electrochemical characterization of the nanoparticles evidences the existence of a preferential {100} and clean structure (within about 40 % of {100} terrace surface). This paper was performed under Ministerio de Ciencia e Innovación-FEDER (Spain) Project PID2019-105653GB-100 and Generalitat Valenciana (Project PROMETEO/2020/063). J.S.G. thanks VITC (Vicerrectorado de Investigación y Transferencia de Conocimiento) of the University of Alicante (UATALENTO16-02). R.M.A and R.M.T thank to the support from FAPESP, Procs. 2019/08051-0, 2017/15469-5 and 15/26308-7. H.E. thanks the Estonian Research Council (grant No PUTJD841).

If were not by their low electrochemical stability, aqueous electrolytes would be the preferred alternative to be used in electrochemical energy storage devices. Their abundance and nontoxicity are key factors for such application, especially in large scale. The development of highly concentrated aqueous electrolytes, so-called water-in-salt electrolytes, has expanded the electrochemical window of aqueous electrolyte up to 3.0 V (whereas salt-in-water electrolytes normally shows up to 1.6 V), showing that water can be an alternative after all. Many devices, ranging from metal-ion batteries to electrochemical capacitors, have been reported recently, making use of such wider electrochemical stability and enhancing devices energy density. Different salts have also been proposed not only to gain in costs but also to improve physicochemical properties.

Herein, we describe the synthesis, characterization and electrochemical performance of four phosphonium-based ionic liquids (ILs) as electrolytes, Physicochemical properties such as viscosity, density, ionic conductivity, and thermal stability of ILs and conventional organic solvent ethylene carbonate (EC)/diethyl carbonate (DEC) were experimentally determined at different temperatures. All ILs showed thermal stability greater than 300 degrees C, surpassing the stability of the conventional organic solvent, whose flash points were 145 and 23 degrees C for EC and DEC, respectively. Nevertheless, at room temperature, all ILs are much more viscous than EC/DEC. The composite Si -[P-2224][FSI] (triethyl-n-butylphosphonium bis(fluoromethylsulfonyl)imide) and Si-EC/DEC anodes exhibit initial specific capacities at 0.15 A/g of 2409 and 2631 mAh/g, respectively. This demonstrates that despite the inferior transport properties of ILs, short alkyl-substituted phosphonium ILs like [P-2224][FSI] are potentially competitive for the new generation of electrolytes for LIBs. NMR, DSC, TGA, and galvanostatic discharged/charged were used as characterization techniques.

International audience; Conducting polymers have been used as support for catalysts towards distinct electrocatalytic reactions. The overall activity of the modified interfaces critically depends on both the processes on the catalyst surface and of the charge compensation within the polymer matrix. Therefore, understand the coupling between surface and volumetric processes in such systems is of utmost importance. In this contribution we report on the experimental investigation of the interplay between surface and volumetric processes during the electrooxidation of formic acid (and also formaldehyde) on platinum modified polyaniline electrodes. The study was performed through in situ nanogravimetry, with the Electrochemical Quartz Crystal Nanobalance (EQCN). We have explored the dynamics of charge and mass changes along several experimental conditions, including the self-organized potential oscillations. The systematic study included the analysis of several configurations: gold electrodes covered with a PANI film and dispersed platinum (Au/PANI/Pt); platinum electrodes covered with PANI (Pt/PANI); and bare platinum electrodes. The methodology introduced includes the detailed analysis of the charge compensation process and of the time-derivative of the mass variations. Typical results for the electro-oxidation of formic acid on PANI supported platinum indicate that the electrocatalysis itself is reflected in the current profile, whereas the charge compensation rules the gravimetric response. This general observation also holds for the oscillatory electro-oxidation of formic acid. The physicochemical description of the support/catalyst systems described here opens interesting perspectives for the investigation of parent systems.

Made available in DSpace on 2022-04-28T19:45:51Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-11-15 The development of negative electrode materials with better performance than those currently used in Li-ion technology has been a major focus of recent battery research. Here, we report the synthesis and electrochemical evaluation of in situ-formed nitrogen-doped carbon/SiOC. The materials were synthesized by a sol–gel process using 3-(aminopropyl)triethoxysilane (APTES), sodium citrate and glycerol. The electrochemical performance of pyrolyzed materials was studied using poly(acrylic acid) binder and commercial organic electrolyte. Our reported approach enables changes in both the amount of nitrogen and the morphology as a function of the molar ratio of APTES:citrate and reaction time. Spherical-shaped NC/SiOC composite electrodes deliver a delithiation capacity of 622 mAh/g at 0.1 A/g and an initial coulombic efficiency of ∼63%, while in the large bulk material, respective values of 367 mAh/g and ∼55% were obtained. After 1000 charge/discharge cycles at 1.6 A/g, the latter material exhibits 98% of the initial capacity once it returned to lower current cycling. Overall, our results indicate that NC/SiOC materials are quite promising for electrochemical applications since both their large capacity and stability demonstrate superior performance compared to traditional graphite. Moreover, our synthesis is simple and, more importantly, environmentally friendly chemicals, such as sodium citrate and glycerol, are used. Departamento de Química Fundamental Instituto de Química – Universidade de São Paulo, Av. Prof. Lineu Prestes 748 Departamento de ciencias Universidad de Ingenieria y Tecnologia – UTEC Instituto de Química. UNESP, Rue Francisco Degni, 55 Department of Chemistry University of Helsinki, A.I. Virtasen Aukio 1 NanoQAM and Département de Chimie Université du Québec à Montréal, Case Postale, 8888 Succursale Centre-Ville Instituto de Química. UNESP, Rue Francisco Degni, 55

Control over the bottom up synthesis of metal nanoparticles (NP) depends on many experimental factors, including the choice of stabilising and reducing agents. By selectively manipulating these species, it is possible to control NP characteristics through solution-phase synthesis strategies. It is not known, however, whether NPs produced from mechanochemical syntheses are governed by the same rules. Using the Au NPs mechanosynthesis as a model system, we investigate how a series of common reducing agents affect both the reduction kinetics and size of Au NPs. It is shown that the relative effects of reducing agents on mechanochemical NP synthesis differ significantly from their role in analogous solution-phase reactions. Hence, strategies developed for control over NP growth in solution are not directly transferrable to environmentally benign mechanochemical approaches. This work demonstrates a clear need for dedicated, systematic studies on NP mechanosynthesis.

Current time-resolvedin situapproaches limit the scope of mechanochemical investigations possible. Here we develop a new, general approach to simultaneously follow the evolution of bulk atomic and electronic structure during a mechanochemical synthesis. This is achieved by coupling two complementary synchrotron-based X-ray methods: X-ray absorption spectroscopy (XAS) and X-ray diffraction. We apply this method to investigate the bottom-up mechanosynthesis of technologically important Au micro and nanoparticles in the presence of three different reducing agents, hydroquinone, sodium citrate, and NaBH4. Moreover, we show how XAS offers new insight into the early stage generation of growth species (e.g.monomers and clusters), which lead to the subsequent formation of nanoparticles. These processes are beyond the detection capabilities of diffraction methods. This combined X-ray approach paves the way to new directions in mechanochemical research of advanced electronic materials.

The use of shape-controlled nanomaterials represents an elegant way to improve the performance of many electrochemical reactions. However, two main aspects must be still optimised: decreasing particle size and increasing their activity. This study shows that the deposition of Pd on different small (3-5 nm) supported Pt materials (displaying a preferential structure containing ∼40% of Pt{100} terraces) leads to a great enhancement in the electrocatalytic activity towards the formic acid electrooxidation reaction. After Pd decoration, the oxidation takes place at lower overpotentials and oxidation current densities are significantly higher than those observed with all the bare Pt/C samples. For the Pt/C 45% catalyst, the intrinsic activity after Pd deposition was more than three times of that without Pd, while the oxidation overpotential shifted about ∼200 mV to lower overpotentials. This work was supported by the Ministerio de Ciencia e Innovación-FEDER (Spain) Project PID2019-105653GB-100 and Generalitat Valenciana (Project PROMETEO/2020/063). R.M.A and R.M.T thank to the support from FAPESP, Procs. 2019/08051-0, 2017/15469-5 and 15/26308-7. H.E. thanks the Estonian Research Council (grant No PUTJD841).

Active Pt-based catalysts at low temperature towards the preferential oxidation of carbon monoxide in hydrogen-rich stream reaction (CO-PROX) are of great importance for H-2-fueled fuel cells, but still remain a challenge. Herein, we propose a simple approach to synthesize a highly active Pt20Fe/CeO2 catalyst employing the borohydride reduction process. Transmission electronic microscopy revealed monodispersed 2.8 nm-Pt nanoparticles on CeO2, and the role of Fe species on the activity is discussed. The excellent CO conversion of 99.6% and CO2 selectivity of 92.3% carried out at ambient temperature meet the CO-PROX requirements for an adequate supply of hydrogen in fuel cell device. (C) 2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Sodium fluorophosphates are among the most promising materials for positive electrodes in sodium-ion batteries; however, their low electronic conductivity, kinetics limitations, and structural instability prevent them from reaching their full potential. We obtained sodium vanadium fluorophosphates (NVPF) doped with Ti4+ (NVTPF) and Nb5+ (NVNPF) via an original low-temperature synthesis. It was observed that Ti4+ doping facilitated access to electrode sites and provided higher capacities at high current densities while Nb5+ provided a 91.7% capacity retention from the 20th to 200th cycle, which was over the 80.1% capacity retention of NVPF. Moreover, both NVTPF and NVNPF provided diffusion coefficients in the range of ~10−10 cm2 s−1, which was better than ~10−12 cm2 s−1 of NVPF. Additionally, electrochemical impedance spectroscopy and ex situ X-ray diffraction measurements confirmed that Ti4+ enhanced the electrode kinetics and stabilized its structure through sodiation/desodiation reactions. The results presented in this paper might provide insights and new directions to enhance the electrochemical storage properties of fluorophosphates.

Electrochemical capacitors show high power density but suffer from low energy density. The use of pseudocapacitive material can increase the cell capacitance and therefore increase the device energy density. In this work, we show that using microtubular conducting polymers, as polypyrrole (PPy) and poly(3,4-ethylenedioxythiophene) (PEDOT), alongside activated carbon (AC) in asymmetrical devices, and highly concentrated aqueous electrolyte (or water-in-salt electrolyte, WiSE), is possible to maintain the polymers electroactivity at the negative polarization and take advantage of the electrolyte electrochemical stability. The polymers electrochemical behaviours were compared in WiSE and aqueous acidic solution, which hinted that the polymers charge compensation are different in the different electrolytes. PPy-AC and PEDOT-AC cells can reach 2.6 and 2.8 V, respectively, and electrodes mass balance greatly depends on the polymers open circuit potential before and after cycling

The localized surface plasmon resonance (LSPR) excitation in plasmonic nanoparticles (NPs) in the visible and near-infrared ranges is currently at the forefront of improving photocatalytic performances via plasmonic photocatalysis. One bottleneck of this field is that the NPs that often display the best optical properties in the visible and near-infrared ranges are based on expensive noble metals such as silver (Ag) and gold (Au). While earth-abundant plasmonic materials have been proposed together with catalytic metals in antenna-reactor systems, their performances remain limited by their optical properties. Importantly, the synthesis of plasmonic photocatalysts remains challenging in terms of scalability while often requiring several steps, high temperatures, and special conditions. Herein, we address these challenges by developing a one-pot, gram-scale, room-temperature synthesis of earth-abundant plasmonic photocatalysts while improving their activities beyond what has been dictated by the LSPR excitation of the plasmonic component. We describe the mechanochemical synthesis of earth-abundant plasmonic photocatalysts by using MoO3 (antenna) and Au (reactor) NPs as a proof-of-concept example and demonstrate that the dual plasmonic excitation of antenna and reactor sites enables the tuning of plasmonic photocatalytic performances toward the reductive coupling of nitrobenzene to azobenzene as a model reaction. In addition to providing a pathway to the facile and gramscale synthesis of plasmonic photocatalysts, the results reported herein may open pathways to improved activities in plasmonic catalysis.

The Nobel Prize in Chemistry 2019 recognized the importance of Li-ion batteries and the revolution they allowed to happen during the past three decades. They are part of a broader class of electrochemical energy storage devices, which are employed where electrical energy is needed on demand and so, the electrochemical energy is converted into electrical energy as required by the application. This opens a variety of possibilities on the utilization of energy storage devices, beyond the well-known mobile applications, assisting on the decarbonization of energy production and distribution. In this series of reviews in two parts, two main types of energy storage devices will be explored: electrochemical capacitors (part I) and rechargeable batteries (part II). More specifically, we will discuss about the materials used in each type of device, their main role in the energy storage process, their advantages and drawbacks and, especially, strategies to improve their performance. In the present part, electrochemical capacitors will be addressed. Their fundamental difference to batteries is explained considering the process at the electrode/electrolyte surface and the impact in performance. Materials used in electrochemical capacitors, including double layer capacitors and pseudocapacitive materials will be reviewed, highlighting the importance of electrolytes. As an important part of these strategies, synthetic routes for the production of nanoparticles will also be approached (part I).

The development of time-resolved in situ approaches for monitoring mechanochemicaltransformations has revolutionized the field of mechanochemistry. Currently, the established insitu approaches greatly limit the scope of investigations that are possible. Here we develop a newapproach to simultaneously follow the evolution of bulk atomic and electronic structure during amechanochemical synthesis. This is achieved by coupling two complementary synchrotron-basedX-ray methods: X-ray absorption spectroscopy and X-ray diffraction. We apply this method toinvestigate the bottom-up mechanosynthesis of technologically important Au nanoparticles in thepresence of three different reducing agents. Moreover, we demonstrate how X-ray absorptionspectroscopy offers unprecedented insight into the early stage generation of growth species (e.g.monomers and clusters), which lead to the subsequent formation of nanoparticles. Theseprocesses are beyond the detection capabilities of diffraction methods. The approach is general,and not limited to monitoring NP mechanosynthesis. This combined X-ray approach paves theway to new directions in mechanochemical research of advanced electronic materials.

Functional surface coatings are a key option for biomedical applications, from polymeric supports for tissue engineering to smart matrices for controlled drug delivery. Therefore, the synthesis of new materials for biological applications and developments is promising. Hence, biocompatible and stimuli-responsive polymers are interesting materials, especially when they present conductive properties. PEDOT-co-PDLLA graft copolymer exhibits physicochemical and mechanical characteristics required for biomedical purposes, associated with electroactive, biocompatible, and partially biodegradable properties. Herein, the study of fibronectin (FN) adsorption onto PEDOT-co-PDLLA carried out by an electrochemical quartz crystal microbalance with dissipation is reported. The amount of FN adsorbed onto PEDOT-co-PDLLA was higher than that adsorbed onto the Au surface, with a significant increase when electrical stimulation was applied (either at +0.5 or −0.125 V). Additionally, FN binds to the copolymer interface in an unfolded conformation, which can promote better NIH-3T3 fibroblast cell adhesion and later cell development.

A quartz crystal microbalance method with dissipation (QCM-D) and attenuated total reflection Fourier-transform infrared (ATR-FTIRS) spectroscopy were used to study the adsorption of L-cysteine (L-Cys) on Pt. Through QCM-D, it was possible to verify that the viscoelastic properties of the adsorbed species play an important role in the adsorption, rendering Sauerbrey's equation inapplicable. The modelling of QCM-D data exposed two different processes for the adsorption reaction. The first one had an activation time and is fast, whereas the second is slow. These processes were also resolved by ATR-FTIRS and identified to be water and anion adsorption preceded by L-Cys adsorption. Both techniques reveal that the degree of surface coverage is pH dependent. Spectroscopic data indicate that the conformation of L-Cys(ads) changes with pH and that the structures do not fully agree with those proposed in literature for other metallic surfaces. The assembling of the adsorbed monolayer appeared to be very fast, and it was not possible to determine or quantify this kinetics. The conformation is also controlled by applied potential, and the anion adsorption and interfacial water depends on the conformation of the adsorbed molecules.

Summary Ionic liquids are liquids containing solely ions having melting points lower than 100 °C. Their potential applications in electrochemical energy storage and conversion were generated mainly by their negligible vapor pressure, in most cases, and by their thermal stability. An overview of these novel materials and their limitations is provided from their fundamental properties to the recent essential advances in the field.

Ionic Liquids (ILs) and poly(Ionic Liquids) (PoILs) have fully tunable properties due to their different ion combinations as well as cation or anion functionalization, which results in smart materials with endless possibilities. In this study, a solid electrochromic PoIL was synthesized using a novel functionalizable and polymerizable IL (1-propyl-3-vinylimidazolium chloride bromide) and a viologen (4,4′-bipyridine) that reacted to form a monomer. Its subsequent polymerization resulted in a mechanically stable, highly ionically and electronically conductive electrochromic polyelectrolyte with a thermal decomposition temperature higher than 309 °C and a glass transition temperature of 13 °C. Spectroelectrochemical studies of the polymer deposited as a thin film over a transparent conductive substrate demonstrated a reversible redox process with reduction and oxidation potentials of − 0.45 and − 0.3 V, respectively, which was accompanied by a reversible color change from colorless (oxidized state) to purple (reduced state) with an optical contrast of 19% at 525 nm, a switching time of nearly 20 s and a coloration efficiency of 60 cm 2 C − 1 . Additionally, the film was repetitively switched from colorless to purple and began to lose electroactivity after approximately 4 h and 400 cycles. However, electroactivity was still observed after 16 h or 1600 cycles. Moreover, quartz crystal microbalance with dissipation monitoring indicated that the polymer charge compensation process was accompanied by a huge viscoelastic change in the film, as demonstrated by the spread of the harmonics and important changes in dissipation.

The application of lithium-sulfur (Li-S) batteries is still limited by their rapid capacity fading. The pulverization of the sulfur positive electrode after the lithiation and the consequence dissolution of long chain polysulfides in organic solvents lead to the shuttle effect. To address these issues, here we report the mechanochemical preparation of ZIF-8 (Zeolitic Imidazole Framework-8)-based composites as sulfur hosts for positive electrodes in Li-S batteries. We studied different methods for the incorporation of conductive carbon. Also, the replacement of Zn2+ metal centers by other bivalent metals (Cu2+, Co2+ and Ni2+), enabled the preparation of other ZIF-8-based materials. The positive electrode ZIF-8/C/S8 showed initial discharges of 772 mA h g−1 while the pristine one, ZIF-8/S8, displayed 502 mA h g−1. The enhanced performance of 54% for ZIF-8/C/S8 indicates that the direct mechanochemical synthesis of ZIF-8 with conductive carbon is beneficial at initials charge/discharge process in comparison to traditional slurry preparation (ZIF-8/S8). Also, the Li2S6 absorption tests shows 87% of discoloration with ZIF-8/C/S8, confirming the better polysulfides absorption.

Ionic liquid consists of an organic cation and generally an inorganic anion. The properties of liquids can be modulated by changing the anion or the cation or both. Two ionic liquids derived from the anion [FSI] were synthesized and characterized: (N-n-butyl-N-methylpyrrolidinium bis(fluorosulfonyl imide), [BMPYR][FSI]) and triethyl-n-pentylphosphonium bis(fluorosulfonyl)imide), [P2225][FSI]). We also report the comparison with [TFSI] based ionic liquids, namely: (N-n-butyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide), [BMPYR][TFSI]), (N-n-butyl-N-methylpiperidinium bis(trifluoromethylsulfonyl)imide), [BMP][TFSI]), triethyl-n-pentylphosphonium bis(trifluoromethylsulfonyl)imide), [P2225][TFSI]) and (triethyl(2-methoxyethyl) phosphonium bis(trifluoromethylsulfonyl imide), [P222201][TFSI]. Thermophysical properties, such as viscosity (298.15–373.15 K), density (298.15–373.15 K), conductivity (298.15–361.15 K), electrochemical (cutoff density current within 150 μA·cm–2), and thermal stability (303...

Low-cost piezoelectric devices, such as simple frequency monitoring quartz crystal microbalance (QCM) devices, have good clinical utility as fast diagnostic tools for the detection of several diseases. However, unspecific antigen recognition, poor molecular probe adsorption and the need for sample dilution are still common drawbacks that hinder their use in routine diagnosis. In this work, piezoelectric sensors were previously coated with thin films of bacterial cellulose nanocrystals (CN) to provide a more sensitive and adapted interface for the attachment of monoclonal immunoglobulin G (IgGNS1) and to favor specific detection of non-structural protein 1 (NS1) of dengue fever. The assembly of the immunochip surface was analyzed by atomic force microscopy (AFM) and the NS1 detection was followed by quartz crystal microbalance with (QCM-D) and without energy dissipation monitoring (QCM). The CN surface was able to immobilize 2.30±0.5mgm-2 of IgGNS1, as confirmed by AFM topography and phase images along with QCM-D. The system was able to detect the NS1 protein in serum with only 10-fold dilution in the range of 0.01-10µgmL-1 by both QCM and QCM-D. The limits of detection of the two devices were 0.1μgmL-1 for QCM-D and 0.32μgmL-1 for QCM. As a result, QCM-D and QCM apparatuses can be used to follow NS1 recognition and have good potential for more sensitive, fast and/or less expensive diagnostic assays for dengue.

Although the very first papers on conducting polymers were published almost 30 years ago, the importance and interest in this class of material have since been continuously renewed by the development of new designs with modified electrodes and their applications. In this review, we discuss the main topics of conducting polymers, especially new trends in material preparation by using template-assisted polymerization-generating materials that have a unique and highly reproducible morphology and using ionic liquids, which appears to be an interesting methodology that has yet to be further explored. There are many different applications of conducting polymers that are found in the literature, and herein, we describe their main aspects in terms of energy, electrochromism, and sensing. Due to the large interest in the energy field, this theme is discussed in terms of storage by means of the description of supercapacitors and conversion, by showing some recent advances in solar cell-modified electrodes. The changes in the optical properties of the conducting polymers in electrochromism are also presented in the discussion on the nanostructure electrode preparation, which aims at a solid-state architecture that can accomplish fast ionic diffusion. Finally, the construction of sensors and biosensors is discussed; due to their intrinsic electrocatalytic properties, conducting polymers are constantly employed for the detection of many different analytes. Additionally, by chemically modifying some functional groups, it is possible to attach different biomolecules, thereby providing a wide range of biosensors and biodetectors.

Mechanochemistry is a promising alternative to solution-based protocols across the chemical sciences, enabling different types of chemistries in solvent-free and environmentally benign conditions. The use of mechanical energy to promote physical and chemical transformations has reached a high level of refinement, allowing for the design of sophisticated molecules and nanostructured materials. Among them, the synthesis of noble metal nanoparticles deserves special attention due to their catalytic applications. In this review, we discuss the recent progress on the development of mechanochemical strategies for the controlled synthesis of noble metal nanostructures. We start by covering the fundamentals of different preparation routes, namely top-down and bottom-up approaches. Next, we focus on the key examples of the mechanochemical synthesis of non-supported and supported metal nanoparticles as well as hybrid nanomaterials containing noble metals. In these examples, in addition to the principles and synthesis mechanisms, their performances in catalysis are discussed. Finally, a perspective of the field is given, where we discuss the opportunities for future work and the challenges of mechanochemical synthesis to produce well-defined noble metal nanoparticles.

Sodium-ion batteries are a promising alternative to lithium-ion devices, but the development of proper negative electrode materials is still challenging. Here, the properties of a low-voltage sodium titanate material are evaluated. Sodium titanate nanotubes (NTO) were produced by an alkalyne alkaline hydrothermal treatment with TiO2 and consisted of a hydrated Na1.4H0.6Ti3O7 with a surface area of 128 m2 g−1. NTO electrode kinetics were studied by cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic intermittent titration techniques. The (de)intercalation of Na+ ions involved two redox pairs at 0.3/0.5 V and 1.0/1.2 V, associated with the present mixture of nanotubes and nanosheets. Surface processes had a 95% coulombic efficiency and a high contribution even at low scan rates, accounting for 47% of the total capacity at 0.5 mV s−1. Upon Na+ removal, the electronic resistance and the semiconductor capacitance increased. Battery tests performed on Na|NTO half-cells showed a reversible capacity of 90 mA h g−1 at 10 mA g−1 and near 100% coulombic efficiency at current rates ranging from 10 mA g−1 to 10 A g−1. Additionally, NTO presented a good capacity retention of 92% after 170 cycles at 100 mA g−1.

In the past two decades, the fabrication of nanolayer coatings on polymeric materials has triggered considerable interest in the tissue-engineering field. Layer-by-Layer (LbL) assembly has attracted substantial attention due to being a convenient and low-cost method to coat materials with biomolecules while keeping their original biofunctionalities. This work aims to access a deeper understanding of the processes of adsorption and desorption of proteins by studying different architectures for the loading and release of model proteins on spin-coated flat surfaces of biodegradable polyesters such as poly(e-caprolactone) (PCL) and poly(L-lactic acid) (PLLA) by the LbL technique. Surfaces of Si-wafers coated with PCL and PLLA were used as substrates for deposition of model proteins such as bovine serum albumin and lysozyme using heparin and chitosan as a pair of polyelectrolytes for LbL assembly. The analysis of the attributes of these protein reservoirs such as the protein layer position, layer thickness, surface morphology, protein adsorption and desorption quantification and kinetics was performed by ellipsometry, atomic force microscopy, fluorescence microscopy, and quartz-crystal microbalance with enhanced dissipation measurements. A homogenous LbL coating on the surface of the polyester films was achieved by assembling ten layer-pairs of reservoirs. The release profiles were evaluated, and the results showed an intricate dependence on the protein volume charge density and its relation to coacervation/complexation processes with both polyelectrolytes. Our results clearly suggest that the protein delivery kinetics can be fully controlled by precisely positioning the protein within the assembly (bottom vs. top position). They also suggest that the size and total charge of the protein are key factors for controlling its total load in the assembly.

La presente obra es el producto de la compilación de los trabajos que se presentaron en el III Congreso Colombiano de Electroquímica, organizado por la Universidad Santiago de Cali y la Facultad de Ciencias Básicas y el grupo de investigación en química y biotecnología (QUIBIO) (quien lideró la organización del evento). El evento se celebró en la ciudad de Cali, Valle del Cauca, Colombia, del 2 al 5 de octubre del 2018 en la sede Pampalinda, de la Universidad Santiago de Cali. El Comité Editorial se encargó de compilar la obra y darle un formato homogéneo. La Dirección de Publicaciones de la Universidad Santiago de Cali se encargó crear el diseño gráfico de la portada y su diagramación. Sin embargo, es necesario aclarar que el contenido científico y las aseveraciones que aparecen en cada trabajo son responsabilidad de sus autores.

An in-depth investigation of the physical and chemical parameters that affect Li-sulfur batteries is imperative to optimize their performances. Here, we report promising [CeO2]100-x-[S8]x nanohybrids for anchoring lithium polysulfides (LiPSs) that are generated during cycling. The composition of [CeO2]100- x-[S8]x (x = 30, 50 and 70%) could be simply controlled by varying the CeO2/S8 mass ratio added in each reaction. Our results indicated that the [CeO2]100- x-[S8]x nanohybrids displayed a crystalline structure composed of both phases (CeO2 and S8), indicating an efficient impregnation process of S8 on the CeO2 nanowire surface. The surface area of CeO2 nanowires decreased as the amount of S8 was increased, and the [CeO2]70-[S8]30 nanohybrid maintained a uniform distribution of S8 over the entire CeO2 nanowires. Remarkably, the [CeO2]70-[S8]30 nanohybrid showed the best Li-storage performance, leading to specific capacities of approximately 600 mA h g–1 over 160 cycles and a Coulombic efficiency of approximately 100%. Moreover, this sample showed excellent rate capability performance (even discharging at 10 A g–1). Additionally, the chemical interaction of CeO2 with LiPS was demonstrated by a visual experiment through the addition of pure CeO2 in a solution of Li2S6. The solution containing CeO2 nanowires became completely colorless after 30 min. To further investigate these improvements, density functional theory (DFT) calculations revealed the formation of strong interactions between the CeO2 nanowire surface and different sulfur species. For instance, the adsorption energies between the CeO2 nanowires and S8, Li2S4, and Li4S8 were –3.95, –5.84 and –7.31 eV, respectively, suggesting that the [CeO2]70-[S8]30 nanohybrid provided an appropriate surface to anchor LiPS by electrostatic interactions, leading to faster redox kinetics in Li-sulfur battery applications.

The use of water-in-salt electrolytes (WiSEs) in electrochemical capacitors is an interesting alternative to state-of-the-art electrolytes based on organic solvents. However, making use of their wide electrochemical stability in electrochemical capacitors has been challenging, as shown in battery materials. In this work, we used three concentrations of LiTf2N in water (7, 15 and 21 mol kg−1) with activated carbon, and the determination of the maximum operating voltage showed stability up to 2.2, 2.4 and 2.6 V, respectively. This determination suggested positive/negative-electrode mass balances of 2.1, 1.5 and 1.2, but the experiments showed that the cycle life of devices using WiSEs of 15 and 21 mol kg−1 can be improved. Thus, we find that increasing the amount of active material in the positive electrode gave higher capacitance retention over cycling. With the optimization for a longer cycle life, the observed capacitance retentions for the devices with WiSEs of 7, 15 and 21 mol kg−1 were 97%, 70% and near 100%, respectively, after 10000 cycles. The higher amount of active material in the positive electrode penalized the energy-power performance, but the higher electrochemical stability compensated for it, and WiSEs of 7, 15 and 21 mol kg−1 stored 15, 16 and 21 W h kg−1 when they operated at 0.1 A g−1.

The influence of LLTO (Li0.33La0.56TiO3) nanoparticles on the conducting properties of PEO (polyethylene oxide)8-LiClO4 polymer-salt complex electrolyte still remains not fully understood. This paper aims to establish the role of LLTO filler concentration, its morphology, agglomeration and charge nanoparticles surface on the ionic transport of (PEO)8-LiClO4-based solid electrolytes. Four samples of (PEO)8-LiClO4- LLTO composites, with 0, 5, 10 and 15 wt% of LLTO filler, were prepared. Several techniques were used to verify the obtainment of the required samples and to find out how the LLTO filler can modify the conductivity of the (PEO)8-LiClO4 polymer-salt complex electrolyte. The obtained results suggest that the transport of Li ions in these nanocomposites occurs predominantly through the polymeric phase, not by the conducting LLTO ceramic employed as filler. The highest conductivity value (10−3 S/cm at 338 K) is reached for 10 wt % of LLTO filler in the composite, where the polymeric phase is completely amorphous.

A critical parameter in the design of EDLCs is the determination of electrochemical stability limits for individual combinations of electrode and electrolyte. Using [EMIm][BF4] as an example we demonstrate that the physical properties of the activated carbon used in the electrodes influence the permissible operating potential of an EDLC, and also that the binder material employed can have further effects. When [EMIm][BF4] electrolyte is coupled with electrodes containing PTFE binder, operating potentials as wide as 3.8 V can be utilised. Due to the differences in response under opposing polarisations, it is necessary to employ an asymmetric mass loading in EDLC cells in order to make full use of the operating window. By balancing the charge in the cell, the differences in stable potential limits and capacitative behaviour can be overcome, however we also found that this balance can be influenced by the rate at which these parameters are determined. Three-electrode measurements show that using an appropriate mass loading ratio results in each electrode operating within their determined stability limits. Stable cycling of a full cell at an operating potential of 3.8 V was demonstrated over 50,000 cycles.

A finite-element method was applied to the problem of measuring near-surface concentration values with a probe placed in front of the electrochemical interface. Those probes, like pH-sensing microelectrodes, interfere with mass transport and unreliable results may be obtained due to the local distortions. A pure diffusion problem was solved for a one-component two-dimensional axisymmetric model, under Dirichlet and Neumann-type boundary conditions at the substrate surface. The generalized results may be used to estimate the effects of the sensor tip-substrate distance on local current density and surface concentrations, and on measurement accuracy in absence of homogeneous reactions. To account for the presence of homogeneous reactions, simulations were performed for specific system compositions, using the near-surface pH measurement in solutions containing a buffering agent as an example. An IrOx microelectrode was used for experime ntal measurements of near-surface pH carried out in solutions displaying different buffering capacities. The results were compared to simulations performed for a one-dimensional model with simplified electrode kinetics, but fully describing the kinetics of homogeneous reactions. It is shown that valuable information on the electrochemical processes may be extracted by using this experimental approach, even when the measured pH does not strictly correspond to the pH effectively experienced by the substrate surface.

Hydrothermally synthesized α-MoO3 nanoribbons were converted to MoS2 whilst retaining the same morphology by a solid–gas reaction at 800 °C in a H2S/H2/N2 atmosphere. In order to keep the nanoribbon morphology from the oxide in the sulfide, it was crucial to have a H2S stream during the whole heating process. Thereby, the first layer of sulfide is formed as soon as the oxide is activated avoiding coalescence of the nanoribbons. Afterwards, the sulfidization takes place from the outer shell to the inner core of the nanoparticles. Both α-MoO3 and MoS2-NR were investigated for the electrochemical intercalation of lithium-ions. The electrochemical insertion and removal of lithium in the molybdenum oxide are accompanied by a change of color, which was measured by in situ UV-Vis. Spectroelectrochemical experiments showed a distinguished electrochromic behavior with a significant potential-dependent change in absorbance at 660 nm upon Li+ insertion. Analysis of in situ voltammetry revealed the presence of three active sites for lithium insertion in the MoO3-NRs, which are accompanied by only two chromophores in the same potential range. Voltammetric measurements of the MoS2 nanoribbons presented a reversible reduction of MoS2 to LixMoS2, followed by Mo and Li2S, which can be further reduced to Li and S at more negative potentials. Such sulfide materials are highly promising for lithium batteries. This template synthesis is a simple method to obtain high purity MoS2 nanoparticles with a controlled morphology of nanoribbons.

In the present work, we studied the performance of different new binders based on poly[ionic liquids] (POILs) using a well-known negative electrode material such as Li4Ti5O12 (LTO) compound and ionic liquids (ILs) as solvents. We used an IL formed by Pip1,4Tf2N with N-butyl-N-methyl piperidinium (Pip1,4) as the cation and bis(trifluoromethanesulfonyl)imide (Tf2N−) as the anion. We tested two POILs as binders, composed of either LiTf2N, Pip1,4Tf2N, and PVDF or poly[diallyldimethylammonium]Tf2N (PDDA) as the polymer precursors (PVDF-IL and PDDA-IL, respectively). The best Li+ transport number as well as the smallest contact angle (electrolyte membrane) was obtained for the PDDA-IL polymer. The swelling effect better facilitates impregnation than the other polymers. The LTO/PDDA-IL combination showed the best specific capacity, 70 mAh g−1, and a stable prolonged cycling. We identified the TiIV/TiIII redox reversible processes by cyclic voltammetry experiments and the differential capacity profiles. Additionally, we measured the Li+ diffusion coefficient to be approximately 10−12 cm2 s−1. When different binders and IL-solvents are employed in a typical LTO cell, we demonstrated that the factors that determine cell performance are the ionic conductivity and the swelling effect. Fil: Chauque, Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; Argentina Fil: Oliva, Fabiana Yolanda. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; Argentina Fil: Camara, Osvaldo Raul. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; Argentina Fil: Torresi, Roberto M.. Universidade de Sao Paulo; Brasil

The influence of glycine on the mechanism of cobalt electrodeposition on Au was studied by using different experimental techniques. From cyclic voltammetry experiments, changes in deposition kinetics were observed in the presence of glycine and as a function of pH. The early stages of deposition and the morphology of the Co films were strongly influenced by the solution pH. The electroactivity of Co(gly)+ was confirmed, with slower processes related to highly coordinated cobalt ions becoming predominant with pH increase. In situ investigations were conducted at solution pH 4 and 6. The infrared spectroelectrochemical experiments showed that the concentrations of cobalt-glycine complexes increased due to changes in the interfacial pH, owing to the hydrogen evolution reaction (HER). Near-surface pH measurements during Co electrodeposition were carried out with an IrOx microelectrode, whose distance to the Au substrate was precisely controlled by using scanning electrochemical microscopy (SECM) equipment. The pH values recorded during electrodeposition were greatly influenced by the acid-base reactions of the amino acid. Although high pH values were readily reached, the accumulation of glycinate at the interface was effective at suppressing the formation of metal-hydroxide species. On the other hand, the proton-donating reactions of glycine enhanced the HER, reducing deposition efficiency.

An all solid-state electrochromic system made of a viologen dissolved in a gelatin-based ionogel called Ion Jelly is presented. The obtained Ion Jelly possesses higher ionic conductivity than the constituent ionic liquid, which is ascribed to the broken ionic aggregates caused by the presence of water. Spectro-electrochemical studies carried out with the solid-state cell show that the kinetics of the reduction process is slower than that of the oxidation process, as denoted by the calculated time constants obtained from current vs. time plots. This may be owing to formation of an insoluble reduced species, which remains at the surface of the current collector, facilitating its oxidation process. The kinetics studies also show that the color change in response to the charge transfer process is faster during the reduction step. Both reversibility and durability of the device, upon successive oxidation/reduction steps, are related with the employed reduction potential, being the best compromise with the color contrast achieved at −0.25 V vs. Ag/Ag+, where 30% of transmittance change is observed up to 75 switching cycles.

Supercapacitors are energy storage devices designed to operate at higher power densities than conventional batteries, but their energy density is still too low for many applications. Efforts are made to design new electrolytes with wider electrochemical windows than aqueous or conventional organic electrolytes in order to increase energy density. Ionic liquids (ILs) with wide electrochemical stability windows are excellent candidates to be employed as supercapacitor electrolytes. ILs containing tetracyanoborate anions [B(CN)4] offer wider electrochemical stability than conventional electrolytes and maintain a high ionic conductivity (6.9 mS cm−1). Herein, we report the use of ILs containing the [B(CN)4] anion for such an application. They presented a high maximum operating voltage of 3.7 V, and two‐electrode devices demonstrate high specific capacitances even when operating at relatively high rates (ca. 20 F g−1 @ 15 A g−1). This supercapacitor stored more energy and operated at a higher power at all rates studied when compared with cells using a commonly studied ILs.

Ionic liquids (ILs) and poly(ionic liquid)s (PILs) are known for their interesting characteristics, such as intrinsic ionic conductivity, high chemical, electrochemical and thermal stabilities, and low volatility. They constitute a versatile class of materials whose structure can be modified to yield a task-specific material with improved performance for a desired application. The physicochemical properties related to ionic transport can be tailored by modifying the cation and/or anion structure in addition to the polymeric matrix and spacer groups in the case of PILs. The properties can be improved for use in electrolytes and polymeric electrolytes for electrochemical devices such as rechargeable batteries and supercapacitors. ILs and PILs that possess good transport properties can be further functionalized to have electrochromic groups attached to their structure to construct electrochromic devices. In addition, these materials also present high selectivity for CO2 absorption, and can be modified to improve the capture capacity and separation efficiency. In this chapter, different aspects regarding the modification of ILs and PILs for different applications will be explored with a focus on the relationship between their structures and physicochemical properties, and the effect on their performance in different devices.